JP2024064526A - Power Amplifiers - Google Patents

Abstract

[Problem] To provide a power amplifier capable of improving efficiency. [Solution] In a power amplifier 6, an amplifier section 16 amplifies an input signal and outputs the amplified output signal from an output terminal T2. A matching circuit (fundamental wave matching circuit 22) is connected to the output terminal T2. An output signal that has passed through the matching circuit is supplied to one end of a transmission line 24, and the transmission line 24 has a predetermined characteristic impedance. A filter 26 passes the fundamental wave contained in the output signal output from the other end of the transmission line 24, and reflects the harmonics contained in the output signal. The length of the transmission line 24 is determined so that the predetermined harmonics contained in the output signal output from the output terminal T2 are returned to the output terminal T2 with a predetermined phase. [Selected Figure] Figure 2

Description

This disclosure relates to a power amplifier that amplifies high-frequency signals.

In recent years, wireless communication systems and wireless power transmission systems have been developed. These technologies use power amplifiers that amplify the power of high-frequency signals and output the amplified signals to a load (see, for example, Patent Document 1).

JP 2000-165163 A

In order to increase the efficiency of high-frequency power amplifiers, a technique is known in which a harmonic reflection circuit is connected after the output terminal of the transistor of the power amplifier. The harmonic reflection circuit reflects harmonics contained in the output signal. For example, in the case of class F operation, the harmonic reflection circuit is designed so that the output terminal of the transistor is short-circuited for even harmonics and open for odd harmonics. This reduces power consumption in the transistor and increases efficiency. However, because the harmonic reflection circuit has losses at the fundamental frequency, the output power and efficiency are reduced compared to the ideal state where no losses are assumed.

This disclosure has been made in light of these problems, and one of its exemplary objectives is to provide a power amplifier that can improve efficiency.

In order to solve the above problems, a power amplifier according to one embodiment of the present disclosure includes an amplifier section that amplifies an input signal and outputs the amplified output signal from an output terminal, a matching circuit connected to the output terminal, a transmission line having a predetermined characteristic impedance, one end of which is supplied with the output signal that has passed through the matching circuit, and a filter that passes the fundamental wave contained in the output signal output from the other end of the transmission line and reflects the harmonics contained in the output signal. The length of the transmission line is determined so that the predetermined harmonics contained in the output signal output from the output terminal are returned to the output terminal with a predetermined phase.

Another aspect of the present disclosure is also a power amplifier. This power amplifier includes an amplifier section that amplifies an input signal and outputs an amplified output signal from an output terminal, an inductive element having one end to which a power supply voltage is supplied and the other end connected to the output terminal, a transmission line having a predetermined characteristic impedance and one end connected to the output terminal, and a filter that passes a fundamental wave included in the output signal output from the other end of the transmission line and reflects harmonics included in the output signal. The power supply voltage is set so that the reciprocal of the real part of the optimal load admittance of the amplifier section that has the predetermined output characteristic is substantially equal to the characteristic impedance. At the frequency of the input signal, the imaginary part of the admittance of the inductive element is substantially equal to the imaginary part of the optimal load admittance. The length of the transmission line is determined so that a predetermined harmonic included in the output signal output from the output terminal is returned to the output terminal with a predetermined phase.

In addition, any combination of the above components, or mutual substitution of the components or expressions of this disclosure between methods, systems, etc., are also valid aspects of this disclosure.

This disclosure provides a power amplifier that can improve efficiency.

FIG. 2 is a circuit diagram of a wireless device of a first comparative example. 1 is a circuit diagram of a wireless device according to a first embodiment; 3 is a diagram showing high-frequency characteristics of the power amplifier of FIG. 2 and the power amplifier of FIG. 1 . FIG. 11 is a circuit diagram of a wireless device of a second comparative example. FIG. 11 is a circuit diagram of a wireless device according to a second embodiment.

The inventors have studied power amplifiers used in wireless devices and have obtained the following findings. FIG. 1 is a circuit diagram of a wireless device 100 of a first comparative example. The wireless device 100 includes a DC power supply 2, a signal source 4, a power amplifier 106, and an antenna 8. The power amplifier 106 includes a power amplifier circuit 110 and a filter 126. The power amplifier circuit 110 includes an input matching circuit 114, an inductor (choke coil) 118, a transistor 120, a fundamental matching circuit 122, and a harmonic reflection circuit 124.

