High frequency power amplifier

The present invention relates to a high frequency power amplifier.

[0002] A high frequency power amplifier is used to supply power to an antenna of a communication device such as a mobile terminal. Since high-frequency power amplifiers are used in mobile terminals and the like, high power gain, high power efficiency, and miniaturization are required.

[0003] In recent years, high-frequency power amplifiers have been designed in which a matching circuit for matching input / output impedances (usually 50Ω) between a high-frequency power amplifier and an antenna is built in a module. Therefore, a miniaturized high-frequency power amplifier while incorporating an external circuit such as a matching circuit as a module is desired.

[0004] As a method for miniaturizing such a high-frequency power amplifier, there are various methods such as miniaturization of a semiconductor chip, high precision of mounting technology, and miniaturization of a pattern of a module substrate. In particular, since the output matching circuit requires a large area, the miniaturization of the output matching circuit has a great effect on the miniaturization of the entire high frequency power amplifier.

FIG. 10 shows a circuit diagram of a conventional typical high frequency power amplifier 600. The input matching circuit is omitted in the drawings. The fundamental wave signal is output from the transistor Tr mounted on the semiconductor chip 10. The fundamental wave signal is matched by the fundamental wave matching circuit 20 formed by the inductor L1 formed on the substrate and the capacitor C1. Normally, the fundamental wave matching circuit 20 matches the impedance of the fundamental wave signal to 50Ω and outputs the fundamental wave signal through the capacitor C4 for the DC current block.

[0006] The power supply circuit 30 has a capacitor C2, an inductor L2, and a DC (Direct Current) power supply 32, and supplies electric power to the transistor Tr. Capacitor C2 is a decoupling capacitor provided to ground high frequency signals. The inductor L2 is set to a length of λ / 4 with respect to the wavelength λ of the fundamental wave, and is a so-called λ / 4 line. As a result, the inductor L2 has a large impedance for the fundamental wave propagating from the transistor Tr to the fundamental wave matching circuit 20. That is, the inductor L2 is in an open state for the fundamental wave at the node 50 in which the feeding circuit 30 is connected to the fundamental wave matching circuit 20. Therefore, the feeding circuit 30 does not affect the fundamental wave matching circuit 20. Further, the inductor L2 short-circuits the second harmonic signal among the output signals from the transistor Tr.

[0007] The high frequency power amplifier 600 further includes a harmonic matching circuit 40 having an inductor L3 and a capacitor C3. The harmonic matching circuit 40 short-circuits the third harmonic signal among the output signals from the transistor Tr.

[0008] When the inductor L2 (λ / 4 line) is formed of a 50Ω line and the frequency of the fundamental wave is 900 MHz, the length of the inductor L2 needs to be about 30 mm. In recent years, due to the demand for miniaturization of the high frequency power amplifier 600, the high frequency power amplifier 600 including the output matching circuit 60 is formed as a square module having a size of 4 mm to 6 mm on each side. Therefore, it is very difficult to accommodate the output matching circuit 60 having the inductor L2 of about 30 mm in the module.

[0009] When the length of the inductor L2 is shortened to less than 30 mm (for example, shortened to 20 mm) in order to solve this problem, the inductor L2 becomes shorter than the ideal λ / 4 line, so that the power supply circuit 30 becomes shorter. It is not open to the fundamental wave. As a result, the power loss of the output matching circuit 60 increases and the output impedance of the transistor Tr fluctuates.

[0010] Further, when the inductor L2 is formed of a transmission line having an impedance higher than that of the 50Ω line, for example, when the width of the transmission line of the inductor L2 is narrowed, the influence of the feeding circuit 30 on the fundamental wave is reduced. can do. However, by narrowing the width of the transmission line, the resistance component of the inductor L2 increases, causing power loss from the DC power supply 32. As a result, the power efficiency of the high frequency power amplifier 600 is reduced. Further, since the voltage drop due to the inductor L2 becomes large, the voltage amplitude during the operation of the transistor Tr is limited, which hinders the linear operation of the high frequency power amplifier 600 and causes a problem that the distortion component increases. Linear operation is important in digital modulation schemes. When the high-frequency power amplifier 600 is for a digital modulation method, an increase in the distortion component causes a significant deterioration in the performance of the high-frequency power amplifier 600.

