Diode mixer

The present invention relates to a diode mixer, and more particularly to a diode mixer used in microwave band and millimeter wave band communication equipment such as for electronic equipment, mobile communication, and wireless communication.

In recent years, communication devices used in the microwave band and millimeter wave band have been required to be smaller and have higher output, and along with this, mixers with high frequency conversion efficiency have been required. However, at the same time, a mixer having good noise characteristics is required. For example, in a communication laser device, if the noise characteristics of the mixer are not good, the S / N value will decrease, the maximum reach of the signal light will decrease, and the system cost will increase in order to maintain high system reliability. There are disadvantages such as an increase. Also, in a system that directly downconverts from the millimeter wave band to a low frequency band where low frequency noise or 1 / f noise greatly affects noise characteristics, such as 100kHz, such as in-vehicle radar, the intermediate frequency signal (hereinafter referred to as IF) is used in the mixer. A homodyne method with a low IF frequency (called a signal) is used.

In this homodyne type mixer, it is effective to use a pn diode with less low frequency noise in order to obtain good noise characteristics. As a known technique of the mixer, there is a known example in which an even harmonic mixer using an anti-parallel diode pair is disclosed. (For example, refer to Patent Document 1, columns 2 to 3 and FIG. 6, columns 4 to 5 and FIG. 1). In addition, as a known technique for electronic high-frequency switches, a coil is connected in parallel to a diode, and the resonance frequency of the resonance circuit composed of the reverse bias capacitance of the diode and the coil is used so as to be close to the frequency of the high-frequency signal used. An example is disclosed in which an attempt is made to improve the isolation by increasing the impedance in the vicinity of the frequency (see, for example, Patent Document 2, page 54, lower left column, and FIG. 6).

Further, as a known technique of a diode switch circuit, an example of configuring a diode switch circuit having excellent high frequency characteristics by connecting a reactors circuit including a series connection circuit of an inductance and a capacitor in parallel with a diode at both ends of the diode. (See, for example, Patent Document 3, page 108, lower left column, and FIG. 1). Further, as a known technique of a λ / 4 type switch circuit, an example in which a circuit in which an inductor having an inductance value that causes parallel resonance with the capacitance of a diode and a capacitor for cutting DC are connected in series is connected in parallel is disclosed ( For example, see Patent Document 4, page 2, lower right column, and Fig. 1). Further, as a known example of the frequency conversion circuit, an example in which a coil is connected in series to each of the diodes constituting the anti-parallel diode pair of the even harmonic mixer to compensate the junction capacitance of the diode and reduce the loss at the time of frequency conversion is disclosed. (For example, see Patent Document 5, FIG. 1).

<patcit num="1"><text>Japanese Patent No. 2795972</text></patcit><patcit num="2"><text>JP-A-55-42412</text></patcit><patcit num="3"><text>JP-A-61-61524</text></patcit><patcit num="4"><text>Japanese Unexamined Patent Publication No. 2-108301</text></patcit><patcit num="5"><text>Japanese Unexamined Patent Publication No. 2004-140438</text></patcit>

<p> However, in a mixer using a pn diode, the frequency conversion efficiency may be lowered in some cases because the diode has a diffusion capacitance. The equivalent circuit of a diode is expressed as a variable resistance component and a variable capacitance component connected in parallel. And the capacitance of the pn diode is shown by Eq. (1). Cj = (Cj₀/ (1-(V / Vf))^M ) + ((qτIs) / (nkT)) exp (qV / (nkT)) (1) Where Cj₀Is the capacitance component at 0V, Vf is the built-in voltage, M is the slope coefficient, q is the elementary charge, τ is the transition time, Is is the saturation current, n is the ideal coefficient, and k is the Boltzmann constant.</p><p> The first term on the right side of equation (1) is the junction capacitance, and the second term is the diffusion capacitance. In addition to the junction capacitance, the capacitance component of the diode includes a diffusion capacitance that changes exponentially with the anode voltage. Therefore, the capacitance component of the diode has a region that increases exponentially as the anode voltage increases. In a diode mixer using a pn diode, when the power of the local oscillation signal (hereinafter referred to as LO signal) increases, that is, when the anode voltage amplitude increases, the built-in voltage at the time of forward bias according to the second term of Eq. (1). The capacitance component of the diode increases exponentially near (or on-voltage or threshold voltage). On the other hand, the non-linearity of the current-voltage characteristics near the built-in voltage is important for mixing, and when the anode voltage amplitude of the LO signal reaches the region where the current near this built-in voltage changes most rapidly, the conversion gain becomes At the largest, slightly lower anode voltage amplitudes in this region, the conversion gain drops sharply.</p><p> Therefore, even if the power of the LO signal increases, the anode amplitude voltage of the LO signal is increased, and the conversion gain of the frequency conversion is increased, the capacitance component of the diode increases exponentially, which contributes to the frequency conversion in the mixer circuit. There is a problem that the power of the LO signal is not effectively input to the variable resistance component of the diode, and good frequency conversion efficiency cannot be obtained. The present invention has been made to solve the above problems, and a first object of the present invention is to provide a diode mixer having a simple configuration, high frequency conversion efficiency, and good noise characteristics.</p>

