Power amplifier without impedance detection

Abstract

The invention discloses a power amplifier without impedance detection, and belongs to the technical field of microwave power amplifiers. The power amplifier comprises a power amplifier module, a mismatch impedance correction network module and a circular polarization radio frequency antenna module, the power amplifier is used for amplifying a power signal; the multi-port mismatch impedance correction network is used for correcting mismatch impedance under a certain mismatch amplitude to a certain fixed impedance so as to complete the anti-mismatch purpose; the radio frequency antenna is used for transmitting a radio frequency power signal to a radio frequency space through the antenna. Impedance correction can be completed without a feedback impedance calculation network. According to the invention, mismatch impedance correction of any phase can be completed, the performance loss is only related to VSWR, and the correction effect is excellent.

Description

Technical Field

[0001] The invention belongs to the technical field of microwave power amplifiers, and in particular designs a power amplifier mismatch impedance correction network structure that does not require impedance detection. Background Art

[0002] With the development of the wireless communication industry, the requirements for information transmission are getting higher and higher. In the field of wireless communication, high-efficiency RF power amplifiers are one of the important components of wireless transceiver systems. In order to adapt to the complex environment faced by modern communications, especially in mobile terminals and other systems, non-standard impedance environments caused by hand effects may be encountered. The change in impedance may affect the power efficiency and linearity of the power amplifier, so the anti-mismatch performance of the power amplifier has received the attention of many researchers.

[0003] At present, there are many directions for the research and analysis of anti-mismatch performance. Most of the research directions are generally based on the performance correction of the power amplifier itself, mainly targeting the output matching network, bias voltage, drain voltage, etc. of the power amplifier. With the in-depth research of scholars, various solutions such as reconfigurable technology, dual-input voltage control technology, and working state switching have been continuously proposed. The main principle of the above technologies is to adjust the impedance of the load network or the impedance required by the transistor, and finally match the two to achieve the purpose of anti-mismatch. Among them, the reconfigurable technology mainly adjusts the output matching network after detecting the specific mismatch impedance, so that it adapts to the impedance change and reduces the impact of mismatch. After detecting the mismatch impedance, the dual-input voltage technology calculates the voltage required by the transistor according to the specific impedance value and adjusts it, so as to maintain the overall performance of the power amplifier. Mode switching often combines two methods to change the entire working state of the power amplifier, thereby achieving the purpose of anti-mismatch.

[0004] There have been many studies on performance recovery in the event of full phase mismatch. However, it is not difficult to find that the above methods all require first testing the value or approximate range of the mismatch impedance before making adjustments, which undoubtedly increases the complexity of system implementation. Summary of the invention

[0005] The prior art can only correct the mismatch in a certain area, and the impedance under the mismatch needs to be measured, and different correction effects are shown under different phase mismatches. The present invention provides a power amplifier that can be implemented without detecting the load impedance, and the port impedance of the power amplifier is adaptively adjusted according to the mismatch impedance of the antenna end face to maintain it at a fixed value, thereby maintaining the performance of the power amplifier unchanged.

[0006] The structure of the present invention is as follows Figure 1As shown, the technical solution is: a power amplifier without impedance detection, the power amplifier comprising: a power amplifier module, a mismatched impedance correction network module, and a circularly polarized radio frequency antenna module;

[0007] The power amplifier module comprises: a first power divider, a first input matching network, a second input matching network, a main transistor, an auxiliary transistor, a first output matching network, a second output matching network, and a post-matching network; the input of the entire power amplifier is first divided into two paths through the first power divider, one path passes through the first input matching network, the main transistor, and the first output matching network in sequence, and the other path passes through the second input matching network, the auxiliary transistor, and the second output matching network in sequence, and the outputs of the first output matching network and the second output matching network are input to the post-matching network together; the common node of the first input matching network and the main transistor, and the common node of the second input matching network and the auxiliary transistor are both connected to the reference voltage VGG; the common node of the main transistor and the first output matching network, and the common node of the auxiliary transistor and the second output matching network are both connected to the input voltage VDD; the output of the post-matching network is the output of the power amplifier module;

[0008] The mismatched impedance correction network module includes: three DC blocking capacitors, three 1 / 4 wavelength microstrip lines, a resistor, and two matching networks. The input of the mismatched impedance correction network module is the output of the power amplifier module. The input is divided into two paths after passing through the first DC blocking capacitor. The first path passes through the first 1 / 4 wavelength microstrip line and the first matching network in sequence, and is connected to one end of the circularly polarized antenna after the second DC blocking capacitor. The second path passes through the second 1 / 4 wavelength microstrip line, the third 1 / 4 wavelength microstrip line, and the second matching network in sequence, and is connected to the other end of the circularly polarized antenna after the third DC blocking capacitor; the common node of the first 1 / 4 wavelength microstrip line and the first matching network is connected to one end of the resistor, and the common node of the second 1 / 4 wavelength microstrip line and the third 1 / 4 wavelength microstrip line is connected to the other end of the resistor.

