RF power amplifier

Abstract

This invention provides an RF power amplifier, including a bias circuit. In this bias circuit, the base of a third transistor is connected to its collector, which is connected to a reference voltage source, and its emitter is connected to the collector of a second transistor. The base of the second transistor is connected to its collector, and its emitter is grounded. The base of a fourth transistor is connected to the base of the third transistor, its collector is connected to a power supply voltage source, and its emitter is connected to the base of a first transistor via a series thermal suppression resistor. A first terminal of a first capacitor is connected to the emitter of the fourth transistor, and its second terminal is grounded. A first terminal of a second capacitor is connected to the base of the fourth transistor, and its second terminal is connected to the collector of the first transistor. Compared with related technologies, the RF power amplifier of this invention has better transistor thermal suppression and provides better quiescent current stability, resulting in higher output power and better consistency.

Description

Technical Field

[0001] This invention relates to the field of radio frequency identification (RFID) technology, and more particularly to a radio frequency power amplifier used in mobile communication devices. Background Technology

[0002] Radio Frequency Identification (RFID) is a key technology for the Internet of Things (IoT). RFID front-end modules include low-noise amplifiers (LNAs), power amplifiers (PAs), filters, switches, and antennas. The power amplifier is a crucial module in the RFID front-end, amplifying the output signal before it is transmitted via the antenna. In 5G wireless communication systems, the power amplifier (RF) at the end of the transmitter stage is a critical module. Its PA directly influences and determines various performance indicators of the transmitter system, including output power, efficiency, gain, linearity, operating bandwidth, and reflection coefficient, thus affecting and determining the overall performance of the 5G wireless communication system. 5G frequency bands are divided into two main ranges: 450MHz–6GHz (Sub6G) and 24.25GHz–52.6GHz (millimeter-wave band). The higher the frequency, the shorter the signal propagation distance. Therefore, the coverage radius of the base station is smaller. Due to the number of base stations and the energy dissipation of high-frequency signal propagation, the millimeter wave band is not easy to achieve widespread use in 5G communication systems for the time being. Among them, the N41, N77, N78, and N79 bands are relatively low in frequency and have a wide bandwidth compared to millimeter waves. Therefore, it is particularly important to propose an RF power amplifier that operates in the N77 band in Sub6G.

[0003] Existing RF power amplifiers include bias circuits, input / output matching networks, transistors, etc. When designing RF power amplifiers using GaAs HBT technology, the requirements for the bias circuits are often quite high. For example... Figure 1 The diagram shown is a schematic of a prior art RF power amplifier circuit. In its bias circuit module, the RF... in For signal input port, RF out For signal output port, V bat V ccI1 is the power supply, Q0 is the bias current of the bias circuit, and Q0 is the transistor. The bias circuit is a crucial component of the RF power amplifier, providing a DC bias point. This bias point directly affects the power gain, efficiency, and linearity of the output power of the RF power amplifier. The stability of the bias circuit directly determines the stability of the functional module. In other words, the role of the bias circuit is to provide a stable and suitable static operating point for the RF power amplifier under given conditions, ensuring the stability of its operating state while suppressing the effects of transistor parameters changing with temperature. For RF power amplifiers supporting 5G mobile communication, the increased power required by 5G networks will significantly increase the thermal effects of transistors. The N77 band in 5G mobile communication operates at 3.3GHz-4.2GHz. Due to its higher frequency, it places higher demands on the output power of the RF power amplifier. With higher output power, the self-heating effect of transistors will be more pronounced, rendering existing bias circuits unsuitable for RF power amplifiers.

[0004] Therefore, it is necessary to provide a new RF power amplifier to solve the above problems. Summary of the Invention

[0005] To address the shortcomings of the existing technologies, this invention proposes a radio frequency power amplifier for use in 5G mobile communication, which has good transistor thermal suppression effect, provides better static current stability, and has high output power and good consistency.

[0006] To address the aforementioned technical problems, the present invention provides an RF power amplifier, comprising an input terminal, an output terminal, a first transistor, and a bias circuit; the base of the first transistor is connected to the input terminal, the emitter of the first transistor is grounded, the collector of the first transistor is connected to the output terminal, and the bias circuit is connected between the base of the first transistor and the input terminal.

[0007] The bias circuit includes: a second transistor, a third transistor, a fourth transistor, a first capacitor, a second capacitor, and a thermal effect suppression resistor;

[0008] The base of the third transistor is connected to the collector of the third transistor, the collector of the third transistor is connected to a reference voltage source, and the emitter of the third transistor is connected to the collector of the second transistor.

