阅读说明：本技术 功率放大器 (Power amplifier ) 是由 吉冈贵章 原内健次 于 2019-04-04 设计创作，主要内容包括：功率放大器的特征在于,具备：多个放大元件；竞赛型电路,其具有配置为竞赛型的多个传输线路,并与所述多个放大元件连接；以及多个差频短路电路,它们与所述竞赛型电路的多个节点分流连接,所述多个差频短路电路分别具有串联连接的电感器和电容器,所述多个差频短路电路的谐振频率越远离所述多个放大元件越小,在所述多个节点中的同一级的多个节点连接有谐振频率相等的所述差频短路电路。(The power amplifier is characterized by comprising: a plurality of amplifying elements; a race type circuit having a plurality of transmission lines configured as a race type and connected to the plurality of amplification elements; and a plurality of difference frequency short-circuit circuits connected in parallel to the plurality of nodes of the race circuit, each of the plurality of difference frequency short-circuit circuits having an inductor and a capacitor connected in series, wherein the resonance frequency of the plurality of difference frequency short-circuit circuits decreases as the difference frequency becomes farther from the plurality of amplification elements, and the difference frequency short-circuit circuits having the same resonance frequency are connected to the plurality of nodes at the same stage among the plurality of nodes.)

1. A power amplifier is provided with:

a plurality of amplifying elements;

a race type circuit having a plurality of transmission lines configured as a race type and connected to the plurality of amplification elements; and

a plurality of difference frequency short-circuit circuits connected in shunt with a plurality of nodes of the race type circuit,

the plurality of difference frequency short-circuit circuits respectively have an inductor and a capacitor connected in series,

the resonance frequency of the plurality of difference frequency short-circuit circuits is smaller as it is farther from the plurality of amplifying elements,

the difference frequency short circuit with the same resonant frequency is connected with a plurality of nodes of the same stage in the plurality of nodes.

2. The power amplifier of claim 1,

the power amplifier includes a package on which the plurality of amplification elements are mounted,

and mounting the difference frequency short circuit with the resonant frequency equal to or greater than a preset specific resonant frequency on the packaging body, and arranging the difference frequency short circuit with the resonant frequency less than the specific resonant frequency outside the packaging body.

3. The power amplifier of claim 2,

the specific resonance frequency is 10 MHz.

4. The power amplifier according to any one of claims 1 to 3,

the inductor is an 1/4-wavelength line at the fundamental frequency of the operating frequency of the power amplifier.

5. The power amplifier of claim 4,

the microwave integrated circuit includes a microwave integrated circuit substrate on which at least one inductor and at least one transmission line are formed.

6. The power amplifier of claim 2 or 3,

the plurality of amplifying elements is provided with 4 amplifying elements,

the packaging body is provided with two difference frequency short-circuit circuits, and the outside of the packaging body is provided with one difference frequency short-circuit.

7. The power amplifier according to any one of claims 1 to 6,

the power amplifier is provided with a complementary difference frequency short circuit which is a series LC circuit connected in shunt with the node to which the difference frequency short circuit is connected in shunt,

the resonance frequency of the complementary difference frequency short circuit is higher than the resonance frequency of the difference frequency short circuit which is far from the plurality of amplifying elements than the complementary difference frequency short circuit.

8. The power amplifier of claim 7,

and a drain bias applying terminal for applying a drain bias to at least two of the plurality of amplifying elements via the inductor of the complementary difference frequency short circuit and the inductor of the difference frequency short circuit connected to the same node as the complementary difference frequency short circuit.

9. The power amplifier according to any one of claims 1 to 6,

and a drain bias applying terminal for applying a drain bias to at least two of the plurality of amplifying elements via the inductor of the difference frequency short circuit.

10. The power amplifier according to any one of claims 1 to 6,

and an open stub of an 1/4-wavelength line connected between the inductor and the capacitor and having a fundamental frequency of the operating frequency of the power amplifier.

11. The power amplifier according to any one of claims 1 to 10,

the race type circuit is a race type synthesizing circuit that synthesizes the amplified signals of the plurality of amplifying elements.

12. The power amplifier according to any one of claims 1, 2, 3, 4, 5, 6, 10,

the race type circuit is a race type distribution circuit that distributes an input signal to the plurality of amplification elements.

13. The power amplifier of claim 12,

the difference frequency short circuit includes a resistor connected in series with the inductor or the capacitor.

14. The power amplifier according to any one of claims 1 to 13,

the resonance frequencies of the plurality of difference frequency short-circuit circuits are present between a minimum value and a maximum value that can be obtained as a difference frequency between a high frequency end and a low frequency end of the high frequency signal amplified by the plurality of amplifying elements.

Technical Field

The present invention relates to power amplifiers.

