TWI743856B - Radio frequency amplifier circuit - Google Patents

Abstract

A radio frequency amplifier circuit is provided. A matching circuit is configured on a RF path of an input or an output of an amplifier. An inductance-capacitance resonance circuit shares an inductance included in the matching circuit and generates a corresponding resonance frequency. The matching circuit provides an input impedance or an output impedance that matches two fundamental tones in a radio frequency signal at a first frequency and a second frequency. The inductance-capacitance resonant circuit provides a filtering path for filtering signal components outside a frequency band formed by the first frequency and the second frequency in the radio frequency signal.

Description

RF amplifier circuit

The present invention relates to an amplifier circuit, and particularly relates to a radio frequency amplifier circuit.

In order to suppress the noise in the RF amplifier circuit, a filter circuit can generally be used to filter the noise. However, some noises with frequencies adjacent to the fundamental tone, such as third-order intermodulation distortion (IM3) noise caused by the nonlinearity of the amplifier or its driving amplifier, are difficult to filter out by this filter circuit. This in turn causes the linearity of the output power of the radio frequency amplifier to decrease.

The invention provides a radio frequency amplifier circuit, which can suppress the noise associated with the two fundamental tones of the input signal and effectively improve the linearity of the output power of the radio frequency amplifier.

The radio frequency amplifier circuit of the present invention includes an amplifier, a first matching circuit, and a first inductance capacitor resonance circuit. The amplifier includes an input terminal and an output terminal. The input terminal is used for receiving the input terminal of the first bias voltage. The first matching circuit is coupled to the output of the amplifier Input or output, where on the radio frequency path, the amplifier receives the radio frequency signal at the input through the first matching circuit to amplify the radio frequency signal, or the amplifier transmits the amplified radio frequency signal through the first matching circuit at the output end. The first inductor-capacitor resonance circuit is coupled to the first matching circuit and connected to the radio frequency path. The first inductor-capacitor resonant circuit includes a first inductor. The first inductor-capacitor resonant circuit and the first matching circuit share the inductor included in the first matching circuit. Has the first resonant frequency. The radio frequency signal includes two fundamental tones at a first frequency and a second frequency. The first matching circuit provides input impedance or output impedance matching the two fundamental tones. The first inductance capacitor resonant circuit provides a first filter path. The signal components outside the frequency band formed by the first frequency and the second frequency in the radio frequency signal are filtered.

Based on the foregoing, the first matching circuit of the embodiment of the present invention is configured on the radio frequency path of the input or output of the amplifier, and the first inductance capacitor resonant circuit and the first matching circuit share the inductance included in the first matching circuit to generate a corresponding resonance. Frequency, wherein the first matching circuit provides the input impedance or output impedance matching the two fundamental tones of the first frequency and the second frequency in the radio frequency signal, and the first inductance-capacitance resonant circuit can provide The first filter path for filtering the signal components outside the frequency band formed by the frequency, which can effectively suppress the noise associated with the two fundamental tones of the radio frequency signal, improve the linearity of the output power of the radio frequency amplifier, and reduce the frequency of the radio frequency amplifier Circuit size.

102: Amplifier

104, 106: matching circuit

108, 110: Inductance capacitor resonance circuit

P1: RF input path

P2: RF output path

SRF1, SRF2: RF signal

VB1, VB2: Bias voltage

202: Bias circuit

T31, T41: Transistor

R11, R41: resistance

D41, D42: Diode

C11, C12, C21, C22, C41, C42, C51: Capacitor

Vcc, Vccb: power supply voltage terminal

Vref: reference bias terminal

L11, L21, L41, L42, L51: inductance

SW1: switch

1-12 are schematic diagrams of radio frequency amplifier circuits according to embodiments of the present invention.

FIG. 1 is a schematic diagram of a radio frequency amplifier circuit according to an embodiment of the present invention. Please refer to FIG. 1. The radio frequency amplifier circuit includes an amplifier 102, matching circuits 104, 106, inductance-capacitance resonant circuits 108 and 110. The matching circuit 104 is coupled to the input end of the amplifier 102 and the resonant circuit 108, and the matching circuit 106 is coupled to the output end of the amplifier 102 and the resonant circuit. 110.

