High frequency switch and electronic device using it

【0001】

[Technical field to which the invention belongs]

The present invention relates to a high frequency switch and an electronic device using the high frequency switch, particularly a high frequency switch used for switching a signal in a millimeter wave band and an electronic device using the same.

【0002】

[Conventional technology]

As a switch used for switching a signal in the millimeter wave band, a switch using a PIN diode is generally used, but a switch using a FET may be used at a relatively low frequency. Among them, there is a switch that uses the line itself through which a high-frequency signal passes as a drain or source of a FET, and specific examples are disclosed in, for example, Patent Document 1, Patent Document 2, Patent Document 3, and Patent Document 4.

【0003】

In Patent Document 1 (conventional example 1), a signal line is divided into a plurality of drain electrodes by a plurality of slits that cross in the width direction thereof, and a source electrode and a gate that also extend in the width direction of the signal line are formed in the slits. A high-frequency switch that uses a part of a signal line as a FET by forming an electrode (line) is disclosed (for example, FIG. 13). Each drain electrode are connected by metal wiring Ru. An inductance element that resonates in parallel with the off capacitance of the FET at the signal frequency is connected between the drain and source of the FET.

【0004】

In Conventional Example 1, the signal line itself is always in a conductive state in terms of direct current, including the portion where the FET is formed. Then, when the FET is turned on, the impedance of the circuit connected between the signal line and the ground becomes small, and a short-circuit state is substantially obtained. As a result, a part of the signal line is substantially grounded, the high frequency signal is reflected, and conduction is blocked. On the contrary, when the FET is off, the impedance at the frequency of the high frequency signal of the circuit connected between the signal line and the ground becomes infinite due to the parallel resonance between the off capacitance of the FET and the inductance element. This means that nothing is connected to the signal line at the frequency of the high frequency signal, so that the high frequency signal is conductive. The switch operation is performed in this way.

【0005】

In Patent Document 2 (conventional example 2), a ground electrode (functioning as a source electrode) is formed adjacent to a part of a signal line (functioning as a drain electrode) along the longitudinal direction thereof, and a gap between the two is formed. Discloses a high frequency switch in which a gate electrode extending along the longitudinal direction of the signal line is formed (for example, FIG. 6).

【0006】

In Conventional Example 2, when the FET is off, a part of the signal line operating as a drain operates as a mere signal line, so that the high frequency signal conducts the signal line. On the other hand, when the FET is on, a part of the signal line that operates as a drain is connected to the ground electrode, so that a part of the signal line is substantially grounded and the high frequency signal is reflected. , Continuity is blocked.

【0007】

In Patent Document 3 (conventional example 3), the FET configuration similar to that of the conventional example 1 (FIG. 8, there is no inductance element for parallel resonance) and the drain, source, and gate of the FET have the same configuration as the signal line. The one configured to extend in the direction (Fig. 1) is disclosed.

【0008】

Also in the conventional example 3, the same operation as in the conventional example 2 is performed in that a part of the signal line is substantially grounded when the FET is turned on to block the high frequency signal.

【0009】

Then, in Patent Document 4 (conventional example 4), a 1/4 wavelength stub is connected to the main line of the signal line, the tip of the stub is used as a drain electrode, and the source electrode is grounded to form an FET. (Figs. 2 and 6) are disclosed. Then, by turning the FET on and off, the stub is operated as a 1/4 wavelength short stub or an open stub.

【0010】

Also in the conventional example 4, the stub becomes an open stub of 1/4 wavelength when the FET is turned off, and a part of the signal line is substantially grounded at the frequency of the high frequency signal to block the high frequency signal. The same operation as in conventional examples 2 and 3 is performed.

【0011】

[Patent Document 1]

Japanese Patent Application Laid-Open No. 6-232601 [Patent Document 2]

Japanese Unexamined Patent Publication No. 10-41404 [Patent Document 3]

Japanese Unexamined Patent Publication No. 2000-294568 [Patent Document 4]

Japanese Unexamined Patent Publication No. 2000-332502 [0012]

[Problems to be Solved by the Invention]

By the way, in the conventional example 1, it is necessary to reduce the conduction resistance when the FET is turned on, but for that purpose, it is necessary to increase the number of divisions of the signal line and increase the number of gate electrodes to increase the total gate width of the FET. There is. Since the off capacitance of the FET inevitably increases when the total gate width is increased, it is necessary to reduce the inductance value of the inductance element for parallel resonance accordingly. However, there is a limit to reducing the shape of the inductance element while maintaining the accuracy of the inductance value. Then, since it is necessary to reduce the inductance value as the signal frequency becomes higher, this configuration includes a problem that it becomes difficult to use as the signal frequency becomes higher.

【0013】

On the other hand, in the conventional example 2, since the resonance phenomenon is not used, there is no problem that it becomes difficult to use when the signal frequency becomes high as described above. However, in the conventional example 1, the main line itself through which the high frequency signal flows when the switch is turned on in the signal line is the drain electrode of the FET. Since at least a part of the drain electrode is formed on the semiconductor active layer, this means that a part of the main line is formed on the semiconductor active layer. A high-frequency signal also flows through this semiconductor active layer as a part of the line, but since the semiconductor active layer is a conductor having a higher resistance than the drain electrode, this means that the resistance of the main line increases. Therefore, in a switch in which the main line itself is the drain electrode of the FET as in Conventional Example 1, there is also a problem that it causes an increase in the insertion loss of the main line.

【0014】

Further, the on-resistance per unit length (per unit gate width) of the FET can be reduced by changing the cross-sectional structure of the FET, but this is not always easy. If the on-resistance per unit length cannot be changed, it is necessary to increase the gate width of the FET in order to sufficiently ground the main line when the FET is turned on. Increasing the gate width of the FET means extending the gate electrode in the longitudinal direction of the signal line, which at the same time means that the drain electrode becomes longer. This means that the switch becomes larger in the longitudinal direction of the main line. Since the drain electrode is also the main line through which the high-frequency signal formed on the semiconductor active layer flows, the tendency to increase the insertion loss of the main line as described above is further strengthened.