<p> The diode mixer according to the present invention includes an inductor connected in series and an inductor.<u style="single">DC cutoff</u>It has a first circuit element part including a capacitor and a first diode connected in parallel to the first circuit element part, and one end of the first circuit element part and an anode of the first diode are A semiconductor portion including a second connection portion in which the other end of the connected first connection portion and the first circuit element portion and the cathode of the first diode are connected, and a first connection portion of the semiconductor portion. Connected to<u style="single">Local oscillation signal</u>A first signal input / output terminal to which is input, a first demultiplexing circuit disposed between the first signal input / output terminal and the first connection portion of the semiconductor portion, and<u style="single">The first connection part or the second connection part of the semiconductor part via the second demultiplexing circuit</u>With the second signal input / output end connected to<u style="single">The second connection part of the semiconductor part via the third demultiplexing circuit</u>With a third signal input / output end connected to<u style="single">Local oscillation signal</u>On the other hand, the inductor and the capacitance component of the first diode form a resonance circuit.</p>

<p> In the diode mixer according to the present invention, since the inductor and the capacitance component of the first diode form a resonance circuit with respect to the first signal, the capacitance and the inductor that rapidly increase in the vicinity of the built-in voltage at the time of forward bias As a result, parallel resonance is generated at the frequency of the first signal, thereby suppressing the leakage of input power due to the increase in the capacitance component of the diode, which increases with the increase in power of the LO signal, and for frequency conversion in the diode mixer. The diode mixer frequency conversion gain can be improved by effectively inputting the LO signal to the resistance component of the contributing diode.</p>

In the following description, a diode mixer using a pn diode will be generally described. However, it is not necessarily limited to the pn diode, and a Schottky diode may be used. Further, not only a pn diode but also a Schottky diode in which a drain and a source of a FET that can be created on the same substrate as a semiconductor amplifier or a semiconductor oscillator are connected may be used. Further, a pn diode between the base and collector of the HBT may be used, or a pn diode between the base and the emitter may be used. Further, in the following embodiments, a diode mixer having a low frequency of the IF signal used in the homodyne system will be described, but the diode mixer is not necessarily limited to this system. Embodiment 1.

FIG. 1 is a block diagram of a diode mixer according to an embodiment of the present invention. In each figure, it is shown that the same reference numerals are the same or equivalent. In FIG. 1, the diode mixer 10 is a single-ended diode mixer, a first circuit element including a diode 12 as a first diode and an inductor and capacitor connected in parallel to the diode 12 and connected in series. The mixer diode section 16 as a semiconductor section composed of the first inductor circuit 14 as a section, and the first connection section 18 to which the anode of the diode 12 and the inductor circuit 14 in the mixer diode section 16 are connected are first. The LO signal port 22 as the first signal input / output terminal connected via the demultiplexer circuit 20 and the second connection portion 24 to which the cathode of the diode 12 in the mixer diode portion 16 and the inductor circuit 14 are connected are connected. The IF signal port 28 as the second signal input / output terminal connected via the 2-demultiplexing circuit 26 and the 3rd signal input / output connected to the 2nd connection portion 24 via the 3rd demultiplexing circuit 30. It is composed of a high frequency signal (hereinafter referred to as RF signal) port 32 as an end.

In the diode mixer 10, an example in which the second demultiplexing circuit 26 and the IF signal port 28 are connected to the second connection portion 24 is shown, but the second demultiplexing circuit 26 and the IF signal port 28 are second. It may be connected to the first connection part 18 instead of the connection part 24. FIG. 2 is a circuit diagram of a diode mixer according to an embodiment of the present invention. The diode mixer 34 in FIG. 2 is an example of the diode mixer 10, and is a single-ended mixer of a down converter used as a receiving mixer of a 76 GHz band in-vehicle millimeter-wave radar used for detecting obstacles, for example. In the diode mixer 34, the LO signal is input from the LO signal port 22, the RF signal is input from the RF signal port 32, and the IF signal with a low frequency, for example, 100 kHz, is output from the IF signal port 28. The diode 12 of the mixer diode section 16 is a pn diode. The first inductor circuit 14 includes a capacitor 14a for cutting off DC and an inductor 14b that resonates in parallel with the variable capacitance component of the diode 12 at the frequency of the LO signal to suppress leakage of input power due to an increase in the capacitance component.

The inductance value of the inductor 14b is such that the anode voltage amplitude of the diode 12 due to the LO signal becomes a value near the built-in voltage of the diode 12, and the variable capacitance component of the diode 12 has a large value and a parallel resonant circuit is formed accordingly. Is set to. The first demultiplexing circuit 20 is composed of a short stub 20a having an electric length of λLO / 4, when the wavelength of the LO signal is λLO. The second demultiplexing circuit 26 is connected to the open stub 29 having an electric length of λLO / 4 connected to the second connection part 24, and λRF when the wavelength of the RF signal is λRF, which is also connected to the second connection part 24. It has an electrical length of / 4, and is composed of a short stub 26b grounded via a DC blocking capacitor 26a. The third demultiplexing circuit 30 is composed of an open stub 29 and a filter 30a shared with the second demultiplexing circuit 26. The short stub 20a, that is, the first demultiplexing circuit 20, blocks the RF signal and the IF signal from the LO signal port 22 and passes the LO signal to the LO signal port 22.