Background

With the increase in the amount of information transmitted in wireless communication, there is an increasing demand for microwave power amplifiers having good distortion characteristics even when the bandwidth of a high-frequency signal for transmitting information is increased. The frequency interval between the high-frequency end and the low-frequency end of the bandwidth of the high-frequency signal is referred to as a detuned width or a detuned frequency, and the frequency corresponding to the width thereof is referred to as a difference frequency or simply a difference frequency. In order to achieve good distortion characteristics, it is effective to estimate the impedance reduction of the matching circuit at the difference frequency from the transistor end. A method of connecting a plurality of resonant circuits having different resonant frequencies to a matching circuit is known.

For example, patent document 1 shows the following method: a capacitor which becomes series resonance at the inductance and difference frequency of a line is connected to the other end of a lambda/4 line having one end connected to the drain terminal of a transistor or the output terminal of an amplifier, thereby preventing the deterioration of distortion characteristics in a microwave power amplifier.

Patent document 1: japanese laid-open patent publication No. 11-150431

In the technique disclosed in patent document 1, the bias circuit impedance at the detuning frequency or lower is set to a sufficiently low value, and the bias circuit impedance at the operating frequency of the amplifier is substantially opened, whereby it is possible to prevent deterioration of distortion characteristics and reduce loss in the operating frequency band due to the bias circuit. However, the above-described technique has the following problems: when the detuning frequency increases to the 100MHz level, a wide frequency band from the 1MHz level to the 100MHz level cannot be obtained, and the impedance of the difference frequency is set to a low value, so that it is not possible to prevent distortion from deteriorating for all desired detuning frequencies.

On the other hand, it is also conceivable to directly connect a plurality of difference frequency short-circuit circuits having different resonance frequencies to the drain terminal. In this case, there is a problem that all the inductors and capacitors constituting the difference frequency short circuit cannot be arranged unless the package size is increased due to the restriction of the mounting area in the package. In order to obtain fundamental characteristics such as high efficiency and output in a microwave power amplifier, it is necessary to equalize the impedance of a matching circuit estimated to be connected to each transistor from the transistor for all transistors, thereby equalizing the operation of the entire transistors.

On the other hand, when the same difference frequency short circuit is provided for all the unit transistors, there is a problem that layout design is restricted, basic characteristics are degraded due to an increase in circuit loss, and miniaturization of products is hindered.

Disclosure of Invention

The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a power amplifier which, in a power amplifier which amplifies microwaves of several GHz or more, for example, reduces the impedance of a connection circuit as viewed from a unit transistor end in a difference frequency for all of a plurality of transistors arranged, without reducing the degree of freedom of layout design and without causing an increase in package size, and which prevents deterioration of distortion characteristics from a minimum detuning frequency to a maximum detuning frequency.

The power amplifier of the present invention is characterized by comprising: a plurality of amplifying elements; a race type circuit having a plurality of transmission lines configured as a race type and connected to the plurality of amplification elements; and a plurality of difference frequency short-circuit circuits connected in parallel to the plurality of nodes of the race circuit, each of the plurality of difference frequency short-circuit circuits having an inductor and a capacitor connected in series, wherein the resonance frequency of the plurality of difference frequency short-circuit circuits decreases as the resonance frequency of the plurality of difference frequency short-circuit circuits increases, and the difference frequency short-circuit circuits having the same resonance frequency are connected to the plurality of nodes of the same stage among the plurality of nodes.

Other features of the present invention are apparent below.

According to the present invention, the resonance frequencies of the plurality of difference frequency short-circuit circuits connected to the race circuit are made smaller as they are farther from the plurality of amplifying elements, and the difference frequency short-circuit circuits having the same resonance frequency are connected to the plurality of nodes at the same stage among the plurality of nodes of the race circuit.

Drawings

Fig. 1 is a circuit diagram of a power amplifier according to embodiment 1.

Fig. 2 is a circuit diagram of a microwave power amplifier of comparative example 1.

Fig. 3 is a diagram showing an example of the difference frequency impedance of the output circuit in comparative example 1.

Fig. 4 is a diagram showing an example of a simulation result of the IM3 of comparative example 1.

Fig. 5 is a circuit diagram of a microwave power amplifier of comparative example 2.

Fig. 6 is a diagram showing an example of the difference frequency impedance of the output circuit in comparative example 2.

Fig. 7 is a diagram showing an example of a simulation result of the IM3 of comparative example 2.

Fig. 8 is a circuit diagram of a microwave power amplifier of comparative example 3.

Fig. 9 is a diagram showing an example of the difference frequency impedance of the output circuit in comparative example 3.

Fig. 10 is a diagram showing an example of the difference frequency impedance of the output circuit of embodiment 1.

Fig. 11 is a diagram showing an example of a simulation result of the IM3 according to embodiment 1.

Fig. 12 is a circuit diagram of a power amplifier according to a modification.

Fig. 13 is a circuit diagram of a power amplifier circuit according to another modification.

