Bias network of power amplifier and power amplifier circuit

Abstract

The invention discloses a bias network of a power amplifier and a power amplifier circuit. The bias network of the power amplifier comprises a direct current power supply and a resonant network. The resonance network is connected between the output end of the power amplifier and the positive electrode of the direct-current power supply, and the negative electrode of the direct-current power supply is grounded; the resonant network controls the frequency response of the bias network, shows high impedance in the band and shows low impedance out of the band. According to the invention, the gain and the output power in the working frequency band can be improved, and the out-of-band gain and the output power outside the working frequency band can be inhibited.

Description

Technical Field

[0001] The present invention relates to the field of electronic technologies, and in particular, to a bias network of a power amplifier and a power amplifier circuit. Background Art

[0002] In a power amplifier circuit, a power amplifier bias network is provided. The bias network can also be referred to as a power supply arm. The power amplifier bias network performs frequency response on the output signal of the power amplifier. In an ideal state, within the operating frequency band, it is necessary to enable the output signal of the power amplifier to be output to the subsequent circuit, having a high gain and output power; outside the operating frequency band, it is necessary to enable the output signal of the power amplifier to pass through the bias network without being output to the subsequent circuit, reducing the out-of-band gain and output power. However, in the existing power amplifier bias network, it is usually impossible to meet such requirements of the frequency response of the power amplifier, and its equivalent inductance cannot simultaneously meet the requirements of gain and power within and outside the operating frequency band. Summary of the Invention

[0003] The present invention provides a bias network of a power amplifier and a power amplifier circuit to simultaneously meet the requirements of gain and power within and outside the operating frequency band.

[0004] According to an aspect of the present invention, a bias network of a power amplifier is provided, including: a DC power supply and a resonant network;

[0005] The resonant network is connected between the output end of the power amplifier and the positive pole of the DC power supply, and the negative pole of the DC power supply is grounded;

[0006] The resonant network controls the frequency response of the bias network, showing a high impedance within the band and a low impedance outside the band.

[0007] Optionally, the resonant network includes: an inductive element and a capacitive element;

[0008] The inductive element is connected in series between the output end of the power amplifier and the positive pole of the DC power supply; the first end of the capacitive element is electrically connected to the output end of the power amplifier, and the second end of the capacitive element is grounded.

[0009] Optionally, the inductive element includes a transmission line, and the length of the transmission line is less than λ / 4;

[0010] The first end of the transmission line is electrically connected to the output end of the power amplifier, and the second end of the transmission line is electrically connected to the positive pole of the DC power supply.

[0011] Optionally, the inductive element includes a choke inductor;

[0012] The first end of the choke inductor is electrically connected to the output end of the power amplifier, and the second end of the choke inductor is electrically connected to the positive pole of the DC power supply.

[0013] Optionally, the inductance of the inductive element and the capacitance of the capacitive element are inversely proportional.

[0014] Optionally, the capacitive element includes a first capacitor;

[0015] The first end of the first capacitor is electrically connected to the output end of the power amplifier, and the second end of the first capacitor is grounded.

[0016] Optionally, the bias network further includes a second capacitor;

[0017] The first end of the second capacitor is electrically connected to the positive pole of the DC power supply, and the second end of the second capacitor is grounded.

[0018] According to another aspect of the present invention, a power amplifier circuit is provided, including a power amplifier and the bias network of the power amplifier described in any of the above items.

[0019] Optionally, the power amplifier circuit further includes an output matching network;

[0020] The output matching network is electrically connected to the output end of the power amplifier, and the output matching network is used to match the load resistance.

[0021] Optionally, the power amplifier circuit further includes a termination load;

[0022] The termination load is electrically connected to the output matching network, and the termination load is used to receive the power signal of the power amplifier.