The open stub 29 has a function of passing RF signals and IF signals and blocking LO signals. The short stub 26b also acts to block the RF signal from the IF signal port 28. Therefore, the second demultiplexing circuit 26 cuts off the RF signal and the LO signal from the IF signal port 28 and allows the IF signal to pass therethrough. Since the filter 30a acts to block the IF signal and allow the RF signal to pass through, by combining the filter 30a and the open stub 29, the third demultiplexer circuit 30 can use the IF signal and LO signal for the RF signal port 32. Is cut off and the RF signal is passed. Next, the operation of the diode mixer 34 will be described. FIG. 3 is an equivalent circuit diagram of a diode used in the diode mixer according to the embodiment of the present invention. The diode 12 of the mixer diode section 16 used in the diode mixer 34 is expressed as a variable resistance component 13 and a variable capacitance component 15 connected in parallel as shown in FIG.

FIG. 4 is a graph showing a change in the capacitance value of the variable capacitance component of the diode with respect to the forward anode voltage of the diode used in the diode mixer according to the embodiment of the present invention. In FIG. 4, the curve a is the measured value for the pn diode, and the curve b is the measured value for the Schottky diode. The LO signal is input to the mixer diode section 16 of the diode mixer 34 from the LO signal port 22 via the first demultiplexing circuit 20, and the RF signal is input from the RF signal port 32 via the third demultiplexing circuit 30. When the LO signal and RF signal are millimeter-wave band signals and are down-converted to a low frequency IF signal such as 100kHz, the noise characteristics largely depend on the low frequency noise (or 1 / f noise) of the diode used. To do. This low frequency noise characteristic shows excellent characteristics of the pn diode. For this reason, the diode mixer 34 uses a pn diode as the diode 12, so that the diode mixer 34 has good noise characteristics. When mixing the LO signal and the RF signal in the diode mixer 34, the signal power of the LO signal is increased to the extent that the forward anode voltage of the diode 12 becomes the built-in voltage of the diode 12 (around Va = 1.2V).

Due to the non-linearity of the current-voltage characteristics near the built-in voltage of the diode 12 to which the forward anode voltage is applied, the LO signal and the RF signal are mixed. From this mixed mixed wave, a signal having a desired frequency is output from the IF signal port 28 as an IF signal via the second demultiplexing circuit 26. Then, in the region where the voltage amplitude of the LO signal is near the built-in voltage of the diode 12 (Va = 1.2V near) and the current changes most rapidly with respect to the anode voltage of the diode 12, the conversion gain of frequency conversion is extremely large. By the way, when the voltage amplitude of the LO signal is 1.1V or less, the conversion gain becomes extremely small. However, as can be seen from FIG. 4, the capacitance Cj of the variable capacitance component 15 of the diode 12 is 20 to 30 fF in the region of Va = 1.1 V or less, but Va = 1.1 V including the built-in voltage exceeding Va = 1.1 V. In the region of about 1.3V, the capacitance Cj changes sharply from 30fF to a maximum of 450fF. For this reason, in the case of a conventional diode mixer, the increase in the capacitance Cj of the variable capacitance component 15 makes it difficult for the LO signal to be input to the variable resistor component 13, and the frequency conversion characteristics have deteriorated.

However, in the diode mixer 34, the first inductor circuit 14 is connected to the mixer diode section 16 in parallel with the diode 12. The first inductor circuit 14 has a circuit in which a capacitor 14a and an inductor 14b are connected in series. Then, the forward anode voltage amplitude of the LO signal becomes a value near the built-in voltage of the diode 12, and the variable capacitance component 15 of the diode 12 has a large capacitance value accordingly, and the variable capacitance component 15 having this large capacitance and the inductor 14b However, the inductance value of the inductor 14b is set so as to form a parallel resonant circuit with respect to the frequency of the LO signal. Therefore, when the LO signal whose power is increased to the extent that the forward anode voltage amplitude of the LO signal is close to the built-in voltage of the diode 12 is applied to the mixer diode section 16, the variable capacitance component 15 and the inductor 14b are displayed. Causes parallel resonance, which suppresses the leakage of input power due to the increase in the capacitance of the variable capacitance component 15, which increases as the anode voltage increases, and the variable resistance component of the diode 12 that contributes to frequency conversion in the diode mixer 34. The LO signal is effectively input to 13, and the frequency conversion gain of the diode mixer 34 can be improved.

As described above, in the diode mixer 34, the noise characteristics are good due to the simple configuration in which the first inductor circuit 14 having the circuit in which the capacitor 14a and the inductor 14b are connected in series is connected in parallel with the diode 12. A diode mixer having a large conversion gain for frequency conversion and high frequency conversion efficiency can be configured. If an inductor is inserted in series with the diode 12, the conversion gain is considered to decrease, especially for LO signals in the millimeter wave band. FIG. 5 is a schematic view of a mixer diode portion used in the diode mixer according to the embodiment of the present invention. In FIG. 5, a microstrip line 38 is used as the inductor 14b. The microstrip line 38 may be composed of a coplanar line or other line. In this case, the circuit area can be reduced.