[0009] Furthermore, the power amplifier operates in a frequency band of 1.7 GHz to 2.7 GHz.

[0010] Furthermore, the characteristic impedances of the first 1 / 4 wavelength microstrip line and the second 1 / 4 wavelength microstrip line are The characteristic impedance of the third 1 / 4 wavelength microstrip line is Z0, and the resistance impedance is 2Z0. Z0 is the port impedance of the impedance correction network and is also the load impedance when designing the front-end power amplifier.

[0011] Furthermore, the S parameter matrix of the mismatch impedance correction network module is:

[0012]

[0013] Among them, a n is the incident wave at port n; bn is the reflected wave at port n.

[0014] The present invention proposes a mismatch impedance correction structure based on a multi-port network. By introducing the mismatch correction structure after the power amplifier, the mismatch performance of the power amplifier is corrected through the anti-mismatch performance under mismatch, and then connected to the radio frequency antenna, thereby achieving the anti-mismatch performance of the overall architecture. The present invention can complete the correction under full phase mismatch through the mismatch correction network without the need for various impedance feedback calculation networks. At the same time, no additional design requirements are proposed for the power amplifier, so a variety of solutions can be used to achieve advantages such as broadband high efficiency, so that the anti-mismatch performance under the requirements of a broadband feedback-free network can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 An implementation structure diagram of a power amplifier anti-mismatch network provided by an embodiment of the present invention;

[0016] Figure 2 A diagram showing the structure of a power amplifier according to an embodiment of the present invention;

[0017] Figure 3 A schematic diagram of a mismatched impedance correction network provided by an embodiment of the present invention;

[0018] Figure 4 A Smith chart of mismatched impedance provided by an embodiment of the present invention;

[0019] Figure 5 A Smith chart of the mismatched impedance provided by the embodiment of the present invention after being corrected by an impedance correction network;

[0020] Figure 6 1 is the power efficiency result of the power amplifier under the nominal impedance of the embodiment of the present invention.

[0021] Figure 7 1 is the power efficiency result of the power amplifier of the embodiment of the present invention under mismatched impedance.

[0022] Figure 8 This is the power amplifier performance result after passing through the multi-port mismatch impedance correction network according to the embodiment of the present invention.

[0023] In the figure: a n is the incident wave at port n; b n is the reflected wave of port n; Z0 is the port impedance of the impedance correction network, which is also the load impedance when designing the front-end power amplifier; Z1, Z2, Z3 are the port impedances of mismatched impedance correction network 1, 2, 3 respectively; Z4 is the port impedance of output port 3; 1, power amplifier input port; 2, mismatched impedance correction network input port; 3, 4, mismatched impedance correction network output ports. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the following specific implementation methods are given to further describe the present invention in detail. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0025] Power amplifier: To produce higher efficiency and output power, a single output architecture is required, and it can produce better output performance under fixed impedance, responsible for providing overall power and efficiency. It should be noted that the power amplifier needs to be designed together with the subsequent mismatch impedance correction network to obtain impedance correction effect. Figure 2 A block diagram of the Doherty power amplifier suitable for this scheme is given. After the signal is input, it is divided into two signals through the power divider, and then matched to the optimal input impedance of the transistor through the main and auxiliary matching networks, and then amplified through the main and peak transistors respectively. After the signal is output, it is matched to the same impedance point through the output matching circuit for synthesis, and then matched to a fixed characteristic impedance Z0 through the post-matching network. It should be noted that Z0 here is the same as the port impedance of the subsequent mismatched impedance correction network, thereby achieving the impedance correction effect.

[0026] Mismatched impedance correction network: The mismatched impedance correction network can be implemented here using a multi-port network. Its main function is to correct the impedance in the mismatched condition to the characteristic impedance of the network, thereby maintaining the overall performance without causing significant performance loss due to load mismatch. Figure 3 The impedance correction network design theoretical analysis diagram is given. The matching network function is to complete the circular polarization antenna matching under the condition of no mismatch, and because the impedance of ports 2 and 3 is consistent, the two matching networks are consistent, so the influence of the DC blocking capacitor and the matching network can be ignored. At this time, its S parameter matrix is ​​as follows:

[0027]

[0028] In this formula, a n is the incident wave at port n; b n is the reflected wave of port n; Z0 in the figure is the port impedance of the impedance correction network, which is also the load impedance when the front-end power amplifier is designed; Z1, Z2, and Z3 are the impedances of ports 1, 2, and 3 respectively; at this time, since 2 and 3 are connected to the same circularly polarized antenna, they can have the same mismatched impedance, so Z2=Z3:

[0029]

[0030]

[0031]

[0032]

[0033]

[0034] Combining the above formulas, we can get:

[0035] b1=0

[0036] At this time, b1 is 0, indicating that there is no reflected wave at port 1, and the port maintains Z0 impedance without being affected. According to relevant theories, when the termination impedances of output port 2 and output port 3 are the same, input port 1 can meet the impedance matching conditions and complete the impedance mismatch correction. In addition, the output powers of the two output ports are the same and the phase difference is 90°, which meets the circularly polarized antenna input conditions.

