Low-loss high-precision impedance detection circuit and method

Abstract

The invention discloses a low-loss high-precision impedance detection circuit and method. The impedance detection circuit comprises a signal sensing circuit and a six-port detection circuit. The input end of the signal sensing circuit is connected with the output end of the amplifier, and the output end of the signal sensing circuit is connected with the antenna load. An input end A of the six-port detection circuit is connected with a coupling end A of the signal sensing circuit, an input end B of the six-port detection circuit is connected with a coupling end B of the signal sensing circuit, and four output ends of the six-port detection circuit are respectively connected with the power detector. The amplitude ratio and the phase difference of vector voltages of the input end and the output end of the sensing circuit are obtained through the coupling end A and the coupling end B of the signal sensing circuit and are fed to the input end A and the input end B of the six-port detection circuit, and the output of the power detector connected with the four output ports of the six-port detection circuit is utilized. The amplitude ratio and the phase difference of the vector voltage of the input end A and the input end B of the six-port circuit are obtained through calculation, and then the impedance of the antenna load is obtained. The circuit is simple in structure, the signal power for impedance detection through sensing circuit coupling is small, power loss caused by impedance detection is reduced, and high measurement precision is achieved on the premise that the working state of the amplifier is not affected.

Description

Technical Field

[0001] The present invention belongs to the field of radio frequency technology, and in particular to a low-loss and high-precision impedance detection circuit and method. Background Art

[0002] Due to their advantages in spatial power synthesis and beam steering, new generation radio systems increasingly rely on phased array and MIMO (multiple input multiple output) systems. A particular challenge in antenna arrays is that the coupling between array elements changes with the scanning angle, resulting in dynamic changes in the driving point impedance at the antenna. This change will cause the power amplifier load impedance to deviate from its optimal impedance, significantly reducing the efficiency, output power, linearity, and ultimately the stability of the power amplifier. In order to solve the degradation of PA (power amplifier) ​​performance due to load changes, an isolator can be placed between the PA and the load, but this solution increases the loss, volume, and cost of the transmitter and is impractical for antenna arrays. Another method is to place a reconfigurable matching network between the PA and the load. At this time, an impedance detection circuit is required to measure the load impedance to compensate for the load changes and restore PA performance.

[0003] At present, there are many methods for detecting load impedance, such as measuring the reflection coefficient by collecting the incident voltage wave signal and the reflected voltage wave signal coupled by the directional coupler. However, the cascade coupler in the signal path does not work for the realization of output matching, which will lead to additional size and loss. Alternatively, the reflection coefficient can be measured by extracting the vector voltage of two nodes on a short-distance transmission line through capacitive coupling. However, if the capacitance value is too large, the power loss caused by impedance detection will increase. If the capacitance value is too small, the accuracy of impedance detection will be affected and it will be difficult to achieve. In addition, the structure of capacitive coupling will introduce errors to the impedance measurement. Summary of the invention

[0004] The purpose of the present invention is to provide a low-loss and high-precision impedance detection circuit and method to address the problems existing in the above-mentioned prior art.

[0005] The technical solution to achieve the purpose of the present invention is: a low-loss and high-precision impedance detection circuit, the circuit comprising a signal sensing circuit and a six-port detection circuit;

[0006] The input end of the signal sensing circuit is connected to the output end of the amplifier, the output end of the signal sensing circuit is connected to the antenna load, and the coupling end A and the coupling end B of the signal sensing circuit couple out vector voltage signals respectively;

[0007] The input terminal A of the six-port detection circuit is connected to the coupling terminal A of the signal sensing circuit, the input terminal B of the six-port detection circuit is connected to the coupling terminal B of the signal sensing circuit, and the four output ports of the six-port detection circuit are respectively connected to the power detector.