Fig. 14 is a circuit diagram of a power amplifier circuit according to another modification.

Fig. 15 is a circuit diagram of a power amplifier circuit according to another modification.

Fig. 16 is a circuit diagram of a power amplifier according to embodiment 2.

Fig. 17 is a circuit diagram of a power amplifier according to a modification.

Detailed Description

A power amplifier according to an embodiment of the present invention will be described with reference to the drawings. The same or corresponding components are denoted by the same reference numerals, and redundant description thereof may be omitted.

Embodiment 1.

Fig. 1 is a circuit diagram of a power amplifier according to embodiment 1. The power amplifier may be provided as a microwave power amplifier. The power amplifier includes transistors Tr1, Tr2, Tr3, and Tr4 as a plurality of amplification elements. The transistor Tr1 is a unit transistor in which transistor cells are connected in parallel. Similarly, the transistors Tr2, Tr3, and Tr4 can be unit transistors in which transistor cells are connected in parallel. According to another example, a plurality of transistor units may be provided as a plurality of amplifying elements.

The drain terminals of the transistors Tr1, Tr2, Tr3, and Tr4 are connected to one ends of the transmission lines TL1, TL2, TL3, and TL4, respectively. The other end of the transmission line TL1 is connected to the other end of the transmission line TL2 at the combining point a 1. The other end of the transmission line TL3 is connected to the other end of the transmission line TL4 at the combining point a 2. One end of the transmission line TL5 and one end of the transmission line TL6 are connected to the synthesis points a1 and a2, respectively. The other end of the transmission line TL5 is connected to the other end of the transmission line TL6 at the combining point B1. The combining point B1 is connected to the transmission line TL 7. The transmission line TL7 is connected to a terminal T2 as an output terminal via a package terminal T1 and the transmission line TL8.

Thus, the transmission lines TL1, TL2, TL3, TL4, TL5, TL6, TL7, TL8 are configured as a racing type. These transmission lines constitute a race circuit connected to transistors Tr1, Tr2, Tr3, and Tr4 as a plurality of amplification elements. The race circuit according to embodiment 1 is a race combining circuit that combines amplified signals of a plurality of amplifying elements. In the race type synthesizing circuit, the following signal synthesis is repeatedly performed: first, the power from the two transistors is combined in a first stage, and then the combined power is further combined in a second stage.

The race circuit is connected with 4 difference frequency short-circuit circuits 11, 12, 21, 31. The difference frequency short-circuit 11 includes: an inductor 11a, which is a λ/4 line having one end connected to the combining point a 1; and a capacitor 11b connected to the other end of the inductor 11 a. The λ/4 line is an 1/4 wavelength line of the fundamental frequency of the operating frequency of the power amplifier. The inductance of inductor 11a is L1. The capacitor 11b has a capacitance C1 that is in series resonance with the inductor 11a at a difference frequency Δ f 1.

The difference frequency short-circuit 12 includes: an inductor 12a, which is a λ/4 line having one end connected to the combining point a 2; and a capacitor 12b connected to the other end of the inductor 12 a. The inductance of inductor 12a is L1. The capacitor 12b has a capacitance C1 that is in series resonance with the inductor 12a at a difference frequency Δ f 1.

The difference frequency short-circuit 21 includes: an inductor 21a, which is a λ/4 line having one end connected to the combining point B1; and a capacitor 21b connected to the other end of the inductor 21 a. The inductance of inductor 21a is L1. The capacitor 21b has a capacitance C2 that is in series resonance with the inductor 21a at a difference frequency Δ f 2.

The difference frequency short-circuit 31 includes: an inductor 31a, which is a λ/4 line having one end connected to a combining point B1 via a transmission line TL 7; and a capacitor 31b connected to the other end of the inductor 31 a. The inductance of inductor 31a is L1. The capacitor 31b has a capacitance C3 that is in series resonance with the inductor 31a at a difference frequency Δ f 3. A terminal T3, which is a Vd terminal to which a drain voltage is applied to the transistors Tr1, Tr2, Tr3, and Tr4, is connected between the inductor 31a and the capacitor 31 b.

The 4 difference frequency short-circuit circuits 11, 12, 21, 31 are connected in shunt to a plurality of nodes of the race type circuit. In any of the difference frequency short circuits, the electrical lengths between the connection point of the difference frequency short circuit and the race circuit and the plurality of transistors that supply power to the connection point are equal. At this time, the following relationship exists among the inductor, the capacitor, and the resonance frequency.

L1×C1＝1/(2πΔf1)2

L1×C2＝1/(2πΔf2)²

L1×C3＝1/(2πΔf3)²

The resonant frequencies of the difference frequency short-circuit circuits Δ f1, Δ f2, and Δ f3 are between the minimum value and the maximum value that can be obtained as the difference frequency (or difference frequency) between the high frequency side and the low frequency side of the high frequency signal amplified by the amplifying elements. Since the setting of the bandwidth varies depending on the communication system, the minimum value and the maximum value vary depending on the communication system. The magnitude relationships of Δ f1, Δ f2, and Δ f3 are as follows.