[0011] In order to solve such a problem, the high frequency power amplifier 700 shown in FIG. 11 has been proposed. The output matching circuit 60 included in the high frequency power amplifier 700 has a parallel resonant circuit 70 including a capacitor C5 and an inductor L4. The resonance frequency of the parallel resonant circuit 70 is the frequency of the fundamental wave (for example, f).₀By setting it to), the impedance of the power supply circuit 32 seen from the node 50 increases. Capacitor C5 capacity C at this time₅And the inductance of the inductor L4 L₄And the angular frequency of the fundamental wave ω₀(= 2πf₀) Is expressed by Equation 1. L₄= 1 / (ω)₀²* C₅) (Equation 1) L₄The value of is C₅Since the value of can be set small by increasing the value of, the inductor L4 can use a small inductor. The inductor L2 also does not need to have a large inductance due to the effect of the resonance circuit. As a result, the length of the inductor L2 can be made shorter than that of the λ / 4 line without the power feeding circuit 32 affecting the fundamental wave matching circuit 20. Since the inductor L4 is small and the length of the inductor L2 is shorter than the λ / 4 line, the high frequency power amplifier 700 can be made smaller than the high frequency power amplifier 600 and the loss of direct current can be reduced. it can.

[0012] However, in the high frequency power amplifier 700, the second harmonic cannot be short-circuited in the power feeding circuit 30. In order to remove the second harmonic from the output signal, the harmonic matching circuit 40 must be a matching circuit for the second harmonic. As a result, the high frequency power amplifier 700 cannot match higher harmonics higher than the third harmonic. Therefore, when adjusting up to the third harmonic as in the high frequency power amplifier 600 shown in FIG. 10, it is necessary to add another harmonic matching circuit to the high frequency power amplifier 700. This increases the number of parts and goes against the demand for miniaturization. Further, adding another harmonic matching circuit may cause loss of the fundamental wave.

[0013] Therefore, an object of the present invention is to provide a high-frequency power amplifier capable of matching high-order harmonics of the second or higher order while having high power efficiency, and which is smaller than the conventional one. Is.

[Means for Solving the Problems] A high-frequency power amplifier according to an embodiment according to the present invention has a transistor that inputs a high-frequency signal, amplifies and outputs the high-frequency signal, and one end to the output of the transistor. A fundamental wave matching circuit that matches at least the impedance of the fundamental wave of the connected and amplified high-frequency signal and outputs it from the other end, and a node between the output of the transistor and the fundamental wave matching circuit to the transistor. A power supply for supplying power to the power supply, a first inductor having one end connected to the power supply, a second inductor connected in series between the other end of the first inductor and the node, and the first inductor. One end is connected between the inductor 1 and the second inductor, and the other end is connected to the reference potential to form a first series resonance circuit with the second inductor, and the first It includes an inductor and a first capacitor that forms a parallel resonance circuit.

[0015] Preferably, the first series resonant circuit and the fundamental wave matching circuit are connected in parallel between the node and the reference voltage.

[0016] Preferably, the ratio of the inductances of the first inductor and the second inductor is about (n).²1): 1 (n is an integer), and the sum of the lengths of the transmission lines forming the first inductor and the second inductor is 1/8 or less of the wavelength of the fundamental wave.

[0017] Preferably, the first inductor and the second inductor are transmission lines integrally formed with each other, and the ratio of the inductances of the first inductor and the second inductor is the first. It is determined by the ratio of the lengths of the respective transmission lines of the inductor and the second inductor.

[0018] Preferably, the high frequency power amplifier is connected in series between the second inductor and the node, and forms the first series resonance circuit together with the second inductor and the first capacitor. One end is connected between the third inductor, the second inductor and the third inductor, and the other end is connected to the reference potential to form a second series resonance circuit with the third inductor. Moreover, the first capacitor and the second capacitor forming a parallel resonance circuit with the first inductor are further provided.

[0019] Preferably, the first inductor, the second inductor, and the third inductor are transmission lines integrally formed with each other, and the first inductor, the second inductor, and the third inductor are used. The ratio of the respective inductances of the inductors is determined by the ratio of the lengths of the respective transmission lines of the first inductor, the second inductor and the third inductor.

[0020] A high-frequency power amplifier according to another embodiment according to the present invention includes a transistor that inputs a high-frequency signal, amplifies and outputs the high-frequency signal, and the amplified one end connected to the output of the transistor. A fundamental wave matching circuit that matches at least the impedance of the fundamental wave of the high-frequency signal and outputs it from the other end, and a power supply that supplies power to the transistor from a node between the output of the transistor and the fundamental wave matching circuit. A first inductor with one end connected to the power supply, a second inductor connected in series between the other end of the first inductor and the node, and a second inductor with one end connected to the node. The inductor of 3 and one end are connected to the other end of the third inductor and the other end is connected to the reference potential to form a first series resonance circuit with the third inductor, and the first It is equipped with one inductor and a first capacitor that forms a parallel resonance circuit.

[0021] In the high frequency power amplifier according to still another embodiment according to the present invention, a transistor that inputs a high frequency signal, amplifies and outputs the high frequency signal, and one end are connected to the output of the transistor and amplified. A fundamental wave matching circuit that matches at least the impedance of the fundamental wave of the high-frequency signal and outputs it from the other end, and a power supply that supplies power to the transistor from a node between the output of the transistor and the fundamental wave matching circuit. A first inductor with one end connected to the power supply, a second inductor connected in series between the other end of the first inductor and the node, and one end connected to the output of the transistor. The third inductor is connected to the other end of the third inductor, and the other end is connected to the reference potential to form a first series resonance circuit with the third inductor. The first inductor and the first capacitor forming a parallel resonance circuit are provided. Preferably, the sum of the lengths of the first inductor and the second inductor is one-eighth or less of the wavelength of the fundamental wave.