The DC power supply 2 supplies a power supply voltage to the drain of the transistor 120 via the inductor 118. The inductor 118 is an inductor for supplying a bias voltage, and its inductance is set so as to provide a sufficiently high impedance at the frequency of the input signal.

The input matching circuit 114 performs impedance conversion between the signal source impedance _ZS of the signal source 4 and the input impedance of the transistor 120. The signal source impedance _ZS is equal to the characteristic impedance _Z0 , and is, for example, 50Ω.

Transistor 120 amplifies the power of an input signal supplied to its gate from signal source 4 via input matching circuit 114, and outputs the amplified signal from its drain to fundamental matching circuit 122. The input signal is a high-frequency signal, and its frequency is, for example, 1 GHz or higher. The power of the output signal from transistor 120 is, for example, 500 mW or higher. Therefore, transistor 120 performs large signal operation.

In large signal operation of the transistor 120, output characteristics such as output power and efficiency change depending on the impedance connected to the drain, even if other conditions are constant. For example, the impedance that provides maximum output power and maximum efficiency when an input signal of a specified input power and a specified input frequency is supplied is called the optimum load impedance Z _opt .

The fundamental wave matching circuit 122 performs impedance conversion between the optimum load impedance Z _opt and the characteristic impedance Z ₀ at the frequency of the fundamental wave. In other words, the fundamental wave matching circuit 122 converts the characteristic impedance Z ₀ to the optimum load impedance Z _opt at the frequency of the fundamental wave. This allows the drain of the transistor 120 to see the optimum load impedance Z _opt at the frequency of the fundamental wave, and the transistor 120 can output an optimum output under predetermined conditions. The output signal output from the transistor 120 is supplied to the harmonic reflection circuit 124 via the fundamental wave matching circuit 122.

The harmonic reflection circuit 124 passes the fundamental wave contained in the output signal that has passed through the fundamental matching circuit 122, and reflects the harmonics. As described above, the harmonic reflection circuit 124 is designed to be short-circuited for even harmonics and open for odd harmonics at the output terminal of the transistor 120, for example, in the case of class F operation. In general, the harmonic reflection circuit 124 mainly reflects second and third harmonics. However, in the harmonic reflection circuit 124, it may be difficult to suppress the second and third harmonics to the unnecessary radiation level generally specified by law. In addition, higher harmonics are not sufficiently reflected by the harmonic reflection circuit 124, and therefore are not sufficiently suppressed in the output signal of the harmonic reflection circuit 124. Therefore, in order to prevent unnecessary waves such as harmonics from being radiated from the antenna 8, a filter 126 for suppressing harmonics is provided, and the output signal that has passed through the harmonic reflection circuit 124 is supplied to the filter 126.

The filter 126 is, for example, a low-pass filter or a band-pass filter, and passes the fundamental wave of the passband and suppresses signals outside the passband. The filter 126 suppresses signals outside the passband by reflecting them. The output signal that has passed through the filter 126 is supplied to the antenna 8. The antenna 8 radiates the output signal supplied from the filter 126.

At the fundamental frequency, the input impedance of each of the filter 126 and the antenna 8 is a characteristic impedance _Z0 .

Here, for example, in a frequency band of 1 GHz or more, the harmonic reflection circuit 124 is often configured using a distributed constant line. In general, the loss of the harmonic reflection circuit 124 at the fundamental frequency is about 0.2 dB or more. If the power of the fundamental wave decreases by 0.2 dB, the drain efficiency decreases by about 4.7%. In addition, using the harmonic reflection circuit 124 complicates the circuit configuration, which increases the size of the power amplifier circuit 110.

The inventor conducted extensive research based on these findings and discovered that by connecting the fundamental matching circuit 122 and the filter 126 with a transmission line and appropriately setting the length of the transmission line, the phase of the reflected harmonics can be appropriately set at the output terminal of the transistor 120, the harmonic reflection circuit 124 can be eliminated, and efficiency can be improved. The embodiment was devised based on these thoughts, and its specific configuration is described below.

Below, the embodiments for implementing the present disclosure will be described in detail with reference to the drawings. Note that in the description, the same elements are given the same reference numerals, and duplicate descriptions will be omitted as appropriate.