【0015】

Next, the conventional example 3 has the same basic configuration as the conventional example 1 and has the same problem.

【0016】

Finally, in the conventional example 4, since the main line through which the high frequency signal flows is not the drain electrode, there is no problem that the insertion loss at the time of switching on increases. However, in order to ground the end of the stub with a sufficiently low resistance value, it is necessary to increase the gate width of the FET. When the gate width of the FET is increased, the capacitance between the drain and the source when the FET is off increases. This means that there is a large capacitance between the tip of the open stub and the ground when the FET is off. If a large capacitance is present at the tip of the open stub, the resonance frequency of the open stub is lowered, so that the resonance frequency is likely to be different from that of the short stub. The fact that the resonance frequencies of the open stub and the short stub cannot be made the same means that the switch does not function normally, which is a big problem.

【0017】

An object of the present invention is to solve the above-mentioned problems. A high-frequency switch that can be used up to a high frequency, has a small insertion loss when the switch is turned on, and has a high signal blocking performance when the switch is turned off, and a high-frequency switch thereof are used. Provide electronic devices.

【0018】

[Means for solving problems]

In order to achieve the above object, the high frequency switch of the present invention has a main line electrode provided between two terminals and a stub line in which one end is connected to the side edge of the main line electrode and the other end is grounded. The stub line electrode and the ground electrode provided adjacent to each other in the width direction of the stub line electrode are provided, and the stub line electrode and the stub line electrode and a substrate portion between the side edge on at least one end side of the stub line electrode and the ground electrode are provided. A semiconductor active layer extending below the ground electrode is formed, and a gate electrode extending along the longitudinal direction of the stub line electrode is provided on the semiconductor active layer between the stub line electrode and the ground electrode. It is characterized in that the FET structure is formed by being formed.

【0019】

Further, a semiconductor active layer extending below the stub line electrode and the ground electrode is formed on the substrate portion between the side edge from one end side to the other end side of the stub line electrode and the ground electrode. At the same time, the FET structure is formed by providing a gate electrode extending along the longitudinal direction of the stub line electrode on the semiconductor active layer between the stub line electrode and the ground electrode.

【0020】

Further, the FET structure is formed on both side edges of the stub line electrode.

【0021】

Further, the stub line electrode on which the FET structure is formed is characterized in that a coplanar wave guide is formed together with the ground electrode.

【0022】

The stub line electrode on which the FET structure is formed is characterized in that it is formed so as to have an electric length of about 90 ° with respect to a flowing high frequency signal.

【0023】

Further, the high frequency switch of the present invention is characterized in that one end of a plurality of stub line electrodes formed with the FET structure is connected to a side edge of the main line electrode.

【0024】

Further, one end of the two stub line electrodes having the FET structure formed therein is connected so as to face each other from both sides in the width direction of the main line electrode.

【0025】

Alternatively, one end of a plurality of formed stub line electrodes having the FET structure is connected to the side edge of the main line electrode at a predetermined interval in the longitudinal direction thereof. Further, one end of the stub line electrodes formed with the plurality of FET structures is connected to the side edge of the main line electrode at intervals of approximately 90 ° in electrical length with respect to the high frequency signal flowing in the longitudinal direction thereof. It is characterized by being.

【0026】

Further, the high-frequency switch of the present invention includes a plurality of the above-mentioned high-frequency switches, and the electrical length of one end of the plurality of high-frequency switches to the connection point of the stub line electrode formed with the FET structure is substantially short. It is characterized by being connected to each other via a 90 ° main line electrode.

【0027】

Further, the high frequency switch of the present invention is characterized in that the gate electrode is drawn out from one end side of the stub line electrode.

【0028】

The electronic device of the present invention is characterized by using the above-mentioned high-frequency switch.

【0029】

With this configuration, the high frequency switch of the present invention can be used up to a high frequency, the insertion loss when the switch is turned on is small, and the signal blocking performance when the switch is turned off is high.

【0030】

Further, in the electronic device of the present invention, it is possible to reduce power consumption and malfunction.

【0031】

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 shows a plan view of an embodiment of the high frequency switch of the present invention. Further, FIG. 2 shows an enlarged cross-sectional view of AA in FIG.

【0032】

In FIG. 1, the high frequency switch 10 has a main line 17 and a stub 18 made of coplanar wave guides formed on the semiconductor substrate 11. The main line 17 is composed of a main line electrode 12 and ground electrodes 16 formed on both sides in the width direction thereof, and one end and the other end are connected to terminals 13 and 14, respectively. The stub 18 is composed of a stub line electrode 15 and ground electrodes 16 formed on both sides in the width direction thereof, and is grounded by connecting one end to the main line 17 and the other end to the ground electrode 16. More precisely, the stub 18 has one end of the stub line electrode 15 connected to the side edge of the main line electrode 12 of the main line 17 and the other end connected to the ground electrode 16. Further, the length of the stub line electrode 15 of the stub 18 is set to have an electrical length of 90 ° with respect to the high frequency signal flowing through the stub 18.

【0033】

On the semiconductor substrate 11, a semiconductor active layer 19 is formed between the stub line electrode 15 and the ground electrode 16 from one end to the other end of the stub 18. The semiconductor active layer 19 extends below the stub line electrode 15 and the ground electrode 16. It should be noted that the semiconductor substrate 11 is substantially an insulator except for the portion where the semiconductor active layer 19 is formed.