[0008] Further, the signal sensing circuit includes two sections of coupling lines and one section of transmission line; the two sections of coupling lines include coupling line 1 and coupling line 2, and the one section of transmission line includes transmission line 1; the coupling line 1 and the coupling line 2 are both provided with Port 1, Port 2, Port 3 and Port 4; Port 1 of the coupling line 1 serves as the input end of the signal sensing circuit, Port 2 of the coupling line 1 is connected to Port 1 of the coupling line 2 through the transmission line 1, Port 3 of the coupling line 1 serves as the coupling end A of the signal sensing circuit, and Port 4 of the coupling line 1 is open; Port 2 of the coupling line 2 serves as the output end of the signal sensing circuit, Port 3 of the coupling line 2 is open, and Port 4 of the coupling line 2 serves as the coupling end B of the signal sensing circuit.

[0009] Further, the six-port detection circuit includes a power divider and three directional couplers; the three directional couplers include directional coupler 1, directional coupler 2 and directional coupler 3, and the directional coupler 1, directional coupler 2 and directional coupler 3 are all provided with an input end, a through end, a coupling end and an isolation end; the power divider is provided with an input end and two output ends;

[0010] The input end of the power divider serves as the input end A of the six-port detection circuit; the input end of the directional coupler 1 is connected to the output end 1 of the power divider, the through end of the directional coupler 1 serves as the output end 1 of the six-port detection circuit, the coupling end of the directional coupler 1 serves as the output end 2 of the six-port detection circuit, and the isolation end of the directional coupler 1 is connected to the input end of the directional coupler 2;

[0011] The through end of the directional coupler 2 is grounded through a load resistor, the coupling end of the directional coupler 2 serves as the input end B of the six-port detection circuit, and the isolation end of the directional coupler 2 is connected to the input end of the directional coupler 3;

[0012] The through end of the directional coupler 3 serves as the output end 3 of the six-port detection circuit, the coupling end of the directional coupler 3 serves as the output end 4 of the six-port detection circuit, and the isolation end of the directional coupler 3 is connected to the output end 2 of the power divider.

[0013] On the other hand, an impedance detection method based on the low-loss impedance detection circuit is provided, the method comprising:

[0014] Step 1, the signal sensing circuit couples the vector voltage signals of its input and output ends to its coupling end A and coupling end B, and the six-port detection circuit obtains the vector voltage signals of the coupling end A and coupling end B of the signal sensing circuit through the input end A and input end B;

[0015] Step 2, combining the output of the power detector connected to the four output terminals of the six-port detection circuit and the S parameter of the six-port detection circuit, calculating the amplitude ratio and phase difference of the vector voltage signal at the input terminal A and the input terminal B of the six-port detection circuit, that is, the amplitude ratio and phase difference of the vector voltage signal at the input terminal and the output terminal of the signal sensing circuit;

[0016] Step 3, combining the calculation result of step 2 and the Z parameter of the signal sensing circuit, calculate and obtain the impedance of the antenna load.

[0017] Furthermore, the phase difference of the vector voltage signals at the two input terminals of the six-port detection circuit is The calculation formula is:

[0018]

[0019] Wherein, B3, B4, B5 and B6 are the output powers of the four output ports of the six-port detection circuit passing through the power detector.

[0020] Furthermore, the calculation formula of the amplitude ratio ε of the vector voltage signals at the two input terminals of the six-port detection circuit is:

[0021]

[0022] Furthermore, for the signal sensing circuit, when only the input and output ports are considered, it is regarded as a two-port network, and the Z matrix of this two-port network is expressed as:

[0023]

[0024] Among them, Z 11 It represents the input impedance to port 1 when port 2 is open in a two-port network; Z 22 It represents the input impedance to port 2 when port 1 is open in a two-port network; Z 12 represents the transfer impedance from port 2 to port 1; Z 21 represents the transfer impedance from port 1 to port 2;

[0025] Therefore, according to the definition of the Z parameter, the relationship between the amplitude ratio and phase difference of the vector voltage signal at the input and output ends of the signal sensing circuit and the antenna load impedance is obtained as follows:

[0026]

[0027] Based on the above relationship, the antenna load impedance Z is obtained L .