[0022] Preferably, one end of the high frequency power amplifier is connected between the first inductor and the second inductor, the other end is connected to the reference potential, and the second inductor and the second inductor are connected. The first capacitor and the first inductor and the second capacitor forming a parallel resonance circuit are further provided.

[0023] Preferably, the first inductor, the second inductor, and the third inductor are transmission lines integrally formed with each other, and the first inductor, the second inductor, and the third inductor are formed. The ratio of the respective inductances of the inductors is determined by the ratio of the lengths of the respective transmission lines of the first inductor, the second inductor and the third inductor.

[0024] Preferably, the transmission line is a stripline or microstripline.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments according to the present invention will be described with reference to the drawings. It should be noted that the present embodiment does not limit the present invention.

FIG. 1 is a circuit diagram of a high frequency power amplifier 100 according to a first embodiment of the present invention. The high-frequency power amplifier 100 includes a semiconductor chip 110 that inputs a high-frequency signal, amplifies and outputs the high-frequency signal, and an output matching circuit 160 that is connected to its output pad by a plurality of gold wires 105. According to this embodiment, the semiconductor chip 110 mounts a heterojunction bipolar transistor (HBT) (hereinafter, simply referred to as a transistor) Tr on a GaAs substrate.

A bias supply circuit (not shown) that supplies a bias to the base of the transistor Tr and an input matching circuit (not shown) that performs impedance matching on the input side are connected to the input pad of the semiconductor chip 110. ing.

[0028] The output matching circuit 160 includes a fundamental wave matching circuit 120 that matches and outputs the impedance of the amplified high-frequency signal, and a feeding circuit 130 having a DC power supply 132 that supplies power to the transistor Tr. The high frequency power amplifier 100 including the output matching circuit 160 is modularized and formed on a dielectric substrate (eg, a ceramic substrate made of alumina).

The fundamental wave matching circuit 120 has an inductor L10 and a capacitor C10. One end of the inductor L10 is connected to the output of the transistor Tr, impedance matching of the fundamental wave signal (wavelength λ) is performed, and the inductor L10 is output from the other end. Generally, the fundamental wave signal is matched to 50Ω. The capacitor C10 is connected between the other end of the inductor L10 and the ground, and impedance matching is performed by the capacitor C10 and the inductor L10, and also serves as a low-pass filter. In the embodiment described below, a ground is used as the reference potential, but another constant potential may be used.

A capacitor (DC blocking capacitor) for cutting off a direct current between the other end of the inductor L10 and the output of the high frequency power amplifier 100.<u style="single">C</u>40 is connected. Capacitor C10, inductor L10 and capacitor<u style="single">C</u>By 40, a high frequency signal of a specific frequency band is output from the output matching circuit 160.

The fundamental wave signal from the semiconductor chip 110 is impedance-matched by the fundamental wave matching circuit 120, and is output from the high-frequency power amplifier 100 via the capacitor C40.

[0032] The power feeding circuit 130 is connected to a node 150 located between the output pad of the semiconductor chip 110 and the fundamental wave matching circuit 120. The power supply circuit 130 includes a DC power supply 132, an inductor L20, an inductor L30, a capacitor C20, and a capacitor C30.

One end of the inductor L20 is connected to the DC power supply 132, and the other end is connected to one end of the inductor L30. The other end of the inductor L30 is connected to the node 150. That is, the inductor L20 and the inductor L30 are connected in series with each other between the DC power supply 132 and the node 150. The inductor L20 is connected to the DC power supply 132 and the inductor L30 is connected to the node 150.

[0034] Capacitor C20 is a decoupling capacitor connected between one end of inductor L20 and ground to ground high frequencies. One end of the capacitor C30 is connected between the inductor L20 and the inductor L30, and the other end is connected to the ground.

In the circuit shown in FIG. 1, the inductor L20 and the inductor L30 are two separate transmission lines. However, preferably, the inductor L20 and the inductor L30 are transmission lines L35 integrally formed with each other. In this case, the capacitor C30 is connected in the middle of the transmission line L35 to separate the transmission line L35 into the inductor L20 and the inductor L30. Therefore, the inductance of the inductor L20 and the inductor L30 is determined by the position where the capacitor C30 is connected to the transmission line L35. Further, when the transmission lines L35 are formed to have the same width, the inductances of the inductor L20 and the inductor L30 are determined by the length of each transmission line. This facilitates the design of the inductor L20 and the inductor L30.