In this embodiment, the radio frequency path may include a radio frequency input path P1, an amplifier 102, and a radio frequency output path P2. The amplifier 102 can receive the radio frequency signal SRF1 through a matching circuit 104 disposed on the radio frequency input path P1, wherein the radio frequency signal SRF1 can be included in For the two fundamental tones of the first frequency and the second frequency, the matching circuit 104 can provide an input impedance matching the two fundamental tones, that is, provide an input impedance matching the amplifier 102. The input terminal and the output terminal of the amplifier 102 can receive bias voltages VB1 and VB2, respectively. The bias voltages VB1 and VB2 can make the amplifier 102 work in the linear region to amplify the radio frequency signal SRF1. The inductance-capacitance resonance circuit 108 is coupled to the matching circuit 104 and connected to the radio frequency input path P1. The inductance-capacitance resonance circuit 108 and the matching circuit 104 can share the inductance included in the matching circuit 104 to generate a corresponding resonance frequency.

The inductance capacitor resonance circuit 108 can provide a filtering path to filter signal components outside the frequency band formed by the first frequency and the second frequency in the radio frequency signal SRF1. For example, the frequency related to the difference between the first frequency and the second frequency can be filtered. Filtering. Enter In one step, the filter path provided by the inductance capacitor resonance circuit 108 is a low impedance path for a signal having a frequency related to the difference between the first frequency and the second frequency, and for the frequency band formed by the first frequency and the second frequency. The signal inside is a high-impedance path, so the signal having a frequency related to the difference between the first frequency and the second frequency can be guided to the filtering path provided by the inductance-capacitance resonant circuit 108 to achieve a filtering effect.

Similarly, the filter path provided by the inductance capacitor resonant circuit 110 can also filter the signal components outside the frequency band formed by the first frequency and the second frequency in the amplified radio frequency signal SRF2, that is, the inductance capacitor resonant circuit 110 can Connected to the radio frequency output path P2, the filter path provided by the inductor-capacitor resonance circuit 110 is a low impedance path for a signal having a frequency related to the difference between the first frequency and the second frequency, and for the first frequency and the second frequency The formed signal in the frequency band is a high-impedance path. In addition, the above-mentioned bias voltage VB2 can be provided by the inductance-capacitance resonance circuit 110. The matching circuit 106 can provide an output impedance matching the two fundamental tones at the first frequency and the second frequency, that is, provide an output impedance matching the amplifier 102. On the radio frequency output path P2, the amplifier 102 transmits the amplified radio frequency signal SRF2 through the matching circuit 106 at the output end.

In this way, the inductance capacitor resonance circuits 108 and 110 provide filter paths to filter out the signal components outside the frequency band formed by the first frequency and the second frequency in the radio frequency signal SRF1, which can effectively suppress the noise associated with the two fundamental tones of the radio frequency signal. Therefore, the linearity of the output power of the radio frequency amplifier is improved. In addition, the circuit size of the radio frequency amplifier can be effectively reduced by sharing the inductance included in the inductance capacitor resonance circuit 108 and the inductance included in the matching circuit 104.

FIG. 2 is a schematic diagram of a radio frequency amplifier circuit according to another embodiment of the present invention. Please refer to FIG. 2. In this embodiment, the radio frequency amplifier circuit may further include a bias circuit 202, and the bias circuit 202 may provide a bias voltage VB1. The bias circuit 202 may include a transistor T41, a resistor R41, a diode circuit (D41, D42), and a capacitor C41. The transistor T41 is, for example, a BJT transistor, which may be an NPN transistor in this embodiment. The second terminal (for example, the emitter) of T41 is coupled to the input terminal of the amplifier 102, the first terminal (for example, the collector) of the transistor T41 is coupled to the power supply voltage Vccb, and the resistor R41 is coupled to the control terminal ( For example, between the base) and the reference bias terminal Vref. The diode circuit is coupled between the control terminal of the NPN transistor T41 and the reference voltage terminal (such as the common voltage terminal or the ground terminal, but not limited to this), and may include diodes D41, D42 or two connected in series. Polar bodies D41 and D42. The capacitor C41 is coupled between the control terminal and the reference voltage terminal of the transistor T41. The transistor T41 can provide a bias voltage VB1 at the second end, and the capacitor C41 and the diode circuit can help the transistor T41 provide a stable bias voltage VB1.

