High frequency amplifier

Abstract

The amplifier element (T1) amplifies an input signal. The higher harmonic matching circuit (3) is connected to the output end of the amplifier element (T1) via a first cable (W1). The higher harmonic matching circuit (3) comprises: a first inductor (L1) connected to the first cable (W1), a first capacitor (C1) connected in series with the first inductor (L1), a second inductor (L2) connected in parallel with the first inductor (L1), and a second capacitor (C2) connected in series with the second inductor (L2). The first inductor (L1) and the second inductor (L2) form a polarity-reducing coupler with a mutual inductance of a reduced polarity.

Description

Technical Field

[0001] The present invention relates to high frequency amplifiers. Background Art

[0002] Low power consumption during operation, that is, high efficiency, is a basic issue in semiconductor amplifiers. In high-frequency amplifiers that amplify power at a high frequency exceeding microwaves, one of the circuit studies on this issue is so-called harmonic processing. Here, the frequency of the signal amplified by the semiconductor is the fundamental wave, and the frequency of multiples of the fundamental wave is the harmonic. Harmonic processing is a technique to achieve high-efficiency operation by controlling the impedance of the peripheral circuit looking back from the semiconductor amplifier in the harmonics.

[0003] As a circuit for realizing high efficiency of a high frequency amplifier, there is, for example, a class F amplifier. In a class F amplifier, under the class F load condition where the load for even-order harmonics observed from the drain terminal of the FET is short-circuited and the load for odd-order harmonics is open-circuited, the time waveform of the drain voltage is made close to a rectangular wave, and the area of ​​the overlapping portion of the time waveform of the drain voltage and the time waveform of the current is reduced. As a result, the power consumed by the FET is reduced, and thus an extremely high drain efficiency can be obtained.

[0004] However, in reality, there are parasitic capacitance and inductance caused by components such as FETs and cables, which affect the time waveforms of the voltage and current at the drain terminal. Therefore, the F-class load circuit needs to be designed to be short-circuited with respect to even-order harmonics and open-circuited with respect to odd-order harmonics based on these parasitic components (for example, refer to Patent Document 1).

[0005] Patent Document 1: Japanese Patent No. 5958834

[0006] However, in conventional high-frequency amplifiers, it is difficult to simultaneously achieve impedance matching at the fundamental wave, the second wave, and the third wave. Summary of the invention

[0007] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to obtain a high-frequency amplifier capable of simultaneously achieving impedance matching at a fundamental wave, a double wave, and a triple wave.

[0008] The high-frequency amplifier of the present invention is characterized in that it includes: an amplifying element that amplifies an input signal; and a higher harmonic matching circuit that is connected to an output end of the amplifying element via a first cable, the higher harmonic matching circuit having: a first inductor connected to the first cable, a first capacitor connected in series with the first inductor, a second inductor connected in parallel with the first inductor, and a second capacitor connected in series with the second inductor, the first inductor and the second inductor forming a subtractive polarity coupler having a mutual inductance with a subtractive polarity.

[0009] In the present invention, the first inductor and the second inductor generate a mutual inductance of subtractive polarity, so that the influence of the parasitic inductance of the first cable can be reduced. In particular, the low inductance required for triple wave matching can be achieved. In addition, the influence of the high-order harmonic matching circuit is reduced by the circuit formed by the first inductor and the first capacitor, so that the matching of the fundamental wave is not affected. Therefore, the impedance under the fundamental wave, double wave, and triple wave can be optimized at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 This is a circuit diagram showing a high-frequency amplifier according to the first embodiment.

[0011] Figure 2 It is a top view showing the high-frequency amplifier according to the first embodiment.

[0012] Figure 3 This is a perspective view showing the high-frequency amplifier according to the first embodiment.

[0013] Figure 4 is a perspective view showing a first inductor and a second inductor.

[0014] Figure 5 This is an equivalent circuit diagram for explaining the circuit operation of the high-frequency amplifier according to the first embodiment.

[0015] Figure 6 This is an equivalent circuit diagram for explaining the circuit operation of the high-frequency amplifier according to the first embodiment.

