High frequency amplifier

Abstract

This invention relates to high-frequency amplifiers. A high-frequency amplifier (1) includes: an input terminal P IN Output terminal P OUT ; transistor (5), which is configured to amplify the input terminal P IN The RF signal; a matching circuit (9) and a reflection circuit (7), the matching circuit (9) for the fundamental frequency of the RF signal, and the reflection circuit (7) for the harmonics relative to the fundamental frequency, the matching circuit (9) and the reflection circuit (7) are connected in series between the transistor (5) and the output terminal P. OUT Between; extraction circuit (13), which is configured to extract the output terminal P OUT The harmonics at the point; processing circuits (15, 17) configured to adjust the phase and intensity of the harmonics extracted by the extraction circuit (13); and multiplexing circuit (19) configured to multiplex the harmonics processed by the processing circuits (15, 17) to the harmonics reflected by the reflection circuit (7) and provide the multiplexed harmonics to the transistor (5).

Description

Technical Field

[0001] This disclosure relates to a high-frequency amplifier for amplifying high-frequency signals. Background Technology

[0002] Conventional high-frequency amplifiers that amplify high-frequency waves such as microwaves have been used for various applications, such as radio communications and radar. Examples of such high-frequency amplifiers include Class F amplifiers and inverse Class F amplifiers capable of efficient operation to suppress power loss. For example, the amplifier disclosed in Japanese Unexamined Patent Publication No. 2005-204208 includes an odd harmonic signal generation circuit that generates odd harmonic signals relative to the fundamental signal to be amplified, and a rectangular wave signal generation circuit that multiplexes the odd harmonic signals to the fundamental signal. Furthermore, the amplifier disclosed in WO2017 / 122271A includes a harmonic supply circuit that supplies harmonics contained in an RF signal amplified by a first transistor to a second transistor, and a fundamental supply circuit that supplies the fundamental wave contained in the RF signal to the second transistor.

[0003] However, the structure disclosed in Japanese Unexamined Patent Publication No. 2005-204208 requires a signal source that generates harmonic signals that increase power consumption. Furthermore, in the structure disclosed in WO2017 / 122271A, parasitic components on the transistor output side cause harmonics to attenuate towards the intrinsic transistor's end face, and the impedance of the harmonics at the intrinsic transistor's end face is not set to a truly optimal impedance. This makes it impossible to sufficiently improve the overall amplifier's power efficiency simply by using passive components for matching. This disclosure provides a high-frequency amplifier capable of significantly improving power efficiency. Summary of the Invention

[0004] A high-frequency amplifier according to one aspect of this disclosure includes: an input terminal; an output terminal; a transistor configured to amplify an input high-frequency signal applied to the input terminal; a matching circuit and a reflection circuit, the matching circuit for the fundamental frequency of the input high-frequency signal and the reflection circuit for harmonics relative to the fundamental frequency, the matching circuit and the reflection circuit being connected in series between the transistor and the output terminal; an extraction circuit configured to extract harmonics appearing at the output terminal; a processing circuit configured to adjust the phase and intensity of the harmonics extracted by the extraction circuit; and a multiplexing circuit configured to multiplex the harmonics processed by the processing circuit to the harmonics reflected by the reflection circuit and provide the multiplexed harmonics to the transistor. Attached Figure Description

[0005] Figure 1 This is a block diagram illustrating a schematic structure of a high-frequency amplifier according to an embodiment;

[0006] Figure 2 It is shown Figure 1 The circuit diagram of the high-frequency amplifier structure is shown below;

[0007] Figure 3A This is a graph showing the output power and power-added efficiency (PAE) of the high-frequency amplifier without multiplexing the second harmonic; and

[0008] Figure 3B This is a graph showing the output power and power-added efficiency (PAE) of the input power when the high-frequency amplifier multiplexes the second harmonic. Detailed Implementation

[0009] The embodiments of the present disclosure will now be described with reference to the accompanying drawings. Note that in the description of the drawings, the same components are indicated by the same reference numerals, and redundant descriptions will be omitted.

