A balanced dual-frequency filter phase shifter

Abstract

The present invention discloses a balanced dual-frequency filter phase shifter, which loads two quarter-wavelength coupling lines at both ends of a pair of parallel microstrip lines, and loads an open-circuit microstrip line, a short-circuit microstrip line and a resistor at the terminal of the coupling line, so as to realize a balanced dual-frequency filter phase shifter with dual-frequency differential mode phase shifting, high frequency selectivity and broadband common mode suppression. Compared with the traditional filter phase shifter, the present invention can not only realize dual-frequency phase shifting, but also has good common mode suppression capability and high frequency selectivity.

Description

Technical Field

[0001] The invention relates to a microwave communication device, in particular to a dual-frequency filtering phase shifter. Background Art

[0002] As wireless communication systems develop towards miniaturization, integration and multi-standard, wireless communication systems have put forward higher requirements on the size of RF front-end circuits. Balanced filter phase shifters have attracted much attention because they integrate differential mode filtering, differential mode phase shifting and common mode suppression functions into one device, which can reduce the number of components in the circuit and reduce the volume of the system. Balanced filter phase shifters can be divided into balanced single-frequency filter phase shifters and balanced dual-frequency filter phase shifters according to the working frequency band. Compared with single-frequency design, balanced dual-frequency filter phase shifters not only have phase control, frequency selection and common mode interference suppression functions, but also have the ability to work in different frequency bands, which can meet different application requirements. Therefore, the volume of the system can be further reduced, which is in line with the development trend of wireless communication systems.

[0003] Existing research on filter phase shifters mainly focuses on single-ended structures, including single-frequency operation and dual-frequency operation. The design methods of single-frequency filter phase shifters include those based on coupled lines, multi-mode resonators and coupled resonator theory. The implementation methods of dual-frequency filter phase shifters include phase shifter cascade band-stop network and multi-open / short-circuit branch loading technology. There are relatively few studies on balanced filter phase shifters, and they all work at a single frequency, mainly using coupled T-type structures, folded asymmetric step impedance resonator structures and two three-terminal coupled lines connecting three half-wavelength microstrip line structures. There is currently no research on balanced dual-frequency filter phase shifters. It is necessary to design a balanced dual-frequency filter phase shifter that has differential mode filtering, differential mode phase shifting, common mode suppression and dual-frequency functions. Summary of the invention

[0004] Purpose of the invention: In view of the above-mentioned prior art, a balanced dual-frequency filtering phase shifter having differential mode filtering, differential mode phase shifting, common mode suppression and dual-frequency working functions is proposed.

[0005] Technical solution: A balanced dual-frequency filtering phase shifter, comprising a reference line and a main line, the reference line and the main line having the same structure, both comprising first to fourth feed lines, first to eighth coupling lines, first to tenth microstrip lines, and a first grounding resistor and a second grounding resistor;

[0006] Wherein, the first to fourth microstrip lines are short-circuited microstrip lines, and the fifth to eighth microstrip lines are open-circuited microstrip lines;

[0007] The first to fourth coupling lines are arranged horizontally from left to right in sequence, the first and second coupling lines are connected in series, and the third and fourth coupling lines are connected in series; the second and third coupling lines are connected in series through the lower terminal, the series connection point is connected to the first grounding resistor, and the upper terminal side of the second and third coupling lines is open; the upper series connection point of the first and second coupling lines is connected to one end of the first feeder, and the lower series connection point is connected to one end of the ninth microstrip line; the upper series connection point of the third and fourth coupling lines is connected to one end of the second feeder, and the lower series connection point is connected to one end of the tenth microstrip line; of the two terminals on the left side of the first coupling line, the upper terminal is connected to the fifth microstrip line, and the lower terminal is connected to the first microstrip line; of the two terminals on the right side of the fourth coupling line, the upper terminal is connected to the sixth microstrip line, and the lower terminal is connected to the second microstrip line; the other end of the first feeder and one end of the second feeder are used as differential input ports;

