A duplexer and a high-precision adjustment method for its coupling coefficient

Abstract

The present invention discloses a duplexer and a high-precision adjustment method for its coupling coefficient, belonging to the field of wireless communication technology. The duplexer includes a receiving frequency selector, a transmitting frequency selector and a combining structure. The receiving frequency selector adopts a parallel pseudo-interdigital circuit architecture, which is implemented based on rectangular metal micro-coaxial technology and is composed of a first resonator, a second resonator, a third resonator and a fourth resonator; the length of the short-circuit branch and the length of the open-end coupling cavity can be used to adjust the coupling coefficient of the parallel pseudo-interdigital circuit resonator in the receiving frequency selector. The present invention has the advantages of small size, light weight, easy integration, adjustable, low loss, no dispersion, wide bandwidth, large power capacity, etc., and has broad prospects in future communication applications.

Description

Technical Field

[0001] The present invention relates to the technical field of wireless communication, and in particular to a duplexer and a high-precision adjustment method of its coupling coefficient. Background Art

[0002] With the continuous development of communication technology, future mobile networks, satellite communications, and dedicated microwave communications will require extensive use of the millimeter wave and terahertz bands of the electromagnetic spectrum to meet the needs of accommodating the increasing amount of data. As one of the most important components in the RF front end of the communication system, the duplexer plays a role in low-loss signal transmission and separation, and its performance directly affects the performance of the entire communication system. Traditional duplexers are mostly implemented in the form of planar transmission line circuits or waveguide transmission circuits. Planar circuit structures such as microstrip lines and substrate integrated waveguides (SIW) at millimeter wave frequencies have the disadvantages of high radiation loss and dielectric loss. The rectangular waveguides made by traditional CNC are large in size and heavy in weight, and require complex and expensive post-processing processes to achieve high precision. Summary of the invention

[0003] In view of this, the present invention provides a duplexer and a high-precision adjustment method for its coupling coefficient. The duplexer has the advantages of small size, light weight, easy integration, adjustability, low loss, no dispersion, wide bandwidth, high power capacity, etc., and has broad prospects in future communication applications.

[0004] In order to achieve the above object, the technical solution adopted by the present invention is:

[0005] A duplexer based on rectangular micro-coaxial parallel pseudo-interdigital resonator technology, comprising a receiving frequency selector 1, a transmitting frequency selector 2 and a combining structure 3, wherein the receiving frequency selector and the transmitting frequency selector 2 are respectively connected to two branch ports of the combining structure 3;

[0006] The receiving frequency selector 1 and the transmitting frequency selector are both parallel pseudo-interdigital circuit structures based on rectangular metal micro-coaxials, and the parallel pseudo-interdigital circuit structures include a first resonator, a second resonator, a third resonator and a fourth resonator; the first resonator and the fourth resonator are arranged in parallel to form a first group of coupling circuits, and the second resonator and the third resonator are arranged in parallel to form a second group of coupling circuits; the second group of coupling circuits is located between the first resonator and the fourth resonator and is parallel to the first resonator; one end of the second group of coupling circuits is provided with an open-end coupling cavity, and the other end is connected to the outer conductor of the rectangular micro-coaxial through a short-circuit branch;

[0007] The transmitting frequency selector 2 further includes a fifth resonator and a sixth resonator; the fifth resonator and the sixth resonator are respectively connected to the input branch and the output branch of the transmitting frequency selector, and both are parallel to the first resonator of the transmitting frequency selector; the fifth resonator and the sixth resonator are both L-shaped structures, and the ends of the two are bent, and the bending length is one quarter of the wavelength;

[0008] The coupling structure 3 is a T-shaped metal micro-coaxial structure.

[0009] Furthermore, the two branch ports of the combining structure are respectively connected to the receiving frequency selector 1 and the transmitting frequency selector through corresponding Z-shaped micro-coaxial cables; the folding angle of the Z-shaped micro-coaxial cable is 90 degrees, and the folding angle is an arc angle.