[0009] The base of the second transistor is connected to the collector of the second transistor, and the emitter of the second transistor is grounded;

[0010] The base of the fourth transistor is connected to the base of the third transistor, the collector of the fourth transistor is connected to the power supply voltage source, and the emitter of the fourth transistor is connected to the base of the first transistor through the thermal effect suppression resistor in series.

[0011] The first terminal of the first capacitor is connected to the emitter of the fourth transistor, and the second terminal of the first capacitor is connected to ground.

[0012] The first terminal of the second capacitor is connected to the base of the fourth transistor, and the second terminal of the second capacitor is connected to the collector of the first transistor.

[0013] Preferably, the bias circuit further includes a first resistor and a second resistor, the collector of the third transistor is connected in series with the second resistor and then connected to the reference voltage source, and the emitter of the second transistor is connected in series with the first resistor and then grounded.

[0014] Preferably, the bias circuit further includes a third resistor connected in series between the base of the fourth transistor and the first terminal of the second capacitor.

[0015] Preferably, the RF power amplifier further includes an input matching network connected in series between the input terminal and the base of the first transistor.

[0016] Preferably, the input matching network is composed of capacitors.

[0017] Preferably, the RF power amplifier further includes an output matching network connected between the collector of the first transistor and the output terminal.

[0018] Preferably, the output matching network consists of an inductor and a third capacitor; one end of the inductor is connected to the collector of the first transistor, and the other end of the inductor is connected to the circuit voltage source; the third capacitor is connected in series between the collector of the first transistor and the output terminal.

[0019] Compared with related technologies, the RF power amplifier of this invention features a simple bias circuit design that supports the operating frequency band of 5G networks (i.e., high-frequency signals). In this 5G operating frequency band, the bias circuit, due to the presence of the first and second capacitors, filters a portion of the lower-frequency high-frequency signals within the operating frequency band to ground via the first capacitor, thus filtering out these lower-frequency high-frequency signals. The remaining portion of the higher-frequency high-frequency signals within the operating frequency band then sequentially passes through the emitter of the fourth transistor, the base of the fourth transistor, the second capacitor, and finally to the collector of the first transistor, forming a feedback structure. This feedback structure can replenish the output signal with any leakage of higher-frequency high-frequency signals within the operating frequency band, thereby effectively improving the high-frequency output power of the RF power amplifier within the operating frequency band. Furthermore, the base potential of the fourth transistor remains unchanged, thus effectively improving the linearity of the RF power amplifier. The bias resistor effectively suppresses the self-heating effect of the transistor, effectively improving the stability of the bias circuit and providing a stable quiescent current. This ensures that the transistor always operates at a stable quiescent operating point, thereby guaranteeing the stability of the power amplifier's gain, output power, and output power linearity. Attached Figure Description

[0020] The present invention will now be described in detail with reference to the accompanying drawings. The above and other aspects of the present invention will become clearer and more readily understood through the detailed description following the accompanying drawings. In the drawings:

[0021] Figure 1 This is a circuit schematic of a conventional radio frequency power amplifier.

[0022] Figure 2 This is a circuit diagram of a prior art radio frequency power amplifier;

[0023] Figure 3 for Figure 2 A schematic diagram of the offset point movement;

[0024] Figure 4 This is a circuit diagram of the radio frequency power amplifier according to Embodiment 1 of the present invention;

[0025] Figure 5 This is a circuit diagram of the radio frequency power amplifier according to Embodiment 2 of the present invention;

[0026] Figure 6 for Figure 2 Simulation results of output power and power-added efficiency obtained from the bias circuit of the existing RF power amplifier in China;

[0027] Figure 7 The simulation results show the output power and power-added efficiency obtained by the bias circuit of the radio frequency power amplifier of the present invention. Detailed Implementation

[0028] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0029] The specific embodiments / examples described herein are specific implementations of the present invention, used to illustrate the concept of the invention, and are illustrative and exemplary, and should not be construed as limiting the implementation methods or scope of the present invention. In addition to the embodiments described herein, those skilled in the art can employ other obvious technical solutions based on the content disclosed in the claims and specification of this application. These technical solutions include those that make any obvious substitutions and modifications to the embodiments described herein, all of which are within the protection scope of the present invention.

[0030] The following descriptions of the embodiments are made with reference to the accompanying drawings, illustrating specific embodiments in which the invention can be implemented. Directional terms used in this invention, such as up, down, front, back, left, right, inside, outside, side, etc., are merely directional references to the accompanying drawings. Therefore, the directional terms used are for illustrative and understanding purposes only, and not for limiting the invention.