(First embodiment)
2 is a circuit diagram of the wireless device 1 according to the first embodiment. The wireless device 1 can be used in, for example, a wireless communication system or a wireless power transmission system. The wireless device 1 includes a DC power supply 2, a signal source 4, a power amplifier 6, and an antenna 8.

The power amplifier 6 amplifies the power of the input signal supplied from the signal source 4 and supplies the amplified signal to the antenna 8. Other high-frequency components such as a switch may be provided between the power amplifier 6 and the antenna 8. An example of the range of the frequency of the input signal and the power of the output signal is the same as in the first comparative example. The DC power supply 2 supplies a DC power supply voltage to the power amplifier 6.

The power amplifier 6 has a power amplifier circuit 10, a transmission line 24, and a filter 26. The power amplifier circuit 10 has an input matching circuit 14, an amplifier section 16, an inductive element 18, and a fundamental wave matching circuit 22. The power amplifier circuit 10 can also be called a power amplifier.

The input matching circuit 14 performs impedance conversion between the signal source impedance _Zs of the signal source 4 and the input impedance of the amplifier section 16 .

The amplifier 16 has a control terminal T1, an output terminal T2, and a ground terminal T3, and amplifies the power of an input signal supplied to the control terminal T1 via the input matching circuit 14, and outputs the amplified output signal from the output terminal T2. The ground terminal T3 is grounded.

The amplifier unit 16 includes a transistor 20 that uses, for example, a compound semiconductor as a semiconductor material. As an example, the transistor 20 is a field effect transistor. In the amplifier unit 16, the control terminal T1 is the gate of the transistor 20, the output terminal T2 is the drain, and the ground terminal T3 is the source.

The inductive element 18 is an inductor that functions as a choke coil, and has one end to which a power supply voltage is supplied from the DC power supply 2 and the other end connected to the output terminal T2 of the amplifier unit 16. One end of the inductive element 18 is AC grounded at the frequency of the input signal by a capacitor (not shown) or the like. The inductive element 18 functions as an inductor for supplying a bias voltage. The inductive element 18 may be a transmission line such as a high-frequency short stub.
A bias voltage is also supplied to the control terminal T1 of the amplifier 16 from a bias circuit (not shown).

The fundamental wave matching circuit 22 is connected to the output terminal T2 of the amplifier section 16, and performs impedance conversion between the optimum load impedance Z _opt and the characteristic impedance Z ₀ at the frequency of the fundamental wave contained in the output signal of the amplifier section 16.

The transmission line 24 has a characteristic impedance Z ₀ , and the output signal that has passed through the fundamental wave matching circuit 22 is supplied to one end thereof, and the other end thereof is connected to the filter 26 .

The filter 26 is connected to the other end of the transmission line 24, and passes a fundamental wave included in the output signal output from the other end of the transmission line 24, and reflects higher harmonics included in the output signal. The filter 26 has an input impedance equivalent to a characteristic impedance _Z0 at the frequency of the fundamental wave. In the filter 26, the reflection coefficient is 1 or close to 1 in a frequency band outside the passband. The output signal that has passed through the filter 26 is supplied to the antenna 8. A known high-frequency filter can be used as the filter 26.

As such, unlike the first comparative example, the fundamental wave matching circuit 22 and the filter 26 are directly connected by the transmission line 24, and no harmonic reflection circuit is provided between the output terminal T2 of the amplifier 16 and the filter 26. The harmonics reflected by the filter 26 return to the output terminal T2 via the transmission line 24 and the fundamental wave matching circuit 22.

When the length of the transmission line 24 is changed, for example, the phases of the second and third harmonics change in a ratio of 2:3. The length of the transmission line 24 is determined in advance so that a predetermined harmonic contained in the output signal output from the output terminal T2 of the amplifier 16 is returned to the output terminal T2 with a predetermined phase. The predetermined phase is, for example, substantially in phase or substantially out of phase. The length of the transmission line 24 is determined in advance so as to suppress a predetermined harmonic contained in the voltage waveform or current waveform of the output signal output from the output terminal T2 of the amplifier 16. By suppressing the harmonics, the overlap between the current waveform flowing from the output terminal T2 to the transistor 20 and the voltage waveform generated at the output terminal T2 is reduced, i.e., the power consumption of the transistor 20 is reduced.