[0023] The bias network of the power amplifier provided by the embodiments of the present invention is provided with a DC power supply and a resonant network. The resonant network can form a resonant network between the equivalent inductance of the resonant network and the output capacitance of the power amplifier by adjusting the equivalent inductance. This resonant network shows a high impedance in the passband, enabling the power amplifier to have a relatively high gain and output power; and shows a low impedance outside the passband, enabling the power amplifier to have a relatively low gain and output power, thereby improving the stability of the power amplifier circuit.

[0024] It should be understood that the content described in this part is not intended to identify the key or important features of the embodiments of the present invention, nor is it used to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. Brief Description of the Drawings

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the accompanying drawings required for the description of the embodiments. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can be obtained based on these drawings.

[0026] Figure 1 is a schematic diagram of a bias network of a power amplifier provided according to an embodiment of the present invention;

[0027] Figure 2 is a schematic diagram of another bias network of a power amplifier provided according to an embodiment of the present invention;

[0028] Figure 3 is a schematic diagram of yet another bias network of a power amplifier provided according to an embodiment of the present invention;

[0029] Figure 4 is a circuit diagram of a power amplifier circuit provided according to an embodiment of the present invention;

[0030] Figure 5 is a Smith chart of a bias network of a power amplifier provided according to an embodiment of the present invention;

[0031] Figure 6 is a Smith chart of another bias network of a power amplifier provided according to an embodiment of the present invention;

[0032] Figure 7 is a Smith chart of yet another bias network of a power amplifier provided according to an embodiment of the present invention;

[0033] Figure 8 is a simulation schematic diagram of a video bandwidth provided according to an embodiment of the present invention. Detailed implementation manners

[0034] In order to enable those skilled in the art to better understand the solutions of the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, rather than all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0035] It should be noted that the terms "first", "second", etc. in the description, claims and above-mentioned drawings of the present invention are used to distinguish similar objects, and do not necessarily need to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged under appropriate circumstances, so that the embodiments of the present invention described here can be implemented in an order other than those illustrated or described here. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device comprising a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0036] Figure 1 FIG. is a schematic diagram of a bias network of a power amplifier provided by an embodiment of the present invention. Refer to Figure 1 , the bias network 1 of the power amplifier is electrically connected to the output end of the power amplifier 3. The bias network 1 performs frequency response on the power amplifier 3, and the output end of the power amplifier 3 is also connected to a backend circuit 2. The bias network 1 includes: a DC power supply 11 and a resonant network 12. The resonant network 12 is connected between the output end of the power amplifier 3 and the positive pole of the DC power supply 11, and the negative pole of the DC power supply 11 is grounded; the resonant network 12 controls the frequency response of the bias network 1, showing a high impedance in the band and a low impedance outside the band.

[0037] Among them, the band is within the working frequency band of the power amplifier circuit, and outside the band is outside the working frequency band of the power amplifier circuit. The DC power supply 11 can provide direct current to the resonant network 12, and the resonant network 12 can control the frequency response of the bias network 1. Specifically, a resonant network is formed by the equivalent inductance of the resonant network 12 and the output capacitance of the power amplifier 3 to control the resonant frequency. Since the size of the output capacitance of the power amplifier 3 is a fixed value, it is necessary to adjust the equivalent inductance of the resonant network 12 to adjust the frequency response of the bias network.

[0038] Specifically, when the bias network of the power amplifier provided by the embodiment of the present invention is applied to a communication system, it is required that the bias network of the power amplifier 3 has good video bandwidth characteristics, that is, frequency response. The calculation formula of the video bandwidth is as follows:

[0039]

[0040] Among them, fr is the video bandwidth, L is the equivalent inductance of the resonant network 12, and C is the output capacitance of the power amplifier 3.