FIG. 6 is a schematic view of a mixer diode portion used in the diode mixer according to the embodiment of the present invention. In FIG. 6, a spiral inductor 40 is used as the inductor 14b. In this case, the circuit area is reduced even when a high inductance value is required when the variable capacitance component 15 of the diode 12 and the inductor 14b form a parallel resonant circuit with respect to the frequency of the LO signal. be able to. FIG. 7 is a schematic view of a mixer diode portion used in the diode mixer according to the embodiment of the present invention. FIG. 7 shows a case where the bonding wire 42 is used as the inductor 14b. In this case, the bonding wire 42 and the chip capacitor 46 as the capacitor 14a are connected in series by using the bonding pad 44 arranged in advance. This makes it possible to select the inductance and capacitance at the time of assembly, and it is possible to deal more finely with the case where the variable capacitance component 15 of the diode 12 and the parallel resonant circuit are configured.

FIG. 8 is a schematic view of a mixer diode portion used in the diode mixer according to the embodiment of the present invention. In FIG. 8, the first inductor circuit 14 is configured by using the interdigital capacitor 48 as the capacitor 14a. In this case, the mixer diode portion 16 can be configured even in the case of the diode 12 which requires the low capacitance capacitor 14a. FIG. 9 is a schematic view of a mixer diode portion used in the diode mixer according to the embodiment of the present invention. In FIG. 9, the first inductor circuit 14 is provided with a resistor 14c in which the capacitor 14a and the inductor 14b are connected in series and further connected in series. The resistor 14c is a resistor having a resistance value larger than that of the variable resistance component 13 of the diode 12 connected in parallel with the first inductor circuit 14. This makes it possible to improve the isolation between the anode and the cathode of the diode 12.

Although the diode mixer 34 shown in FIG. 2 has been described as a down converter diode mixer, the LO signal is input from the LO signal port 22 and the IF signal is input from the IF signal port 28 with exactly the same configuration. In this case, the RF signal is output from the RF signal port 32, and it can be configured as a transmission mixer as an upconverter. Even in this case, the same effect as in the case of the receiving mixer of the down converter is obtained.

FIG. 10 is a circuit diagram of a diode mixer according to an embodiment of the present invention. The diode mixer 50 shown in FIG. 10 is an example in which the second demultiplexing circuit 26 and the IF signal port 28 are connected to the first connection portion 18 instead of the second connection portion 24. The first demultiplexing circuit 20 is composed of an open stub 20b having an electric length of λRF / 4 connected to the first connection portion 18 and a capacitor 20c. The capacitor 20c is connected between the open stub 20b and the LO signal port 22. The second demultiplexing circuit 26 is composed of an open stub 20b shared with the first demultiplexing circuit 20 and a short stub 26c having an electric length of λLO / 4. The third demultiplexing circuit 30 includes an open stub 29 having an electrical length of λLO / 4 connected to the second connection portion 24 and a short stub 30b having an electrical length of λRF / 4 connected to the second connection portion 24. It is composed of.

The open stub 20b allows the LO and IF signals to pass through and blocks the RF signal. Further, the capacitor 20c has a large impedance for an IF signal having a low frequency, and allows the LO signal to pass through the LO signal port 22. Therefore, the first demultiplexing circuit 20 passes the LO signal through the LO signal port 22. The open stub 20b passes the LO signal and the IF signal and acts to block the RF signal, and the short stub 26c blocks the LO signal and passes the IF signal to the IF signal port 28. Therefore, the second demultiplexing circuit 26 passes the IF signal through the IF signal port 28. The open stub 29 has a function of passing RF signals and IF signals and blocking LO signals. The short stub 30b blocks the IF signal from the RF signal port 32 and allows the RF signal to pass through. Therefore, the RF signal is passed through the RF signal port 32.

In the diode mixer 50 configured in this way, the first inductor circuit 14 is connected in parallel with the diode 12 to the mixer diode section 16 in the same manner as the diode mixer 34. The first inductor circuit 14 has a circuit in which a capacitor 14a and an inductor 14b are connected in series. Therefore, when the LO signal whose forward anode voltage amplitude of the LO signal is increased to be close to the built-in voltage of the diode 12 is applied to the mixer diode section 16, parallel resonance occurs due to the variable capacitance component 15 and the inductor 14b. The leakage of input power due to the increase in the capacitance of the variable capacitance component 15 that occurs and increases as the anode voltage increases is suppressed, and the LO signal is sent to the variable resistance component 13 of the diode 12 that contributes to frequency conversion in the diode mixer 34. Is effectively input, and the frequency conversion gain of the diode mixer 34 can be improved.

As described above, in the diode mixer 50, the first inductor circuit 14 having a circuit in which the capacitor 14a and the inductor 14b are connected in series is connected in parallel with the diode 12 as in the diode mixer 34. It is possible to construct a diode mixer having good noise characteristics, a large conversion gain for frequency conversion, and high frequency conversion efficiency.

FIG. 11 is a block diagram of a diode mixer according to an embodiment of the present invention. In FIG. 11, in the diode mixer 55, the LO signal port 22 passes through the first demultiplexing circuit 20, the IF signal port 28 passes through the second demultiplexing circuit 26, and the RF signal port 32 passes through the third demultiplexing circuit 26. The anode of the diode 12 in the mixer diode section 16 and the first inductor circuit 14 are connected to the first connection section 18 via the wave circuit 30, respectively, and the cathode and the first inductor of the diode 12 in the mixer diode section 16 are connected to each other. The second connection portion 24 to which the circuit 14 is connected is grounded. This configuration is also a single-ended diode mixer, and like the diode mixer 34, the first inductor circuit 14 is connected in parallel with the diode 12 to the mixer diode section 16. The first inductor circuit 14 has a circuit in which a capacitor 14a and an inductor 14b are connected in series.