【0034】

Between the stub line electrode 15 and the ground electrode 16 of the stub 18, a gate electrode 20 extending along the longitudinal direction of the stub line electrode 15 is formed on the semiconductor active layer 19. The gate electrode 20 is connected to the gate voltage input terminal 21 from the other end side of the stub line electrode 15. The wiring from the gate electrode 20 to the gate voltage input terminal 21 has a portion that overlaps with the ground electrode 16, but in this region, it is assumed that both are insulated by an insulating layer or the like. Although the gate electrode 20 is represented by a line in FIG. 1, it is actually an electrode having a certain width as shown in FIG.

【0035】

Further, in FIGS. 1 and 2, all the main line electrodes 12 are formed directly on the semiconductor substrate 11, but the inactive portion of the semiconductor substrate 11 is not necessarily a sufficient insulator, so an unnecessary leak is required. It is desirable to provide an insulating film between the main line electrode 12 and the semiconductor substrate 11 in order to prevent the above.

【0036】

As shown in the enlarged cross-sectional view of AA in FIG. 2, in the region where the semiconductor active layer 19 is formed, electrodes are formed on both sides of the gate electrode 20, so that the overall structure is FET. I understand. At that time, if the stub line electrode 15 is used as the drain, the ground electrode 16 becomes the source. Of course, the reverse is also possible. The connection between the gate electrode 15 and the semiconductor active layer 19 must be a Schottky connection, and the connection between the line electrode 15 or the ground electrode 16 and the semiconductor active layer 19 must be an ohmic connection. Then, a depletion layer 22 is formed in the semiconductor active layer 19 under the gate electrode 20.

【0037】

In the high frequency switch 10 configured in this way, if the DC potentials of the drain and source (stub line electrode 15 and ground electrode 16) are set to 0V, for example, and the DC potential of the gate electrode 20 is set to 0V, the gate drains. And the drain and the source are almost short-circuited through the semiconductor active layer 19 over the entire longitudinal direction of the stub line electrode 15 so that the depletion layer 22 becomes smaller without being biased with respect to the source.

【0038】

Figure 3 shows the equivalent circuit of the high-frequency switch 10 in this state. In FIG. 3, Rst is the resistance component per unit length of the stub line electrode 15, and Ron is the on-resistance of the FET portion per unit length of the stub line electrode 15. Since Rst and Ron are small values and have a large number of Rst and Ron in series and in parallel, the high frequency switch 10 is equivalently the stub line of the stub line electrode 15 with the main line electrode 12 as shown in FIG. At the base of the electrode 15 (the position connected to the main line electrode 12), the ground electrode 16 is substantially short-circuited. That is, the main line 17 is in a state of being grounded on the way.

【0039】

In this state, the high-frequency signal flowing through the high-frequency switch 10 is almost totally reflected at this grounding point and is not propagated from one end to the other end. That is, the terminals 13 and 14 are turned off.

【0040】

On the other hand, if the DC potentials of the drain and source (stub line electrode 15 and ground electrode 16) are set to, for example, 0V, and the DC potential of the gate electrode 20 is set to, for example, -3V, the gate is reverse biased with respect to the drain and source. Due to the state, the depletion layer 22 becomes large, the semiconductor active layer 19 is divided, and the drain and the source are cut off.

【0041】

Figure 5 shows the equivalent circuit of the high-frequency switch 10 in this state. Since the FET portion is cut off, the high frequency switch 10 is simply a stub line electrode 15 connected to the main line electrode 12. Since the stub line electrode 15 is a short-circuited stub at the other end having an electrical length of 90 ° with respect to the flowing high-frequency signal, the stub is ideally infinite when viewed from the connection point with the main line electrode 12. It becomes impedance. Therefore, the high frequency switch 10 is equivalently composed of only the main line electrode 12 at the signal frequency as shown in FIG.

【0042】

In this state, the high frequency signal flowing through the high frequency switch 10 can freely propagate. That is, the terminals 13 and 14 are turned on.

【0043】

As described above, in the high frequency switch 10, the switch operation can be performed between the terminals 13 and 14 by the DC voltage applied to the gate electrode 20.

【0044】

Here, FIG. 7 shows the pass characteristic S21 and the reflection characteristic S11 when the high frequency switch 10 is on and off. In FIG. 7, the solid line is the characteristic when the high frequency switch 10 is on, and the broken line is the characteristic when the high frequency switch 10 is off.

【0045】

As can be seen from FIG. 7, when the high-frequency switch 10 is on, the pass characteristic S21 becomes very small at 76 GHz, which is the frequency of the high-frequency signal, and the reflection characteristic S11 becomes about -35 dB, and sufficient signal pass characteristics are obtained. Has been done. On the other hand, when the high frequency switch 10 is off, the pass characteristic S21 is about -8 dB and the reflection characteristic S11 is about -4 dB at 76 GHz, and almost satisfactory signal cutoff characteristics are obtained.

【0046】

In the high-frequency switch 10 configured in this way, only the stub line electrode 15 is used as a part of the FET, and the main line electrode 12 through which the high-frequency signal mainly flows is not a part of the FET. .. Therefore, unlike the conventional examples 1 to 3, the problem that the insertion loss of the main line increases because the high frequency signal flows through the highly resistant conductor made of the semiconductor active layer when the switch is turned on does not occur.

【0047】

Further, since the stub line electrode 15 extends in the direction orthogonal to the main line electrode 12, there is no problem that the switch becomes larger in the longitudinal direction of the main line as in the conventional example 2.

【0048】

Further, the stub line electrode 15 functions as a short stub when the FET is off, but does not function as a stub when the FET is on. That is, it is not due to resonance that a part of the main line electrode 12 is grounded when the FET is on. Therefore, the length of the stub line electrode 15 only needs to be set considering that it operates as a short stub having an electric length of 90 ° when the FET is off, and it is not necessary to consider when the FET is on. .. Therefore, the problem as in the conventional example 4 does not occur.

【0049】

Further, the fact that resonance is not used for the grounding of a part of the main line electrode 12 means that the grounded state does not have a frequency characteristic that is effective only at a specific signal frequency. Therefore, when the FET is turned on and the high frequency switch 10 is turned off, the off state is maintained in a wide frequency range. That is, high isolation characteristics can be obtained.