[0010] Furthermore, the combining end of the combining structure 3, the input end of the receiving frequency selector and the output end of the transmitting frequency selector are all air coplanar waveguide metal quasi-coaxial interface circuits; the air coplanar waveguide metal quasi-coaxial interface circuit includes a central signal conductor 302 and a peripheral metal ground conductor 303, and the peripheral metal ground conductor 303 includes a fully wrapped section and a semi-wrapped section, wherein the fully wrapped section is connected to the internal micro-coaxial; the central signal conductor 302 is fixed to the center of the peripheral metal ground conductor through a supporting structure, and the upper surface of the central signal conductor 302 and the upper surface of the semi-wrapped section of the peripheral metal ground conductor are in the same plane.

[0011] Furthermore, the air coplanar waveguide metal quasi-coaxial interface circuit is connected to the internal micro-coaxial through a gradual transition structure 7 for realizing impedance transformation.

[0012] A method for precisely adjusting the coupling coefficient of each resonator in a duplexer is used to adjust the coupling coefficient of the above-mentioned duplexer based on rectangular micro-coaxial parallel pseudo-interdigital resonator technology, and the specific steps are as follows:

[0013] Step 1, placing the duplexer in a closed space for preheating, and filling the closed space with inert gas;

[0014] Step 2, the laser beam in the confined space is focused on the short-circuit branch and the open-circuit end coupling cavity of the receiving frequency selector and the short-circuit branch and the open-circuit end coupling cavity of the transmitting frequency selector in turn, and the short-circuit branch and the open-circuit end coupling cavity are cut respectively to complete the adjustment of the length of the short-circuit branch and the open-circuit end coupling cavity;

[0015] Step 3, clean the duplexer adjusted in step 2, remove excess debris, and finally seal the adjustment window with metal tape.

[0016] The beneficial effects of the above technical solution of the present invention are:

[0017] The adjustment window of the present invention can expose the short-circuit branches and the open-ended coupling cavity in the receiving and transmitting frequency selectors to the outside, so as to facilitate subsequent precise adjustment. In terms of the specific adjustment mechanism, for the receiving frequency selector, the coupling coefficient between the resonators 104 and 105 can be precisely adjusted by adjusting the length of the short-circuit branch 107; by adjusting the length L of the coupling cavity 108 h2 It is possible to precisely adjust the coupling coefficients between resonators 103 and 104, and between 105 and 106; for the transmission frequency selector, by adjusting the length L of the short-circuit branch 209 h3 The coupling coefficient between resonators 206 and 207 can be precisely adjusted by adjusting the length L of the coupling cavity 210. h4 Precise adjustment of the coupling coefficients between resonators 205 and 206, and between 207 and 208 can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 An oblique isometric diagram of a duplexer based on rectangular micro-coaxial parallel pseudo-interdigital resonator technology provided by an embodiment of the present invention;

[0019] Figure 2 A top view of a duplexer based on rectangular micro-coaxial parallel pseudo-interdigital resonator technology provided by an embodiment of the present invention;

[0020] Figure 3 An oblique cross-sectional view of a duplexer based on rectangular micro-coaxial parallel pseudo-interdigital resonator technology provided by an embodiment of the present invention;

[0021] Figure 4 A cross-sectional top view of a duplexer based on rectangular micro-coaxial parallel pseudo-interdigital resonator technology provided by an embodiment of the present invention;

[0022] Figure 5 A dimensioned diagram of a cross-sectional top view of a duplexer based on rectangular micro-coaxial parallel pseudo-interdigital resonator technology provided by an embodiment of the present invention;

[0023] Figure 6 A layered cross-sectional view of a micro-coaxial transmission line provided by an embodiment of the present invention;

[0024] Figure 7 A projection view of a metal quasi-coaxial interface circuit based on air coplanar waveguide provided by an embodiment of the present invention;

[0025] Figure 8 A schematic diagram of a coupling circuit of a parallel pseudo-interdigital resonator provided in an embodiment of the present invention;

[0026] Fig. 9 The present invention provides a duplexer implementation example simulation result based on rectangular micro-coaxial parallel pseudo-interdigital resonator technology provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0027] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0029] This embodiment is a duplexer based on rectangular micro-coaxial parallel pseudo-interdigital resonator technology, and specifically takes a duplexer operating in the receiving frequency band of 17-21 GHz and the transmitting frequency band of 27-31 GHz as an example.