[0036] According to the present embodiment, the inductors L10, L20, and L30 are transmission lines formed on the dielectric substrate, and are, for example, strip lines or microstrip lines. In the case of a dielectric substrate using alumina as the dielectric material, these transmission lines have a width substantially the same as the thickness of the dielectric substrate, so that the characteristic impedance can be set to about 50Ω. Capacitors C10, C20, and C30 are formed by mounting chip components with a base of 0.5 mm x 1 mm and a thickness of 0.5 mm or chip components with a base of 0.3 mm x 0.6 mm and a thickness of 0.3 mm on a dielectric substrate. It is formed.

The inductor L20 and the capacitor C30 form a parallel resonant circuit 170. The parallel resonance frequency of the parallel resonance circuit 170 is set to the frequency of the fundamental wave. By setting the parallel resonant circuit 170 in this way, the impedance of the feeding circuit 130 as seen from the node 150 with respect to the fundamental wave becomes large. In other words, due to the effect of the parallel resonant circuit 170, the feeding circuit 130 is open for the fundamental wave. As a result, the feed circuit 130 does not affect the fundamental wave to the fundamental wave matching circuit 20.

[0038] Inductance L of inductor L20₂The magnitude of is determined by the parallel resonance state, that is, the impedance becomes open (infinity) at the frequency of the fundamental wave seen from the node 150. For example, the angular frequency ω of the fundamental wave₁(= 2π * f₁: Here f₁Is the frequency of the fundamental wave), inductance L₂And capacity C₃The relationship is expressed by Equation 2. L₂= 1 / (ω)₁²* C₃) (Equation 2) As the capacity of the capacitor C30, an appropriate capacity C that can be used in the chip parts.₃If is selected, the inductor L20 can be properly determined based on Equation 2.

[0039] Further, the inductor L30 and the capacitor C30 are connected in series between the node 150 and the ground to form a harmonic matching circuit 140. The harmonic matching circuit 140 is a series resonant circuit set to resonate with the frequency of the nth harmonic. The harmonic matching circuit 140 causes the inductor L30 and the capacitor C30 to short-circuit the nth harmonic from the high-frequency signal output from the semiconductor chip 110.

[0040] Inductance L of inductor L30₃And the capacitance C of capacitor C30₃The magnitude of may be determined by the frequency of the harmonics. For example, when short-circuiting the nth harmonic, the angular frequency ω of the nth harmonic_n, Inductance L₃And capacity C₃The relationship is expressed by Equation 3. In addition, ω_n= n * ω₁And n is an integer. L₃= 1 / ((n²-1) * ω₁²* C₃) (Equation 3) Capacitor C30 is shared by both the harmonic matching circuit 140 and the parallel resonant circuit 170. Therefore, capacity C₃Has already been determined by Equation 2, so the inductance L is based on Equation 3.₃Can be determined appropriately.

[0041] For example, when short-circuiting the second harmonic, each capacitance and inductance may be determined so as to satisfy Equations 2 and 3 with n = 2. At this time, first, as the capacitance of the capacitor C30, a capacitance that can be used as a chip component, for example, several pF is selected. The larger the capacity value, the more L₂Since the value of is small, the length of the inductor L20 can be set short by selecting an appropriate capacitance value. The length of the inductor L30 can be seen from Equations 2 and 3 of the length of the inductor L20 (n).²Since it is 1 / -1), it can be shorter than the λ / 4 line as a whole.

[0042] As described above, the present embodiment includes both the harmonic matching circuit 140 and the parallel resonant circuit 170. Even if the length of the transmission line L35 is shorter than the λ / 4 line by the parallel resonant circuit 170, a sufficiently high impedance can be obtained with respect to the fundamental wave, and the nth harmonic is short-circuited by the harmonic matching circuit 140. can do.

[0043] The sum of the lengths of the inductor L20 and the inductor L30, that is, the length of the integrally formed transmission line L35 is about 1/8 of the wavelength λ of the fundamental wave by selecting an appropriate capacitance of the capacitor C30. Can be about 1/12 in length. Therefore, according to the present embodiment, the length of the transmission line L35 can be reduced to about 1/2 to 1/3 of the λ / 4 line. As a result, the high frequency power amplifier 100 can be made smaller than before.

Since the length of the transmission line L35 is about 1/2 to 1/3 of that of the λ / 4 line, the resistance component of the transmission line L35 is about 1/2 to 1/1/ of the resistance component of the λ / 4 line. Reduce to 3. As a result, the loss of the direct current from the DC power supply 132 is reduced, and as a result, the current can be supplied to the transistor Tr with high efficiency. Further, the voltage amplitude of the high frequency signal from the transistor Tr becomes larger, and as a result, the distortion component is reduced, and a good linear operation can be obtained.

[0045] The effect described above becomes more remarkable as the length of the transmission line L35 becomes smaller. The length that appeared as a particularly obvious effect was when the length of the transmission line L35 was less than half that of the λ / 4 line.