[0016] Figure 7 : is a graph showing the frequency dependency of the ratio n of the current flowing through the first inductor and the second inductor.

[0017] Figure 8 : is a circuit diagram showing a high-frequency amplifier of a comparative example.

[0018] Fig. 9 This is a diagram showing the locus of output impedance viewed from the output terminal of the transistor in the first embodiment.

[0019] Fig.101 is a diagram showing the locus of output impedance viewed from the output terminal of the transistor in the comparative example.

[0020] Fig.11 1 is a diagram showing the locus of output impedance viewed from the output terminal of the transistor in the comparative example.

[0021] Fig.12 This is a circuit diagram showing a high-frequency amplifier according to the second embodiment.

[0022] Fig.13 It is a top view showing a high-frequency amplifier according to the second embodiment.

[0023] Fig.14 This is a circuit diagram showing a high-frequency amplifier according to a third embodiment.

[0024] Fig.15 1 is a diagram showing output impedance viewed from the output terminal of the transistor in the fourth embodiment.

[0025] Fig.16 This is a circuit diagram showing a high-frequency amplifier according to a fifth embodiment.

[0026] Fig.17 This is a diagram showing the locus of output impedance viewed from the output terminal of the transistor in the fifth embodiment. DETAILED DESCRIPTION

[0027] A high frequency amplifier according to an embodiment will be described with reference to the drawings. The same reference numerals are used for the same or corresponding components, and duplicate descriptions may be omitted.

[0028] Implementation method 1.

[0029] Figure 1 This is a circuit diagram showing a high-frequency amplifier according to the first embodiment. Figure 2 1 is a plan view showing a high frequency amplifier according to Embodiment 1. A circuit module of the high frequency amplifier is formed using a multilayer glass epoxy substrate 1 .

[0030] The transistor T1 and the input matching circuit MC1 are fixed to the metal 2 on the top layer of the glass epoxy substrate 1 by a conductive adhesive. The input matching circuit MC1 is connected to the gate of the transistor T1. The transistor T1 is an amplifier element that amplifies the input signal input from the input terminal P1 via the input matching circuit MC1, and is, for example, a GaN-based HEMT chip. The metal 2 on the top layer is connected to the ground layer on the back side of the glass epoxy substrate 1 through a through hole. The output end of the transistor T1, that is, the drain pad, is connected to a higher harmonic matching circuit 3 via a cable W1. The cable W1 has a parasitic inductance L3.

[0031] The harmonic matching circuit 3 includes a first inductor L1 connected to the cable W1, a first capacitor C1 connected in series with the first inductor L1, a second inductor L2 connected in parallel with the first inductor L1, and a second capacitor C2 connected in series with the second inductor L2. The first capacitor C1 and the second capacitor C2 are chip capacitors.

[0032] One end of a fundamental wave matching circuit MC2 for matching impedance with respect to a fundamental wave of an input signal is connected to a connection point between the cable W1 and the harmonic matching circuit 3. The other end of the fundamental wave matching circuit MC2 is connected to an output terminal P2 of the high frequency amplifier.

[0033] Figure 3 This is a perspective view showing the high-frequency amplifier according to the first embodiment. Figure 4 : is a three-dimensional diagram showing a first inductor and a second inductor. The first inductor L1 is formed by a first wiring layer and a third wiring layer from the surface of the glass epoxy substrate 1. The second inductor L2 is formed by a second wiring layer of the glass epoxy substrate 1. In a top view observed from above the glass epoxy substrate 1, the first inductor L1 is wound clockwise from the drain of the transistor T1 toward the first capacitor C1. When observed from above, the second inductor L2 is wound counterclockwise from the drain of the transistor T1 toward the second capacitor C2. The first inductor L1 and the second inductor L2 are wound in opposite directions to each other and overlap, thereby forming a subtractive polarity coupler with a mutual inductance of subtractive polarity.