[0031] Please combine Figure 2-3 As shown, where, Figure 2 This is a circuit diagram of a prior art radio frequency power amplifier and a schematic diagram of its bias point movement. Figure 3 for Figure 2 A schematic diagram of the offset point movement. Figure 2 In the bias circuit module of the existing RF power amplifier, RF in For signal input port, RF out This is the signal output port, Q0 is a transistor, and R1 and R2 are voltage divider resistors. That is, the bias circuit of a current RF power amplifier consists of two voltage divider resistors connected in series. Combined with... Figure 2-3 As shown, when a large input signal is applied, the forward voltage and reverse current on the base-emitter junction diode of Q0 are limited due to the clamping characteristic of the diode. The average DC current I after rectification by the base-emitter junction diode is... rec The voltage V across the base-emitter junction will increase with increasing input power due to the transistor's self-heating effect. be Reduced ΔV be Moving the bias point from S to L1 will result in reduced transconductance, gain, and phase distortion. To compensate for gain compression and phase distortion under large-signal conditions, the large-signal transconductance and small-signal transconductance must be kept consistent. Therefore, the bias point L1 should be moved to L2. However, in the design of power amplifiers (PAs) in the frequency bands N77 (3.3GHz-4.2GHz) and N79 (4.5GHz-5GHz), the problem of lower high-frequency output power than low-frequency output power is unavoidable. Therefore, this invention improves the bias circuit to overcome the above problems.

[0032] Please refer to Figure 4 The diagram shown is a circuit diagram of an RF power amplifier according to Embodiment 1 of the present invention. Embodiment 1 of the present invention provides an RF power amplifier 100, which includes an input terminal RF... in RF output terminal out The first transistor Q0 and the bias circuit 10.

[0033] The base of the first transistor Q0 is connected to the input terminal RF. in The emitter of the first transistor Q0 is grounded, and the collector of the first transistor Q0 is connected to the output terminal RF. out The bias circuit 10 is connected to the base of the first transistor Q0 and the input terminal RF. in between.

[0034] Specifically, in this embodiment, the bias circuit 10 includes: a second transistor Q1, a third transistor Q2, a fourth transistor Q3, and a first capacitor C. L1 Second capacitor C L2 Thermal effect suppression resistor R bias Among them, the first capacitor C L1 Second capacitor C L2 All of these are filter capacitors.

[0035] The base of the third transistor Q2 is connected to the collector of the third transistor Q2, and the collector of the third transistor Q2 is connected to the reference voltage source V. reg The emitter of the third transistor Q2 is connected to the collector of the second transistor Q1.

[0036] The base of the second transistor Q1 is connected to the collector of the second transistor Q1, and the emitter of the second transistor Q1 is grounded.

[0037] The base of the fourth transistor Q3 is connected to the base of the third transistor Q2, and the collector of the fourth transistor Q3 is connected to the power supply voltage source V. bat The emitter of the fourth transistor Q3 is connected in series with the thermal suppression resistor R. bias It is then connected to the base of the first transistor Q0.

[0038] The first capacitor C L1 The first terminal is connected to the emitter of the fourth transistor Q3, and the first capacitor C L1 The second end is connected to ground.

[0039] The second capacitor C L2 The first terminal is connected to the base of the fourth transistor Q3, and the second capacitor C L2The second terminal is connected to the collector of the first transistor Q0.

[0040] In this embodiment, more preferably, to improve reliability, the bias circuit 10 further includes a first resistor R1 and a second resistor R2, and the collector of the third transistor Q2 is connected in series with the second resistor R2 and then connected to the reference voltage source V. reg The emitter of the second transistor Q1 is connected in series with the first resistor R1 and then grounded.

[0041] To achieve better impedance matching in the circuit, the RF power amplifier 100 also includes a component connected in series to the input terminal RF. in An input matching network is established between the transistor Q0 and its base. In this embodiment, specifically, the input matching network is composed of a capacitor C.

[0042] Similarly, the RF power amplifier 100 also includes an output matching network, which is connected to the collector of the first transistor Q0 and the output terminal RF. out In this embodiment, specifically, the output matching network consists of an inductor L and a third capacitor C3; one end of the inductor L is connected to the collector of the first transistor Q0, and the other end of the inductor L is connected to the circuit voltage source V. cc The third capacitor C3 is connected in series with the collector of the first transistor Q0 and the output terminal RF. out between.