Δf3＜Δf2＜Δf1

Namely, C1, C2 and C3 have a relationship of C1 < C2 < C3. Therefore, the resonance frequency of the plurality of difference frequency short-circuit circuits 11, 12, 21, 31 becomes smaller as it becomes farther from the plurality of transistors Tr1, Tr2, Tr3, Tr4. The inductance L1 of the λ/4 line is the same value for all λ/4 lines constituting the difference frequency short circuit.

A transmission line connected between the unit transistor end and the package terminal T1 and an inductor which is a λ/4 line in the same area can be formed with a metal pattern on a Microwave Integrated Circuit (MIC) substrate S. The substrate S, the transistors Tr1, Tr2, Tr3, and Tr4, and the capacitors 11b, 12b, and 21b are mounted on the package 10 using solder or the like.

Distortion characteristics of a high-frequency signal having a wide bandwidth are generally evaluated by inputting two sinusoidal signals having a single frequency at the low-frequency end and the high-frequency end and equal signal strength to an amplifier and using the generated third-order intermodulation distortion IM3 as an index. The interval between the high-frequency end and the low-frequency end of the high-frequency signal having a bandwidth, that is, the interval between two single-frequency signals in the evaluation of IM3 is referred to as a detuned width or a detuned frequency, and a frequency corresponding to this width is referred to as a difference frequency or simply a difference frequency. In addition, for example, the detuning frequency of a high-frequency signal used in a transmission system for satellite communication has been conventionally about 5MHz at maximum, but in recent years, it has been required to expand the frequency to the order of 100MHz, about 200MHz at maximum.

In order to easily understand the significance of the power amplifier of embodiment 1, 4 structures of the microwave power amplifiers in comparative examples 1, 2, and 3 and embodiment 1 were examined. Comparative example 1 is a known microwave power amplifier, comparative example 2 is an example in which 3 difference frequency short-circuit circuits are arranged outside a package in the known microwave power amplifier, and comparative example 3 is an example in which a difference frequency short-circuit is arranged near the drain end of a unit transistor on the side wall of the package in the known microwave power amplifier. In each configuration, description will be made in order using a circuit diagram, an example in which an impedance in a difference frequency of an output circuit (hereinafter, referred to as a difference frequency impedance) is estimated from a drain terminal of a transistor in the circuit, and a simulation result of IM 3.

Comparative example 1

First, a known microwave power amplifier is considered in terms of a circuit configuration, a difference frequency impedance of its output circuit, and IM 3. Fig. 2 is a circuit diagram of a microwave power amplifier of comparative example 1. The microwave power amplifier is composed of transistors Tr1, Tr2, Tr3, and Tr4, and a race type combining circuit that combines outputs of these at combining points a1, a2, and B1. A differential frequency short circuit having an inductor 31a and a capacitor 31b is connected to a package terminal T1 connected to the transmission line TL 7. The inductor 31a is a lambda/4 line. The capacitor 31b has a capacitance C3 that is in series resonance with the inductor 31a at the difference frequency Δ f.

At this time, the inductor 31a, the capacitor 31b, and the resonance frequency have the following relationship.

L1×C3＝1/(2πΔf)²

Fig. 3 is a diagram showing an example of the difference frequency impedance of the output circuit in the microwave power amplifier of comparative example 1. The impedance of the output circuit side as viewed from the drain end of the transistor from 1MHz to 1GHz is shown in fig. 3 in logarithmic representation with two axes. In this example of the circuit configuration, by appropriately setting L1 and C3, a resonance point is created at 5MHz, and the impedance in the vicinity of 5MHz is reduced to 10 Ω or less. On the other hand, the impedance in the order of 100MHz distant from the resonance frequency takes a large value of 100 Ω or more. The impedance in 200MHz is 250 omega, for example.

Fig. 4 is a diagram showing an example of a simulation result of IM3 in the microwave power amplifier of comparative example 1 shown in fig. 2. The simulation example calculates the relationship between the output power of the microwave amplifier and IM3 when a 2-wave input signal having a detuned frequency of 200MHz is input to the transistor. Distortion components appearing on the low frequency side of the input signal are indicated by solid lines and distortion components appearing on the high frequency side are indicated by broken lines in two IMs 3 appearing near the input signal in fig. 4. As can be seen from fig. 4, for example, the maximum value of the two distortion components, which is the worst value of IM3 at an output power of 44dBm, is-15 dBc.