[0030] See also Figures 1 to 6 , this embodiment includes: a receiving frequency selector 1, a transmitting frequency selector 2 and a common end combining structure 3. The structure adopts a planar layout, and the receiving frequency selector 1 and the transmitting frequency selector 2 are placed on both sides of the common end combining structure 3, and the three are in the same horizontal plane; wherein the input end of the receiving frequency selector 1 and the output end of the transmitting frequency selector 2 are respectively connected to the two branch ports of the combining structure 3, using a Z-shaped micro coaxial line; the output port of the receiving frequency selector 1 and the input port of the transmitting frequency selector 2 are perpendicular to the common port of the combining structure 3; the combining structure 3 adopts a T-type circuit structure design, and the T-type circuit adds a matching structure 8 to achieve impedance matching between the frequency selector and the combining port, and its common port is responsible for the common transmission of receiving and transmitting signals.

[0031] The receiving frequency selector 1 is a parallel pseudo-interdigital circuit architecture, specifically composed of input and output ports 101, 102 and four micro-coaxial resonators, namely a first resonator 103, a second resonator 104, a third resonator 105 and a fourth resonator 106. The shielding structure 109 wraps each resonator and the micro-coaxial transmission line as a whole inside, which serves the purpose of electromagnetic shielding and signal grounding loop. Each resonator is fixed inside the micro-coaxial transmission line through a supporting structure 5.

[0032] The input and output ports 102 and 103 of the receiving frequency selector 1 are connected to the first resonator 103 and the fourth resonator 106 respectively, and the specific tap position can be completed with the assistance of electromagnetic field design software; one end of the micro-coaxial resonator is short-circuited and the other end is open-circuited, the short-circuited end current is strong, and the open-circuited end electric field is strong, and the micro-coaxial resonators 103, 104 and 105, 106 constitute a parallel pseudo-interdigital structure; wherein the first resonator 103 and the fourth resonator 106 constitute a first group of coupling circuits, and the second resonator 104 and the third resonator 105 constitute a second group of coupling circuits.

[0033] In terms of circuit structure implementation, the second group of coupling circuits is embedded in the first group of coupling circuits, thereby providing a path for cross-coupling and source-load coupling to form a hybrid coupling, thereby causing the receiving frequency selector 1 to generate two transmission zeros in the transmitting frequency band, thereby improving the suppression of the transmitting frequency band on the receiving frequency band.

[0034] The circuit position of the short-circuit end of the first group of coupling circuits of the receiving frequency selector 1 corresponds to the open-circuit end of the second group of coupling circuits. Similarly, the circuit position of the short-circuit end of the second group of coupling circuits corresponds to the open-circuit end of the first group of coupling circuits. The short-circuit end of the resonator and the external shielding structure 109 are integrally formed by multi-layer micro-coaxial technology; the open-circuit end of the second group of coupling circuits is designed with an open-circuit end coupling cavity 108, and a short-circuit branch 107 is designed at the short-circuit end. By adjusting the length L of the short-circuit branch 107 h1 and the length L of the open-ended coupling cavity 108 h2 The coupling coefficient between resonators in a parallel pseudo-interdigital circuit is adjusted.

[0035] The transmitting frequency selector 2 is also a parallel pseudo-interdigital circuit architecture, specifically composed of input and output ports 201, 202 and six micro-coaxial resonators, namely the first resonator 208, the second resonator 207, the third resonator 206, the fourth resonator 205, the fifth resonator 204, and the sixth resonator 203. The shielding structure 211 wraps each resonator and the micro-coaxial transmission line as a whole inside, which serves the purpose of electromagnetic shielding and signal grounding loop. Each resonator and the micro-coaxial transmission line are fixed by a support structure 5 located inside the micro-coaxial.

[0036] The input and output ports 201 and 202 of the transmission frequency selector 2 are connected to the fifth resonator 204 and the sixth resonator 203 respectively, and the specific tap positions can be completed with the assistance of electromagnetic field design software; one end of the micro-coaxial resonator is short-circuited and the other end is open-circuited, the short-circuited end current is strong, and the open-circuited end electric field is strong, and the micro-coaxial resonators 208, 206 and 207, 205 constitute a parallel pseudo-interdigital structure; wherein the first resonator 208 and the fourth resonator 205 constitute a first group of coupling circuits, and the second resonator 207 and the third resonator 206 constitute a second group of coupling circuits. In terms of circuit structure implementation, the second group of coupling circuits is embedded in the first group of coupling circuits, thereby providing a path for cross coupling and source load coupling, forming a hybrid coupling, and then the transmission frequency selector 2 generates two transmission zeros on the right side of the transmission frequency band passband, thereby improving the transmission frequency band selectivity.