[0043] Continue to combine Figure 4 The second transistor Q1 and the third transistor Q2 form a clamping voltage, ensuring that the current I2 is a stable current. Adjusting the values ​​of the first resistor R1 and the second resistor R2 can adjust the magnitude of the current I2. The third transistor Q2 and the fourth transistor Q3 form a current mirror. Due to the amplification function of the third transistor Q3, the emitter current of the third transistor Q3 is amplified by the mirror. Since the current I2 is a stable current, the current I1 = βI2, where β is the amplification factor. When the input power increases and the RF power amplifier 100 is operating at high power, the DC current of the first transistor Q0 increases. Due to the transistor's self-heating effect and the diode's rectification characteristics, the base potential V of the first transistor Q0... b0 The signal will decrease, and the signal on the RF line will leak into the bias circuit 10. This is due to the first capacitor C. L1 Second capacitor C L2 Due to the presence of the capacitor C, a portion of the high-frequency signal first passes through the first capacitor C. L1 Upon reaching the ground, another portion of the high-frequency signal sequentially passes through the emitter of the fourth transistor Q3, the base of the fourth transistor Q3, and the second capacitor C. L2The feedback structure, connected to the collector of the first transistor Q0, can supplement the leaked signal into the output signal, thus increasing the high-frequency output power of the first transistor Q0 while effectively improving the linearity of the RF power amplifier 100. Due to rectification, the voltage V between the base and emitter of the fourth transistor Q3... be3 The voltage decreases because the base potential of transistor Q3 remains constant, thus reducing the base voltage V of transistor Q0. b0 Effective compensation is applied to reduce the gain, ensuring that the first transistor Q0 maintains its quiescent operating point under high input and output power conditions, thus effectively suppressing gain compression. Simultaneously, the bias resistor R... bias It can effectively suppress the self-heating effect of the first transistor Q0, thereby improving the stability of the bias circuit 10 and providing a stable quiescent current. Therefore, it can keep the first transistor Q0 working at a stable quiescent operating point, thereby ensuring the stability of the power amplifier's gain, output power, and output power linearity.

[0044] The bias circuit 10 of the present invention forms an active bias circuit with temperature compensation. The output power remains essentially constant within the operating frequency band, thus providing a superior improvement to the technical problem addressed by the present invention.

[0045] It should be noted that increasing the bias resistor R within a certain range... bias This can effectively improve the stability of the quiescent operating point of the RF power amplifier 100, but beyond this range, if the bias resistor R is further increased... bias This will increase the nonlinearity of the RF power amplifier when the large signal input is 100. Increasing the bias resistor R... bias The magnitude of the bias resistor affects the linearity of the output power by first increasing and then decreasing. Therefore, when designing the bias circuit 10, the bias resistor R is selected. bias The size of the bias resistor R needs to be determined based on the operating requirements of the RF power amplifier 100. bias The size is generally a compromise between natural effects and linearity.

[0046] Please combine Figure 6-7 As shown, Figure 6 for Figure 2 Simulation results of output power and power-added efficiency obtained from the bias circuit of the existing RF power amplifier in China; Figure 7 The above diagram shows the simulation results of the output power and power-added efficiency obtained from the bias circuit of the RF power amplifier of this invention. Figure 6 As can be seen, the 1dB power compression point of the existing RF power amplifier circuit is 36.5dBm. And... Figure 7As can be seen, the 1dB power compression point of the RF power amplifier circuit of this invention is 38dBm. Comparison with simulation results shows that using the bias circuit of this invention significantly improves the high-frequency output power of the RF power amplifier.

[0047] In this invention, the traditional bias circuit of the prior art is improved, and the structure is simple and easy to implement. The bias circuit of this invention has a good improvement on the thermal effect of the transistor in the radio frequency power amplifier and can provide a stable current. At the same time, it can also compensate for the high frequency output power of the radio frequency power amplifier, so as to achieve the purpose of consistent output power at low frequency, medium frequency and high frequency.

[0048] This invention also provides another embodiment, please refer to... Figure 5 As shown, Figure 5 This is a circuit diagram of the radio frequency power amplifier according to Embodiment 2 of the present invention. This embodiment is similar to the one described above. Figure 4 The implementation shown is basically the same, except that the bias circuit 100 further includes a third resistor R3, which is connected in series with the base of the fourth transistor Q3 and the second capacitor C. L2 Between the first and second ends.