Comparative example 2

Next, a circuit configuration in a case where 3 difference frequency short-circuit circuits are disposed outside the package 10 in the known microwave power amplifier, difference frequency impedance of its output circuit, and IM3 will be considered. Fig. 5 is a circuit diagram of a microwave power amplifier of comparative example 2. 3 difference frequency short-circuit circuits are arranged outside the package 10. Specifically, the inductor 41a and the capacitor 41b connected to the package terminal T1 are a first difference frequency short circuit, the inductor 42a and the capacitor 42b connected to the package terminal T1 are a second difference frequency short circuit, and the inductor 43a and the capacitor 43b connected to the package terminal T1 are a third difference frequency short circuit. The inductors 41a, 42a, 43a may be used as λ/4 lines. The capacitors 41b, 42b, and 43b have capacitances C1, C2, and C3 that are in series resonance with the inductors 41a, 42a, and 43a at difference frequencies Δ f1, Δ f2, and Δ f3, respectively. The configuration inside the package 10 is the same as the circuit configuration shown in fig. 2.

At this time, the following relationship is provided among the inductor, the capacitor, and the resonance frequency.

L1×C1＝1/(2πΔf1)²

L1×C2＝1/(2πΔf2)²

L1×C3＝1/(2πΔf3)²

Fig. 6 is a diagram showing an example of the difference frequency impedance of the output circuit in the microwave power amplifier of comparative example 2. In fig. 6, similarly to fig. 3, the impedance of the output circuit side as viewed from the transistor end of 1MHz to 1GHz is shown in logarithmic representation on two axes. In this example of the circuit configuration, by appropriately setting L1 and C1, C2, and C3, resonance points are created at 3 positions of 5MHz, 30MHz, and 100MHz, and the impedances in the vicinity of 5MHz, 30MHz, and 100MHz are lowered compared to the impedance at the peripheral frequency. As a result, the impedance at 200MHz was 150 Ω, which was lower than the impedance shown in fig. 3. Thus, the impedance of 100MHz order is lower than that of the value at the peripheral frequency even in the vicinity of the resonance frequency, but the absolute value cannot be lowered to the value of 1MHz order. This is because a transmission line exists at a connection point from a transistor terminal to the difference frequency short circuit, and therefore a reflection phase generated in the transmission line cannot be ignored for a frequency of the order of 100MHz, and an ideal short circuit point cannot be formed. On the other hand, for frequencies of the order of 1MHz, the electrical length from the transistor terminal to the connection point of the difference frequency short circuit appears to be short enough to be negligible, and a substantially ideal short circuit point can be formed.

Fig. 7 is a diagram showing an example of a simulation result of IM3 in the microwave power amplifier of comparative example 2 shown in fig. 5. In the same manner as in fig. 4, the simulation example calculates the relationship between the output power of the microwave amplifier and IM3 when a 2-wave input signal having a detuned frequency of 200MHz is input to the transistor. It can be seen in FIG. 7 that the worst value of IM3 at an output power of 44dBm is-17 dBc. The result of fig. 7 can therefore be said to be an improvement of 2dB over the worst value of IM3 shown in fig. 4, but the amount of improvement is not said to be sufficient because the reduction in difference frequency impedance is insufficient.

Comparative example 3

Next, in order to solve the above problem, it is considered that the differential frequency short circuit is directly connected to the drain terminal of the transistor, and a transmission line from the transistor terminal to the connection point of the differential frequency short circuit is shortened as much as possible. However, there is no space between the transistor chip on which the transistor is arranged and the substrate S on which the transmission line is patterned, for arranging only the capacitor and grounding it, and therefore it is impossible to connect a difference frequency short circuit to the drain terminals of all the unit transistors. Even if a sufficient space is secured, if the differential frequency short circuit is connected to the drain terminals of all the unit transistors, the circuit area and the package size are increased, and the cost of manufacturing the components is increased. The difference frequency short circuit is thus connected only to the drain terminals of the transistors Tr1, Tr4 near the side wall portion of the package 10. Therefore, in the known microwave power amplifier, as comparative example 3, a circuit configuration when a difference frequency short circuit is arranged at the drain terminals of the transistors Tr1 and Tr4 near the side wall of the package 10, and a difference frequency impedance of an output circuit thereof are considered.

Fig. 8 is a circuit diagram of a microwave power amplifier of comparative example 3. A difference frequency short circuit having an inductor 51a and a capacitor 51b, and a difference frequency short circuit having an inductor 52a and a capacitor 52b are arranged in the package 10. A difference frequency short circuit having an inductor 51a and a capacitor 51b is connected to the drain terminal of the transistor Tr1 near the side wall portion of the package 10. The difference frequency short circuit having the inductor 52a and the capacitor 52b is connected to the drain terminal of the transistor Tr4 near the side wall portion of the package 10. A difference frequency short circuit including an inductor 31a and a capacitor 31b having a capacitance of C3 is disposed outside the package 10. The circuit configuration is the same as that shown in fig. 2 except for the difference frequency short-circuit.