[0008] The fifth to eighth coupling lines are arranged horizontally from left to right, the fifth and sixth coupling lines are connected in series, and the seventh and eighth coupling lines are connected in series; the sixth and seventh coupling lines are connected in series through the upper terminal, the series connection point is connected to the second grounding resistor, and one side of the upper terminal of the sixth and seventh coupling lines is open; the lower series connection point of the fifth and sixth coupling lines is connected to one end of the third feeder line, and the upper series connection point is connected to the other end of the ninth microstrip line; the lower series connection point of the seventh and eighth coupling lines is connected to one end of the fourth feeder line, and the upper series connection point is connected to the other end of the tenth microstrip line; of the two terminals on the left side of the fifth coupling line, the lower terminal is connected to the seventh microstrip line, and the upper terminal is connected to the third microstrip line; of the two terminals on the right side of the eighth coupling line, the lower terminal is connected to the eighth microstrip line, and the upper terminal is connected to the fourth microstrip line; the other end of the third feeder line and one end of the fourth feeder are used as differential output ports;

[0009] The phase difference caused by the difference between the physical size of the feeder in the reference line structure and the physical size of the corresponding feeder in the main line structure is used as the phase shift reference value of the phase shifter.

[0010] Furthermore, the electrical lengths of the first to tenth microstrips are all one quarter of a wavelength, and the electrical lengths of the first to eighth coupling lines are all one quarter of a wavelength.

[0011] Furthermore, the structures of the reference line and the main line are both centrosymmetric structures.

[0012] Furthermore, when differential-mode signal excitation is used, under the joint action of the coupling line, the open-circuit microstrip line and the short-circuit microstrip line, six differential-mode transmission poles and three differential-mode transmission zeros can be obtained, and a differential-mode transmission zero is distributed in the middle of the six differential-mode transmission poles, thereby forming two differential-mode working passbands; and the frequencies of the two passbands are adjusted by regulating the impedance of the open-circuit microstrip line and the short-circuit microstrip line;

[0013] When a common-mode signal is used for excitation, three common-mode transmission zeros can be obtained under the joint action of the coupled line, the open-circuit microstrip line and the short-circuit microstrip line, forming a broadband common-mode suppression covering two differential-mode passbands.

[0014] Furthermore, the phase slope is controlled by adjusting the impedance of the ninth and tenth microstrip lines to form a broadband differential mode phase shift.

[0015] Beneficial effects: Existing balanced filter phase shifters do not have dual-frequency working capabilities, and the filter phase shifters with dual-frequency working capabilities are all single-ended structures and lack common-mode suppression capabilities. The present invention realizes a balanced dual-frequency filter phase shifter with dual-frequency differential mode phase shifting, high frequency selectivity and broadband common-mode suppression by loading two quarter-wavelength coupling lines at both ends of a pair of parallel microstrip lines, and loading an open-circuit microstrip line, a short-circuit microstrip line and a resistor at the terminal of the coupling line. Compared with traditional filter phase shifters, the present invention can not only realize dual-frequency phase shifting, but also has good common-mode suppression capabilities and higher frequency selectivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is the circuit model of balanced dual-frequency filter phase shifter;

[0017] Figure 2 The differential mode of the balanced dual-frequency filter phase shifter S Parameter simulation results;

[0018] Figure 3 Common mode for balanced dual-band filter phase shifter S Parameter simulation results;

[0019] Figure 4 This is the simulation result of low-frequency passband differential-mode phase shifting of balanced dual-frequency filter phase shifter;

[0020] Figure 5 This is the simulation result of the high-frequency passband differential-mode phase shift of the balanced dual-frequency filter phase shifter. DETAILED DESCRIPTION

[0021] The present invention will be further explained below in conjunction with the accompanying drawings.

[0022] A balanced dual-frequency filtering phase shifter includes a reference line and a main line with the same structure. The main line structure is used as an example for explanation. Figure 1 As shown, the main line structure is centrally symmetrical as a whole, and consists of feed lines 4, 8, 17, 21, quarter-wavelength short-circuited microstrip lines 1, 11, 14, 24, quarter-wavelength open-circuited microstrip lines 2, 10, 15, 23, quarter-wavelength coupled lines 3, 5, 7, 9, 16, 18, 20, 22, quarter-wavelength microstrip lines 12, 13, and grounding resistors 6, 19.

[0023] Among them, the quarter-wavelength coupling lines 3, 5, 7, and 9 are arranged horizontally from left to right, coupling lines 3 and 5 are connected in series, and coupling lines 7 and 9 are connected in series; coupling lines 5 and 7 are connected in series through the lower terminal, and the series connection point is connected to the grounding resistor 6; one side of the upper terminal of coupling lines 5 and 7 is open; the upper series connection point of coupling lines 3 and 5 is connected to one end of the feed line 4, and the lower series connection point is connected to one end of the microstrip line 12; the upper series connection point of coupling lines 7 and 9 is connected to one end of the feed line 8, and the lower series connection point is connected to one end of the microstrip line 13; of the two terminals on the left side of coupling line 3, the upper terminal is connected to the open microstrip line 2, and the lower terminal is connected to the short-circuited microstrip line 1; of the two terminals on the right side of coupling line 9, the upper terminal is connected to the open microstrip line 10, and the lower terminal is connected to the short-circuited microstrip line 11. The physical dimensions of feed line 4 and feed line 8 are the same, and the other end of feed line 4 and one end of feed line 8 are used as differential input ports A and B.