[0028] Compared with the prior art, the present invention has the following significant advantages:

[0029] (1) The signal sensing circuit of the present invention is composed of two coupling lines and one transmission line. Compared with the directional coupler, the size is smaller, and the transmission line can participate in output matching, thereby improving area utilization.

[0030] (2) The signal sensing circuit of the present invention adjusts the strength of the coupling signal by controlling the coupling spacing of the coupling line, thereby reducing the power loss caused by impedance detection while ensuring the measurement accuracy, and does not affect the working state of the amplifier.

[0031] (3) The influence of the signal sensing circuit of the present invention on the load impedance of the antenna to be measured can be calibrated by impedance transformation when the characteristic impedance and electrical length of the transmission line in the signal sensing circuit are known, thereby improving the measurement accuracy.

[0032] (4) The six-port impedance detection circuit of the present invention has a simple structure, low cost, and can achieve a broadband structure.

[0033] The present invention is further described in detail below in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 FIG. 4 is a block diagram of a low-loss and high-precision impedance detection circuit according to an embodiment of the present invention.

[0035] Figure 2 FIG. 4 is a block diagram of a signal sensing circuit of the present invention in one embodiment.

[0036] Figure 3 FIG. 4 is a block diagram of a six-port detection circuit of the present invention in one embodiment. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0038] In one embodiment, in combination Figure 1 , provides a low-loss and high-precision impedance detection circuit, the circuit comprising a signal sensing circuit and a six-port detection circuit;

[0039] The input end of the signal sensing circuit is connected to the output end of the amplifier, the output end of the signal sensing circuit is connected to the antenna load, and the coupling end A and the coupling end B of the signal sensing circuit couple out vector voltage signals respectively;

[0040] The input terminal A of the six-port detection circuit is connected to the coupling terminal A of the signal sensing circuit, the input terminal B of the six-port detection circuit is connected to the coupling terminal B of the signal sensing circuit, and the four output ports of the six-port detection circuit are respectively connected to the power detector.

[0041] Further, in one embodiment, in combination Figure 2 , the signal sensing circuit includes two sections of coupling lines and one section of transmission line; the two sections of coupling lines include coupling line 1 and coupling line 2, and the one section of transmission line includes transmission line 1; the coupling line 1 and the coupling line 2 are both provided with Port 1, Port 2, Port 3 and Port 4; Port 1 of the coupling line 1 serves as the input end of the signal sensing circuit, Port 2 of the coupling line 1 is connected with Port 1 of the coupling line 2 through the transmission line 1, Port 3 of the coupling line 1 serves as the coupling end A of the signal sensing circuit, and Port 4 of the coupling line 1 is open; Port 2 of the coupling line 2 serves as the output end of the signal sensing circuit, Port 3 of the coupling line 2 is open, and Port 4 of the coupling line 2 serves as the coupling end B of the signal sensing circuit.

[0042] Further, in one embodiment, in combination Figure 3 , the six-port detection circuit includes a power divider and three directional couplers; the three directional couplers include directional coupler 1, directional coupler 2 and directional coupler 3, and the directional coupler 1, directional coupler 2 and directional coupler 3 are all provided with an input end, a through end, a coupling end and an isolation end; the power divider is provided with an input end and two output ends;

[0043] The input end of the power divider serves as the input end A of the six-port detection circuit; the input end of the directional coupler 1 is connected to the output end 1 of the power divider, the through end of the directional coupler 1 serves as the output end 1 of the six-port detection circuit, the coupling end of the directional coupler 1 serves as the output end 2 of the six-port detection circuit, and the isolation end of the directional coupler 1 is connected to the input end of the directional coupler 2;

[0044] The through end of the directional coupler 2 is grounded through a load resistor, the coupling end of the directional coupler 2 serves as the input end B of the six-port detection circuit, and the isolation end of the directional coupler 2 is connected to the input end of the directional coupler 3;

[0045] The through end of the directional coupler 3 serves as the output end 3 of the six-port detection circuit, the coupling end of the directional coupler 3 serves as the output end 4 of the six-port detection circuit, and the isolation end of the directional coupler 3 is connected to the output end 2 of the power divider.