On the other hand, due to the influence of the parasitic resistance of the chip component of the capacitor C30 and the parasitic resistance component of the inductor L20, the characteristics of the parallel resonant circuit 170 cannot realize a large impedance at resonance as the inductor L20 is shortened. As a result, the feeding circuit 130 cannot be ignored with respect to the fundamental wave signal, a loss occurs, or the fundamental wave matching circuit 120 is affected, so that the performance deteriorates. This effect appears in the region where the length of the transmission line L35 is shorter than 1/3 of the λ / 4 line. Therefore, it is preferable that the length of the transmission line L35 is set as large as about 1/3 or more of the λ / 4 line. However, since the degree of deterioration of this performance is frequency-dependent, the minimum length is not particularly limited.

The harmonic matching circuit 140 resonates at, for example, the frequency of the second harmonic, and the parallel resonant circuit 170 resonates at the frequency of the fundamental wave. As derived from Equations 2 and 3, the inductance ratio of inductor L20 to inductor L30 is about 3: 1. According to this embodiment, the capacitor C30 may be connected at a position where the transmission line L35 is separated at a ratio of about 3: 1. If the harmonic matching circuit 140 resonates at the nth harmonic frequency, the inductance ratio of inductor L20 to inductor L30 is (n).²-1): 1 (n is an integer).

[0048] In an actual circuit, since the parasitic inductance of the chip component of the capacitor C30 and the inductance component of the gold wire 105 exist, the inductance required for the inductor L30 becomes small. Therefore, in the actual circuit, the ratio is (n)²-1): May be greater than 1.

In the conventional high-frequency power amplifiers 600 and 700, it is necessary to separately provide the harmonic matching circuit 40, but according to the present embodiment, the inductor L30 and the capacitor C30 incorporated in the power feeding circuit 130 are provided. The harmonic matching circuit 140 is formed by the above. Therefore, in this embodiment, it is not necessary to newly provide the harmonic matching circuit 40 as a separate component or a separate circuit. Therefore, the output matching circuit 160 becomes a smaller module than the conventional one, and as a result, the high frequency power amplifier 100 can be miniaturized.

[0050] The high frequency power amplifier 100 operates as follows. The high frequency signal (not shown) amplified by the transistor Tr is transmitted from the output pad to the output synthesis circuit 160 through the gold wire 105. This high frequency signal includes not only the fundamental wave but also the second harmonic, the third harmonic and higher harmonics of the fundamental wave. When such harmonics leak to the outside, they become jamming radio waves of other wireless systems, so it is necessary to remove harmonic components from high-frequency signals.

Since the harmonic matching circuit 140 is a series resonant circuit including an inductor L30 and a capacitor C30, the second harmonic, that is, the second harmonic is short-circuited at the node 150, and the second harmonic is generated from the high frequency signal. Remove. The parallel resonant circuit 170 consisting of the inductor L20 and the capacitor C30 has a impedance so large that the feeding circuit 130 can ignore the fundamental wave at the node 150. Therefore, the fundamental wave can proceed to the fundamental wave matching circuit 120 without being affected by the feeding circuit 130. As a result, according to the present embodiment, a high frequency signal having a reduced harmonic component can be sent to the fundamental wave matching circuit 120 without affecting the fundamental wave component.

[0052] The fundamental wave matching circuit 120 outputs a high-frequency signal matched to a predetermined impedance. At this time, the high frequency signal is filtered by the inductor L10 and the capacitor C10, and the direct current is blocked by the capacitor C40.

FIG. 2 is a circuit diagram of a high-frequency power amplifier 800 substantially equivalent to the high-frequency power amplifier published in Japanese Patent Application Laid-Open No. 11-127045. At first glance, the high frequency power amplifier 100 is similar to the high frequency power amplifier 800.

However, the transmission line L2 of the high frequency power amplifier 800 is a λ / 4 line. When the transmission line L2 is less than λ / 4, it is clearly stated that "it has a non-negligible effect in terms of the impedance of the fundamental frequency". Further, the capacitor C3 is only used as an element of the harmonic matching circuit 40.

On the other hand, the transmission line 35 of the high frequency power amplifier 100 is about 1/2 to 1/3 of the λ / 4 line. Further, the capacitor C30 is shared as an element of the harmonic matching circuit 140 and the parallel resonant circuit 170.

[0056] Since the transmission line 35 is about 1/2 to 1/3 of the λ / 4 line, the above-mentioned effect can be obtained. Further, even if the transmission line 35 is about 1/2 to 1/3 of the λ / 4 line, the inductor L20 and the capacitor C30 form the parallel resonant circuit 170, so that the fundamental wave is not affected by the feeding circuit 130.