For example, the length of the transmission line 24 is determined so that the impedance when looking from the output terminal T2 towards the filter 26 is substantially zero with respect to a predetermined even-order harmonic contained in the output signal. In other words, the output terminal T2 is substantially short-circuited with respect to the predetermined even-order harmonic. This suppresses the predetermined even-order harmonic contained in the voltage waveform of the output signal. An impedance that is substantially zero means that the impedance is low enough to obtain an efficiency equal to or greater than a predetermined value. The predetermined even-order harmonic is, for example, a second harmonic. By suppressing the relatively large second harmonic, it is easier to increase efficiency. There may be multiple predetermined even-order harmonics.

Instead of determining the length of the transmission line 24 with respect to the even harmonics, the length of the transmission line 24 may be determined so that the impedance when looking from the output terminal T2 toward the filter 26 is substantially infinite with respect to the predetermined odd harmonics contained in the output signal. In other words, the output terminal T2 may be substantially open with respect to the predetermined odd harmonics. This suppresses the predetermined odd harmonics contained in the current waveform of the output signal. The impedance being substantially infinite means that the impedance is high enough to obtain an efficiency equal to or greater than a predetermined value. The predetermined odd harmonic is, for example, a third harmonic. By suppressing the relatively large third harmonic, it is easy to increase efficiency. The predetermined odd harmonics may be multiple.

These may also be combined. That is, the length of the transmission line 24 may be determined so that the impedance seen from the output terminal T2 toward the filter 26 is substantially zero for a predetermined even-order harmonic contained in the output signal, and is substantially infinite for a predetermined odd-order harmonic contained in the output signal. Furthermore, the output terminal T2 may be substantially short-circuited for a predetermined odd-order harmonic, and substantially open for a predetermined even-order harmonic.

In this way, the length of the transmission line 24 is determined so that a predetermined level of efficiency or higher is obtained. The optimal value for the length of the transmission line 24 can be determined as appropriate through experiments or simulations.

Next, the results of simulations in the comparative example configuration of FIG. 1 and the configuration of FIG. 2 will be described. In the simulation, the phases of the second harmonic and the third harmonic are independently optimized using the harmonic reflection circuit 124 in the comparative example configuration of FIG. 1. In the configuration of FIG. 1 and the configuration of FIG. 2, a common simulation model is used for the transistors 20 and 120, and a common simulation model is used for the filters 26 and 126. A commercially available filter model is used as the simulation model for the filters 26 and 126. The characteristic impedance _Z0 is 50Ω. The frequency of the fundamental wave is 5.8 GHz. In the configuration of FIG. 2, the length of the transmission line 24 is 3.5 mm, and its electrical length at 5.8 GHz is 40°. The characteristics obtained at the output of the filters 26 and 126 will be described below.

Figure 3 shows the high frequency characteristics of the power amplifier 6 in Figure 2 and the power amplifier 106 in Figure 1. Figure 3(a) shows the input power dependence of the output power, gain, drain efficiency, and power added efficiency of the power amplifier 6 in Figure 2. When the input power rfin is 30 dBm, the gain Gain is 11.268 dB, the output power Pout is 41.268 dBm, the power added efficiency PAE is 65.245%, and the drain efficiency Pdf is 70.511%.

Figure 3(b) shows the input power dependence of the output power, gain, drain efficiency, and power added efficiency of the power amplifier 106 of the first comparative example in Figure 1. When the input power rfin is 30 dBm, the gain Gain is 11.234 dB, the output power Pout is 41.234 dBm, the power added efficiency PAE is 65.577%, and the drain efficiency Pdf is 70.914%.

In the characteristics of FIG. 3(b), the loss of the fundamental wave in the harmonic reflection circuit 124 is ignored. If we assume that the loss of the fundamental wave in the harmonic reflection circuit 124 is 0.2 dB, the drain efficiency taking this loss into account is 70.914-4.7 ≒ 66.2%. Compared to the characteristics of the first comparative example taking into account the loss of the harmonic reflection circuit 124, in this embodiment, the gain increases by approximately 0.2 dB and the drain efficiency improves by approximately 4.3%.

According to the embodiment, the phase of the harmonics reflected by the filter 26 at the output terminal T2 can be adjusted according to the length of the transmission line 24, so that the impedance to the harmonics when viewed from the output terminal T2 toward the filter 26 can be set to substantially zero or substantially infinity. Therefore, the efficiency of the power amplifier 6 can be increased without providing a high-frequency reflection circuit. Because no high-frequency reflection circuit is provided, losses can be reduced more than in the first comparative example.