[0041] Under normal circumstances, the power amplifier 3 is composed of transistors. After the type of transistor is determined, its output capacitance is fixed, that is, C remains unchanged. The change of the equivalent inductance L in the resonant network 12 can change the resonant frequency. By reducing the equivalent inductance of the resonant network 12, the resonant frequency is increased. The higher the resonant frequency indicates the wider the video bandwidth, making the linearity of the communication system better and meeting the requirements of high linearity under the high peak-to-average ratio of the communication system. In order to meet the requirements of the stability and harmonic suppression of the power amplifier circuit, the power amplifier circuit needs to input more of its output signals into the resonant network 12 outside the band, reduce the out-of-band gain and output power, and ensure that the subsequent circuit is not affected by out-of-band high frequencies and out-of-band low frequencies. Further, the resonant frequency is the center frequency within the band. At the resonant frequency, the bias network 1 of the power amplifier 3 exhibits a high impedance, which is beneficial for making the bias network 1 equivalent to an open circuit, so that almost all the output signals of the power amplifier 3 can be output to the subsequent circuit 2. The power amplifier circuit can output a higher gain and output power within the band; outside the band, the low-frequency impedance and high-frequency impedance are close to the short-circuit point, which is beneficial for making the bias network 1 equivalent to a short circuit, so that almost all the output signals of the power amplifier 3 can be output to the bias network 1 rather than the subsequent circuit 2. The power amplifier circuit can output a lower gain and output power outside the band.

[0042] When the bias network of the power amplifier provided by the embodiment of the present invention is applied to a non-communication system, the principle is the same. When in the band, the resonant network 12 exhibits a high impedance, making the power amplifier 3 have a relatively high gain and output power. When at out-of-band high frequencies and out-of-band low frequencies, the equivalent inductance of the resonant network 12 is reduced, and the resonant network 12 exhibits a low impedance outside the band, making the power amplifier 3 have a relatively low gain and output power.

[0043] In summary, the bias network of the power amplifier provided by the embodiment of the present invention is provided with a DC power supply 11 and a resonant network 12. The resonant network 12 can adjust the equivalent inductance to form a resonant network between the equivalent inductance of the resonant network 12 and the output capacitance of the power amplifier 3. This resonant network exhibits a high impedance within the band, making the power amplifier 3 have a relatively high gain and output power; it exhibits a low impedance outside the band, making the power amplifier 3 have a relatively low gain and output power, thereby improving the stability of the power amplifier circuit.

[0044] Figure 2 For the schematic diagram of another bias network of the power amplifier provided by the embodiment of the present invention, refer to Figure 2, based on the above embodiments, optionally, the resonant network 12 includes: an inductive element 121 and a capacitive element 122. The inductive element 121 is connected in series between the output terminal of the power amplifier 3 and the positive pole of the DC power supply 11. The first end of the capacitive element 122 is electrically connected to the output terminal of the power amplifier 3, and the second end of the capacitive element 122 is grounded.

[0045] Among them, both the inductive element 121 and the first end of the capacitive element 122 are electrically connected to the output terminal of the power amplifier 3. The inductive element 121 has the function of passing low frequencies and blocking high frequencies; the capacitive element 122 has the function of passing high frequencies and blocking low frequencies. In the out-of-band low frequency, the inductive element 121 plays a major role, allowing the signal output by the power amplifier 3 to pass through, showing a low impedance; in the out-of-band high frequency, the capacitive element 122 plays a major role, allowing the signal output by the power amplifier 3 to pass through, showing a low impedance. Using the parallel structure of the inductive element 121 and the capacitive element 122, this parallel structure and the equivalent capacitance of the power amplifier 3 together form a resonant network, making the impedance at the center frequency within the band the largest and the impedance at the out-of-band high frequency and low frequency the smallest, playing a filtering role. When the bias network of this power amplifier is within the band, the resonant network 12 is close to an open circuit, and the output power of the power amplifier 3 is high. When out of the band, the resonant network 12 is close to a short circuit, which can minimize the out-of-band gain and output power of the power amplifier 3, and can improve the stability and harmonic suppression ability of the power amplifier 3.

[0046] Continue to refer to Figure 2 , based on the above embodiments, optionally, the inductive element 121 includes a transmission line 1211, and the length of the transmission line 1211 is less than λ / 4. The first end of the transmission line 1211 is electrically connected to the output terminal of the power amplifier 3, and the second end of the transmission line 1211 is electrically connected to the positive pole of the DC power supply 11.