In this embodiment, the matching circuit 104 includes a capacitor C11 and an inductor L11. One end of the capacitor C11 is used to receive the radio frequency signal SRF1, the other end is coupled to one end of the inductor L11, and the other end of the inductor L11 is coupled to the amplifier 102. The inductor-capacitor resonance circuit 108 connected to the radio frequency input path P1 includes a capacitor C41 and an inductor L41. The inductor L41 is coupled between the capacitor C41 and the common junction of the capacitor C11 and the inductor L11, and the capacitor C41 is coupled to the inductor L41 and the reference voltage terminal. between. The capacitor C11 and the inductor L11 can form a radio frequency input path P1 and enable the matching circuit 104 to provide an input impedance matching the amplifier 102. The input impedance provided by the matching circuit 104 can be made up of capacitors C11 and C41 and The inductances L11 and L41 are determined. By sharing the capacitance C41 and the inductance L41 of the inductance-capacitance resonant circuit 108, the capacitance value of the capacitance C11 and the inductance value of the inductance L11 can be smaller, which helps to reduce the RF amplifier circuit size.

The amplifier 102 can be implemented by a transistor T31, such as a BJT transistor, and in this embodiment, it can be an NPN transistor, but it is not limited to this. For example, in other embodiments, it can also be implemented by, for example, a MOS transistor. The control terminal (for example, the base) of the transistor T31 is coupled to the inductor L11, the second terminal (for example, the emitter) of the transistor T31 is coupled to the reference voltage terminal, and the first terminal (for example, the collector) of the transistor T31 is The matching circuit 106 and the resonance circuit 110 are coupled. The inductor-capacitor resonant circuit 108 can share the inductor L11 with the matching circuit 104. The resonant frequency of the inductor-capacitor resonant circuit 108 can be determined by the capacitor C41 and the inductors L11 and L41. Therefore, the required inductance value of the inductor L41 is reduced, which helps to reduce the radio frequency. The size of the amplifier circuit. The inductance capacitor resonance circuit 108 can provide a low impedance path at a frequency related to the difference between the first frequency and the second frequency, and provide a high impedance at the first frequency and the second frequency (its impedance is much greater than the input impedance of the amplifier 102). ), and can effectively filter out signals with frequencies related to the difference between the first frequency and the second frequency. It is worth noting that, in some embodiments, the positions of the capacitor C41 and the inductor L41 are interchangeable, and are not limited to the coupling method of FIG. 2. It is worth noting that, in some embodiments, the capacitor C41 can be a variable capacitor, so that the capacitance value of the capacitor C41 can be adjusted according to the working conditions of the radio frequency amplifier circuit (such as operating bandwidth or operating frequency) to adjust the impedance. .

In this embodiment, the matching circuit 106 includes an inductor L21, capacitors C21 and C22, and the inductor-capacitor resonance circuit 110 includes an inductor L51 and a capacitor C51. One end of the inductor L21 is coupled to the first end of the transistor T31, and the other end is coupled to the capacitor C22, the capacitor C22 It is coupled between the inductor L21 and the output terminal of the matching circuit 106, and the capacitor C21 is coupled between the common node of the inductor L21 and the capacitor C22 and the reference voltage terminal. The inductor L51 is coupled between the first terminal of the transistor T31 and the power voltage terminal Vcc, and provides a bias voltage VB2 at the first terminal of the transistor T31, and the capacitor C51 is coupled between the power voltage terminal Vcc and the reference voltage terminal . The inductor L21 and the capacitor C22 form a radio frequency output path P2, and the inductor L21 and the capacitor C21 are used to provide an impedance matching the output impedance of the amplifier 102. The inductance L51 can be implemented as a choke coil, for example, which can be, for example, a 1/4 wavelength transmission line with the radio frequency signal SRF1. The inductor L51 and the capacitor C51 can provide a low impedance path at a frequency related to the difference between the first frequency and the second frequency, and provide a high impedance at the first frequency and the second frequency (its impedance is much greater than the output impedance of the amplifier 102 ), and can effectively filter out signals with frequencies related to the difference between the first frequency and the second frequency.