Therefore, when the LO signal whose forward anode voltage amplitude of the LO signal is increased to be close to the built-in voltage of the diode 12 is applied to the mixer diode section 16, parallel resonance occurs due to the variable capacitance component 15 and the inductor 14b. The leakage of input power due to the increase in the capacitance of the variable capacitance component 15 that occurs and increases as the anode voltage increases is suppressed, and the LO signal is sent to the variable resistance component 13 of the diode 12 that contributes to frequency conversion in the diode mixer 34. Is effectively input, and the frequency conversion gain of the diode mixer 34 can be improved. As described above, in the diode mixer 55, the first inductor circuit 14 having a circuit in which the capacitor 14a and the inductor 14b are connected in series is connected in parallel with the diode 12 as in the diode mixer 34. It is possible to construct a diode mixer having good noise characteristics, a large conversion gain for frequency conversion, and high frequency conversion efficiency.

As described above, in the diode mixer according to this embodiment, the diode 12 having good noise characteristics is used, and the first inductor circuit 14 having a circuit in which the capacitor 14a and the inductor 14b are connected in series is the diode 12. The variable capacitance component 15 of the diode 12 and the inductor 14b when the mixer diode section 16 connected in parallel with the diode 12 has a capacitance value corresponding to the anode voltage near the built-in voltage of the diode 12 are set to the frequency of the LO signal. On the other hand, it is set to form a parallel resonance circuit. For this reason, the forward anode voltage amplitude of the LO signal applied to the diode 12 of the diode mixer is set near the built-in voltage of the diode 12 having a high frequency conversion gain, and the variable capacitance component 15 of the diode 12 and the inductor 14b are the LO signals. Since the leakage of the input power due to the increase in the capacitance of the variable capacitance component 15 of the diode 12, which increases in the vicinity of the built-in voltage due to the resonance, is suppressed, a high conversion gain for frequency conversion can be obtained. Therefore, the simple configuration in which the first inductor circuit 14 having the circuit in which the capacitor 14a and the inductor 14b are connected in series is connected in parallel with the diode 12 has good noise characteristics and a large conversion gain for frequency conversion. A diode mixer having high frequency conversion efficiency can be configured. Embodiment 2.

FIG. 12 is a block diagram of a diode mixer according to an embodiment of the present invention. The diode mixer 60 is basically the same as the diode mixer 10 of the first embodiment, but the difference between the diode mixer 60 and the diode mixer 10 is that it is connected in antiparallel in addition to the diode 12 in the mixer diode section 16. Another point is that the diode 62 as a second diode has been added. In FIG. 12, the diode 62 is connected antiparallel to the diode 12. That is, the cathode of the diode 62 is connected to the first connection portion 18, and the anode of the diode 62 is connected to the second connection portion 24, respectively. Therefore, the first inductor circuit 14 including the inductor and the capacitor connected in series is connected in parallel with the diode 12 and the diode 62, respectively. Similar to the diode mixer 10, in the diode mixer 60, an example in which the second demultiplexing circuit 26 and the IF signal port 28 are connected to the second connection portion 24 is shown, but the second demultiplexing circuit 26 and the IF are shown. The signal port 28 may be connected to the first connection portion 18 instead of the second connection portion 24.

FIG. 13 is a circuit diagram of a diode mixer according to an embodiment of the present invention. The diode mixer 64 in FIG. 13 is an example of the diode mixer 60, and is an even harmonic mixer of a down converter used as a receiving mixer of a 76 GHz band in-vehicle millimeter wave radar used for detecting obstacles, for example. In the diode mixer 64, an LO signal of, for example, 38 GHz is input from the LO signal port 22, an RF signal of, for example, 76.0001 GHz is input from the RF signal port 32, and an IF of a low frequency, for example, 100 kHz, is input from the IF signal port 28. A signal is output. The diode 12 of the mixer diode section 16 in this diode mixer 64 is a pn diode. Similarly to the diode mixer 34, the first inductor circuit 14 of the diode mixer 64 resonates in parallel with the variable capacitance component of the diode 12 at the frequency of the capacitor 14a for DC interruption and the LO signal, and the input power due to the increase of the capacitance component It contains an inductor 14b that suppresses leakage.

The first demultiplexing circuit 20 is composed of a short stub 20a having an electric length of λLO / 4. The second demultiplexing circuit 26 has an open stub 29 having an electric length of λLO / 4 connected to the second connection part 24 and an electric length of λRF / 4 connected to the second connection part 24, and cuts off DC. It is composed of a short stub 26b grounded via a capacitor 26a of the above. Since λLO 2λRF in the diode mixer 64, the open stub 29 is an open stub having an electric length of λLO / 4 and an electric length of λRF / 2. The third demultiplexing circuit 30 is composed of an open stub 29 shared with the second demultiplexing circuit 26 and a filter 30a composed of a coupling line having an electric length of λRF / 4. Therefore, the first demultiplexing circuit 20 acts to block the RF signal and the IF signal from the LO signal port 22 and pass the LO signal to the LO signal port 22. The second demultiplexing circuit 26 cuts off the RF signal and the LO signal from the IF signal port 28 and allows the IF signal to pass therethrough. Further, the third demultiplexing circuit 30 cuts off the IF signal and the LO signal from the RF signal port 32 and allows the RF signal to pass therethrough.