In addition, the line length of the transmission line 24 in the embodiment is a maximum electrical length of 180 degrees. On the other hand, the harmonic reflection circuit 124 in the first comparative example is generally configured by combining multiple transmission lines with an electrical length of 90 degrees. Therefore, the transmission line 24 can be realized with an area smaller than the area of the harmonic reflection circuit 124. Therefore, the size of the power amplifier 6 can be made smaller than that of the first comparative example.

In addition, in the first comparative example, the harmonic reflection circuit affects the impedance of the fundamental wave, making it difficult to design the fundamental wave matching circuit and the harmonic reflection circuit independently, but in this embodiment, such design difficulties can be avoided.

(Second Comparative Example)
Here, a second comparative example will be described in which a harmonic reflection circuit 124 is combined with the power amplifier invented by the present inventor and described in JP 2021-118482 A.

4 is a circuit diagram of a wireless device 100A of a second comparative example. In the second comparative example, as described in JP 2021-118482 A, the power supply voltage supplied from the DC power supply 2 is increased to increase the optimal load resistance R _opt , and the value of the inductor 118 is appropriately set to cancel the capacitance on the output side of the transistor 120 and eliminate the fundamental wave matching circuit. A harmonic reflection circuit 124 is directly connected to the drain of the transistor 120.

This configuration has the advantage over the first comparative example that a fundamental matching circuit is not required. However, in the second comparative example, as in the first comparative example, the use of the harmonic reflection circuit 124 causes losses at the fundamental frequency, complicates the circuit configuration, and increases the size of the power amplifier 106.

Therefore, even in the power amplifier 106 that does not have a fundamental wave matching circuit, the phase of the harmonics reflected by the filter 126 is adjusted by the length of the transmission line without using the harmonic reflection circuit 124. The specific configuration is described below.

Second Embodiment
Fig. 5 is a circuit diagram of a wireless device 1A according to the second embodiment. As shown in Fig. 5, the second embodiment differs from the first embodiment in that a fundamental wave matching circuit is not provided. The following description will focus on the differences from the first embodiment.

A filter 26 is directly connected to an output terminal T2 of the amplifier section 16 of the power amplifier circuit 10A via a transmission line 24 having a predetermined characteristic impedance _Z0 . In other words, there is no output matching circuit or harmonic reflection circuit between the output terminal T2 and the filter 26. The characteristic impedance _Z0 is substantially equal to the optimum load resistance _Ropt . The filter 26 has an input impedance equivalent to the optimum load resistance _Ropt at the frequency of the fundamental wave. The characteristic impedance _Z0 is generally 50Ω, but may be another value, for example, 10Ω to 100Ω.

An example of a compound semiconductor used for the transistor 20 of the amplifier section 16 is a nitride semiconductor such as gallium nitride (GaN). The transistor 20 is preferably a high electron mobility transistor using gallium nitride, i.e., a GaN-HEMT (High Electron Mobility Transistor).

The inductive element 18 is an inductor with an inductance L1, which is smaller than that of the first embodiment. Details of the inductance L1 will be described later.

The optimum load admittance Y _opt (=1/Z _opt ) at which the output characteristic of the amplifier unit 16 becomes a predetermined characteristic is the admittance seen from the output terminal T2 of the amplifier unit 16 to the filter 26 side. The output characteristic becoming a predetermined characteristic means, for example, that the output power is maximized, the drain efficiency or the power added efficiency is maximized, etc.

The optimum load is inductive and is represented by a parallel connection of an optimum load resistor R _opt and an inductor L _opt . Therefore, the optimum load admittance Y _opt can be expressed by the following equation (1).
Y _opt =1/R _opt +1/jωL _opt (1)

When the power supply voltage is increased while keeping the output power constant, the optimum load resistance R _opt increases, so that when the power supply voltage is increased, the optimum load admittance Y _opt moves on the admittance chart in the direction of lower conductance.