Fig. 9 is a diagram showing an example of the difference frequency impedance of the output circuit in the microwave power amplifier of comparative example 3. In fig. 9, similarly to fig. 3, impedance of the output circuit side as viewed from the transistor end of 1MHz to 1GHz is shown in logarithmic representation with two axes. The dotted line represents the impedance viewed from the unit transistor near the side wall of the package, and the solid line represents the impedance viewed from the unit transistor near the center of the package. In the same manner as in fig. 6, resonance points were created at 3 positions of 5MHz, 30MHz, and 100MHz, and the impedance in the vicinity of 5MHz, 30MHz, and 100MHz was lowered as compared with the value at the peripheral frequency. As a result, the impedance at 200MHz is 20 Ω when viewed from the unit transistor near the package sidewall, and is significantly lower than the impedance shown in fig. 3. On the other hand, however, the impedance in 200MHz is 40 Ω when viewed from the unit transistor near the center of the package. It is also known that the impedance from the second half of 10MHz to the 100MHz is different depending on the unit transistor. This is because the reflection phase generated in the transmission line from the transistor end to the connection point of the difference frequency short circuit cannot be ignored in the unit transistor near the center of the package.

(example of embodiment mode 1)

In order to compare with the above 3 comparative examples, the difference frequency impedance of the output circuit in embodiment 1 and IM3 were considered. In embodiment 1, the difference frequency short circuit 31 having a resonant frequency so small that the reflection phase can be ignored is disposed outside the package 10, and the difference frequency short circuits 11, 12, and 21 having a resonant frequency that the reflection phase cannot be ignored are disposed inside the package 10. For example, the resonant frequency of the order of 1MHz is a resonant frequency of which the reflection phase can be ignored, and the resonant frequency of the order of 10 to 100MHz is a resonant frequency of which the reflection phase cannot be ignored. According to an example, the difference frequency short circuit having the resonance frequency equal to or higher than the predetermined specific resonance frequency can be mounted on the package 10, and the difference frequency short circuit having the resonance frequency lower than the specific resonance frequency can be provided outside the package 10. Such a specific resonance frequency is for example 10 MHz. .

In the example of fig. 1, the difference frequency short circuit 11, 12 having the largest resonance frequency among the plurality of difference frequency short circuits is disposed at the position closest to the transistors Tr1, Tr2, Tr3, Tr4, the difference frequency short circuit 21 having the larger resonance frequency is disposed at the position farther from the transistors Tr1, Tr2, Tr3, Tr4 than the difference frequency short circuit 11, 12, and the difference frequency short circuit 31 having the smallest resonance frequency is disposed at the position farthest from the transistors Tr1, Tr2, Tr3, Tr4. Thus, the resonance frequencies of the differential short-circuit circuits 11, 12, 21, and 31 are smaller as the transistors Tr1, Tr2, Tr3, and Tr4 are farther away.

In all of the transistors Tr1, Tr2, Tr3, and Tr4, the difference frequency short circuit arranged at the position closest to the transistors Tr1, Tr2, Tr3, and Tr4 is arranged at or after the point where the two transmission lines connected to the two transistors are combined, so that the impedance of the output circuit viewed from the transistors is uniform. The uniform impedance includes not only the case where the impedances are completely uniform but also the case where the impedances are substantially the same.

As a result, a difference frequency short circuit having the same resonance frequency is connected to a plurality of nodes at the same stage among the plurality of nodes of the race circuit. Specifically, the difference frequency short circuits 11 and 12 having the same resonance frequency are connected to the combining points a1 and a2 of the nodes of the race circuit, respectively. In this case, the connection point of the difference frequency short circuit can be as close as possible to the combining point of the transmission line so as to minimize the influence of the reflection phase.

Fig. 10 is a diagram showing an example of the difference frequency impedance of the output circuit in the power amplifier of embodiment 1. In fig. 10, similarly to fig. 3, impedance of the output circuit side as viewed from the transistor end in the range from 1MHz to 1GHz is shown in logarithmic representation with two axes. In this circuit configuration example, the difference frequency short-circuit circuits are connected in this order, whereby an ideal short-circuit point can be formed in all the arranged difference frequency short-circuit circuits. As a result, it was found that the impedance at the vicinity of 3 positions of 5MHz, 30MHz, and 100MHz, which create the resonance point, can be reduced to approximately the same level. In this case, the impedance value is equal regardless of the transistor. As a result, the impedance at 200MHz is reduced to 20 Ω compared to the impedance shown in fig. 3.

Fig. 11 is a diagram showing an example of simulation results of the IM3 having the configuration of embodiment 1. In the simulation example, similarly to fig. 4, the relationship between the output power of the microwave amplifier and IM3 when a 2-wave input signal having a detuning frequency of 200MHz is input to the transistor was calculated. In FIG. 11, it can be seen that the worst value of IM3 is-23 dBc at an output power of 44 dBm. This value is an improvement of around 8dB over the worst value of IM3 shown in fig. 4.