[0034] Without considering the mutual inductance, due to the influence of the parasitic inductance L3 of the cable W1, the resonant frequency of the double wave resonant circuit composed of the second inductor L2 and the second capacitor C2 is set to be higher than 2fo relative to the frequency fo of the fundamental wave. Therefore, the impedance of the double wave resonant circuit shows capacitive characteristics relative to the frequency below the double wave, and shows inductive characteristics relative to the triple wave. Since the capacitance based on the double wave resonant circuit is reduced relative to the fundamental wave, the impedance of the resonant circuit composed of the first inductor L1 and the first capacitor C1 is set to show inductive characteristics relative to the fundamental wave.

[0035] Next, the circuit operation in consideration of mutual inductance will be described. Figure 5 as well as Figure 6 This is an equivalent circuit diagram for explaining the circuit operation of the high-frequency amplifier of Embodiment 1. For the sake of simplicity, the fundamental matching circuit MC2 is treated as an open circuit. The internal load of the transistor T1 is set to Rds, and the parasitic capacitance of the transistor T1 is set to Cds. The current flowing in the first inductor L1 is set to i1, and the current flowing in the second inductor L2 is set to i2. The inductance of the first inductor L1 is set to L(L1), the inductance of the second inductor L2 is set to L(L2), and the mutual inductance is set to -M.

[0036] In order to make the high-frequency amplifier perform ideal Class F operation, it is preferred that the impedance of the harmonic matching circuit 3 viewed from the output end of the transistor T1 be open circuit with respect to the fundamental wave, short circuit with respect to the double wave, and open circuit with respect to the triple wave by resonating with the parasitic capacitance Cds of the transistor T1.

[0037] exist Figure 5 In Figure 1 The first inductor L1 and the second inductor L2 are replaced with inductors without coupling. Inductor L4 corresponds to the mutual inductor of the subtractive polarity generated by the first inductor L1 and the second inductor L2. The inductance of the fundamental wave inductor L1a becomes L(L1)+M, the inductance of the higher harmonic inductor L2a becomes L(L2)+M, and the inductance of the inductor L4 becomes -M. The constants are adjusted so that the circuit formed by L1a, L2a, C1, and C2 becomes an open circuit at the fundamental wave. As a result, the circuit can be made not to affect the output impedance looking back from the output end of the transistor T1 at the fundamental wave.

[0038] exist Figure 5 Both current i1 and current i2 flow through inductor L4. Figure 6 In Figure 5 The inductor L4 is virtually divided into an inductor L4a through which only the current i1 flows, and an inductor L4b through which only the current i2 flows.

[0039] The inductance of the inductor L4a is represented by L(M1a), and the inductance of the inductor L4b is represented by L(M1b). Figure 5 The node N1 and Figure 6 The nodes N11 and N12 are at the same potential, so L(M1a) and L(M1b) can be expressed as follows.

[0040] L(M1a)=-(i1+i2) / i1×M

[0041] L(M1b)=-(i1+i2) / i2×M

[0042] Here, n=i1 / i2. N represents the ratio of the current flowing through the first inductor L1 and the second inductor L2. The above-mentioned L(M1a) and L(M1b) can be represented by n as follows.

[0043] L(M1a)=-(1+1 / n)×M

[0044] L(M1b)=-(1+n)×M

[0045] The series connection of the inductor L1a and the inductor L4a is referred to as the inductor L1b. The inductance L(L1b) of the inductor L1b as the fundamental wave inductance can be expressed as follows.

[0046] L(L1b)=L(L1a)+L(M1a)=L(L1)-(1 / n)×M

[0047] The series connection of the inductor L2a and the inductor L4b is referred to as the inductor L2b. The inductance L (L2b) of the inductor L2b as the double wave inductance can be expressed as follows.

[0048] L(L2b)=L(L2a)+L(M1b)=L(L2)-n×M

[0049] Figure 7 This is a graph showing the frequency dependency of the ratio n of the current flowing through the first inductor and the second inductor. Since only the LC circuit is connected to the path where the current i1 and the current i2 flow, the value of n is a real number. Although L4b, L2a, and C2 mainly affect the impedance of the higher harmonics, since the value of n increases with frequency, it can be seen that the equivalent inductance L (L2b) can be reduced with frequency.