[0037] In addition, the resonators 203 and 204 form an L-shaped quarter-wavelength resonator and generate two frequency zeros in the receiving frequency band, wherein the designed resonant frequency of the sixth resonator 203 is the lower frequency limit of the receiving frequency band, and the designed resonant frequency of the fifth resonator 204 is the upper frequency limit of the receiving frequency band, thereby improving the noise suppression performance of the receiving frequency band. The L-shaped quarter-wavelength resonator 203 is connected to the output end 202 of the transmitting frequency selector 2 in a T-shaped connection manner, and the L-shaped quarter-wavelength resonator 204 is connected to the input end 201 of the transmitting frequency selector 2 in a T-shaped connection manner, and the quarter-wavelength resonator is implemented by a 90-degree right-angle folding structure; the open-end outer conductor of the L-shaped quarter-wavelength resonator 203 and 204 is connected to the transmitting frequency selector 2 at a position without a release hole to improve the stability of the structure.

[0038] The circuit position of the short-circuit end of the first group of coupling circuits in the transmitting frequency selector 2 corresponds to the open-circuit end of the second group of coupling circuits. Similarly, the circuit position of the short-circuit end of the second group of coupling circuits corresponds to the open-circuit end of the first group of coupling circuits. The short-circuit end of the resonator and the external shielding structure 211 are integrally formed by multi-layer micro-coaxial technology; the open-circuit end of the second group of coupling circuits is designed with an open-circuit end coupling cavity 210, and a short-circuit branch 209 is designed at the short-circuit end. By adjusting the length L of the short-circuit branch 209 h3 and the length L of the open-ended coupling cavity 210 h4 The coupling coefficient between resonators in a parallel pseudo-interdigital circuit is adjusted.

[0039] For the external interface circuit of the duplexer, the present invention also proposes an air coplanar waveguide metal quasi-coaxial interface circuit, which includes a central signal conductor 302, a peripheral metal ground conductor 303 and an air cavity 305. The specific implementation is as follows Figure 7 As shown, the central signal conductor 302 is located in the third layer of the micro-coaxial structure, and its upper surface is on the same horizontal plane as the upper surface of the peripheral metal ground conductor. In order to improve the microwave performance at the interface, there is no insulating medium filled between the signal conductor and the ground conductor of the interface circuit mentioned in the present invention, and the spacing between the central signal conductor and the peripheral metal ground is 130um.

[0040] The duplexer based on the rectangular micro-coaxial parallel pseudo-interdigital resonator technology proposed in the present invention is implemented by using the micro-coaxial technology. The present invention also proposes a method for realizing the precise adjustment of the coupling coefficient of each resonator, specifically: firstly, an adjustment window 6 is formed on the upper surface of the receiving frequency selector 1 and the transmitting frequency selector 2, and the window exposes the short-circuited branches 107, 209 and the open-ended coupling cavities 108, 210 in the receiving and transmitting frequency selectors to the outside; for the receiving frequency selector, by adjusting the length L of the short-circuited branch 107 h1The coupling coefficient between the resonators 104 and 105 can be precisely adjusted by adjusting the length L of the coupling cavity 108. h2 It is possible to precisely adjust the coupling coefficients between resonators 103 and 104, and between 105 and 106; for the transmission frequency selector, by adjusting the length L of the short-circuit branch 209 h3 The coupling coefficient between resonators 206 and 207 can be precisely adjusted by adjusting the length L of the coupling cavity 210. h4 Precise adjustment of the coupling coefficients between resonators 205 and 206, and between 207 and 208 can be achieved.

[0041] The implementation principle is as follows: The performance of the duplexer is mainly affected by the coupling coefficient between the resonators in the parallel pseudo-interdigital circuit. The coupling coefficient depends on the characteristic frequency fc of the coupling circuit and the intrinsic frequency fi of each resonator itself, which is determined by the following formula:

[0042]

[0043] Where Kc is the coupling coefficient, f c1 and f c2 is the characteristic frequency of the first and second sets of coupling circuits in the frequency selector, f i1 is the resonant frequency of the first and fourth resonators in the first set of coupling circuits, f i2 is the resonant frequency of the second and third resonators in the second set of coupling circuits.