[0046] In some embodiments, the structure of the six-port detection circuit can be replaced by a six-port structure composed of microwave branching elements with special properties such as directional couplers, power dividers or phase shifters. The six-port detection circuit requires that the phase difference of the output signals of output terminal 1 and output terminal 2 is constant within the working frequency band, and the phase difference of the output signals of output terminal 3 and output terminal 4 is constant.

[0047] In one embodiment, an impedance detection method based on the low-loss and high-precision impedance detection circuit is provided, the method comprising:

[0048] Step 1, the signal sensing circuit couples the vector voltage signals of its input and output ends to its coupling end A and coupling end B, and the six-port detection circuit obtains the vector voltage signals of the coupling end A and coupling end B of the signal sensing circuit through the input end A and input end B;

[0049] Step 2, combining the output of the power detector connected to the four output terminals of the six-port detection circuit and the S parameter of the six-port detection circuit, calculating the amplitude ratio and phase difference of the vector voltage signal at the input terminal A and the input terminal B of the six-port detection circuit, that is, the amplitude ratio and phase difference of the vector voltage signal at the input terminal and the output terminal of the signal sensing circuit;

[0050] Step 3: Combine the calculation result of step 2 and the Z parameter of the signal sensing circuit to calculate the impedance of the antenna load.

[0051] Here, the four output ports of the six-port detection circuit are connected to the two input ports through the amplitude ratio ε and phase difference of the vector voltage of the power detector output. The relationship is:

[0052]

[0053]

[0054]

[0055]

[0056] Therefore, the amplitude ratio ε and phase difference of the vector voltage signals at the two input terminals of the six-port detection circuit are The calculation formula is:

[0057]

[0058]

[0059] Wherein, B3, B4, B5 and B6 are the output powers of the four output ports of the six-port detection circuit through the power detector.

[0060] Here, for the signal sensing circuit, when only the input and output ports are considered, it is regarded as a two-port network, and the Z matrix of this two-port network is expressed as:

[0061]

[0062] Among them, Z 11 It represents the input impedance to port 1 when port 2 is open in a two-port network; Z 22 It represents the input impedance to port 2 when port 1 is open in a two-port network; Z 12 represents the transfer impedance from port 2 to port 1; Z 21 represents the transfer impedance from port 1 to port 2;

[0063] Therefore, according to the definition of the Z parameter, the relationship between the amplitude ratio and phase difference of the vector voltage signal at the input and output ends of the signal sensing circuit and the antenna load impedance is obtained as follows:

[0064]

[0065] Based on the above relationship, the antenna load impedance Z is obtained L .

[0066] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A low-loss and high-precision impedance detection circuit, characterized in that: The circuit includes a signal sensing circuit and a six-port detection circuit; The input end of the signal sensing circuit is connected to the output end of the amplifier, the output end of the signal sensing circuit is connected to the antenna load, and the coupling end A and the coupling end B of the signal sensing circuit couple out vector voltage signals respectively; The input terminal A of the six-port detection circuit is connected to the coupling terminal A of the signal sensing circuit, the input terminal B of the six-port detection circuit is connected to the coupling terminal B of the signal sensing circuit, and the four output ports of the six-port detection circuit are respectively connected to the power detector.