FIG. 3 is a graph comparing the primary adjacent channel leakage power (ACPR1) and current consumption (Ic) of the high frequency power amplifier 100 and the high frequency power amplifier 800, respectively. The horizontal axis shows the output power (Pout).

[0058] This graph shows the results when the high frequency power amplifier 100 and the high frequency power amplifier 800 are formed as power amplifiers for IS-95 (Interim Standard-95) signals in the 900 MHz band. The length of the transmission line L2 of the high-frequency power amplifier 800 was about 32 mm. The capacitance of the capacitor C3 was 7pF, and the length of the inductor L2a was about 1.5mm.

On the other hand, the capacitance of the capacitor C30 of the high-frequency power amplifier 100 is 6 pF, the length of the inductor L30 is about 2.3 mm, and the length of the inductor L20 is about 9.2 mm. The length ratio is different from 1: 3 because the length of the inductor L30 has become smaller due to the influence of the chip component of the capacitor C30 and the inductance component of the gold wire 105. As a result, the impedance of the feeding circuit 130 with respect to the fundamental wave can be set to about 1 kΩ, and the impedance with respect to the second harmonic can be set to almost zero (short-circuit state).

[0060] Generally, in IS-95, it is preferable to secure the primary adjacent channel leakage power (ACPR1) of -50 dBc or less. As shown in FIG. 3, the maximum output power when ACPR1 is -50 dBc or less is about 27.5 dBm for both the high-frequency power amplifier 100 and the high-frequency power amplifier 800.

Comparing the current consumption (collector current Ic of the transistor Tr) when the output power is about 27.5 dBm, the high frequency power amplifier 100 is about 10 mA lower than the high frequency power amplifier 800. That is, it can be seen that the high-frequency power amplifier 100 consumes less current and is more efficient than the high-frequency power amplifier 800.

[0062] FIG. 4 is a circuit diagram of a high-frequency power amplifier 900 substantially equivalent to the amplifier circuit published in Japanese Patent Application Laid-Open No. 4-77009. The high frequency power amplifier 900 has a capacitor C3 shared by the harmonic matching circuit 40 and the parallel resonant circuit 70.

[0063] However, the inductance L2a of the high frequency power amplifier 900 is connected in series between the semiconductor chip 10 and the fundamental wave matching circuit 20. That is, the fundamental wave matching circuit 20 is connected between the inductance L2a forming the series resonant circuit and the capacitor C3. Therefore, the harmonic (for example, the second harmonic) leaks to the fundamental wave matching circuit 20 before being short-circuited by the resonance between the inductance L2a and the capacitor C3.

[0064] On the other hand, in the high-frequency power amplifier 100 shown in FIG. 1, the inductor L10 and the capacitor C10 and the inductor L30 and the capacitor C30 are connected in parallel between the node 150 and the ground. Therefore, the harmonics (for example, the second harmonic) are short-circuited by the series resonant circuit including the inductor L30 and the capacitor C30, and do not leak to the fundamental wave matching circuit 120.

FIG. 5 is a graph comparing the outputs of the second harmonics of the high frequency power amplifier 100 and the high frequency power amplifier 900. From this graph, the output of the second harmonic of the high frequency power amplifier 100 is reduced by about 8 dBc as compared with the high frequency power amplifier 900. dBc indicates the dB value for the fundamental wave output. -8dBc corresponds to a reduction of about 84%. That is, it can be seen that the high frequency power amplifier 100 leaks the second harmonic to the fundamental wave matching circuit 120 by about 84% less than that of the high frequency power amplifier 900. This graph shows the output of the second harmonic when the output power is 27.5 dBm.

FIG. 6 is a circuit diagram of a high frequency power amplifier 200 according to a second embodiment of the present invention. According to the first embodiment, there is no capacitor C30, and the inductor L21 and the capacitor C21 are connected in series from the node 150 to the ground, which is different from the first embodiment.

[0067] In the present embodiment, the inductor L21 and the capacitor C21 form a harmonic matching circuit 240, and short-circuit the secondary harmonics by forming a series resonant circuit. Further, the inductor L11 and the capacitor C21 form a parallel resonant circuit 270, and the impedance of the fundamental wave at the node 150 with respect to the feeding circuit 230 is large.

[0068] The inductor L11 and the capacitor C21 are set to resonate with the frequency of the fundamental wave.

[0069] More specifically, the inductance L of the inductor L21.₂₁And the capacitance C of capacitor C21₂₁The magnitude of may be determined by the frequency of the harmonics. For example, when short-circuiting the nth harmonic, the angular frequency ω of the nth harmonic_n, Inductance L₂₁And capacity C₂₁The relationship is expressed by Equation 4. L₂₁= 1 / (n²* ω₁²* C₂₁) (Equation 4) ω_n= n * ω₁And ω₁Is the angular frequency of the fundamental wave.

[0070] As the capacity of the capacitor C21, an appropriate capacity C that can be used in the chip component.₂₁If is selected, the inductor L21 can be properly determined based on Equation 4.