[0047] Among them, the transmission line 1211 can be used to transmit electrical energy and electrical signals, and its inductive reactance is variable, capable of showing a high impedance with the capacitor 122 within the band and a low impedance with the capacitor 122 outside the band. The prior art sets the length of the transmission line to λ / 4. In the embodiment of the present invention, the length of the transmission line 1211 is set to be less than λ / 4, and a capacitive element 122 is provided in the resonant network 12, which can reduce the equivalent inductance of the resonant network 12, and the shorter transmission line 1211 can also reduce the signal transmission loss and improve the signal transmission efficiency of the bias network of the power amplifier. The high impedance within the band is achieved through the resonance of the transmission line 1211 less than λ / 4 and the capacitor 122.

[0048] Figure 3 This is a schematic diagram of another bias network of the power amplifier provided by the embodiment of the present invention. Refer to Figure 3, based on the above embodiments, optionally, the inductive element 121 includes a choke inductor 1212. The first end of the choke inductor 1212 is electrically connected to the output end of the power amplifier 3, and the second end of the choke inductor 1212 is electrically connected to the positive pole of the DC power supply 11.

[0049] Among them, the choke inductor 1212 can be regarded as a pure inductive element. In the embodiment of the present invention, the inductance value of the choke inductor 1212 is set to be smaller than that of the choke inductor in the prior art, and a capacitive element 122 is arranged in the resonant network 12. The choke inductor 1212, the capacitive element 122 and the equivalent capacitance of the power amplifier 3 form a resonant network, which can make the impedance of the resonant network maximum at the center frequency within the band and minimum at high and low frequencies outside the band, playing a filtering role and improving the stability and harmonic suppression ability of the power amplifier 3.

[0050] Based on the above embodiments, optionally, the inductance of the inductive element 121 and the capacitance of the capacitive element 122 are inversely proportional.

[0051] Taking the inductive element 121 as the transmission line 1211 as an example, the length of the transmission line 1211 is proportional to the magnitude of the inductance. When the capacitance of the capacitive element 122 is small, the length of the transmission line 1211 needs to be increased adaptively to increase the inductance value, but it is necessary to ensure that the maximum value of the length of the transmission line 1211 is less than 1 / 4 wavelength, so that the transmission line 1211 shows inductance and forms resonance with the capacitive element 122. By setting the inductance of the inductive element 121 and the capacitance of the capacitive element 122 to be inversely proportional, the equivalent inductance at low frequencies can also be reduced, the video bandwidth and linearity of the power amplifier 3 can be improved, and the out-of-band gain and output power can be effectively reduced.

[0052] Continue to refer to Figure 3 , based on the above embodiments, optionally, the capacitive element 122 includes a first capacitor C1. The first end of the first capacitor C1 is electrically connected to the output end of the power amplifier 3, and the second end of the first capacitor C1 is grounded.

[0053] Among them, when the bias network of the power amplifier is outside the band, the resonant network 12 is close to being short-circuited, and high-frequency and low-frequency signals outside the band flow into the resonant network 12. The first capacitor C1 has the function of passing alternating current and blocking direct current, and can consume the high-frequency signals outside the band through the first capacitor C1 and flow out through the grounding end, ensuring the safe operation of the bias network of the power amplifier and ensuring the stable operation state of the bias network of the power amplifier outside the band.

[0054] Continue to refer to Figure 3 , based on the above embodiments, optionally, the bias network of the power amplifier further includes a second capacitor C2. The first end of the second capacitor C2 is electrically connected to the positive pole of the DC power supply 11, and the second end of the second capacitor C2 is grounded.

[0055] Among them, the second capacitor C2 can filter out unnecessary interference signals. By being electrically connected to the positive electrode of the DC power supply 11, when an AC signal is output at the output end of the power amplifier 3, the second capacitor C2 is equivalent to a short circuit. Then, the AC signal can be consumed through the second capacitor C2, making the output voltage of the DC power supply 11 more stable.