[0010] [Structure of a high-frequency amplifier]

[0011] Figure 1 This is a block diagram illustrating the structure of a high-frequency amplifier 1 according to an embodiment. For example, the high-frequency amplifier 1 is used in radio communication or radar to amplify high-frequency signals. Figure 1 As shown, the high-frequency amplifier 1 includes input terminal P IN Output terminal P OUT The circuit consists of an input matching circuit 3, a transistor 5, a harmonic reflection circuit 7, a fundamental frequency matching circuit 9, a harmonic extraction circuit 13, a phase shifter 15, an amplifier 17, and a multiplexing circuit 19. Input terminal P. IN A high-frequency signal (RF signal) is received from the high-frequency signal source 21 via a transmission line 23 having a characteristic impedance Z0. On the other hand, the output terminal P... OUT Connect to a load 25 with characteristic impedance Z0. Harmonic reflection circuit 7, fundamental frequency matching circuit 9, and harmonic extraction circuit 13 are connected to input terminal P. IN With output terminal P OUT They are connected in series.

[0012] The input matching circuit 3 matches the input impedance of transistor 5 with the characteristic impedance of transmission line 23. Specifically, the input matching circuit 3 matches the impedance of transistor 5 when viewed from its control terminal (gate terminal) with the characteristic impedance of transmission line 23 when viewed from the terminal of the input matching circuit 3 connected to transmission line 23.

[0013] For example, transistor 5 is a field-effect transistor (FET) for amplifying RF signals. The following description will use FETs as transistors, but the same description applies to bipolar transistors. The RF signal is input to the gate of transistor 5 via transmission line 23 and input matching circuit 3. The source of transistor 5 is grounded, and its drain is connected to the output terminal P via harmonic reflection circuit 7 and fundamental frequency matching circuit 9. OUT .

[0014] Both the harmonic reflection circuit 7 and the fundamental frequency matching circuit 9 are formed by transmission lines and have specific impedances and lengths. The harmonic reflection circuit 7 transmits the fundamental frequency component contained in the output of transistor 5 and reflects the harmonic components back to transistor 5. The fundamental frequency matching circuit 9 will output the component P when viewed from the drain side of transistor 5. OUT The impedance is matched to the optimal load impedance that allows for optimization of design parameters such as the output power and power-added efficiency of transistor 5.

[0015] Typically, from input terminal P IN The input RF signal contains not only the fundamental frequency but also harmonic components. Furthermore, the input and output characteristics of transistor 5 are non-linear, and even when the input RF signal does not contain distortion (no harmonic components), significant harmonic components appear in the signal resulting from the amplification of the RF signal. Harmonic reflection circuit 7 reflects this harmonic component back to transistor 5 and transmits only the fundamental frequency. Fundamental frequency matching circuit 9 performs impedance matching on the optimal load impedance on the transmitted fundamental frequency.

[0016] Harmonic extraction circuit 13 extracts the harmonic components that have passed through fundamental frequency matching circuit 9 and outputs them at terminal P. OUT The harmonic reflection circuit 7 reflects most of the harmonic components appearing at the output of transistor 5; however, it is theoretically impossible to make the transmission amount zero. Furthermore, the fundamental frequency matching circuit 9 only transmits the fundamental frequency and also reflects or absorbs harmonic components other than the fundamental frequency; however, it is impossible to make the harmonic components at the output of the fundamental frequency matching circuit 9 zero. At the output terminal P... OUT A small but noticeable harmonic component will appear at point P. The harmonic extraction circuit 13 extracts the component appearing at the output terminal P. OUT The phase of the harmonic component is adjusted by the phase shifter (processing circuit) 15 by rotating the phase, and the intensity of the harmonic component is adjusted by the amplifier (processing circuit) 17 by amplifying or attenuating the harmonic component. Then, the harmonic component processed as described above is multiplexed by the harmonic multiplexing circuit 19 to the harmonic reflected by the harmonic reflection circuit 7, and the multiplexed harmonic is provided to the drain of the transistor 5.

[0017] As described above, the output signal of transistor 5 always contains harmonic components. When these harmonic components are supplied to the load 25 via external circuitry such as the output transmission line, additional power is consumed in the drain resistance of transistor 5 or the external circuitry. Therefore, it is preferable that the reflection intensity for harmonics is set higher when the load 25 is viewed from the drain output of transistor 5. This is equivalent to the case where no harmonic components are output to the external circuitry. Furthermore, the reflected harmonics cause waveform shaping at the drain end face of transistor 5, which can suppress power loss.