【0050】

The isolation characteristic here means S21 at the time of switch-off, and it is considered that the larger the decibel display (the smaller the absolute value), the better the isolation characteristic.

【0051】

In the case of Conventional Example 4, when the switch is off, a part of the main line electrode is grounded by resonance and operates as a high frequency switch by limiting it to a specific frequency. Therefore, the high frequency switch 10 of the present invention is also in this respect. Has excellent performance. When the high frequency switch is on, there is no difference in performance because both the present invention and the conventional example 4 utilize the resonance of the stub.

【0052】

By the way, in the high frequency switch 10 shown in FIG. 1, in order to substantially ground the main line electrode 12 at the connected position of the stub line electrode 15 when the FET is on, one end to the other end of the stub line electrode 15 is substantially grounded. It is not necessary for the FET to be formed all over. It is sufficient that at least one end side of the stub line electrode 15, that is, the side connected to the main line electrode 12, is a FET for a certain length and can be grounded with a sufficiently low resistance value when the FET is turned on.

【0053】

Therefore, FIG. 8 shows a plan view of another embodiment of the high frequency switch of the present invention. In FIG. 8, the same symbols are assigned to the same or equivalent parts as those in FIG. 1, and the description thereof will be omitted. The cross-sectional view of the FET portion is the same as in FIG. 2, and is omitted.

【0054】

The high frequency switch 30 shown in FIG. 8 has a stub 31 instead of the stub 18 in the high frequency switch 10. In the stub 31, the semiconductor active layer 32 is formed between the stub line electrode 15 and the ground electrode 16 in about half of the one end side of the stub 31. Between the stub line electrode 15 and the ground electrode 16 of the stub 31, a gate electrode 33 extending along the longitudinal direction of the stub line electrode 15 is formed on the semiconductor active layer 32 across the semiconductor active layer 32. .. The gate electrode 33 is connected to the gate voltage input terminal 21. The gate electrode 33 is formed not only on the semiconductor active layer 32 but also on the portion between the stub line electrode 15 and the ground electrode 16 that is not the semiconductor active layer, except on the semiconductor active layer 32. Since the portion formed in the above does not operate as a FET but functions as a mere signal line, it is not regarded as a gate electrode here.

【0055】

Even in the high-frequency switch 30 configured in this way, the portion having the FET structure operates in the same manner as in the case of the high-frequency switch 10. Therefore, Fig. 9 shows the equivalent circuit of the high-frequency switch 30 when the FET is turned on. In FIG. 9, the same symbols are attached to the parts that are the same as or equivalent to those in FIG.

【0056】

In FIG. 9, the part of the stub line electrode 15 that is not a part of the FET remains as the line 15', but one end side connected to the main line electrode 12 is the same as in the case of the high frequency switch 10. It is connected to the ground electrode 16 via a large number of Rsts and Rons. Therefore, in the high frequency switch 30, similarly to the high frequency switch 10, the main line electrode 12 is substantially grounded at the root portion of the stub line electrode 15. That is, the main line 17 is in a state of being grounded on the way.

【0057】

Then, in this state, the high-frequency signal flowing through the high-frequency switch 30 is almost totally reflected at this grounding point and is not propagated from one end to the other end. That is, the terminals 13 and 14 are turned off.

【0058】

On the other hand, when the FET is off, the FET portion is cut off, so that the high frequency switch 30 is simply a stub line electrode 15 connected to the main line electrode 12. Since the stub line electrode 15 is a short-circuited stub at the other end having an electric length of 90 ° with respect to the flowing high frequency signal, the high frequency switch 30 is equivalently composed of only the main line electrode 12 at the signal frequency. It becomes.

【0059】

In this state, the high frequency signal flowing through the high frequency switch 30 can freely propagate. That is, the terminals 13 and 14 are turned on.

【0060】

The length of the gate electrode (gate width) may be a length that can realize a sufficient short-circuit state with the ground electrode 16 when the FET is turned on on one end side of the stub line electrode 15. Therefore, the length is not limited to half of the length of the stub line electrode such as the high frequency switch 30, and may be less than half or more than half.

【0061】

Further, when the FET is off, the off capacitance exists in a distributed manner between the drain and the source. Therefore, the distributed capacitance between the stub line electrode 15 and the ground electrode 16 differs between the portion where the semiconductor active layer 32 exists and the portion where it does not exist. Further, the distributed inductance component of the line electrode 15 also differs strictly depending on whether or not it is located on the semiconductor active layer. Therefore, it is possible that the characteristic impedance of the stub 31 differs depending on the location. Therefore, the length and width of the stub 31 must be determined in consideration of such a partial change in the characteristic impedance of the stub 31.

【0062】

As a practical matter, the stub in this case adjusts the electrical length by changing not only the total length of the stub line electrode but also the width of the stub line electrode between the FET part and the non-FET part and the distance from the ground electrode. It is quite possible to do so.

【0063】

By the way, in the high frequency switch 30, the gate width, which is the length of the gate electrode, is shorter than that in the high frequency switch 10. Therefore, the off capacitance formed between the drain and source of the FET portion is also reduced. This off capacitance is related to the time constant that determines the speed of switching operation of the high frequency switches 10 and 30. That is, the smaller the off capacitance, the smaller the time constant and the faster the switching operation. Therefore, the high-frequency switch 30 has an excellent advantage that it can support high-speed switching operation as compared with the high-frequency switch 10.

【0064】

Further, in general, the gate electrode is usually formed in a straight line, and it is not always easy to form the gate electrode by bending it. Therefore, in the high frequency switch 10, the stub line electrode 15 of the stub 18 has to be formed linearly. In this case, it may be difficult to miniaturize the high frequency switch.