Further, the inductance L of the inductor L11₁₁The magnitude of is determined from the fact that the impedance at the frequency of the fundamental wave seen from the node 150 to the feeding circuit 230 becomes infinite (open). For example, the angular frequency ω of the fundamental wave₁, Inductance L₁₁And capacity C₂₁The relationship is expressed by Equation 5. L₁₁= (n²-1) / (n²* ω₁²* C₂₁) (Equation 5) Capacitor C21 is shared by both the harmonic matching circuit 140 and the parallel resonant circuit 170. Therefore, capacity C₂₁Has already been determined by Equation 4, so the inductance L is based on Equation 5.₂₁Can be determined appropriately.

[0072] For example, when short-circuiting the second harmonic, each capacitance and inductance may be determined so as to satisfy Equations 4 and 5 with n = 2. At this time, for the capacitance of the capacitor C21, a capacitance that can be used as a chip component, for example, several pF is selected. The larger the capacitance value of the capacitor C21, the smaller the value of the inductor L11. Therefore, the length of the inductor L11 can be set short by selecting an appropriate capacitance value. From Equations 4 and 5, the length of the inductor L21 is the length of the inductor L11 (n).²-1) Since it is 1 / 1, it can be shortened as a whole.

Further, comparing Equations 2 and 3 with Equations 4 and 5, in the present embodiment, (n) is compared with the size of the inductor L35 of the embodiment shown in FIG.²-1) / n²It is getting smaller. Therefore, despite the increase in the circuit area due to the addition of the harmonic matching circuit 240, the area of the entire power feeding circuit 230 does not increase so much as compared with the form shown in FIG.

[0074] According to the present embodiment, both the harmonic matching circuit 240 and the parallel resonant circuit 270 are provided. Even if the length of the transmission line L11 is shorter than the λ / 4 line by the parallel resonant circuit 170, a sufficiently high impedance can be obtained with respect to the fundamental wave, and the nth harmonic is short-circuited by the harmonic matching circuit 240. can do. Further, the same effect as that of the first embodiment can be obtained.

FIG. 7 is a circuit diagram of a high frequency power amplifier 300 according to a third embodiment of the present invention. This embodiment differs from the first embodiment in that an inductor L22 and a capacitor C22 connected in series from the node 150 to the ground are added. The inductor L22 and the capacitor C22 form a series resonant circuit as the second harmonic matching circuit 342. The second harmonic matching circuit 342 can match higher harmonics that cannot be matched by the first harmonic matching circuit 340. For example, the first harmonic matching circuit 340 shorts the second harmonic and the second harmonic matching circuit 340 shorts the third harmonic. Thereby, it is possible to output a high frequency signal having less harmonic components than in the first embodiment.

[0076] More specifically, when a fundamental wave in the 900 MHz band is used, the impedance of the third harmonic can be short-circuited by setting the inductor L22 to about 2.0 mm and the capacitor C22 to 3 pF. ..

[0077] According to the present embodiment, the parallel resonant circuit 370 includes not only the inductor L20 and the capacitor C30 but also the capacitor C22. That is, the inductor L20 and the capacitors C30 and C22 form a parallel resonant circuit 370 to increase the impedance in the fundamental wave of the feeding circuit 330.

[0078] The sizes of the inductors L30 and L22 and the sizes of the capacitors C30 and C22 are dependent on each other. Therefore, the design of the high frequency power amplifier 300 is more complicated than that of the first embodiment. However, due to recent improvements in simulation technology, it is not difficult to predict the impedance of the power supply circuit 330 as seen from the transistor Tr. Therefore, it is not difficult to find the constants of the inductors L30, L22, the capacitors C30, and C22 so that the impedance of the feeding circuit 330 with respect to the fundamental wave at the node 150 is similar to that of the first embodiment.

[0079] According to the present embodiment, the second harmonic matching circuit 342 can output a high frequency signal having less harmonic components than the first embodiment. According to the present embodiment, although the number of components is larger than that of the first embodiment, since the parallel resonant circuit 370 is adopted, the length of the transmission line L35 including the inductors L20 and L30 is λ /. It is less than half of the four tracks. Therefore, the present embodiment can be miniaturized in the same manner as the first embodiment. Further, in this embodiment, the current consumption is small and the power efficiency is good.

[0080] An additional series resonant circuit (not shown) may be provided between the node 150 and ground in parallel with the second harmonic matching circuit 342. Thereby, harmonics of the third order or higher can be short-circuited.

FIG. 8 is a circuit diagram of a high frequency power amplifier 400 according to a fourth embodiment of the present invention. According to this embodiment, a plurality of capacitors C24 and C25 are connected in the middle of the integrally formed transmission line L36 in the power feeding circuit 430. As a result, the transmission line L36 is separated into three inductors L23, L24 and L25.