[0044] The characteristic frequency depends on the coupling capacitance between the resonators, refer to Figure 8 The coupling capacitor circuit model of each resonator in the rectangular micro-coaxial parallel pseudo-interdigital resonator proposed in the present invention is given, where C pc1 ~C pc3 is the equivalent coupling capacitance between the resonators, C hc3 , C hc4 is the edge coupling capacitance of the resonator. By adjusting the length L of the short-circuit branches 107 and 209 h1 and L h3 It can realize C pc1 ~C pc3 The equivalent coupling capacitance between the resonators is adjusted by adjusting the length L of the coupling cavities 108 and 210. h2 and L h4 It can realize C hc3 , C hc4 The resonator edge coupling capacitance is adjusted to achieve the purpose of precisely adjusting the duplexer performance. The adjustment method can be achieved through laser material addition or MEMS micromachining technology.

[0045] The size of each resonator in the duplexer based on the rectangular micro-coaxial parallel pseudo-interdigital resonator technology proposed by the present invention depends on the eigenfrequency of each resonator itself. Figure 5 , which is a dimensioned diagram of a cross-sectional top view of a duplexer based on a rectangular micro-coaxial parallel pseudo-interdigital resonator technology provided by an embodiment of the present invention. Taking the duplexer working in the receiving 17-21 GHz and transmitting 27-31 GHz frequency band as an example, the length L of the micro-coaxial line of the input and output port 101 of the receiving frequency selector 1 is p2 =1500um, length of micro coaxial line of input and output port 102 L c1 =1025um, the lengths of resonators 103, 104, 105, and 106 are L r1 =3960um,L r2 =4050um,L r3 =4020um,L r4 =3930um. The center spacings of resonators 103, 104, 105, and 106 are S 12 =260um,S 23 =250um,S 34 = 260um. The length of the micro coaxial line L of the input and output port 201 of the transmitting frequency selector 2 p3 =1500um, length of the micro coaxial line of the input and output port 202 c4 =1480um, the lengths of resonators 205, 206, 207, and 208 are L r5 =2820um,L r6 =2600um,L r7 =2620um,L r8 =2650um. The center spacings of resonators 205, 206, 207, and 208 are S 56 =300um,S 67 =290um,S 78 =300um. The lengths of the quarter-wavelength resonators 204 and 203 are L r9 =4540um,L r10 =3630um. The length of the common port 301 of the combining structure 3 is L p1 =990um, the length of the coaxial line connecting the receiving frequency selector 1 and the combining structure 3 is L c2 = 2010um, the length of the coaxial line connecting the receiving frequency selector 2 and the combining structure 3 is L c4 =2190um.

[0046] The duplexer based on rectangular micro-coaxial parallel pseudo-interdigital resonator technology utilizes 5-layer rectangular micro-coaxial line technology, such as Figure 6As shown, the signal conductor of the rectangular micro-coaxial line is located on the third layer, its cross-sectional size is 140um×100um, its outer conductor size is 300um×300um, and the metal wall thickness is 100um.

[0047] The duplexer structure based on the rectangular micro-coaxial parallel pseudo-interdigital resonator technology is designed with periodically arranged release holes 4 for washing out the photoresist in the coaxial cavity in the final stage of the processing process. The size of the release holes 4 is 250um×200um×200um.

[0048] The duplexer based on rectangular micro-coaxial parallel pseudo-interdigital resonator technology is designed with a periodically arranged Su8 dielectric support structure 5 (dielectric constant is 2.85, loss tangent is 0.045) on the fourth layer to support the third layer signal conductor. The thickness is 20um and the cross-sectional size is 100um×20um.

[0049] See also Fig. 9 , which is the simulation result of a duplexer based on rectangular micro-coaxial parallel pseudo-interdigital resonator technology provided by an embodiment of the present invention. Wherein f1 is the receiving frequency band, f2 is the transmitting frequency band, and according to the simulation results, the return loss in the receiving frequency band is less than 19dB, the insertion loss in the band is less than 1.8dB, and the suppression of the receiving frequency band on the transmitting frequency band is greater than 76dB, the return loss in the transmitting frequency band is less than 16dB, the insertion loss in the band is less than 1.9dB, and the suppression of the receiving frequency band on the transmitting frequency band is greater than 67dB.