In the diode mixer 64, the LO signal (frequency fLO) is input from the LO signal port 22, the RF signal (frequency fRF) is input from the RF signal port 32, and the signal power of the LO signal is the forward anode of the diode 12 and the diode 62. The voltage is increased to the extent that it becomes the built-in voltage of the diode 12 (around Va = 1.2V). Due to the non-linearity of the current-voltage characteristics near the built-in voltage of the diode 12 and the diode 62 to which the forward anode voltage is applied, the LO signal and the RF signal are mixed. A signal having a desired frequency is output from the mixed mixed wave via the second demultiplexing circuit 26 as an IF signal (frequency fIF) from the IF signal port 28. At this time, the IF signal with fIF = fRF-2fLO is taken out.

Conversion of frequency conversion in the region where the voltage amplitude of the LO signal is near the built-in voltage of the diode 12 and the diode 62 (around Va = 1.2V) and the current changes most rapidly with respect to the anode voltage of the diode 12 and the diode 62. The gain is extremely large. However, in the vicinity of the built-in voltage of the diode 12 and the diode 62, the capacitance Cj of the variable capacitance component 15 of the diode 12 and the diode 62 steeply increases from 30 fF to a maximum of 450 fF in the diode mixer 34 of the first embodiment as described with reference to FIG. Changes to.

For this reason, in the case of a conventional diode mixer, the LO signal is less likely to be input to the variable resistance component 13 of the diode 12 and the diode 62 due to the increase in the capacitance Cj of the variable capacitance component 15 of the diode 12 and the diode 62, and the frequency conversion characteristic. Was deteriorating. However, in the diode mixer 64, the first inductor circuit 14 is connected in parallel to each of the diode 12 and the diode 62 to the mixer diode section 16. The first inductor circuit 14 has a circuit in which a capacitor 14a and an inductor 14b are connected in series. Then, the forward anode voltage amplitude of the LO signal becomes a value near the built-in voltage of the diode 12 and the diode 62, and the variable capacitance component 15 of the diode 12 and the diode 62 has a large capacitance value accordingly, and the diode having this large capacitance. The variable capacitance component 15 and the inductor 14b of the 12 or the variable capacitance component 15 and the inductor 14b of the diode 62 having a large capacitance form a parallel resonance circuit with respect to the frequency of the LO signal, that is, the diode 12 and the inductor 14b. The inductance value of the inductor 14b is set so that a parallel resonance circuit is formed by the variable capacitance component 15 of each diode 62 and the inductor 14b.

Therefore, when the LO signal whose power is increased so that the forward anode voltage amplitude of the LO signal becomes close to the built-in voltage of the diode 12 and the diode 62 is applied to the mixer diode section 16, the variable capacitance of the diode 12 is increased. The capacitance of the variable capacitance component 15 of each of the diode 12 and the diode 62 increases as the anode voltage increases due to parallel resonance caused by the component 15 and the inductor 14b, and the variable capacitance component 15 of the diode 62 and the inductor 14b, respectively. The leakage of input power due to the increase in the number of diodes is suppressed, and the LO signal is effectively input to the variable resistance component 13 of the diode 12 and the diode 62, which contribute to frequency conversion in the diode mixer 34, so that the diode mixer 64 The frequency conversion gain of the diode can be improved.

FIG. 14 is a graph showing the relationship between the conversion gain and the local oscillation signal power of the mixer diode portion of the diode mixer according to the embodiment of the present invention. In FIG. 14, the unit on the vertical axis is dB, and the unit on the horizontal axis is dBm. However, dBm is a decibel display of the unit of power mW, 1mW is 0dBm, and 1000mW is 30dBm. The curve a in FIG. 14 shows the relationship of the conversion gain with respect to the local oscillation signal power of the mixer diode section 16 calculated for the case where the inductor 14b is added in the mixer diode section having the antiparallel diode pair of the diode mixer 64. For comparison, the curve b shows the calculated values when the inductor 14b is removed from the mixer diode section 16. As can be seen from FIG. 14, when the inductor 14b is not inserted, the conversion gain Gc drops sharply when the local oscillation signal power exceeds 8 dBm. However, when the inductor 14b is added, the conversion gain Gc can increase the local oscillation signal power to about 14 dBm while maintaining a high conversion gain even if the local oscillation signal power exceeds 8 dBm.

In this way, in the diode mixer 64, the first inductor circuit 14 having a circuit in which the capacitor 14a and the inductor 14b are connected in series is connected in parallel with the diode 12 and the diode 62, respectively, and has noise characteristics. It is possible to construct an even harmonic type diode mixer having good frequency conversion, a large conversion gain for frequency conversion, and high frequency conversion efficiency. As the specific circuit of the diode mixer 64 as the first inductor circuit 14, the circuit shown in FIGS. 5 to 9 of the first embodiment is applied.