【0065】

On the other hand, in the high frequency switch 30, the gate electrode 33 need only be formed along one end side of the stub line electrode 15. Therefore, as shown in the schematic view in FIG. 10, it is possible to bend the other end side of the stub line electrode 15 in which the gate electrode 33 is not formed. This makes it possible to reduce the size of the high frequency switch.

【0066】

As described above, the high-frequency switch 30 has the advantages that the switching operation can be performed at a higher speed than the high-frequency switch 10 and that the stub can be bent, so that the size can be further reduced.

【0067】

Although the high-frequency switch 10 and the high-frequency switch 30 have FET structures formed on both sides of the stub line electrode, they may be formed on only one side. In this case, the resistance value when the FET is turned on becomes slightly large, but except for this point, almost the same effect as that of the above-described embodiment can be obtained.

【0068】

Further, in the high frequency switch 10 and the high frequency switch 30, the main line and the stub are symmetrical coplanar wave guides, and in the stub, the ground electrode for the symmetrical coplanar wave guide is used as the source electrode of the FET. It was. However, the main line and the stub are not limited to the symmetrical coplanar wave guide, and may be, for example, an asymmetrical coplanar wave guide having a ground electrode on only one side. Alternatively, it may be another transmission line such as a microstrip line that does not have a ground electrode along the line electrode. However, in that case, it is necessary to separately provide a ground electrode adjacent to the stub line electrode. At the same time, the characteristic impedance of the stub changes due to the adjacent ground electrode as compared with the case of the ideal microstrip line, so this point should be taken into consideration when determining the length of the stub line electrode. There is a need to. However, except for these points, the high-frequency switch can obtain almost the same effects as those in the above-described embodiment.

【0069】

Hereinafter, another embodiment of the high frequency switch using the stub on which the above-mentioned FET structure is formed will be described. In the following examples, the stub structure of the high frequency switch 30 is adopted, but of course, the stub structure of the high frequency switch 10 may be used.

【0070】

First, FIG. 11 shows a schematic view of still another embodiment of the high frequency switch of the present invention. FIG. 11 is a simplified diagram for showing only the characteristic parts, and the same symbols are added to the parts that are the same as or equivalent to those in FIG. 1, and the description thereof will be omitted.

【0071】

In the high-frequency switch 40 shown in FIG. 11, 41 and 42 mean the stub line electrodes of the stub on which the FET structure is formed. The lines on both sides of the track mean the gate track. The description of the ground electrode and the gate voltage input terminal is omitted.

【0072】

As shown in FIG. 11, in the high-frequency switch 40, two stub line electrodes 41 and 42 are provided on the side edges of the main line electrodes 12 so as to face each other from both sides in the width direction. In the high-frequency switch 40 configured in this way, the stubs including the stub line electrodes 41 and 42 each perform the same function as the stub 31 in the high-frequency switch 30.

【0073】

Therefore, by turning on / off the FETs of the two stubs at the same time in response to the on / off of the high frequency switch 40, the main line electrode 12 can be grounded in the middle when the high frequency switch is turned off. Moreover, in the case of the high frequency switch 30, only one side edge of the main line electrode 12 at a predetermined position is grounded, whereas in the high frequency switch 40, both side edges of the main line electrode 12 at a predetermined position are grounded. It is grounded at the same time. This means that the point is grounded through half the resistance value as compared with the case of the high frequency switch 30, and it means that the cutoff state when the high frequency switch 40 is off can be made more complete. That is, the isolation characteristics can be further improved.

【0074】

Also, from a different point of view, it means that the length (gate width) of the gate electrode of each stub can be shortened if the ground resistance can be the same. The fact that the gate width can be shortened means that the switching operation can be further speeded up as described above. In addition, since the gate electrodes in the stub line electrodes 41 and 42 are formed, the part that must be linear is shortened, which means that the degree of freedom in stub shape is increased and the high frequency switch can be further miniaturized. To do.

【0075】

As described above, in the high-frequency switch 40, the blocking performance of the high-frequency signal when it is off can be further improved, or the switching operation can be speeded up or downsized.

【0076】

Further, FIG. 12 shows a schematic view of still another embodiment of the high frequency switch of the present invention. FIG. 12 is a simplified diagram for showing only the characteristic parts, and the same symbols are added to the parts that are the same as or equivalent to those in FIG. 1, and the description thereof will be omitted.

【0077】

In the high frequency switch 50 shown in FIG. 12, 51 and 52 mean the stub line electrodes of the stub on which the FET structure is formed. The lines on both sides of the track mean the gate track. The description of the ground electrode and the gate voltage input terminal is omitted.

【0078】

As shown in FIG. 12, in the high-frequency switch 50, the two stub line electrodes 51 and 52 are located 90 ° apart in electrical length in the longitudinal direction of the main line electrode 12 on one side edge of the main line electrode 12. It is provided by connecting to. In the high frequency switch 50 configured in this way, the stubs including the stub line electrodes 51 and 52 each perform the same function as the stub 31 in the high frequency switch 30.

【0079】

Therefore, by turning on / off the FETs of the two stubs at the same time in response to the on / off of the high frequency switch 50, the main line electrode 12 can be grounded at two places in the middle when the high frequency switch is turned off. .. By grounding two places in this way, even if the length of the gate electrode of each stub is short and grounding at one place is not always sufficient, the high frequency signal is reflected more completely and the high frequency switch 50 is cut off. Can be made to. Moreover, since the two stubs are connected and provided at positions 90 ° apart in electrical length in the longitudinal direction of the main line electrode 12, the impedance of the other stub as seen from one stub becomes infinite, which is practical. The reflected signal from one stub does not adversely affect the characteristics of the other stub, especially the ground contact condition.

【0080】

Here, FIG. 13 shows the pass characteristic S21 and the reflection characteristic S11 when the high frequency switch 50 is on and off. In FIG. 13, the solid line is the characteristic when the high frequency switch 50 is on, and the broken line is the characteristic when the high frequency switch 50 is off.