As described above, according to the configuration of embodiment 1, since the impedance of the output circuit viewed from the connection side can be equally reduced for all the transistors from Δ f1 to Δ f3, the distorted voltage component generated at the detuned frequency can be continuously suppressed in the frequency band from Δ f1 to Δ f 3. As a result, when a desired detuning frequency is increased in a layout of actual elements that avoids an increase in size, deterioration of distortion characteristics can be prevented from the minimum detuning frequency to the maximum detuning frequency.

The transmission line connected between the transistor terminal and the package terminal T1 and the inductor as the λ/4 line are patterned on the same substrate, whereby the number of components can be reduced.

The power amplifier of embodiment 1 can be variously modified within a range in which the characteristics thereof are not lost. For example, in embodiment 1, 3 difference frequency short-circuit circuits are arranged in the package 10, but the number thereof can be increased or decreased while considering the restriction of the component mounting region in the package 10. Fig. 12 is a circuit diagram of a power amplifier according to a modification. In this example, the difference frequency short-circuit circuits 11 and 12 are connected to the combining points a1 and a2 closest to the transmission lines of the transistors, and the difference frequency short-circuit is not connected to the combining point B1. Two difference frequency short circuits 11, 12 are present in the package 10. The capacitances of the capacitor 11b and the capacitor 12b are C1.

A difference frequency short circuit 31 is provided outside the package 10. The capacitance of the capacitor 31b is C3. When the resonance frequency of the difference frequency short-circuit circuits 11 and 12 provided in the package 10 is Δ f1 and the resonance frequency of the difference frequency short-circuit 31 provided outside the package 10 is Δ f3, Δ f3 < Δ f1, that is, C1 < C3, is satisfied.

When a difference frequency short circuit is connected to a certain combining point and a difference frequency short circuit is not connected to the other combining points, the power amplifier can be miniaturized.

Fig. 1 is a circuit diagram of a power amplifier circuit according to another modification. The power amplifier circuit includes complementary difference frequency short-circuiting circuits 61 and 62. The complementary difference frequency short-circuit 61 is a series LC circuit connected in shunt to a combining point a1 which is a node connected in shunt to the difference frequency short-circuit 11. The complementary difference-frequency short-circuit 61 includes an inductor 61a and a capacitor 61 b. The complementary difference frequency short-circuit 62 is a series LC circuit connected in shunt to a combining point a2, which is a node connected in shunt to the difference frequency short-circuit 12. The complementary difference-frequency short-circuit 62 includes an inductor 62a and a capacitor 62 b.

A plurality of difference frequency short circuits can be connected at such a combining point. In the configuration of fig. 13, the resonance frequencies of the plurality of difference frequency short-circuit circuits 11, 61, 12, 62, 31 become smaller as they become farther from the plurality of transistors Tr1, Tr2, Tr3, Tr4. However, the difference frequency short circuit 11 and the complementary difference frequency short circuit 61 connected to the same combining point may have the same resonance frequency or different resonance frequencies. The difference frequency short circuit 12 and the complementary difference frequency short circuit 62 connected to the same combining point may have the same resonance frequency or different resonance frequencies. The resonance frequency of the complementary difference frequency short circuits 61, 62 is higher than the resonance frequency of the difference frequency short circuit 31 which is far from the plurality of transistors than the complementary difference frequency short circuits 61, 62.

Fig. 14 is a circuit diagram of a power amplifier circuit according to another modification. The power amplifier circuit in fig. 14 is a circuit in which the drain bias application terminals Vd2 and Vd1 are applied to the power amplifier circuit in fig. 13, and the terminal T3 is removed. The drain bias application terminal Vd2 is a terminal for applying a drain bias to at least two of the plurality of amplification elements via the inductor 61a of the complementary difference short circuit 61 and the inductor 11a of the difference short circuit 11 connected to the same node as the complementary difference short circuit 61. The drain bias applying terminal Vd1 is a terminal for applying a drain bias to at least two of the plurality of amplification elements via the inductor 62a of the complementary difference frequency short circuit 62 and the inductor 12a of the difference frequency short circuit 12 connected to the same node as the complementary difference frequency short circuit 62.

Thus, the λ/4 line in the package can be effectively used as a path for applying drain bias. Since a current can be caused to flow in the parallel circuit including the inductor 61a and the inductor 11a by the drain bias application terminal Vd2, the allowable amount of the drain current can be increased. Since a current can flow through the parallel circuit including the inductor 62a and the inductor 12a via the drain bias application terminal Vd1, the allowable amount of the drain current can be increased.