[0037] RF antenna: The main function of the RF antenna here is to transmit the received power signal and complete the function of the overall transmitter. At the same time, the mismatch at the antenna end can be reflected to the mismatch correction network through the connection port. The RF antenna here needs to be designed jointly with the mismatch impedance correction network. According to the previous analysis, the two input signals here are two signals of the same size and a phase difference of 90 degrees, which meet the circular polarization input conditions, and the circular polarization antenna can generate consistent mismatch impedance when mismatched, meeting the anti-mismatch conditions, so a circular polarization antenna structure is required here.

[0038] In view of the problems existing in the prior art, the present invention provides a power amplifier anti-mismatch structure without an impedance calculation network. The main protection points of the present invention are the network structure composed of a power amplifier and a multi-port mismatch impedance correction module and a subsequent circularly polarized antenna.

[0039] How the components might connect and work:

[0040] 1. Signal input: The signal is first input into the power amplifier. The power amplifier should be designed to meet high efficiency, and the output impedance during design should be consistent with the characteristic impedance of the subsequent equipment to obtain a good impedance correction effect. After being amplified, the signal will be output through a single port to the subsequent mismatch impedance correction network.

[0041] 2. Impedance correction: The amplified signal is input into the impedance correction network, which then inputs the signal into the subsequent RF antenna. The impedance correction network is mainly implemented using a multi-port network. When a mismatch occurs, the mismatched impedance of circular polarization can achieve the same impedance size. According to the previous analysis, in the case of a mismatch, the same impedance will be corrected to a fixed impedance through the impedance correction network, thereby maintaining the overall performance unchanged.

[0042] 3. RF antenna: The power signal is then output to the RF antenna network through multiple ports and radiated into the free space through the antenna port. The RF antenna here can reflect the RF impedance to the impedance correction network connected to the front end. The RF antenna is mainly implemented using a circularly polarized antenna network. The circularly polarized antenna can not only reflect the RF impedance to the front-end correction network, but also complete the RF power transmission of the two ports to ensure the overall power performance. Since the power output by the previous characteristic impedance correction network is two power amplifiers with the same power and a phase difference of 90°. In order to be able to transmit this power to free space, a circularly polarized antenna is selected to transmit the signal. At the same time, when a mismatch occurs, the mismatch impedance of the circularly polarized antenna can also be corrected through the impedance correction network, thereby reducing the impact on the power amplifier. In addition, it should be noted that for the overall performance of the system, the circularly polarized antenna should also work under the input impedance condition of Z0 during design, thereby completing the overall impedance correction network structure.

[0043] In summary, the structure proposed in the present invention includes three modules: a power amplifier module, an impedance correction network, and a circularly polarized antenna module. The main effect of the present invention is that it can correct the full phase mismatch through the mismatch correction network without the need for various impedance feedback calculation networks.

[0044] like Figure 1 As shown, an implementation example provided by an embodiment of the present invention.

[0045] The signal enters through input port 1, and then the power amplifier outputs the power signal from the output port to the impedance correction network. At the same time, the power amplifier should be designed to work under 50 ohm load conditions. The impedance correction network is a multi-port network, as shown in the figure Figure 3 As shown. According to the previous analysis, the network can meet the following requirements: when the impedances connected to ports 3 and 4 are the same, the impedance of port 2 is a fixed 50 ohms. Therefore, when a mismatch occurs, the mismatched impedance does not affect the output port impedance of the power amplifier, thereby maintaining the overall performance under mismatch. Subsequently, the two output power signals show the characteristics of equal power and a phase difference of 90 degrees, which meets the input power requirements of the circularly polarized antenna. Therefore, the signal can be output to the circularly polarized antenna, thereby radiating the overall natural power into free space.

[0046] The following will describe the mismatch performance correction effect of a specific power amplifier and the proposed multi-port mismatch impedance correction network as an implementation example.

[0047] like Figure 2 As shown: To verify the effectiveness of the system, a Doherty power amplifier module that can be applied to the system is designed, and its characteristic impedance when working is Z0. The performance of its power amplifier is shown in Figure 6 As shown, the saturation power of the amplifier is about 38.5dBm at the operating frequency of 2.2GHz, and the back-off point efficiency is about 50%.