[0018] However, conventional output matching circuits that only include a fundamental frequency matching circuit cannot sufficiently improve the reflection intensity of harmonic components. Even with optimal matching to the fundamental frequency, harmonic components are not necessarily endowed with optimal reflection conditions. Furthermore, the configuration of a harmonic reflection circuit and a fundamental frequency matching circuit connected in series can cause the harmonic reflection circuit to shift the matching conditions used for the fundamental frequency from their optimal values. One of the harmonic reflection circuit and the fundamental frequency matching circuit can become a component that worsens the optimal conditions of the other.

[0019] Furthermore, transistor 5 typically includes a component portion (a portion included within a semiconductor element) and a portion (bonding wire, bonding pad, lead terminal, etc.) that extends outward as part of the component portion and connects the component portion to an external circuit. For the component portion, even when matching and reflection conditions are met for both the fundamental and harmonic frequencies, it is difficult to obtain a satisfactory combination of matching and reflection conditions using a circuit formed as an actual device including bonding wires, bonding pads, lead terminals, etc.

[0020] According to this embodiment, a method is provided that appears at output terminal P. OUT The harmonic components at the output are amplified or attenuated and then supplied to the drain output of transistor 5, thereby increasing the harmonic reflection intensity of transistor 5 and increasing the harmonic reflection at the output terminal P. OUT The fundamental component appears at that location.

[0021] refer to Figure 2 A description of the specific circuit structure of high-frequency amplifier 1 will be given.

[0022] like Figure 2 As shown, the high-frequency amplifier 1 includes a main transmission line and a secondary transmission line. The main transmission line includes transmission lines 21a to 21d and a planar waveguide 31 represented by a parallel circuit of an inductor and a capacitor, and is connected to the transistor 5 and the output terminal P. OUT Between them, the secondary transmission line extends from node C2 of the primary transmission line to node C4 of the primary transmission line via transistor 17a.

[0023] The harmonic reflection circuit 7 is connected to node C1 of the main transmission line located between the fundamental matching circuit 9 and the multiplexing circuit 19, and includes a transmission line 7a with a length equal to λ / 8. Here, λ represents the wavelength of the fundamental wave, and λ / 8 is equal to one-quarter of the wavelength of the second harmonic. One end of the transmission line 7a is open; therefore, node C1 on the main transmission line can be considered short-circuited with respect to the second harmonic component, thus forming a reflection circuit for the second harmonic propagating through the main transmission line.

[0024] The harmonic extraction circuit 13 includes two transmission lines 13a and 13b, each with a length equal to λ / 4 of the fundamental frequency. One end of transmission line 13b is open, and the other end is connected to one end of transmission line 13a. The other end of transmission line 13a is connected to the output terminal P via node C2 on the main transmission line. OUT As a result, node C3, located between the two transmission lines 13a and 13b on the secondary transmission line, can be considered short-circuited for the fundamental frequency. On the other hand, node C3 is open for the second harmonic. Since the length of transmission line 13a is equal to λ / 4 of the fundamental frequency, node C2, connected to the other end of transmission line 13a on the main transmission line, is open for both the fundamental and second harmonic frequencies.

[0025] Transmission line 13a and two transmission lines 21c and 21d form the fundamental frequency matching circuit 9. Specifically, since transmission line 7a, which forms a reflection circuit for the second harmonic, is inserted into the main transmission line, the characteristic impedance of the main transmission line interfered with by transmission line 7a must match the fundamental frequency from the downstream side of the main transmission line via transmission line 7a. Because the lengths of the two transmission lines 13a and 13b are equal to half the wavelength of the second harmonic, transmission lines 13a, 21c, and 21d forming the fundamental frequency matching circuit 9 do not affect the second harmonic. As a result, some second harmonics that are not reflected by transmission line 7a and leak into the secondary transmission line from node C2.

[0026] The second harmonic flowing into the secondary transmission line through node C3 reaches transistor 17a, which amplifies or attenuates the second harmonic, via transmission lines 15a and 17b, and then reaches multiplexing circuit 19 via transmission lines 17c and 15b. Transistor 17a is the same type and size as transistor 5. Transmission lines 15a and 15b form a phase shifter 15 that shifts the phase of the second harmonic flowing into the secondary transmission line. Furthermore, one end of transmission line 15a is connected to a filter circuit 29 comprising resistors, inductors, and capacitors. Filter circuit 29 is inserted between harmonic extraction circuit 13 and transistor 17a to remove the fundamental component flowing into the secondary transmission line to prevent transistor 17a from being affected by the fundamental component. Typically, the fundamental component is overwhelmingly larger in amplitude than the second harmonic component. Although transmission lines 21c, 21d, and 13a, which form fundamental matching circuit 9, suppress the inflow of the fundamental component into the secondary transmission line, filter circuit 29 prevents the fundamental component flowing into the secondary transmission line from reaching transistor 17a. Therefore, it is desirable for filter circuit 29 to have a filter structure with excellent frequency cutoff characteristics. The other end of transmission line 17c is connected to one end of transmission line 15b, which forms phase shifter 15.