2. The low-loss and high-precision impedance detection circuit according to claim 1, characterized in that: The signal sensing circuit includes two sections of coupling lines and one section of transmission line; the two sections of coupling lines include coupling line 1 and coupling line 2, and the one section of transmission line includes transmission line 1; the coupling line 1 and the coupling line 2 are both provided with Port 1, Port 2, Port 3 and Port 4; Port 1 of the coupling line 1 serves as the input end of the signal sensing circuit, Port 2 of the coupling line 1 is connected with Port 1 of the coupling line 2 through the transmission line 1, Port 3 of the coupling line 1 serves as the coupling end A of the signal sensing circuit, and Port 4 of the coupling line 1 is open; Port 2 of the coupling line 2 serves as the output end of the signal sensing circuit, Port 3 of the coupling line 2 is open, and Port 4 of the coupling line 2 serves as the coupling end B of the signal sensing circuit.

3. The low-loss and high-precision impedance detection circuit according to claim 1, characterized in that: The six-port detection circuit includes a power divider and three directional couplers; the three directional couplers include directional coupler 1, directional coupler 2 and directional coupler 3, and the directional coupler 1, directional coupler 2 and directional coupler 3 are all provided with an input end, a through end, a coupling end and an isolation end; the power divider is provided with an input end and two output ends; The input end of the power divider serves as the input end A of the six-port detection circuit; the input end of the directional coupler 1 is connected to the output end 1 of the power divider, the through end of the directional coupler 1 serves as the output end 1 of the six-port detection circuit, the coupling end of the directional coupler 1 serves as the output end 2 of the six-port detection circuit, and the isolation end of the directional coupler 1 is connected to the input end of the directional coupler 2; The through end of the directional coupler 2 is grounded through a load resistor, the coupling end of the directional coupler 2 serves as the input end B of the six-port detection circuit, and the isolation end of the directional coupler 2 is connected to the input end of the directional coupler 3; The through end of the directional coupler 3 serves as the output end 3 of the six-port detection circuit, the coupling end of the directional coupler 3 serves as the output end 4 of the six-port detection circuit, and the isolation end of the directional coupler 3 is connected to the output end 2 of the power divider.

4. An impedance detection method based on the low-loss and high-precision impedance detection circuit according to any one of claims 1 to 3, characterized in that: The method comprises: Step 1, the signal sensing circuit couples the vector voltage signals of its input and output ends to its coupling end A and coupling end B, and the six-port detection circuit obtains the vector voltage signals of the coupling end A and coupling end B of the signal sensing circuit through the input end A and input end B; Step 2, combining the output of the power detector connected to the four output terminals of the six-port detection circuit and the S parameter of the six-port detection circuit, calculating the amplitude ratio and phase difference of the vector voltage signal at the input terminal A and the input terminal B of the six-port detection circuit, that is, the amplitude ratio and phase difference of the vector voltage signal at the input terminal and the output terminal of the signal sensing circuit; Step 3: Combine the calculation result of step 2 and the Z parameter of the signal sensing circuit to calculate the impedance of the antenna load.

5. The impedance detection method according to claim 4, characterized in that: The phase difference of the vector voltage signal at the two input terminals of the six-port detection circuit is The calculation formula is: Wherein, B3, B4, B5 and B6 are the output powers of the four output ports of the six-port detection circuit through the power detector.

6. The impedance detection method according to claim 5, characterized in that: The calculation formula of the amplitude ratio ε of the vector voltage signals at the two input terminals of the six-port detection circuit is:

7. The impedance detection method according to claim 6, characterized in that: For the signal sensing circuit, when only the input and output ports are considered, it is regarded as a two-port network. The Z matrix of this two-port network is expressed as: Among them, Z 11 It represents the input impedance to port 1 when port 2 is open in a two-port network; Z 22 It represents the input impedance to port 2 when port 1 is open in a two-port network; Z 12 represents the transfer impedance from port 2 to port 1; Z 21 represents the transfer impedance from port 1 to port 2; Therefore, according to the definition of the Z parameter, the relationship between the amplitude ratio and phase difference of the vector voltage signal at the input and output ends of the signal sensing circuit and the antenna load impedance is obtained as follows: Based on the above relationship, the antenna load impedance Z is obtained L .

Images