The power supply voltage is set in advance so that the reciprocal of the real part of the optimum load admittance Y _opt , that is, the optimum load resistance R _opt , is substantially equal to a predetermined characteristic impedance Z _0. When the reciprocal of the real part of the optimum load admittance Y _opt is in the range of −10% to 20% of the characteristic impedance Z ₀ , the reciprocal of the real part of the optimum load admittance Y _opt is said to be substantially equal to the characteristic impedance Z _0. It is preferable that the reciprocal of the real part of the optimum load admittance Y _opt is set within the range of ±5% of the characteristic impedance Z ₀ , and it is preferable that the difference between the reciprocal of the real part of the optimum load admittance Y _opt and the characteristic impedance Z ₀ is small. This is because the smaller the difference, the closer the output power to the optimum output power can be obtained. The power supply voltage is set so as not to exceed the maximum rated source-drain voltage of the transistor 20.

At the frequency of the input signal, the imaginary part (-1/ωL1) of the admittance of the inductive element 18 is substantially equal to the imaginary part (-1/ωL _opt ) of the optimum load admittance Y _opt . In other words, the inductance L1 of the inductive element 18 is substantially equal to L _opt . It can also be said that the inductive component of the optimum load admittance Y _opt is realized by the inductive element 18. Note that when the imaginary part of the admittance of the inductive element 18 is within a range of ±10% of the imaginary part of the optimum load admittance Y _opt , the imaginary part of the admittance of the inductive element 18 is said to be substantially equal to the imaginary part of the optimum load admittance Y _opt . It is preferable that the imaginary part of the admittance of the inductive element 18 is set within a range of ±5% of the imaginary part of the optimum load admittance Y _opt , and it is also preferable that the difference between the imaginary part of the admittance of the inductive element 18 and the imaginary part of the optimum load admittance Y _opt is small. This is because the smaller the difference is, the closer the output power to the optimum output power can be obtained.

The configuration in which the optimal load resistance R _opt is increased by increasing the power supply voltage and the value of the inductive element 18 is appropriately set to eliminate the output matching circuit uses the technology described in JP 2021-118482 A. Further explanation will be omitted.

The harmonics reflected by the filter 26 return to the output terminal T2 via the transmission line 24. As in the first embodiment, the length of the transmission line 24 is determined in advance so as to obtain an efficiency equal to or greater than a predetermined value.

According to this embodiment, the phase of the harmonics reflected by the filter 26 at the output terminal T2 can be adjusted according to the length of the transmission line 24, so the efficiency of the power amplifier 6A can be increased without providing a high-frequency reflection circuit. Since no high-frequency reflection circuit is provided, losses can be reduced more than in the second comparative example. The size of the power amplifier 6A can also be made smaller than in the second comparative example.

In addition, since the reciprocal of the real part of the optimum load admittance Y _opt is substantially equal to the characteristic impedance Z ₀ and the imaginary part is realized by the inductive element 18 for supplying the bias voltage, by directly connecting a filter having a characteristic impedance Z ₀ to the output terminal T2 of the amplifier unit 16 via a transmission line 24 having a characteristic impedance Z ₀ , it is possible to make the optimum load admittance Y _opt appear at the output terminal T2 of the amplifier unit 16. As a result, the power amplifier 6 can output a desired optimum output power. Compared to the first embodiment, it is not necessary to use an output matching circuit, so the loss of output power can be reduced. Therefore, the drain efficiency and power added efficiency can be improved compared to the first embodiment. Also, it is possible to reduce the size and weight of the power amplifier 6A compared to the first embodiment.

In addition, by using a compound semiconductor transistor 20, the maximum rated source-drain voltage is higher than that of a silicon (Si) transistor, so that the power supply voltage can be increased and the range of options for the real part of the optimal load admittance Y _opt can be expanded.

In addition, by using the nitride semiconductor transistor 20, the maximum rated source-drain voltage is higher than that of a transistor such as gallium arsenide (GaAs), so that the power supply voltage can be increased and the range of selection for the real part of the optimal load admittance Y _opt can be increased.

Furthermore, by using a GaN-HEMT as the transistor 20, it is possible to achieve higher output operation compared to a FET, and it is also possible to improve characteristics such as output power at frequencies of 1 GHz or higher.

The present disclosure has been described above based on the embodiments. It will be understood by those skilled in the art that the present disclosure is not limited to the above embodiments, that various design changes are possible, that various modifications are possible, and that such modifications are also within the scope of the present disclosure.