[0027] The multiplexing circuit 19 includes two transmission lines 19a and 19b, each with a length equal to λ / 4 of the fundamental frequency. That is, the lengths of transmission lines 19a and 19b are equal to half the wavelength of the second harmonic. One end of transmission line 19b is open, and the other end is connected to one end of transmission line 19a. The other end of transmission line 19a is connected to node C4 located between transistor 5 on the main transmission line and transmission line 7a. Since one end of transmission line 19b is open, node C5 located between the two transmission lines 19a and 19b can be considered short-circuited for the fundamental frequency and open for the second harmonic. As a result, node C4 on the main transmission line can be considered open for both the fundamental and second harmonic frequencies. That is, the multiplexing circuit 19 exhibits the same effect as the two transmission lines 13a and 13b included in the harmonic extraction circuit 13. Specifically, transmission lines 21a and 21b on the main transmission line and transmission line 19a serve as a matching circuit for the fundamental frequency and have no effect on the second harmonic.

[0028] The aforementioned high-frequency amplifier 1 can extract the second harmonic from the output of transistor 5 after adjusting the amplitude and phase of the second harmonic and feed it back to the drain of transistor 5. This allows for a higher intensity of the second harmonic at the drain of transistor 5 and makes it appear at the output terminal P. OUT The fundamental frequency is relatively higher at this point, which in turn improves the overall power efficiency of the high-frequency amplifier 1. More specifically, compared to a structure where the harmonic processing circuit is formed solely by passive circuitry, this allows for higher reflection intensity of the second harmonic and reduces heat loss due to waveform shaping, which in turn improves the power efficiency of the high-frequency amplifier 1.

[0029] Figure 3A and Figure 3B The output power and power-added efficiency (PAE) of the high-frequency amplifier 1 are shown. Figure 3A This is the evaluation result of output power and PAE when the second harmonic is not multiplexed in this embodiment, and Figure 3B This is an evaluation result of the output power and PAE when the second harmonic is multiplexed in this embodiment. In each graph, curve G1 represents the change in output power relative to the input power, and curve G2 represents the PAE relative to the input power. As shown in the graphs, although the output power is approximately equal to 31 dBm when the input power is 20 dBm in each graph, in this embodiment including the multiplexing circuit for the second harmonic, the maximum power-added efficiency is increased from 62% of the conventional efficiency to approximately 73%.

[0030] According to this embodiment, returning the second harmonic to the drain of transistor 5 enables equivalent amplification of the second harmonic reflected by harmonic reflection circuit 7, which in turn improves the efficiency for the fundamental frequency. Specifically, in high-frequency amplifier 1, the harmonics reflected by transmission line 7a, as well as the harmonics extracted and adjusted in amplitude and phase by harmonic extraction circuit 13, phase shifter 15, amplifier 17, and multiplexing circuit 19, are multiplexed to the output at the drain of transistor 5. This allows for a substantial increase in the voltage reflection coefficient Γ of the harmonics at the intrinsic portion of transistor 5.

[0031] Furthermore, in the high-frequency amplifier 1, the harmonic extraction circuit 13 includes transmission lines 13a and 13b, and the multiplexing circuit 19 includes transmission lines 19a and 19b. This structure allows the harmonic extraction circuit 13 and the multiplexing circuit 19 to extract and multiplex harmonics to the output without affecting the propagation characteristics of the fundamental frequency of the transistor 5 output.

[0032] The high-frequency amplifier 1 further includes a filter circuit 29. This enables the efficient extraction of harmonics from the output of transistor 5 and the feedback of harmonics to the output.

[0033] Furthermore, according to this embodiment, a second harmonic corresponding to twice the fundamental frequency is extracted from the drain of transistor 5 and fed back. This structure can effectively generate a voltage signal converted into a pseudo-rectangular wave at the drain of transistor 5.