[0050] In higher harmonic matching, especially triple wave matching, at a frequency three times higher than the fundamental wave, it is necessary to reduce the value of the inductance that resonates with the parasitic capacitance Cds of the transistor T1. However, this is difficult to achieve in conventional circuits without coupling. In contrast, in this embodiment, since a mutual inductance with a subtractive polarity is generated by the first inductor L1 and the second inductor L2, the influence of the parasitic inductance L3 of the cable W1 can be reduced. In particular, the low inductance required for triple wave matching can be achieved. In addition, since the influence of the higher harmonic matching circuit 3 is reduced by the circuit formed by the first inductor L1 and the first capacitor C1, the matching of the fundamental wave is not affected. Therefore, the impedance under the fundamental wave, double wave, and triple wave can be optimized at the same time.

[0051] Next, the effects of the present embodiment will be described in comparison with the comparative example. Figure 8 : is a circuit diagram of a high frequency amplifier of a comparative example. The high-order harmonic matching circuit 3 has: a resonance circuit for double wave composed of an inductor L4 and a capacitor C3, and a resonance circuit for triple wave composed of an inductor L5 and a capacitor C4. In the comparative example, the inductor L4 and the inductor L5 do not form a subtractive polarity coupler.

[0052] Fig. 9 This is a diagram showing the locus of output impedance viewed from the output terminal of the transistor in the first embodiment. Fig.10 as well as Fig.111 is a diagram showing the trajectory of the output impedance looking back from the output end of the transistor in the comparative example. In the figure, fl, fc, and fh respectively represent the impedance at the lower limit, center, and upper limit of the fundamental frequency band. 2fl, 2fc, and 2fh respectively represent the impedance at the lower limit, center, and upper limit of the double frequency band. 3fl, 3fc, and 3fh respectively represent the impedance at the lower limit, center, and upper limit of the triple frequency band. fc_o represents the impedance at the center of the fundamental frequency band when the harmonic matching circuit 3 is not included. The output impedance of the transistor T1 is the impedance looking back at the harmonic matching circuit 3 from the drain end of the transistor T1, the internal current source Is, or the internal load Rds.

[0053] Depend on Figures 9-11 It can be seen that, while the frequencies of the fundamental wave, double wave, and triple wave are matched in Embodiment 1, the double wave is not matched in the comparative example. In addition, the triple wave frequency characteristics of Embodiment 1 are better than those of the comparative example.

[0054] Depend on Fig.10 It can be seen that in the comparative example, by optimizing L4, C3, L5, and C4, the conditions of short circuit at double wave and open circuit at triple wave, which are necessary conditions for Class F operation, are satisfied. However, the impedance at the fundamental wave shifts from fc_o to fc.

[0055] In an amplifier, the width of the frequency range in which matching is achieved below a certain reflection coefficient is called broadband. Generally, it is known that the broadband of an amplifier is inversely proportional to the Rds·Cds of transistor T1. Fig.10 As shown, fc deviates from the impedance fc_o when the harmonic circuit is not included. If the equivalent parasitic capacitance of transistor T1 is set to Cds', Cds < Cds' becomes Cds<Cds', which deteriorates the broadband performance. In addition, if Cds' becomes larger, a circuit with an increased amount of compensation capacitance is required, which results in an increase in the loss of the output matching circuit.

[0056] exist Fig.11 In the figure, the impedances for the fundamental wave and the triple wave are fixed. As can be seen from the figure, if the impedance for the fundamental wave is fixed to fc_o, and the impedances 3f1, 3fc, and 3fh for the triple wave are fixed to open circuit, the impedances 2f1, 2fc, and 2fh for the double wave have the problem of being offset from the short-circuited end. Therefore, it is difficult to achieve impedance matching at the fundamental wave, double wave, and triple wave at the same time in the comparative example.

[0057] In contrast, in the present embodiment, even when there is parasitic inductance caused by the cable W1 connecting the drain pad of the transistor T1 , which is a major parasitic component in the high-frequency amplifier, to the harmonic matching circuit 3 , impedance matching can be simultaneously achieved at the fundamental wave, double wave, and triple wave.