[0048] like Figure 4 As shown: In order to verify the mismatch impedance correction characteristics of the present invention, a certain degree of full-phase mismatch impedance points are given for experimental verification. The mismatch impedance VSWR selected here is 2.0, and 8 mismatch impedance points are selected under 0-360° phase mismatch for mismatch impedance correction experiment.

[0049] like Figure 5 As shown: Figure 4 The mismatched impedance shown is then connected to the load end of the multi-port mismatched impedance correction network for correction, and the impedance value at the input port of the mismatched impedance correction network is detected. The mismatched impedance correction network operates in the 2.2GHz frequency band. The correction result is as follows Figure 5 As shown, the input impedance is corrected to about 50 ohms, proving that the structure can effectively achieve impedance correction results.

[0050] like Figure 7 As shown: Figure 4 The mismatched impedance in the circuit is connected to the RF power amplifier to verify the mismatched impedance test results of the power amplifier without the anti-mismatch network. It can be seen that the performance shows different performance characteristics at different phases, where the lowest power is about 37dBm, and the reduction is about 1.5dBm. The back-off point efficiency is reduced to 36%, and the reduction is about 14%. The overall mismatch performance loss is large when the VSWR is 2.

[0051] like Figure 8 As shown, Figure 4 The mismatched impedance is corrected by a multi-port mismatched impedance correction network and then connected to a Doherty power amplifier to verify the combined anti-mismatch performance of the two. Since the multi-port mismatched impedance correction network here is a two-port output network, the power calculation here is the sum of the output powers of the two ports. It can be seen that since the mismatched impedance correction network can correct the full-phase mismatched impedance to 50Ohm, it will not show different performance due to different phases. And the saturated power is 38, a reduction of about 0.5dBm; the back-off point efficiency is 45%, a reduction of about 5%. Compared with the case where the mismatched impedance correction network is not applied, the overall anti-mismatch characteristics are good.

[0052] It can be seen that this embodiment provides a power amplifier anti-mismatch structure that does not require an impedance detection network. After the power signal is amplified by the power amplifier, the mismatch impedance is self-corrected through the multi-port load impedance correction network. As a result, the overall performance is corrected in the full phase mismatch situation and the full phase correction effect is consistent.

[0053] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with the technical field within the technical scope disclosed by the present invention and within the spirit and principle of the present invention should be covered by the protection scope of the present invention.

Claims

1. A power amplifier without impedance detection, the power amplifier comprising: Power amplifier module, mismatched impedance correction network module, circularly polarized RF antenna module; The power amplifier module comprises: a first power divider, a first input matching network, a second input matching network, a main transistor, an auxiliary transistor, a first output matching network, a second output matching network, and a post-matching network; the input of the entire power amplifier is first divided into two paths through the first power divider, one path passes through the first input matching network, the main transistor, and the first output matching network in sequence, and the other path passes through the second input matching network, the auxiliary transistor, and the second output matching network in sequence, and the outputs of the first output matching network and the second output matching network are input to the post-matching network together; the common node of the first input matching network and the main transistor, and the common node of the second input matching network and the auxiliary transistor are both connected to the reference voltage VGG; the common node of the main transistor and the first output matching network, and the common node of the auxiliary transistor and the second output matching network are both connected to the input voltage VDD; the output of the post-matching network is the output of the power amplifier module; The mismatched impedance correction network module includes: three DC blocking capacitors, three 1 / 4 wavelength microstrip lines, a resistor, and two matching networks. The input of the mismatched impedance correction network module is the output of the power amplifier module. The input is divided into two paths after passing through the first DC blocking capacitor. The first path passes through the first 1 / 4 wavelength microstrip line and the first matching network in sequence, and is connected to one end of the circularly polarized antenna after the second DC blocking capacitor. The second path passes through the second 1 / 4 wavelength microstrip line, the third 1 / 4 wavelength microstrip line, and the second matching network in sequence, and is connected to the other end of the circularly polarized antenna after the third DC blocking capacitor; the common node of the first 1 / 4 wavelength microstrip line and the first matching network is connected to one end of the resistor, and the common node of the second 1 / 4 wavelength microstrip line and the third 1 / 4 wavelength microstrip line is connected to the other end of the resistor.

2. A power amplifier without impedance detection as claimed in claim 1, characterized in that: The power amplifier operates in a frequency band of 1.7 GHz to 2.7 GHz.

3. A power amplifier without impedance detection as claimed in claim 1, characterized in that: The characteristic impedance of the first 1 / 4 wavelength microstrip line and the second 1 / 4 wavelength microstrip line is: The characteristic impedance of the third 1 / 4 wavelength microstrip line is Z0, the resistance impedance is 2Z0, and Z0 is the port impedance of the mismatched impedance correction network module.

4. A power amplifier without impedance detection as claimed in claim 1, characterized in that: The S-parameter matrix of the mismatched impedance correction network module: Among them, a n is the incident wave at port n; b n is the reflected wave at port n.

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