[0056] The present invention also provides a power amplifier circuit. Figure 4 As the circuit diagram of a power amplifier circuit provided by an embodiment of the present invention, the power amplifier circuit includes a power amplifier 3 and the bias network of the power amplifier provided in any of the above embodiments, and has the corresponding beneficial effects of the bias network of the power amplifier, which will not be elaborated here.

[0057] Continuing to refer to Figure 4 , on the basis of the above embodiments, optionally, the backend circuit 2 further includes an output matching network 21. The output matching network 21 is electrically connected to the output end of the power amplifier 3, and the output matching network 21 is used to match the load resistance.

[0058] Among them, the output matching network 21 can transform the load resistance into the optimal load resistance required by the power amplifier 3 to ensure maximum output power, reduce link reflection, reduce noise interference, improve the signal-to-noise ratio, and make the output efficiency of the power amplifier 3 higher.

[0059] Continuing to refer to Figure 4 , on the basis of the above embodiments, optionally, the backend circuit 2 further includes a termination load 22. The termination load 22 is electrically connected to the output matching network 21, and the termination load 22 is used to receive the power signal of the power amplifier.

[0060] Figure 5 As the Smith chart of the bias network of a power amplifier provided by an embodiment of the present invention, referring to Figure 5 , as a comparative example, only the λ / 4 transmission line scheme is used in the resonant network of the bias network of the power amplifier.

[0061] Among them, the Smith chart represents the impedance from low to high from left to right, and represents the frequency from low to high from top to bottom. In the figure, the straight line corresponding to the line 6 is the center frequency of the resonant frequency. Taking the center frequency of 1.13 GHz as an example, at this time, the operating point m1 tends to the center frequency, and the corresponding impedance value is relatively large, meeting the requirement that the bias network of the power amplifier shows a high impedance at the center frequency. When the resonant frequency is a high frequency greater than the center frequency and a low frequency less than the center frequency, the impedance values of the corresponding operating points m2 and m3 are relatively low, basically meeting the requirement that the low-frequency impedance and the high-frequency impedance are close to the short-circuit point.

[0062] Figure 6A circular diagram of the bias network of another power amplifier provided by an embodiment of the present invention. Refer to Figure 6 , as a comparative example, the resonant network in the bias network of the power amplifier is a scheme that only uses a choke inductor.

[0063] Among them, the operating point m4 tends to the center frequency, and the corresponding impedance value is relatively large, basically meeting the requirement that the bias network of the power amplifier shows a high impedance at the center frequency. When the resonant frequency is a high frequency greater than the center frequency and a low frequency less than the center frequency, the impedance values of the corresponding operating points m5 and m6 are still relatively large, not meeting the requirement that the low-frequency impedance and high-frequency impedance in the band approach the short-circuit point.

[0064] Figure 7 A circular diagram of the bias network of yet another power amplifier provided by an embodiment of the present invention. Refer to Figure 7 , as a technical solution provided by an embodiment of the present invention, the resonant network in the bias network of the power amplifier is a scheme configured with an inductive element and a capacitive element.

[0065] Among them, the operating point m7 tends to the center frequency, and the corresponding impedance value is relatively large, meeting the requirement that the bias network of the power amplifier shows a high impedance at the center frequency. When the resonant frequency is a high frequency greater than the center frequency and a low frequency less than the center frequency, the impedance values of the corresponding operating points m8 and m9 are relatively small, meeting the requirement that the low-frequency impedance and high-frequency impedance in the band approach the short-circuit point.

[0066] Comparing Figure 5 , Figure 6 and Figure 7 , when the resonant frequency is the center frequency, the impedances of m7, m1, and m4 are all relatively large. At this time, the power amplifier circuit is in the band, and a high impedance can be provided, enabling the power amplifier to have a higher gain and output power. When the resonant frequency is a low frequency less than the center frequency, the impedance value m5 > m2 > m8; when the resonant frequency is a high frequency greater than the center frequency, the impedance value m6 > m3 > m9. At this time, the power amplifier circuit is out of the band, and the impedance value of the resonant network provided by the present invention is lower, reducing the out-of-band gain and output power, and making the power amplifier circuit operate more stably.