[0082] According to the first embodiment, a single capacitor C30 is connected in the middle of the transmission line L35. Therefore, the first embodiment comprises a single harmonic matching circuit 140 (see FIG. 1). However, according to this embodiment, the inductor L25 and the capacitor C25 form a series resonant circuit as the first harmonic matching circuit 440, and the inductors L25, L24 and the capacitor C24 are connected in series as the second harmonic matching circuit 442. It forms a resonance circuit. Further, the capacitors C24 and C25 and the inductor L23 form a parallel resonant circuit 470.

[0083] According to the third embodiment, in order to form the second harmonic matching circuit 342, it is necessary to provide a transmission line for the inductor L22 separately from the transmission line L35 (see FIG. 7). .. However, according to the present embodiment, since a part of the transmission line L36 is used as the second harmonic matching circuit 442, it is not necessary to form a transmission line separately from the transmission line L36.

[0084] In the high-frequency power amplifier circuit 400 according to the present embodiment, the second harmonic and the third harmonic can be short-circuited by the first harmonic matching circuit 440 and the second harmonic matching circuit 442. Since the parallel resonant circuit 470 is used in this embodiment, the length of the entire feeder line is less than half that of the λ / 4 line. Therefore, the high-frequency power amplifier circuit 400 can be made smaller than before. Further, since the high frequency power amplifier circuit 400 does not need to provide a transmission line in addition to the transmission line L36, it can be made smaller than the third embodiment. Further, the present embodiment is more power efficient than the third embodiment.

[0085] The present embodiment includes a harmonic matching circuit for the second harmonic and the third harmonic. However, as with the capacitors C24 and C25, by connecting an additional capacitor to the transmission line 36, higher order harmonics can be short-circuited. In this case as well, the constants of the inductor and the capacitor may be adjusted so that the parallel resonant circuit in the fundamental wave is realized.

FIG. 9 is a circuit diagram of a high frequency power amplifier 500 according to a fifth embodiment of the present invention. In this embodiment, the second harmonic matching circuit 542 is directly connected to the output pad of the semiconductor chip 110 by the gold wire 106 without being connected to the node 150. Other configurations are the same as in the third embodiment.

[0087] According to the third embodiment, since the second harmonic matching circuit 342 is connected to the node 150, the third harmonic is completely short-circuited by the inductance from the output pad to the node 150. I couldn't. This is because the inductance from the output pad to the node 150 acts in the same way as the inductor L2a shown in FIG.

[0088] According to the present embodiment, the inductance from the output pad to the inductor L22 via the gold wire 106 is included in the inductance component of the second harmonic matching circuit 542. Therefore, the third harmonic can be completely short-circuited as compared with the third embodiment.

[0089] When there are a plurality of series resonance circuits, by connecting all the series resonance circuits directly to the output pad of the transistor Tr instead of the node 150, not only the third harmonic but also the second harmonic and the fourth harmonic can be connected. The next and higher harmonics can also be short-circuited more completely.

[Effect of the Invention] A high-frequency power amplifier according to the present invention can match high-order harmonics of the second or higher order while having high power efficiency, and can be made smaller than the conventional one. ..

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a circuit diagram of a high frequency power amplifier 100 according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram of a high-frequency power amplifier 800 substantially equivalent to the high-frequency power amplifier published in Japanese Patent Application Laid-Open No. 11-127045.

FIG. 3 is a graph of ACPR1 and Ic of the high frequency power amplifier 100 and the high frequency power amplifier 800, respectively.

FIG. 4 is a circuit diagram of a high-frequency power amplifier 900 substantially equivalent to the amplifier circuit published in Japanese Patent Application Laid-Open No. 4-77009.

FIG. 5 is a graph comparing the outputs of the second harmonics of the high frequency power amplifier 100 and the high frequency power amplifier 900.

FIG. 6 is a circuit diagram of a high frequency power amplifier 200 according to a second embodiment of the present invention.

FIG. 7 is a circuit diagram of a high frequency power amplifier 300 according to a third embodiment of the present invention.

FIG. 8 is a circuit diagram of a high frequency power amplifier 400 according to a fourth embodiment of the present invention.

FIG. 9 is a circuit diagram of a high frequency power amplifier 500 according to a fifth embodiment of the present invention.

FIG. 10 is a circuit diagram of a conventional typical high frequency power amplifier 600.

FIG. 11 is a circuit diagram of a conventional high frequency power amplifier 700.

[Description of Code] 100, 200, 300, 400, 500 High Frequency Power Amplifier 110 Semiconductor Chip Tr Transistor 120 Fundamental Wave Matching Circuit 130 Feeding Circuit 132 DC Power Supply 140 Harmonic Matching Circuit 150 Node 160 Output Matching Circuit 170 Parallel Resonance Circuit L10, L20, L30, L35 Inductors C10, C20, C30, C40 Capacitors