FIG. 15 is a circuit diagram of a diode mixer according to an embodiment of the present invention. The diode mixer 66 shown in FIG. 15 is an example in which the second demultiplexing circuit 26 and the IF signal port 28 are connected to the first connection portion 18 instead of the second connection portion 24. In the diode mixer 66, the demultiplexing circuit 68 has a type in which the first demultiplexing circuit and the second demultiplexing circuit are shared. The demultiplexer circuit 68 has a short stub 68b having an electrical length of λLO / 4 in which one end is grounded via a capacitor 68a and the other end is connected to the first connection portion 18, and the short stub 68b and the LO signal port 22. It is connected to and is composed of a capacitor 68c. Since the short stub 68b has an electrical length of λLO / 4, it will have an electrical length of λRF / 2 for the RF signal, so the RF signal is the same as being shorted at the short stub end of the short stub 68b. .. Also, for the LO signal, it is open at the short stub end of the short stub 68b. Since the impedance of the capacitor 68c is low at high frequencies such as the LO signal, it can be input from the LO signal port 22.

The frequency of the IF signal is much lower than that of the LO signal and RF signal, and the capacitor 68c has a large impedance, so it is output to the IF signal port 28. The third branch circuit 30 is composed of an open stub 29 having an electric length of λLO / 4 and a short stub 30b having an electric length of λRF / 4 for DC grounding. In the diode mixer 66, the LO signal (frequency fLO) is input from the LO signal port 22, the RF signal (frequency fRF) is input from the RF signal port 32, and the signal power of the LO signal is the forward anode of the diode 12 and the diode 62. The voltage is increased to the extent that it becomes the built-in voltage of the diode 12 (around Va = 1.2V). Due to the non-linearity of the current-voltage characteristics near the built-in voltage of the diode 12 and the diode 62 to which the forward anode voltage is applied, the LO signal and the RF signal are mixed. In the diode mixer 66 as well, the first inductor circuit 14 is connected in parallel with the diode 12 and the diode 62 in the mixer diode section 16. The first inductor circuit 14 has a circuit in which a capacitor 14a and an inductor 14b are connected in series.

Therefore, the diode mixer 66 has the same function and effect as the diode mixer 64, and the first inductor circuit 14 having a circuit in which the capacitor 14a and the inductor 14b are connected in series is parallel to the diode 12 and the diode 62, respectively. With a simple configuration of being connected, it is possible to construct an even harmonic type diode mixer having good noise characteristics, a large conversion gain for frequency conversion, and high frequency conversion efficiency. As described above, in the even harmonic diode mixer according to this embodiment, the diode 12 and the diode 62 having good noise characteristics are used, and the first circuit has a circuit in which the capacitor 14a and the inductor 14b are connected in series. The variable capacitance of the diode 12 when the inductor circuit 14 has a mixer diode section 16 connected in parallel with the diode 12 and the diode 62, respectively, and has a capacitance value corresponding to an anode voltage near the built-in voltage of the diode 12 and the diode 62. The component 15 and the inductor 14b, and the variable capacitance component 15 of the diode 62 and the inductor 14b, respectively, are set to form a parallel resonance circuit with respect to the frequency of the LO signal.

Therefore, the forward anode voltage amplitude of the LO signal applied to the diode 12 and the diode 62 of the diode mixer is set near the built-in voltage of the diode 12 and the diode 62 having a high frequency conversion gain, and the variable capacitance component 15 of the diode 12 is set. And the inductor 14b, and the input due to the increase in the capacitance of the diode 12 and the variable capacitance component 15 of the diode 62, which increase near the built-in voltage due to the resonance of the variable capacitance component 15 of the diode 62 and the inductor 14b by the LO signal, respectively. Since the leakage of power is suppressed, a high conversion gain for frequency conversion can be obtained. Therefore, the simple configuration in which the first inductor circuit 14, which has a circuit in which the capacitor 14a and the inductor 14b are connected in series, is connected in parallel with the diode 12 and the diode 62, respectively, has good noise characteristics and frequency conversion. A diode mixer having a large conversion gain and high frequency conversion efficiency can be configured. Embodiment 3.

FIG. 16 is a block diagram of a diode mixer according to an embodiment of the present invention. The diode mixer 70 shown in FIG. 16 is a balanced diode mixer, and is a diode as a second diode connected in antiparallel to the diode 12 of the first mixer diode section 16 in addition to the first mixer diode section 16. It further includes a second mixer diode section 77, which includes a 74 and a second inductor circuit 76 as a second circuit element section connected in parallel to the diode 74. The anode of the diode 74 of the second mixer diode portion 77 and one end of the second inductor circuit 76 are connected to the second connection portion 24 of the first mixer diode portion 16, and the cathode of the diode 74 and the other end of the second inductor circuit 76. Is connected to the third connection part 78. Then, the first connection portion 18 and the third connection portion 78 are connected to the LO signal port 22 and the RF signal port 32 via the demultiplexing circuit 72 in which the first demultiplexing circuit and the third demultiplexing circuit are integrally formed. It is connected to the.