[0067] Figure 8 A simulation schematic diagram of the video bandwidth provided by an embodiment of the present invention. Refer to Figure 8, taking the center frequency of 1.13 GHz as an example, when the resonant network only uses a choke inductor, corresponding to the curve on the far left, when the output capacitance of the power amplifier and the choke inductor reach the maximum resonant value, the formed video bandwidth signal is 210 MHz. When the resonant network 12 only uses a λ / 4 transmission line, corresponding to the curve in the middle, when the output capacitance of the power amplifier and the λ / 4 transmission line reach the maximum resonant value, the formed video bandwidth signal is 590 MHz. When using the resonant network provided by the embodiment of the present invention, corresponding to the curve on the far right, when the output capacitance of the power amplifier and the resonant network reach the maximum resonant value, the formed video bandwidth signal is as high as 900 MHz. It can be seen that the power amplifier circuit provided by the embodiment of the present invention forms the highest video bandwidth signal, which will greatly increase the video bandwidth, improve the linearity of the signal, make the digital pre-distortion more friendly, and reduce the out-of-band gain.

[0068] It should be understood that various forms of the processes shown above can be used, with steps reordered, added, or deleted. For example, the steps described in the present invention can be executed in parallel, sequentially, or in a different order, as long as the desired results of the technical solution of the present invention can be achieved, and no limitations are imposed herein.

[0069] The above specific embodiments do not constitute a limitation to the protection scope of the present invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A bias network for a power amplifier, characterized in that, Comprising: A DC power supply and a resonant network; The resonant network is connected between the output terminal of the power amplifier and the positive pole of the DC power supply, and the negative pole of the DC power supply is grounded; The resonant network controls the frequency response of the bias network, showing a high impedance within the band and a low impedance outside the band.

2. The bias network of the power amplifier according to claim 1, characterized in that, The resonant network includes: an inductive element and a capacitive element; The inductive element is connected in series between the output terminal of the power amplifier and the positive pole of the DC power supply; the first end of the capacitive element is electrically connected to the output terminal of the power amplifier, and the second end of the capacitive element is grounded.

3. The bias network of the power amplifier according to claim 2, characterized in that, The inductive element includes a transmission line, and the length of the transmission line is less than λ / 4; The first end of the transmission line is electrically connected to the output terminal of the power amplifier, and the second end of the transmission line is electrically connected to the positive pole of the DC power supply.

4. The bias network of the power amplifier according to claim 2, wherein The inductive element includes a choke inductor; The first end of the choke inductor is electrically connected to the output terminal of the power amplifier, and the second end of the choke inductor is electrically connected to the positive pole of the DC power supply.

5. The bias network of the power amplifier according to claim 2, wherein The inductance of the inductive element and the capacitance of the capacitive element are inversely proportional.

6. The bias network of the power amplifier according to any one of claims 2-5, characterized in that, The capacitive element includes a first capacitor; The first end of the first capacitor is electrically connected to the output terminal of the power amplifier, and the second end of the first capacitor is grounded.

7. The bias network of the power amplifier according to claim 1, characterized in that It further includes a second capacitor; The first end of the second capacitor is electrically connected to the positive pole of the DC power supply, and the second end of the second capacitor is grounded.

8. A power amplifier circuit, characterized in that, It includes a power amplifier and a bias network of the power amplifier according to any one of claims 1-7.

9. The power amplifier circuit according to claim 8, wherein It further includes an output matching network; The output matching network is electrically connected to the output terminal of the power amplifier, and the output matching network is used to match the load resistance.

10. The power amplifier circuit according to claim 9, wherein It further includes a terminal load; The terminal load is electrically connected to the output matching network, and the terminal load is used to receive the power signal of the power amplifier.

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