[0058] Implementation method 2.

[0059] Fig.12 This is a circuit diagram showing a high-frequency amplifier according to the second embodiment. Fig.13 1 is a top view of a high-frequency amplifier according to Embodiment 2. The higher harmonic matching circuit 3 is connected to the drain of the transistor T1 via a cable W1. On the other hand, the fundamental wave matching circuit MC2 is connected to the drain of the transistor T1 via a cable W2 provided separately. The cable W2 has a parasitic inductor L5. The fundamental wave matching circuit MC2 and the higher harmonic matching circuit 3 of the fundamental wave are separated at the drain of the transistor T1. The cable W2 is arranged obliquely relative to the cable W1. Therefore, the coupling between the cables can be reduced, and the interference between the fundamental wave matching circuit MC2 and the higher harmonic matching circuit 3 is less. Therefore, the fundamental wave matching circuit MC2 and the higher harmonic matching circuit 3 can be optimized separately, making the circuit design easy.

[0060] Implementation method 3.

[0061] Fig.14 : This is a circuit diagram of a high-frequency amplifier according to Embodiment 3. The second capacitor C2 of Embodiment 1 corresponds to a frequency three times higher than the fundamental frequency. For example, if it is an amplifier in the 3 GHz band, the second capacitor C2 corresponds to 9 GHz. Therefore, the capacitance value of the second capacitor C2 is less than 1 pF, and precision is required. In Embodiment 1, a chip capacitor is used as the second capacitor C2. However, the capacitance value of the chip capacitors sold on the market has a rough step size of 0.1 pF. In addition, the pad for mounting the chip capacitor is large and has a parasitic capacitance of a fraction of 1 pF. Therefore, it is difficult to fine-tune the capacitance value of the second capacitor C2.

[0062] Therefore, in this embodiment, the second capacitor C2 of embodiment 1 is replaced by an open short stub STB1. Therefore, the capacitance value can be fine-tuned. In addition, since a pad for mounting the capacitor is not required, the circuit scale can be reduced. In addition, an interlayer capacitor formed by a glass epoxy substrate 1 and wiring can be used instead of the open short stub STB1.

[0063] Implementation method 4.

[0064] In this embodiment, in the circuit structure of Embodiment 1, the constants of the first inductor L1, the first capacitor C1, the second inductor L2, and the second capacitor C2 are set such that the impedance of the harmonic matching circuit 3 viewed from the output end of the transistor T1 becomes an open circuit with respect to the resonance of the double wave and the parasitic capacitance Cds in the transistor T1, and becomes a short circuit with respect to the triple wave. Thus, the harmonic condition for the high-frequency amplifier to perform the reverse F-class operation can be satisfied.

[0065] Fig.15 This is a diagram showing the output impedance viewed from the output end of the transistor in Embodiment 4. By adjusting the constants, although the fundamental wave is greatly affected, it is known that the impedance condition of the inverse F-class amplifier can be realized, that is, the state of being open circuit with respect to the frequency of the double wave and being short circuit with respect to the triple wave. In addition, with respect to the triple wave, the short circuit condition is satisfied in a wide frequency band by utilizing the mutual inductance of the subtractive polarity.

[0066] Implementation method 5.

[0067] Fig.16 : is a circuit diagram showing a high frequency amplifier according to Embodiment 5. In addition to the configuration of Embodiment 4, a transmission line TRL1 having an electrical length of λ / 4 with respect to a wavelength λ of a fundamental wave is connected between the first inductor L1 and the first capacitor C1.

[0068] In Embodiment 4, the impedance with respect to the fundamental wave viewed from the current source of the transistor T1 is greatly affected by the two LC resonance circuits. In contrast, by inserting the transmission line TRL1, the influence on the fundamental wave can be reduced, making the circuit design easier.

[0069] Fig.17 This is a diagram showing the locus of output impedance viewed from the output terminal of the transistor in Embodiment 5. It can be seen that the influence on the fundamental wave is reduced by inserting the transmission line TRL1.