[0050] The above is a description of a duplexer and its implementation method provided by the present invention. For those skilled in the art, according to the idea of ​​the embodiments of the present invention, there may be changes in the specific implementation and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A duplexer based on rectangular micro-coaxial parallel pseudo-interdigital resonator technology, comprising a receiving frequency selector (1), a transmitting frequency selector (2) and a combining structure (3), wherein the receiving frequency selector and the transmitting frequency selector (2) are respectively connected to two branch ports of the combining structure (3); characterized in that: The receiving frequency selector (1) and the transmitting frequency selector are both parallel pseudo-interdigital circuit structures based on rectangular metal micro-coaxials, and the parallel pseudo-interdigital circuit structure comprises a first resonator, a second resonator, a third resonator and a fourth resonator; the first resonator and the fourth resonator are arranged in parallel to form a first group of coupling circuits, and the second resonator and the third resonator are arranged in parallel to form a second group of coupling circuits; The second set of coupling circuits is located between the first resonator and the fourth resonator and is parallel to the first resonator; an open-ended coupling cavity is provided at one end of the second set of coupling circuits, and the other end is connected to the outer conductor of the rectangular micro-coaxial through a short-circuit branch; The transmission frequency selector (2) further comprises a fifth resonator and a sixth resonator; the fifth resonator and the sixth resonator are respectively connected to the input branch and the output branch of the transmission frequency selector, and both are parallel to the first resonator of the transmission frequency selector; the fifth resonator and the sixth resonator are both L-shaped structures, and the ends of both are bent, and the bending length is one quarter of the wavelength; The circuit combining structure (3) is a T-shaped metal micro-coaxial structure; The two branch ports of the combining structure are respectively connected to the receiving frequency selector (1) and the transmitting frequency selector through corresponding Z-shaped micro-coaxials; the folding angle of the Z-shaped micro-coaxial is 90 degrees, and the folding angle is a circular arc angle; The combining end of the combining structure (3), the input end of the receiving frequency selector and the output end of the transmitting frequency selector are all air coplanar waveguide metal quasi-coaxial interface circuits; the air coplanar waveguide metal quasi-coaxial interface circuit comprises a central signal conductor (302) and a peripheral metal ground conductor (303), and the peripheral metal ground conductor (303) comprises a fully wrapped section and a semi-wrapped section, wherein the fully wrapped section is connected to the internal micro-coaxial; the central signal conductor (302) is fixed to the center of the peripheral metal ground conductor through a supporting structure, and the upper surface of the central signal conductor (302) and the upper surface of the semi-wrapped section of the peripheral metal ground conductor are in the same plane.

2. A duplexer based on rectangular micro-coaxial parallel pseudo-interdigital resonator technology according to claim 1, characterized in that: The air coplanar waveguide metal quasi-coaxial interface circuit is connected to the internal micro-coaxial circuit via a gradual transition structure (7) for realizing impedance transformation.

3. A duplexer based on rectangular micro-coaxial parallel pseudo-interdigital resonator technology according to claim 2, characterized in that: The top of the micro-coaxial axis facing the short-circuit branch and the top of the micro-coaxial axis facing the open-circuit end coupling cavity are both provided with adjustment windows for adjusting the coupling coefficient.

4. A high-precision adjustment method for duplexer coupling coefficient, characterized in that: For adjusting the coupling coefficient of a duplexer based on rectangular micro-coaxial parallel pseudo-interdigital resonator technology as claimed in claim 2, the specific steps are as follows: Step 1, placing the duplexer in a closed space for preheating, and filling the closed space with inert gas; Step 2, the laser beam in the confined space is focused on the short-circuit branch and the open-circuit end coupling cavity of the receiving frequency selector and the short-circuit branch and the open-circuit end coupling cavity of the transmitting frequency selector in turn, and the short-circuit branch and the open-circuit end coupling cavity are cut respectively to complete the adjustment of the length of the short-circuit branch and the open-circuit end coupling cavity; Step 3, clean the duplexer adjusted in step 2, remove excess debris, and finally seal the adjustment window with metal tape.

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