[0024] The quarter-wavelength coupling lines 16, 18, 20, and 22 are arranged horizontally from left to right, the coupling lines 16 and 18 are connected in series, and the coupling lines 20 and 22 are connected in series; the coupling lines 18 and 20 are connected in series through the upper terminal, and the series connection point is connected to the grounding resistor 19; one side of the lower terminal of the coupling lines 18 and 20 is open; the lower series connection point of the coupling lines 16 and 18 is connected to one end of the feed line 17, and the upper series connection point is connected to the other end of the microstrip line 12; the lower series connection point of the coupling lines 20 and 22 is connected to one end of the feed line 21, and the upper series connection point is connected to the other end of the microstrip line 13; of the two terminals on the left side of the coupling line 16, the lower terminal is connected to the open microstrip line 15, and the upper terminal is connected to the short-circuited microstrip line 14; of the two terminals on the right side of the coupling line 22, the lower terminal is connected to the open microstrip line 23, and the right side of the upper terminal is connected to the short-circuited microstrip line 24. The physical dimensions of the feeder 17 and the feeder 21 are the same, and the other end of the feeder 17 and one end of the feeder 21 serve as differential output ports C and D.

[0025] In the present invention, the reference line and the main line structure of the phase shifter are the same, the difference is that the physical size values ​​of the corresponding parts of the two are different. Feed lines 4, 8, 17, 21 have a phase delay effect at the same time, that is, the phase difference generated by the feed line in the reference line structure and the feed line in the main line structure is used as the phase shift reference value of the phase shifter. The impedance of microstrip lines 12 and 13 can be used to adjust the phase slope to form a broadband differential mode phase shift.

[0026] For the proposed balanced dual-frequency filter phase shifter, when differential signal excitation is used, the longitudinal symmetry plane is equivalent to an ideal electric wall, and the resistance does not work. Under the joint action of the coupling line, the open microstrip line and the short-circuited microstrip line, six differential transmission poles and three differential transmission zeros can be obtained. A differential transmission zero is distributed in the middle of the six differential transmission poles, thus forming two differential working passbands. The transmission zero is mainly regulated by four open microstrip lines and four short-circuited microstrip lines. When the impedance of the four open microstrip lines increases, the left transmission zero of the low-frequency passband and the right transmission zero of the high-frequency passband approach the center frequency; when the impedance of the four short-circuited microstrip lines increases, the left transmission zero of the low-frequency passband and the right transmission zero of the high-frequency passband are far away from the center frequency. Therefore, the frequency selectivity of the two passbands can be improved by regulating the impedance of the open microstrip line and the short-circuited microstrip line.

[0027] When using common-mode signal excitation, Figure 1 The longitudinal symmetry plane in the structure is equivalent to an ideal magnetic wall. Under the joint action of the coupled line, open microstrip line and short microstrip line, three common-mode transmission zero points can be obtained, forming a broadband common-mode suppression covering two differential-mode passbands. In addition, the two resistors can improve the common-mode suppression capability without affecting the differential-mode performance.

[0028] Compared with the traditional filter phase shifter, the present invention can not only realize dual-frequency phase shifting, but also has good common-mode suppression capability and high frequency selectivity. The structural schematic diagrams of the main line and reference line of the balanced dual-frequency filter phase shifter of this embodiment are shown in FIG. Figure 1 As shown in the figure, RO4003C substrate is used, with a dielectric constant of 3.38, a loss angle of 0.0027, and a thickness of 0.813 mm. Differential mode phase shifts of 45° and 90° are achieved in the dual-band passband, with center frequencies of 1.34 GHz and 2.4 GHz, respectively. The simulated frequency response is shown in Figure 2 As shown. Figure 3 and Figure 4 It can be obtained that for the reference line, the 10-dB differential mode impedance matching relative bandwidth is 35.6% and 19.6% respectively, the differential mode 3-dB relative bandwidth is 37.8% and 19.6% respectively, the minimum insertion loss in the two passbands is 0.86 dB and 1.32 dB respectively, and the common mode rejection is greater than 13 dB; for the main line, the 10-dB differential mode impedance matching relative bandwidth is 34.8% and 20% respectively, the 3-dB relative bandwidth is 37% and 22% respectively, the minimum insertion loss in the two passbands is 0.92dB and 1.27 dB respectively, and the common mode rejection is greater than 13.8 dB. Figure 4 and Figure 5 It can be obtained that the differential mode phase shift bandwidths of 45°±2° and 90°±5° in the two passbands are 32.6% and 17.1% respectively. The common mode suppression bandwidth of the present invention can fully cover the differential mode working passband.