For example, even in a configuration without the complementary difference frequency short circuit shown in fig. 12, a drain bias application terminal connected to an inductor of the difference frequency short circuit may be provided. In this case, the drain bias can be applied to at least two of the plurality of amplification elements from the drain bias application terminal via the inductor of the difference frequency short-circuit.

Fig. 15 is a circuit diagram of a power amplifier circuit according to another modification. The power amplifier circuit in fig. 15 is a circuit in which open stubs OS1, OS2, and OS3 are added to the power amplifier circuit in fig. 1. The open stub OS1 is a λ/4 line having one end connected between the inductor 11a and the capacitor 11 b. The open stub OS2 is a λ/4 line having one end connected between the inductor 12a and the capacitor 12 b. The open stub OS3 is a λ/4 line having one end connected between the inductor 21a and the capacitor 21 b. The λ/4 line is an 1/4 wavelength line of the fundamental frequency of the operating frequency of the power amplifier.

By arranging the open stubs OS1, OS2, and OS3, an ideal short-circuit point is formed at the base of the open stub in the operating frequency of the amplifier, and therefore the connected difference frequency processing circuit can be seen more open. This reduces the influence of impedance mismatch at the operating frequency due to the connection of the difference frequency processing circuit, thereby suppressing deterioration of the basic characteristics.

In all of the power amplifiers described above, it is possible to determine whether to connect several difference frequency short-circuit circuits to one node or to dispose the difference frequency short-circuit circuits inside or outside the package, while taking into consideration the restrictions on the component mounting area. In the above example, at least one inductor and at least one transmission line are formed on the substrate S as the microwave integrated circuit substrate, but all circuits including the inductor, the transmission line, and the transistor may be formed by MMIC.

In the above embodiment, all the inductors constituting the difference frequency short circuit are λ/4 lines having an inductance L1, but the inductors do not necessarily need to be λ/4 lines, and it is not necessary to unify inductances in all the difference frequency short circuit. The characteristics of the inductor and the capacitor may be set so that the product of the capacitance and the inductance of the difference frequency short circuit becomes a desired value. The power amplifier described above may be provided as a high-frequency power amplifier that amplifies high-frequency signals such as microwaves and millimeter waves.

The modification mentioned in embodiment 1 can also be applied to the power amplifier of the following embodiment.

Embodiment 2.

Fig. 16 is a circuit diagram of a power amplifier according to embodiment 2. This power amplifier applies the technical features described in embodiment 1 to the gate sides of the transistors Tr1, Tr2, Tr3, Tr4. The power amplifier of embodiment 2 can be obtained by inverting the input/output with respect to the transistor in the structure described in embodiment 1. The race circuit according to embodiment 2 is a race distribution circuit having transmission lines TL1, TL2, TL3, TL4, TL5, TL6, TL7, and TL8, and distributing input signals to a plurality of amplification elements. The race type synthesizing circuit described in embodiment 1 can be connected to the output sides of the transistors Tr1, Tr2, Tr3, and Tr4. The terminal T2 in embodiment 2 functions as an input terminal, and the terminal T3 functions as a gate voltage application terminal of a transistor. The various technical features described in embodiment 1 can also be implemented in a circuit on the input side of a transistor.

According to the configuration of embodiment 2, by providing the difference frequency short circuit described in embodiment 1 on the input side of the transistor, the impedance of the input circuit as viewed from the transistor connection side can be reduced equally for all the transistors from Δ f1 to Δ f 3. Therefore, the distorted voltage component generated at the detuned frequency can be continuously suppressed for the frequency bands from Δ f1 to Δ f 3. Thus, even when the detuning frequency is widened, deterioration of distortion characteristics can be prevented from the minimum detuning frequency to the maximum detuning frequency.

Fig. 17 is a circuit diagram of a power amplifier according to a modification. The difference frequency short circuit of the power amplifier includes a resistor connected in series with an inductor or a capacitor. Specifically, the difference frequency short circuit 11 includes a resistor R1, the difference frequency short circuit 12 includes a resistor R1, and the difference frequency short circuit 21 includes a resistor R2. Resistor R1 of difference frequency short-circuit 11 is connected between inductor 11a and capacitor 11b, but may be provided at another position as long as it is connected in series with inductor 11a or capacitor 11 b. Resistor R1 of difference frequency short-circuit 12 is connected between inductor 12a and capacitor 12b, but may be provided at other positions as long as it is connected in series with inductor 12a or capacitor 12 b. Resistor R2 of difference frequency short-circuit 21 is connected between inductor 21a and capacitor 21b, and may be provided at another position as long as it is connected in series with inductor 21a or capacitor 21 b. The resistors R1 and R2 can suppress unnecessary oscillation.

The features of embodiments 1 and 2 described above can be combined.

Description of the reference numerals

Tr1, Tr2, Tr3, tr4.. transistors; TL1, TL2, TL3, TL4, TL5, TL6, TL7, tl8.. transmission lines; 11. 12, 21, 31.