【0081】

As can be seen from FIG. 13, when the high frequency switch 50 is on, the loss of the pass characteristic S21 becomes very small and close to 0 dB at the frequency of the high frequency signal of 76 GHz, and the reflection characteristic S11 becomes -40 dB or less. Sufficient signal passage characteristics have been obtained. On the other hand, when the high frequency switch 50 is off, the passing characteristic S21 is about -19dB and the reflection characteristic S11 is about -4dB at 76GHz, and the passing amount is further smaller than that of the high frequency switch 10, and sufficient signal blocking characteristics are obtained. Has been obtained.

【0082】

As described above, in the high frequency switch 50, the cutoff characteristic at the time of switch off can be further improved.

【0083】

The high-frequency switch 50 uses two stubs having a FET structure, but if each stub is connected to the main line electrode 12 at a position 90 ° apart in electrical length in the longitudinal direction. For example, the number of stubs may be three or more.

【0084】

Further, in the high frequency switch 50, each stub is provided by being connected only to one side edge of the main line electrode 12, but it may be provided by being connected to either side edge of the main line electrode 12. is there.

【0085】

By the way, in the high frequency switch 50, in order to avoid mutual influence, two stubs are connected to each other at a position 90 ° apart in the electrical length in the longitudinal direction of the main line electrode 12, but the stubs are closer to each other. It is also possible to provide one.

【0086】

Therefore, FIG. 14 shows a schematic view of still another embodiment of the high frequency switch of the present invention. FIG. 14 is also a simplified diagram for showing only the characteristic parts, and the same symbols are added to the parts that are the same as or equivalent to those in FIG. 1, and the description thereof will be omitted.

【0087】

In the high-frequency switch 60 shown in FIG. 14, 61, 62, 63, and 64 all mean the stub line electrodes of the stub on which the FET structure is formed. The lines on both sides of the track mean the gate track. The description of the ground electrode and the gate voltage input terminal is omitted.

【0088】

As shown in FIG. 14, in the high-frequency switch 60, the four stub line electrodes 61, 62, 63, and 64 have electrical lengths in the longitudinal direction of the main line electrode 12, respectively, on one side edge of the main line electrode 12. It is connected to a position 16 ° away. The length of each stub line electrode is set to 110 ° in electrical length at the signal frequency. The characteristic impedance of the main line is set to 75Ω, and the characteristic impedance of the stub is set to 35Ω. In the high frequency switch 60 configured in this way, the stubs including the stub line electrodes 61, 62, 63, 64 each perform the same function as the stub 31 in the high frequency switch 30.

【0089】

Even in the high frequency switch 60, by turning on and off the FETs of the four stubs at the same time in response to the on / off, the main line electrode 12 can be grounded at four points in the middle when the high frequency switch is turned off. it can. By grounding the four locations in this way, the grounding state can be made more sufficient than in the case of the two locations, and the high-frequency signal can be reflected more completely to shut off the high-frequency switch 60.

【0090】

In the high frequency switch 60, the distance between the stubs in the longitudinal direction of the main line electrode 12 is 16 °. Therefore, there is no merit that the stubs cannot be seen from each other and the adverse effects of each other can be avoided. However, on the contrary, there is an advantage that the frequency band is widened in the reflection characteristics when the FET is off (switch on) and matching can be performed at other frequencies. Further, since the stub spacing is short, the size of the high frequency switch in the longitudinal direction can be reduced. Further, since the length of the main line is shortened, the insertion loss at the time of switching on can be reduced.

【0091】

In addition, due to the large number of stubs, the reflection of high-frequency signals between each stub and the ground resistance of each stub when the FET is on increases the power consumption of each stub and the insertion loss when the switch is off. There is a merit.

【0092】

Here, FIG. 15 shows the pass characteristic S21 and the reflection characteristic S11 when the high frequency switch 60 is on and off. In FIG. 15, the solid line is the characteristic when the high frequency switch 60 is on, and the broken line is the characteristic when the high frequency switch 60 is off.

【0093】

As can be seen from FIG. 15, when the high frequency switch 60 is on, the loss of the pass characteristic S21 becomes very small and close to 0 dB at 76 GHz, which is the frequency of the high frequency signal, and the reflection characteristic S11 is -15 dB or less in a wide band. Therefore, sufficient signal passing characteristics are obtained. On the other hand, when the high-frequency switch 60 is off, the pass characteristic S21 is about -33 dB and the reflection characteristic S11 is about -3 dB at 76 GHz, and the pass amount is significantly smaller than that of the high-frequency switch 10, which is sufficient signal cutoff characteristic. It can be seen that is obtained.

【0094】

The reason why there are two valleys in the reflection characteristic S11 when the switch is turned on is that the number of stubs is large. Characteristics such as the frequency of the valley, the interval, and the amount of reflection between the valleys can be set by appropriately adjusting the stub interval, the length and characteristic impedance of the stub, and the characteristic impedance of the main line. This is the reason why the stub length of the high frequency switch 60 is set to 110 ° in terms of electrical length.

【0095】

As described above, in the high frequency switch 60, the cutoff characteristic at the time of off can be further improved.

【0096】

In the high frequency switch 60, the distance between the stubs is 16 °, but this is just one example and may be freely set as needed. Also, the number of stubs can be freely set as long as it is two or more.

【0097】

Further, in the high frequency switch 60, the stubs are connected only to one side edge of the main line electrode 12, but stubs may be connected to both side edges as in the high frequency switch 70 shown in FIG. 16, for example. In particular, when the stubs are connected alternately like the high frequency switch 70, the distance between the stubs can be further narrowed as compared with the case where the stubs are connected only to one side edge, and the high frequency switch can be further miniaturized. It is also possible to plan.