[0070] Description of Reference Numerals

[0071] 1...glass epoxy substrate; 3...higher harmonic matching circuit; C1...first capacitor; C2...second capacitor; L1...first inductor; L2...second inductor; MC2...fundamental matching circuit; STB1...open stub; T1...transistor (amplifier); TRL1...transmission line; W1...first cable; W2...second cable.

Claims

1. A high frequency amplifier, characterized in that: have: an amplifying element that amplifies an input signal; and a high-order harmonic matching circuit connected to the output end of the amplifying element via a first cable, The harmonic matching circuit includes: a first inductor connected to the first cable, a first capacitor connected in series with the first inductor, a second inductor connected in parallel with the first inductor, and a second capacitor connected in series with the second inductor. The first inductor and the second inductor form a polarity-reducing coupler having a mutual inductance of a polarity-reducing type. When looking back at the impedance of the higher harmonic matching circuit from the output end of the amplifying element, it becomes an open circuit with respect to the fundamental wave of the input signal, a short circuit with respect to the second wave, and an open circuit with respect to the third wave, and the high-frequency amplifier performs a Class F operation.

2. The high frequency amplifier according to claim 1, characterized in that: The first inductor and the second inductor are wound in opposite directions to each other and overlap each other.

3. The high-frequency amplifier according to claim 1 or 2, characterized in that: The impedance of the resonance circuit formed by the second inductor and the second capacitor is capacitive with respect to frequencies below the double wave, and is inductive with respect to the triple wave. The impedance of the resonance circuit formed by the first inductor and the first capacitor shows inductance with respect to the fundamental wave.

4. A high frequency amplifier, characterized in that: have: an amplifying element that amplifies an input signal; and a high-order harmonic matching circuit connected to the output end of the amplifying element via a first cable, The harmonic matching circuit includes: a first inductor connected to the first cable, a first capacitor connected in series with the first inductor, a second inductor connected in parallel with the first inductor, and a second capacitor connected in series with the second inductor. The first inductor and the second inductor form a polarity-reducing coupler having a mutual inductance of a polarity-reducing type. When looking back at the impedance of the harmonic matching circuit from the output end of the amplifying element, it becomes an open circuit with respect to the double wave of the input signal and a short circuit with respect to the triple wave, and the high-frequency amplifier performs an inverse class F operation.

5. The high frequency amplifier according to claim 4, characterized in that: The first inductor and the second inductor are wound in opposite directions to each other and overlap each other.

6. The high-frequency amplifier according to claim 4 or 5, characterized in that: The device further includes a transmission line connected between the first inductor and the first capacitor, wherein the electrical length of the transmission line is λ / 4 with respect to the wavelength λ of the input signal.

7. The high frequency amplifier according to any one of claims 1, 2, 4 and 5, characterized in that: The device further includes a fundamental wave matching circuit connected to a connection point between the first cable and the higher harmonic matching circuit.

8. The high frequency amplifier according to any one of claims 1, 2, 4 and 5, characterized in that: A fundamental wave matching circuit is further provided, and the fundamental wave matching circuit is connected to the output end of the amplifying element through a second cable.

9. The high frequency amplifier according to claim 8, characterized in that: The second cable is arranged obliquely with respect to the first cable.

10. The high frequency amplifier according to any one of claims 1, 2, 4, 5 and 9, characterized in that: The first capacitor and the second capacitor are chip capacitors.

11. The high frequency amplifier according to any one of claims 1, 2, 4, 5 and 9, characterized in that: The second capacitor is an interlayer capacitor formed by a multilayer glass epoxy substrate and wiring.

12. The high frequency amplifier according to any one of claims 1, 2, 4, 5 and 9, characterized in that: The second capacitor is an open circuit stub.

13. The high frequency amplifier according to any one of claims 1, 2, 4, 5, and 9, characterized in that: The amplifying element is a GaN HEMT chip. The first inductor and the second inductor are formed by a wiring layer of a glass epoxy substrate.

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