In addition, the implementation of the matching circuit 104 is not limited to the embodiment in FIG. 2. For example, in the embodiment in FIG. Between ends. In addition, in some embodiments, the capacitor C41 can also be a variable capacitor.

FIG. 4 is a schematic diagram of a radio frequency amplifier circuit according to another embodiment of the present invention. Please refer to FIG. 4. Compared with the embodiment in FIG. 2, the inductor-capacitor resonance circuit 108 of this embodiment may further include a capacitor C42 and an inductor L42, and the capacitor C42 and the inductor L42 are connected in series between the common contact of the capacitor C11 and the inductor L11 and the reference voltage terminal. The capacitor C42 and the inductor L42 can provide another low-impedance path, and increase the operating bandwidth of the inductor-capacitor resonant circuit 108, so that the inductor-capacitor resonant circuit 108 can further effectively filter out A signal having a frequency related to the difference between the first frequency and the second frequency.

FIG. 5 is a schematic diagram of a radio frequency amplifier circuit according to another embodiment of the present invention. Please refer to FIG. 5. Compared with the embodiment in FIG. 2, the inductor-capacitor resonance circuit 108 of this embodiment includes a switch SW1, and the switch SW1 is coupled between the inductor L41 and the common junction of the capacitor C11 and the inductor L11. When the power of the radio frequency signal SRF1 is lower than the preset value, the switch SW1 can be controlled by the control circuit to enter the off state to reduce the loss of the radio frequency signal SRF1, and when the power of the radio frequency signal SRF1 is higher than or equal to the preset value At this time, the switch SW1 is controlled by the control circuit and enters the conducting state for filtering processing.

FIG. 6 is a schematic diagram of a radio frequency amplifier circuit according to another embodiment of the present invention. Please refer to FIG. 6. Compared with the embodiment in FIG. 2, the inductor-capacitor resonant circuit 108 of this embodiment further includes a resistor R41, which is coupled between the capacitor C41 and the inductor L41, so that the operating bandwidth of the inductor-capacitor resonant circuit 108 can be increased, so that The inductor-capacitor resonance circuit 108 can further effectively filter out signals having frequencies related to the difference between the first frequency and the second frequency.

FIG. 7 is a schematic diagram of a radio frequency amplifier circuit according to another embodiment of the present invention. Please refer to FIG. 7. Compared with the embodiment in FIG. 2, the matching circuit 104 of this embodiment further includes a resistor R11, and the resistor R11 is connected in parallel with the capacitor C11, which can effectively improve the stability of the radio frequency amplifier circuit. In some embodiments, the capacitor C41 can be a variable capacitor.

FIG. 8 is a schematic diagram of a radio frequency amplifier circuit according to another embodiment of the present invention. Please refer to FIG. 8. Compared with the embodiment in FIG. 2, the inductance and capacitance of this embodiment are harmonic The oscillator circuit 108 can be coupled to the input terminal of the amplifier 102, and the inductor-capacitor resonance circuit 110 can be coupled to the common junction of the inductor L21 and the capacitor C22. In this way, the resonance frequency of the inductor-capacitor resonant circuit 110 can be determined by the inductor L51 and the capacitor C51 and the inductance L21 of the matching circuit 106, and the output impedance provided by the matching circuit 106 can be determined by the inductors L21, L51 and the capacitors C21, C22, C51, by sharing The inductance and capacitance of the matching circuit 106 and the inductance-capacitance resonance circuit 110 can effectively reduce the size of the radio frequency amplifier circuit. In addition, the matching circuits 104, 106 can provide matching input and output impedances of the amplifier 102, and the inductance-capacitance resonant circuits 108, 110 can filter out the implementation details and implementation details of signals having frequencies related to the difference between the first frequency and the second frequency. The foregoing embodiment is similar, so it will not be repeated here.