The outline of one aspect of the present disclosure is as follows. A power amplifier according to one aspect of the present disclosure includes an amplifier section that amplifies an input signal and outputs the amplified output signal from an output terminal, a matching circuit connected to the output terminal, a transmission line having a predetermined characteristic impedance, one end of which is supplied with the output signal that has passed through the matching circuit, and a filter that passes a fundamental wave contained in the output signal output from the other end of the transmission line and reflects harmonics contained in the output signal, and the length of the transmission line is determined so that the predetermined harmonics contained in the output signal output from the output terminal are returned to the output terminal with a predetermined phase.

This aspect can improve efficiency.

A power amplifier according to another aspect of the present disclosure includes an amplifier section that amplifies an input signal and outputs the amplified output signal from an output terminal, an inductive element having one end to which a power supply voltage is supplied and the other end connected to the output terminal, a transmission line having a predetermined characteristic impedance and one end connected to the output terminal, and a filter that passes a fundamental wave included in the output signal output from the other end of the transmission line and reflects harmonics included in the output signal, the power supply voltage is set so that the reciprocal of the real part of the optimal load admittance of the amplifier section that has the predetermined output characteristic is substantially equal to the characteristic impedance, and the length of the transmission line is determined so that at the frequency of the input signal, the imaginary part of the admittance of the inductive element is substantially equal to the imaginary part of the optimal load admittance, and the predetermined harmonics included in the output signal output from the output terminal are returned to the output terminal with a predetermined phase.

This aspect can improve efficiency.

A harmonic reflection circuit does not need to be provided between the output terminal and the filter. In this case, the power amplifier can be made smaller.

The length of the transmission line may be determined so that the impedance seen from the output terminal toward the filter is substantially zero for a predetermined even-order harmonic contained in the output signal. In this case, the efficiency of the power amplifier can be improved.

The length of the transmission line may be determined so that the impedance seen from the output terminal toward the filter is substantially infinite for a given odd-order harmonic contained in the output signal. In this case, the efficiency of the power amplifier can be improved.

1, 1A...radio device, T1...control terminal, T2...output terminal, T3...ground terminal, 6, 6A...power amplifier, 10, 10A...power amplifier circuit, 14...input matching circuit, 16...amplifier section, 18...inductive element, 20...transistor, 22...fundamental wave matching circuit, 24...transmission line, 26...filter.

Claims (5)

an amplifier section that amplifies an input signal and outputs the amplified output signal from an output terminal;
a matching circuit connected to the output terminal;
a transmission line having a predetermined characteristic impedance, one end of which is supplied with the output signal having passed through the matching circuit;
a filter that passes a fundamental wave included in the output signal output from the other end of the transmission line and reflects higher harmonics included in the output signal;
Equipped with
The length of the transmission line is determined so that a predetermined harmonic contained in the output signal output from the output terminal is returned to the output terminal with a predetermined phase.
1. A power amplifier comprising: an amplifier section that amplifies an input signal and outputs the amplified output signal from an output terminal;
an inductive element having one end to which a power supply voltage is supplied and the other end connected to the output terminal;
a transmission line having a predetermined characteristic impedance and one end connected to the output terminal;
a filter that passes a fundamental wave included in the output signal output from the other end of the transmission line and reflects higher harmonics included in the output signal;
Equipped with
the power supply voltage is set so that the reciprocal of the real part of the optimum load admittance of the amplifier section, which has a predetermined output characteristic, is substantially equal to the characteristic impedance;
at a frequency of the input signal, an imaginary part of the admittance of the inductive element is substantially equal to an imaginary part of the optimum load admittance;
The length of the transmission line is determined so that a predetermined harmonic contained in the output signal output from the output terminal is returned to the output terminal with a predetermined phase.
1. A power amplifier comprising: No harmonic reflection circuit is provided between the output terminal and the filter.
3. The power amplifier according to claim 1, wherein the first and second inputs are connected to the first and second inputs. a length of the transmission line is determined so that an impedance seen from the output terminal to the filter side is substantially zero with respect to a predetermined even-order harmonic contained in the output signal.
3. The power amplifier according to claim 1, wherein the first and second inputs are connected to the first and second inputs. a length of the transmission line is determined so that an impedance when the filter side is viewed from the output terminal is substantially infinite with respect to a predetermined odd-order harmonic contained in the output signal.
3. The power amplifier according to claim 1, wherein the first and second inputs are connected to the first and second inputs.

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