[0049] The third resistor R3 can adjust the feedback depth. Adjusting the third resistor R3 and the first capacitor C... L1 The value of K can be adjusted to increase the stability of the circuit (stability coefficient K value), and the base potential Vb3 of the fourth transistor Q3 remains unchanged, thus further improving the linearity of the RF power amplifier 100.

[0050] In addition to the differences mentioned above, and Figure 4 The embodiments shown are identical, and they solve the same technical problems and achieve the same technical effects.

[0051] Compared with related technologies, the RF power amplifier of this invention features a simple bias circuit design that supports the operating frequency band of 5G networks (i.e., high-frequency signals). In this 5G operating frequency band, the bias circuit, due to the presence of the first and second capacitors, filters a portion of the lower-frequency high-frequency signals within the operating frequency band to ground via the first capacitor, thus filtering out these lower-frequency high-frequency signals. The remaining portion of the higher-frequency high-frequency signals within the operating frequency band then sequentially passes through the emitter of the fourth transistor, the base of the fourth transistor, the second capacitor, and finally to the collector of the first transistor, forming a feedback structure. This feedback structure can replenish the output signal with any leakage of higher-frequency high-frequency signals within the operating frequency band, thereby effectively improving the high-frequency output power of the RF power amplifier within the operating frequency band. Furthermore, the base potential of the fourth transistor remains constant, thus effectively improving the linearity of the RF power amplifier. The bias resistor effectively suppresses the self-heating effect of the transistor, effectively improving the stability of the bias circuit and providing a stable quiescent current. This ensures that the transistor always operates at a stable quiescent operating point, thereby ensuring the stability of the power amplifier's gain, output power, and output power linearity.

[0052] It should be noted that the various embodiments described above with reference to the accompanying drawings are merely illustrative of the present invention and not intended to limit its scope. Those skilled in the art should understand that any modifications or equivalent substitutions made to the present invention without departing from its spirit and scope should be included within the scope of the present invention. Furthermore, unless the context otherwise requires, words appearing in the singular include those in the plural, and vice versa. Additionally, unless specifically stated otherwise, all or part of any embodiment may be used in conjunction with all or part of any other embodiment.

Claims

1. A radio frequency power amplifier, comprising an input terminal, an output terminal, a first transistor, and a bias circuit; the base of the first transistor is connected to the input terminal, the emitter of the first transistor is grounded, the collector of the first transistor is connected to the output terminal, and the bias circuit is connected between the base of the first transistor and the input terminal, characterized in that, The bias circuit includes: Second transistor, third transistor, fourth transistor, first capacitor, second capacitor, thermal effect suppression resistor; The base of the third transistor is connected to the collector of the third transistor, the collector of the third transistor is connected to a reference voltage source, and the emitter of the third transistor is connected to the collector of the second transistor. The base of the second transistor is connected to the collector of the second transistor, and the emitter of the second transistor is grounded; The base of the fourth transistor is connected to the base of the third transistor, the collector of the fourth transistor is connected to the power supply voltage source, and the emitter of the fourth transistor is connected to the base of the first transistor through the thermal effect suppression resistor in series. The first terminal of the first capacitor is connected to the emitter of the fourth transistor, and the second terminal of the first capacitor is grounded. The first terminal of the second capacitor is connected to the base of the fourth transistor, and the second terminal of the second capacitor is connected to the collector of the first transistor.

2. The radio frequency power amplifier according to claim 1, characterized in that, The bias circuit further includes a first resistor and a second resistor. The collector of the third transistor is connected in series with the second resistor and then connected to the reference voltage source. The emitter of the second transistor is connected in series with the first resistor and then grounded.

3. The radio frequency power amplifier according to claim 1, characterized in that, The bias circuit further includes a third resistor connected in series between the base of the fourth transistor and the first terminal of the second capacitor.

4. The radio frequency power amplifier according to claim 1, characterized in that, The radio frequency power amplifier also includes an input matching network connected in series between the input terminal and the base of the first transistor.

5. The radio frequency power amplifier according to claim 4, characterized in that, The input matching network is composed of capacitors.

6. The radio frequency power amplifier according to claim 1, characterized in that, The radio frequency power amplifier further includes an output matching network connected between the collector of the first transistor and the output terminal.

7. The radio frequency power amplifier according to claim 6, characterized in that, The output matching network consists of an inductor and a third capacitor; one end of the inductor is connected to the collector of the first transistor, and the other end of the inductor is connected to the circuit voltage source; the third capacitor is connected in series between the collector of the first transistor and the output terminal.

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