It is worth noting that in some embodiments, the radio frequency amplifier circuit may only include an inductance capacitor resonant circuit. For example, in the embodiment of FIG. 9, the radio frequency amplifier circuit may omit the inductance capacitor resonant circuit 110, while in FIG. 10 In an embodiment, the RF amplifier circuit may omit the inductance capacitor resonance circuit 108. In addition, in the case where the radio frequency amplifier circuit includes a series-connected multi-stage amplifier, the amplifier 102 described in the above embodiment may be the first stage amplifier or the last stage amplifier in the multi-stage amplifier. For example, in the embodiment of FIG. 11, the amplifier 102 is the last stage of the multi-stage amplifier. In the embodiment of FIG. 12, the amplifier 102 is the first stage of the multi-stage amplifier. Since the implementations of the matching circuits 104, 106 and the inductor-capacitor resonant circuits 108, 110 in FIGS. 9 to 12 are similar to the implementations of the matching circuits 104, 106 and the inductor-capacitor resonant circuits 108, 110 of the above-mentioned embodiment, there are general The knowledgeable person should be able to infer the details of its implementation based on the above-mentioned embodiments, so it will not be repeated here.

In summary, the matching circuit of the embodiment of the present invention can be configured on the RF path of the input or output of the amplifier. The inductance capacitor resonant circuit and the matching circuit can share the inductance included in the matching circuit to generate a corresponding resonant frequency. The circuit can provide input impedance or output impedance matching the two fundamental tones of the first frequency and the second frequency in the radio frequency signal, and the inductance capacitor resonance circuit can provide signals outside the frequency band formed by the first frequency and the second frequency in the radio frequency signal. The filtering path through which the components are filtered can effectively suppress the noise associated with the two fundamental tones of the radio frequency signal, improve the linearity of the output power of the radio frequency amplifier, and reduce the circuit size of the radio frequency amplifier.

102: Amplifier

104, 106: matching circuit

108, 110: Inductance capacitor resonance circuit

P1: RF input path

P2: RF output path

SRF1, SRF2: RF signal

VB1, VB2: Bias voltage

Claims (20)