【0098】

In each of the above embodiments, an example of a so-called SPST (Single Pole Single Through, one-to-one) switch that conducts or cuts off between two terminals has been described, but a plurality of high-frequency switches of the present invention may be used. For example, a so-called SPxT (Single Pole x Through, one-to-many) switch can be configured.

【0099】

FIG. 17 shows a schematic view of still another embodiment of the high frequency switch of the present invention. FIG. 17 is a simplified diagram for showing only the characteristic parts, and the same symbols are added to the parts that are the same as or equivalent to those in FIG. 1, and the description thereof will be omitted.

【0100】

In the high-frequency switch 80 shown in FIG. 17, two high-frequency switches 60 shown in FIG. 14 are used, and one ends thereof are connected to each other to form a third terminal. In FIG. 17, one end of one high frequency switch 60 is connected to terminal 81, one end of the other high frequency switch 60 is connected to terminal 82, and the other ends of the two high frequency switches 60 are connected to each other and terminal 83. It is connected to the. Then, the length of the main line electrode 12 from the connection point to the connection point of the nearest stub line electrode in each high frequency switch 60 is set so that the electric length with respect to the high frequency signal is approximately 90 °.

【0101】

In the high-frequency switch 80 configured in this way, each high-frequency switch 60 operates as a low-loss switch. Moreover, since the length of the main line electrode 12 from the connection point to the connection point of the nearest stub line electrode in each high frequency switch 60 is set so that the electrical length with respect to the high frequency signal is approximately 90 °, on the other hand. When the high frequency switch 60 is on and the other high frequency switch 60 is off, the off high frequency switch 60 appears to have infinite impedance with respect to the main line electrode 12. That is, it is the same as if there is no high frequency switch 60 in the off state. Therefore, an SPDT (Single Pole Dual Through, 1 to 2) switch with less inconsistency and insertion loss when the switch is turned on can be realized.

【0102】

In the above embodiment, the length of the main line electrode 12 from the connection point between the other ends of the two high frequency switches 60 to the connection point of the nearest stub line electrode in each high frequency switch 60 is the electrical length with respect to the high frequency signal. Is set to be approximately 90 °, which is the ideal condition where the resistance value between the FET of each stub and the ground when it is on is sufficiently small. Actually, it is conceivable that the length of the line electrode 12 in this portion becomes about 80 ° in terms of electrical length.

【0103】

Although the SPDT switch is realized in the high frequency switch 80, it is also possible to configure the SPxT switch by the same method using, for example, three or more high frequency switches 60.

【0104】

By the way, each of the above embodiments has the structure of the high frequency switch 10 shown in FIG. 1 as a basic structure. Then, in the high frequency switch 10, when the switch is turned off, that is, when the FET portion is turned on, the DC potential of the gate is set to 0 V, which is the same as that of the drain and source, so that the gate is not biased with respect to the drain and source. It is said. However, the depletion layer exists even when the gate is not biased. Therefore, it is conceivable to further reduce the depletion layer by making the gate forward biased with respect to the drain and the source.

【0105】

When the gate is biased forward with respect to the drain and source, gate current flows. When the gate width is long, a potential difference occurs between the position near the gate voltage input terminal and the position far from the gate voltage input terminal due to the presence of resistance in the gate electrode. As a result, as shown in FIG. 18, the closer to the gate voltage input terminal, the larger the potential difference between the drain and the source, and the larger the gate forward current that flows. The larger the gate forward current, the smaller the depletion layer, and therefore the smaller the resistance between the drain and the source. If this is applied to the high frequency switch 10, the on-resistance Ron of the FET portion per unit length of the stub line electrode 15 is on one end side of the stub line electrode 15 (the side connected to the main line electrode 12). Larger and smaller on the other end side. This is not necessarily ideal from the point of view of the present invention that at least one end side of the stub line electrode 15 should be grounded with a sufficiently low resistance value.

【0106】

Therefore, FIG. 19 shows a plan view of still another embodiment of the high-frequency switch of the present invention in which this point is improved. In FIG. 19, the same symbols are added to the parts that are the same as or equivalent to those in FIG. 1, and the description thereof will be omitted. Since the cross-sectional view of the FET portion is the same as in FIG. 2, it is omitted.

【0107】

The high-frequency switch 10'shown in FIG. 19 differs from the high-frequency switch 10 only in that the gate electrode 20 is pulled out from one end side of the stub line electrode 15 and connected to the gate voltage input terminal 21. In this gate electrode lead-out configuration, the wiring from the gate electrode 20 to the gate voltage input terminal 21 has a portion that overlaps with the main line electrode 12 and the ground electrode 16, but in this region, one straddles the other in an air bridge structure. It is assumed that the two are insulated by means of an insulating layer in between.

【0108】

In the high frequency switch 10'configured in this way, if the DC potentials of the drain and source (stub line electrode 15 and ground electrode 16) are set to, for example, 0V, and the DC potential of the gate electrode 20 is set to, for example, + 1V, Since the gate is in a forward biased state with respect to the drain and source and the depletion layer 22 becomes smaller, the drain and source are almost short-circuited through the semiconductor active layer 19 over the entire longitudinal direction of the stub line electrode 15.

【0109】

Moreover, when the gate is placed in a forward bias state with respect to the drain and source, the on-resistance Ron of the FET portion per unit length becomes smaller as it is closer to the gate voltage input terminal as described above, so that the high frequency switch 10' In, a better short-circuit state can be obtained toward one end side of the stub line electrode 15. As a result, the high frequency switch 10'can realize a better off state than the case of the high frequency switch 10. When the switch is on, the gate is placed in a reverse bias state with respect to the drain and source, so there is no characteristic difference between the high frequency switches 10 and 10'.

【0110】

In this way, by adopting the configuration of the high frequency switch 10', the cutoff characteristic at the time of switch off can be improved. Since this configuration improves the short-circuited state on one end side of the stub line electrode, it can be similarly applied to the high frequency switch 30 shown in FIG. 8, and the same effect can be obtained.