[0034] Furthermore, according to this embodiment, amplifier 17 includes transistor 17a, which has the same dimensions as transistor 5. This structure allows the two transistors to have common design parameters.

[0035] The principles of the present invention have been described and illustrated with reference to preferred embodiments. Those skilled in the art will understand that modifications in arrangement and detail can be made to the invention without departing from these principles. The invention is not limited to the specific structures disclosed in this embodiment. Therefore, all modifications and alterations derived from the scope and spirit of the claims are protected.

[0036] According to the above embodiment, the second harmonic is extracted from the output of transistor 5 by harmonic extraction circuit 13, and the extracted second harmonic is multiplexed to the output of transistor; however, the second harmonic can be any harmonic such as the third or fourth harmonic. Alternatively, another structure can be used, in which multiple harmonic processing circuits are provided, such as the sub-transmission line according to the above embodiment, and each processing corresponds to one of the different harmonics. Even with such a structure, the voltage reflection coefficient Γ of the harmonics at the end face of the intrinsic portion of transistor 5 can be sufficiently increased to improve power efficiency.

Claims

1. A high-frequency amplifier comprising: an input terminal; an output terminal; a transistor configured to amplify an input high-frequency signal applied to the input terminal; a matching circuit for a fundamental wave of the input high-frequency signal and a reflection circuit for a harmonic wave with respect to the fundamental wave, the matching circuit and the reflection circuit being connected in series between the transistor and the output terminal; an extraction circuit configured to extract the harmonic wave present at the output terminal; a processing circuit configured to adjust a phase and an intensity of the harmonic wave extracted by the extraction circuit; and a multiplexing circuit configured to multiplex the harmonic wave processed by the processing circuit to the harmonic wave reflected by the reflection circuit and to supply the multiplexed harmonic wave to the transistor, wherein the extraction circuit comprises: one transmission line having one end open and a length equal to one quarter of a wavelength of the fundamental wave; and another transmission line having a length equal to one quarter of a wavelength of the fundamental wave and having one end connected to the other end of the one transmission line and the other end connected to the output terminal.

2. The high-frequency amplifier according to claim 1, wherein the harmonic wave is a second harmonic wave of the fundamental wave.

3. The high-frequency amplifier according to claim 1 or claim 2, wherein the reflection circuit is a transmission line having one end connected to a transmission line extending between the transistor and the matching circuit and the other end open, the reflection circuit having a length equal to one quarter of a wavelength of the harmonic wave.

4. The high-frequency amplifier according to claim 1 or claim 2, wherein the multiplexing circuit comprises: one transmission line having one end open and a length equal to one quarter of a wavelength of the fundamental wave; and another transmission line having a length equal to one quarter of a wavelength of the fundamental wave and having one end connected to the other end of the one transmission line and the other end connected to a transmission line extending between the transistor and the matching circuit.

5. The high-frequency amplifier according to claim 1 or claim 2, wherein the processing circuit comprises: another transistor configured to amplify or attenuate the extracted harmonic wave; and a transmission line configured to shift the phase of the extracted harmonic wave, the other transistor and the transistor being identical in size.

6. The high-frequency amplifier according to claim 5, wherein the processing circuit further comprises a filter provided between the extraction circuit and the other transistor, the filter being configured to remove the fundamental wave.

7. A high-frequency amplifier comprising: an input terminal; an output terminal; a transistor configured to amplify an input high-frequency signal applied to the input terminal; ​ a matching circuit for a fundamental wave of the input high-frequency signal, and a reflection circuit for a harmonic wave with respect to the fundamental wave, the matching circuit and the reflection circuit being connected in series between the transistor and the output terminal; an extraction circuit configured to extract the harmonic wave present at the output terminal; a processing circuit configured to adjust a phase and an intensity of the harmonic wave extracted by the extraction circuit; and a multiplexing circuit configured to multiplex the harmonic wave processed by the processing circuit to the harmonic wave reflected by the reflection circuit, and to supply the multiplexed harmonic wave to the transistor, wherein the multiplexing circuit includes: one transmission line that is open at one end and has a length equal to one quarter of a wavelength of the fundamental wave; and another transmission line that has a length equal to one quarter of a wavelength of the fundamental wave, and that is connected at one end to the other end of the one transmission line, and at the other end to a transmission line extending between the transistor and the matching circuit.

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