[0029] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A balanced dual-frequency filtering phase shifter, characterized in that: It includes a reference line and a main line, and the reference line and the main line have the same structure, and both include first to fourth feed lines, first to eighth coupling lines, first to tenth microstrip lines, and a first grounding resistor and a second grounding resistor; Wherein, the first to fourth microstrip lines are short-circuited microstrip lines, and the fifth to eighth microstrip lines are open-circuited microstrip lines; The first to fourth coupling lines are arranged horizontally from left to right in sequence, the first and second coupling lines are connected in series, and the third and fourth coupling lines are connected in series; the second and third coupling lines are connected in series through the lower terminal, the series connection point is connected to the first grounding resistor, and the upper terminal side of the second and third coupling lines is open; the upper series connection point of the first and second coupling lines is connected to one end of the first feeder, and the lower series connection point is connected to one end of the ninth microstrip line; the upper series connection point of the third and fourth coupling lines is connected to one end of the second feeder, and the lower series connection point is connected to one end of the tenth microstrip line; of the two terminals on the left side of the first coupling line, the upper terminal is connected to the fifth microstrip line, and the lower terminal is connected to the first microstrip line; of the two terminals on the right side of the fourth coupling line, the upper terminal is connected to the sixth microstrip line, and the lower terminal is connected to the second microstrip line; the other end of the first feeder and one end of the second feeder are used as differential input ports; The fifth to eighth coupling lines are arranged horizontally from left to right, the fifth and sixth coupling lines are connected in series, and the seventh and eighth coupling lines are connected in series; the sixth and seventh coupling lines are connected in series through the upper terminal, the series connection point is connected to the second grounding resistor, and the lower terminal side of the sixth and seventh coupling lines is open; the lower series connection point of the fifth and sixth coupling lines is connected to one end of the third feeder line, and the upper series connection point is connected to the other end of the ninth microstrip line; the lower series connection point of the seventh and eighth coupling lines is connected to one end of the fourth feeder line, and the upper series connection point is connected to the other end of the tenth microstrip line; of the two terminals on the left side of the fifth coupling line, the lower terminal is connected to the seventh microstrip line, and the upper terminal is connected to the third microstrip line; of the two terminals on the right side of the eighth coupling line, the lower terminal is connected to the eighth microstrip line, and the upper terminal is connected to the fourth microstrip line; the other end of the third feeder line and one end of the fourth feeder are used as differential output ports; The phase difference caused by the difference between the physical size of the feeder in the reference line structure and the physical size of the corresponding feeder in the main line structure is used as the phase shift reference value of the phase shifter.

2. The balanced dual-frequency filtering phase shifter according to claim 1, characterized in that: The electrical lengths of the first to tenth microstrips are all one-quarter wavelength, and the electrical lengths of the first to eighth coupled lines are all one-quarter wavelength.

3. The balanced dual-frequency filtering phase shifter according to claim 1, characterized in that: The structures of the reference line and the main line are both centrally symmetrical structures.

4. The balanced dual-frequency filtering phase shifter according to any one of claims 1 to 3, characterized in that: When using differential signal excitation, under the joint action of the coupling line, the open microstrip line and the short-circuited microstrip line, six differential transmission poles and three differential transmission zeros can be obtained. A differential transmission zero is distributed in the middle of the six differential transmission poles, thus forming two differential working passbands. The frequencies of the two passbands can be adjusted by adjusting the impedance of the open microstrip line and the short-circuited microstrip line. When a common-mode signal is used for excitation, three common-mode transmission zeros can be obtained under the joint action of the coupled line, the open-circuit microstrip line and the short-circuit microstrip line, forming a broadband common-mode suppression covering two differential-mode passbands.

5. The balanced dual-frequency filtering phase shifter according to claim 4, characterized in that: The phase slope is controlled by adjusting the impedance of the ninth and tenth microstrip lines to form a broadband differential mode phase shift.

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