【0111】

Further, by adopting this gate electrode lead-out configuration, it is possible to improve the cutoff characteristic at the time of switch-off per one stub line electrode, so that the characteristic can be improved even in a switch using a plurality of stub line electrodes. .. That is, for example, when the high-frequency switch 60 shown in FIG. 14 adopts the gate electrode lead-out configuration of the high-frequency switch 10', the same isolation characteristics can be obtained with a smaller number of stub line electrodes. The fact that the number of stub line electrodes can be reduced means that the area of the high-frequency switch can be reduced accordingly. In addition, the fact that the number of stub line electrodes can be reduced also means that the insertion loss at the time of switch-on can be reduced accordingly. And this effect is not limited to the SPST switch such as the high frequency switch 10 and 60, and can be similarly obtained in the SPxT switch including the SPDT switch such as the high frequency switch 80 shown in FIG.

【0112】

Finally, FIG. 20 shows a block diagram of an embodiment of the electronic device of the present invention. In FIG. 20, the electronic device 90 is a radar device, which is composed of a transmission / reception circuit 91, a high frequency switch 92 of the present invention, and four antennas 93, 94, 95, 96. Of these, the high-frequency switch 92 is a 1-input 4-output high-frequency switch with four built-in high-frequency switches. Each built-in switch is turned on one by one, and the transmission / reception circuit 91 is connected via the built-in switch in the on state. The antenna is connected and signals are transmitted and received. The four antennas 93, 94, 95, and 96 all have different directivity directions, and can be operated as radars in four directions by switching the built-in switch of the high-frequency switch 92.

【0113】

In the electronic device 90 configured in this way, since the high frequency switch 92 of the present invention is used, the insertion loss at the time of switching on is small, so that the signal loss can be reduced and the power consumption can be reduced. it can. In addition, since it has excellent cutoff characteristics when the switch is turned off, malfunctions such as emitting radar waves in different directions and detecting objects in different directions are reduced.

【0114】

Although the radar device is shown as the electronic device in FIG. 20, any electronic device may be used as long as it uses the high frequency switch of the present invention.

【0115】

[Effect of the invention]

In the high frequency switch of the present invention, the width of the main line electrode provided between the two terminals, the stub line electrode having one end connected to the side edge of the main line electrode and the other end grounded, and the width of the stub line electrode. A semiconductor active layer extending below the stub line electrode and the ground electrode is provided on the substrate portion between the side edge on at least one end side of the stub line electrode and the ground electrode, which is provided with the ground electrode provided adjacent to each other in the direction. Along with the formation, the FET structure is formed by providing a gate electrode extending along the longitudinal direction of the stub line electrode on the semiconductor active layer between the stub line electrode and the ground electrode.

【0116】

Then, by turning on this FET, a part of the main line electrode is grounded to block the high frequency signal flowing through the main line electrode, and by turning off the FET, it is operated as a switch for conducting the high frequency signal flowing through the main line electrode. be able to.

【0117】

Moreover, in the high-frequency switch of the present invention, since the main line electrode is not a part of the FET, the insertion loss at the time of switching on can be reduced. In addition, since a grounded state without frequency characteristics is realized, high-frequency signals can be stably blocked when the switch is turned off. As a result, high isolation characteristics can be obtained.

【0118】

Further, according to the electronic device of the present invention, it is possible to reduce the current consumption and the malfunction by using the high frequency switch of the present invention.

[Simple explanation of drawings]

FIG. 1 is a plan view showing an embodiment of a high frequency switch of the present invention.

2 is an enlarged cross-sectional view of AA of the high frequency switch of FIG. 1. FIG.

FIG. 3 is an equivalent circuit diagram when the high frequency switch of FIG. 1 is off.

FIG. 4 is a substantially equivalent circuit diagram when the high frequency switch of FIG. 1 is turned off.

5 is an equivalent circuit diagram when the high frequency switch of FIG. 1 is turned on.

FIG. 6 is a substantially equivalent circuit diagram when the high frequency switch of FIG. 1 is turned on.

7 is a characteristic diagram showing the switch characteristics of the high-frequency switch of FIG. 1. FIG.

FIG. 8 is a plan view showing another embodiment of the high frequency switch of the present invention.

9 is a substantially equivalent circuit diagram when the high frequency switch of FIG. 8 is off.

10 is a plan view showing a variation of the high frequency switch of FIG. 8. FIG.

FIG. 11 is a plan view showing still another embodiment of the high frequency switch of the present invention.

FIG. 12 is a plan view showing still another embodiment of the high frequency switch of the present invention.

13 is a characteristic diagram showing the switch characteristics of the high-frequency switch of FIG. 12. FIG.

FIG. 14 is a plan view showing still another embodiment of the high frequency switch of the present invention.

15 is a characteristic diagram showing the switch characteristics of the high-frequency switch of FIG. 14. FIG.

FIG. 16 is a plan view showing still another embodiment of the high frequency switch of the present invention.

FIG. 17 is a plan view showing still another embodiment of the high frequency switch of the present invention.

FIG. 18 is a characteristic diagram showing the relationship between the position on the gate electrode and the gate forward current.

FIG. 19 is a plan view showing still another embodiment of the high frequency switch of the present invention.

FIG. 20 is a block diagram showing an embodiment of the electronic device of the present invention.

[Explanation of symbols]

10, 30, 40, 50, 60, 70, 80, 10'... High frequency switch 11 ... Semiconductor substrate 12 ... Main line electrodes 13, 14, 81, 82, 83 ... Terminals 15, 41 , 42, 51, 52, 61, 62, 63, 64, 71, 72, 73, 74 ... Stub line electrode 16 ... Ground electrode 17 ... Main line 18, 31 ... Stub 19, 32 ... Semiconductor active layers 20, 33 ... Gate electrodes 21 ... Gate voltage input terminals 22 ... Depleted layers 90 ... Electronic devices