On the other hand, the second connection portion 24 is connected to the IF signal port 28 via the second distribution circuit 26. The second inductor circuit 76 has an inductor and a capacitor connected in series like the first inductor circuit 14. FIG. 17 is a circuit diagram of a diode mixer according to an embodiment of the present invention. The diode mixer 80 in the circuit diagram of FIG. 17 is an example of the diode mixer 70. In the diode mixer 80, the Lange coupler 82 is used as the demultiplexing circuit 72. Further, the second demultiplexing circuit 26 has an inductor 26d and a capacitor 26e connected in series between the second connection portion 24 and the IF signal port 28, and further, a connection point between the inductor 26d and the capacitor 26e and a ground end. It contains a capacitor 26f shunted in between. In this diode mixer 80 as well, similarly to the first inductor circuit 14, the second inductor circuit 76 resonates in parallel with the variable capacitance component of the diode 74 at the frequency of the capacitor 76a for DC interruption and the LO signal to increase the capacitance component. It includes an inductor 76b that suppresses the accompanying leakage of input power.

The inductance value of the inductor 76b is such that the anode voltage amplitude of the diode 74 due to the LO signal becomes a value near the built-in voltage of the diode 74, and the variable capacitance component of the diode 74 has a large value and a parallel resonant circuit is formed accordingly. Is set to. Therefore, similarly to the diode mixer 34 of the first embodiment, the LO signal whose power is increased so that the forward anode voltage amplitude of the LO signal becomes close to the built-in voltage of the diode 12 and the diode 74 is the mixer diode portion 16 and the LO signal. When applied to the second mixer diode section 77, parallel resonance occurs due to the variable capacitance component 15 of the diode 12 and the inductor 14b, and the variable capacitance component 15 of the diode 74 and the inductor 76b, which increases as the anode voltage increases. The leakage of input power due to the increase in the capacitance of the variable capacitance component 15 of each of the diode 12 and the diode 74 is suppressed, and the variable resistance component 13 of each of the diode 12 and the diode 74 that contributes to frequency conversion in the diode mixer 80 is LO. The signal is effectively input, and the frequency conversion gain of the diode mixer 80 can be improved.

As described above, in the diode mixer 80, the first inductor circuit 14 having a circuit in which the capacitor 14a and the inductor 14b are connected in series is connected in parallel with the diode 12, and the capacitor 76a and the inductor 76b are connected in series. A diode mixer having good noise characteristics, a large frequency conversion conversion gain, and a high frequency conversion efficiency can be configured by a simple configuration in which the second inductor circuit 76 having the above circuit is connected in parallel with the diode 74. .. In parallel with the diode of the diode mixer, connect a circuit in which a capacitor for blocking DC and an inductor that resonates in parallel with the variable capacitance component of the diode at the frequency of the LO signal and suppresses the increase in the capacitance component are connected in series. Therefore, configuring a diode mixer having good noise characteristics, a large conversion gain for frequency conversion, and high frequency conversion efficiency is not limited to the diode mixer described in the above embodiment, but also for diode mixers having other configurations. Play the effect of. Further, although the pn diode has been described as the diode in the above embodiment, the same effect can be obtained with various Schottky diodes.

As described above, the diode mixer according to the present invention is suitable for use in electronic devices such as in-vehicle radar millimeter wave radar, and communication devices for microwave band and millimeter wave band for mobile communication and wireless communication. There is.

<figref num="1">It is a block diagram of the diode mixer which concerns on one Embodiment of this invention.</figref><figref num="2">It is a circuit diagram of the diode mixer which concerns on one Embodiment of this invention.</figref><figref num="3">It is an equivalent circuit diagram of the diode used in the diode mixer which concerns on one Embodiment of this invention.</figref><figref num="4">It is a graph which shows the change of the capacitance value of the variable capacitance component of a diode with respect to the forward anode voltage of the diode used in the diode mixer which concerns on one Embodiment of this invention.</figref><figref num="5">It is a schematic diagram of the mixer diode part used in the diode mixer which concerns on one Embodiment of this invention.</figref><figref num="6">It is a schematic diagram of the mixer diode part used in the diode mixer which concerns on one Embodiment of this invention .</figref><figref num="7">It is a schematic diagram of the mixer diode part used in the diode mixer which concerns on one Embodiment of this invention.</figref><figref num="8">It is a schematic diagram of the mixer diode part used in the diode mixer which concerns on one Embodiment of this invention.</figref><figref num="9">It is a schematic diagram of the mixer diode part used in the diode mixer which concerns on one Embodiment of this invention.</figref><figref num="10">It is a circuit diagram of the diode mixer which concerns on one Embodiment of this invention.</figref><figref num="11">It is a block diagram of the diode mixer which concerns on one Embodiment of this invention.</figref><figref num="12">It is a block diagram of the diode mixer which concerns on one Embodiment of this invention.</figref><figref num="13">It is a circuit diagram of the diode mixer which concerns on one Embodiment of this invention.</figref><figref num="14">It is a graph which shows the relationship of the conversion gain with respect to the local oscillation signal power of the mixer diode part of the diode mixer which concerns on one Embodiment of this invention.</figref><figref num="15">It is a circuit diagram of the diode mixer which concerns on one Embodiment of this invention.</figref><figref num="16">It is a block diagram of the diode mixer which concerns on one Embodiment of this invention.</figref><figref num="17">It is a circuit diagram of the diode mixer which concerns on one Embodiment of this invention.</figref>

Code description

14 1st inductor circuit, 12 diode, 16 mixer diode part, 22 LO signal port, 20 1st demultiplexing circuit, 26 2nd demultiplexing circuit, 28 IF signal port, 30 3rd demultiplexing circuit, 32 RF signal port, 62 diode, 76 second inductor circuit, 74 diode, 14c resistor.