A radio frequency amplifier circuit includes: an amplifier including an input terminal for receiving a first bias voltage and an output terminal; a first matching circuit coupled to the input terminal or the output terminal of the amplifier, wherein On a radio frequency path, the amplifier receives a radio frequency signal at the input terminal through the first matching circuit to amplify the radio frequency signal, or the amplifier transmits an amplified radio frequency signal through the first matching circuit at the output terminal; and A first inductance capacitor resonant circuit coupled to the first matching circuit and connected to the radio frequency path, the first inductance capacitor resonant circuit includes a first inductor, the first inductance capacitor resonant circuit and the first matching circuit share the The inductance included in the first matching circuit has a first resonant frequency; wherein the radio frequency signal includes two fundamental tones at the first frequency and the second frequency, and the first matching circuit provides input impedance or matching to the two fundamental tones. Output impedance, the first inductance capacitor resonant circuit provides a first filter path, and the first filter path filters signal components outside the frequency band formed by the first frequency and the second frequency in the radio frequency signal. The radio frequency amplifier circuit described in claim 1, wherein the first matching circuit is coupled to the input end of the amplifier to provide input impedance matching the two fundamental tones, and on the radio frequency path, the amplifier The radio frequency signal is received at the input terminal through the first matching circuit, and the radio frequency amplifier circuit further includes: a second matching circuit coupled to the output terminal of the amplifier for providing matching The output impedance of the two fundamental tones, and on the radio frequency path, the amplifier transmits the amplified radio frequency signal through the second matching circuit at the output end. According to the radio frequency amplifier circuit described in item 2 of the scope of patent application, the radio frequency amplifier circuit further includes: a second inductance capacitor resonant circuit, coupled to the output end of the amplifier and connected to the radio frequency path, the second inductance capacitor The resonant circuit has a second resonant frequency, wherein the second inductive capacitor resonant circuit provides a second filter path, and the second filter path is outside the frequency band formed by the first frequency and the second frequency in the amplified radio frequency signal The signal component of is filtered, and the second inductance capacitor resonant circuit provides a second bias voltage at the output terminal of the amplifier. The radio frequency amplifier circuit according to claim 1, wherein the first inductor-capacitor resonance circuit includes: a first capacitor, the first terminal of which is coupled to the reference voltage terminal; and a first inductor, the first terminal of which is coupled The second terminal of the first capacitor is connected, and the second terminal of the first inductor is coupled to the first matching circuit. The radio frequency amplifier circuit according to claim 4, wherein the first matching circuit includes: a second capacitor coupled between the input terminal of the first matching circuit and the first inductance capacitor resonance circuit; and A second inductor is coupled between the first inductor-capacitor resonance circuit and the input terminal of the amplifier. The radio frequency amplifier circuit as described in item 5 of the scope of patent application, wherein The first matching circuit further includes: a third capacitor coupled between the common junction of the second capacitor and the second inductor and the reference voltage terminal. According to the radio frequency amplifier circuit described in item 4 or item 6 of the scope of patent application, the first capacitor is a variable capacitor. According to the radio frequency amplifier circuit described in claim 5, the first inductor-capacitor resonance circuit further includes: a first resistor coupled between the first capacitor and the first inductor. According to the radio frequency amplifier circuit described in item 5 of the scope of patent application, the first matching circuit further includes: a second resistor, connected in parallel with the second capacitor to the input end of the first matching circuit and resonates with the first inductance capacitor Between circuits. In the radio frequency amplifier circuit described in item 9 of the scope of patent application, the first capacitor is a variable capacitor. According to the radio frequency amplifier circuit described in claim 4, the first inductance capacitor resonance circuit further includes: a fourth capacitor; and a third inductor, which is connected in series with the fourth capacitor to the first inductor of the first inductor Between the two terminals and the reference voltage terminal. The radio frequency amplifier circuit described in item 3 of the scope of patent application, wherein the second inductance capacitor resonance circuit includes: a fifth capacitor; and A fourth inductor and the fifth capacitor are coupled between the output terminal of the amplifier and the reference voltage terminal, the common node of the fifth capacitor and the fourth inductor is coupled to a power supply voltage, and the output of the amplifier The terminal provides the second bias voltage. The radio frequency amplifier circuit described in claim 1, wherein the first matching circuit is coupled to the output end of the amplifier to provide an output impedance matching the two fundamental tones, and on the radio frequency path, the amplifier The amplified radio frequency signal is transmitted through the first matching circuit at the output terminal, and the first inductance capacitor resonance circuit provides a second bias voltage at the output terminal of the amplifier. According to the radio frequency amplifier circuit described in claim 1, wherein: the first inductance capacitor resonant circuit further includes a first switch coupled to the first matching circuit and connected to the radio frequency path. The radio frequency amplifier circuit according to the first item of the scope of patent application, wherein the radio frequency amplifier circuit includes a series-connected multi-stage amplifier, and the amplifier is the first stage amplifier or the last stage amplifier among the amplifiers. The radio frequency amplifier circuit according to item 3 of the scope of patent application, wherein the second matching circuit includes: a sixth capacitor; a fifth inductor, which is connected in series with the sixth capacitor to the output terminal of the amplifier and the second matching circuit Between the output terminals of the circuit; and a seventh capacitor, coupled between the common node of the sixth capacitor and the fifth inductor and the reference voltage terminal. The radio frequency amplifier circuit according to claim 16, wherein the second inductance-capacitance resonance circuit is coupled to the second matching circuit, and the second inductance-capacitance resonance circuit includes: a sixth inductor; and an eighth capacitor, And the sixth inductor are connected in series between the common node of the sixth capacitor and the fifth inductor and the reference voltage terminal, the common node of the sixth inductor and the eighth capacitor is coupled to a power supply voltage, and The common junction of the sixth capacitor and the fifth inductor provides a third bias voltage. The radio frequency amplifier circuit described in claim 1, wherein the amplifier includes: a first transistor, the control terminal of which is coupled to the first matching circuit, and the first terminal of the first transistor is coupled to a second In the matching circuit, the second terminal of the first transistor is coupled to the reference voltage terminal. The radio frequency amplifier circuit described in item 1 of the scope of patent application further includes: a bias circuit coupled to the input terminal of the amplifier to provide the first bias voltage. The radio frequency amplifier circuit according to item 19 of the scope of patent application, wherein the bias circuit includes: a second transistor, the second end of which is coupled to the control end of the first transistor, and the second end of the second transistor One end is coupled to a power voltage terminal; a third resistor is coupled between the control terminal of the second transistor and a reference bias terminal; A diode circuit is coupled between the control terminal of the second transistor and the reference voltage terminal; and a ninth capacitor is coupled between the control terminal of the second transistor and the reference voltage terminal.

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