A compact waveguide-microstrip duplexer

Abstract

The application relates to the field of radio frequency microwave circuit technology and discloses a compact waveguide-microstrip duplexer which comprises a first rectangular waveguide, a second rectangular waveguide and a dielectric substrate circuit. The first rectangular waveguide constitutes an input channel of electromagnetic wave signals. The second rectangular waveguide is short-circuited at the terminal end. The dielectric substrate is placed on the cross-section position of the precise and close butt joint between the waveguide openings of the first and second rectangular waveguides. On the dielectric substrate in the internal region of the rectangular waveguide, circuits with narrow-band frequency excitation coupling output characteristics for input signals are respectively made on the two surfaces of the substrate, and a band-pass filter with a corresponding passband is made on the output strip line of the excited signals. Before the two excitation signals of the duplexer pass out of the metal outer wall of the rectangular waveguide and take the form of a microstrip line as an output interface, the coupling and filtering integration function of the input signals is realized in the input rectangular waveguide, and the compact overall circuit structure is characterized.

Description

Technical Field

[0001] This invention relates to the field of radio frequency microwave circuit technology, and more specifically to a compact waveguide-microstrip duplexer. Background Technology

[0002] Microwave duplexers are key components in microwave communication systems, primarily used for isolating and selecting transmit and receive signals. They can separate transmit and receive signals using two sets of bandpass filters at different frequencies, preventing transmit signals from interfering with the receiver and ensuring simultaneous normal operation of the transmitting and receiving systems, thus achieving signal isolation. Alternatively, in dual-frequency duplex systems, filters can be used to tune to the transmit and receive frequency bands for frequency allocation, enabling antenna sharing. Furthermore, by sharing antennas and paths, they can reduce the number of devices, simplify the system, and improve the utilization of communication resources. They have wide applications in full-duplex communication systems, base station equipment, and radar systems.

[0003] The main technical specifications of a duplexer include operating bandwidth, passband insertion loss, out-of-band rejection, transmit / receive isolation, and voltage standing wave ratio (VSWR) at each port. Among these, the isolation between the transmit and receive ports is one of the core parameters for evaluating device performance.

[0004] Currently, duplexers based on waveguide-microstrip hybrid integrated circuits are typically designed by separately optimizing the transmit and receive filters, and then integrating the two filters through a matching network at a common port. This network synthesis-based design method involves the input signal first passing through an impedance matching network at the common port, and then connecting filters to their respective output channels to achieve frequency selection and signal separation. Summary of the Invention

[0005] This invention provides a compact waveguide-microstrip duplexer. By fabricating circuit structures with narrow-band frequency excitation coupling output characteristics for input signals on both sides of a dielectric substrate located inside the cross-section of a rectangular waveguide, and by fabricating bandpass filters with corresponding passbands on the output band lines of the excited signals, the duplexer achieves integrated coupling and filtering of input signals inside the input rectangular waveguide before the two excitation signals pass through the outer metal wall of the rectangular waveguide and are output via microstrip lines.

[0006] This invention provides a compact waveguide-microstrip duplexer, comprising:

[0007] The first rectangular waveguide forms the input channel for electromagnetic wave signals;

[0008] The second rectangular waveguide is terminated by a metal enclosure to form a short surface.

[0009] A dielectric substrate is located between the end cross-section of the first rectangular waveguide and the beginning cross-section of the second rectangular waveguide. The dielectric substrate includes an upper surface and a lower surface opposite to each other. A first output circuit is disposed on the upper surface, and a second output circuit is disposed on the lower surface.

[0010] In one optional embodiment, both the first rectangular waveguide and the second rectangular waveguide include metal sidewalls, and the metal sidewalls of the first rectangular waveguide and the second rectangular waveguide are correspondingly disposed. The metal sidewalls include a pair of opposing narrow metal sidewalls and a pair of opposing wide metal sidewalls. The length and width dimensions of the waveguide openings of the first rectangular waveguide and the second rectangular waveguide are the same.

[0011] The first output circuit and the second output circuit each include a circuit located in the inner region of the rectangular waveguide, a circuit corresponding to the narrow side metal wall, and a circuit extending to the outer region of the narrow side metal wall.

[0012] In one alternative implementation, the circuit located in the region inside the rectangular waveguide includes:

[0013] A grounded metal strip line is perpendicular to the wide side of the rectangular waveguide and extends to the metal sidewall;

[0014] The first metal strip is perpendicular to and spaced apart from the grounding metal strip.

[0015] The second metal strip is connected to the first metal strip.

[0016] The grounded metal strip, the first metal strip, and the second metal strip together constitute a circuit structure that excites a narrowband signal from the input master mode signal in an electrically coupled manner, and then outputs the signal to the outside of the rectangular waveguide.

[0017] In one alternative implementation, the second metal strip is directed vertically to one of the narrow metal sidewalls of the rectangular waveguide for transmitting the excited narrowband output signal.

[0018] In one alternative implementation, the width of the first metal strip is different from that of the second metal strip.

[0019] In one alternative embodiment, one or more metal-free regions (13) of geometric shapes such as circles, rectangles or crescents arranged in the direction of excitation signal transmission are formed on the second metal strip to form a filter circuit structure for further improving frequency selection characteristics.

[0020] Beneficial effects: This invention fundamentally changes the traditional duplexer design mode of separating and cascading filters and common port networks by fabricating circuits with narrow-band frequency excitation coupling output characteristics for input signals on both sides of a dielectric substrate located inside a rectangular waveguide, and fabricating corresponding passband bandpass filters on the transmission line of the excited signal. This allows the two excitation signals of the duplexer to complete the coupling and filtering of the input signal inside the input rectangular waveguide before passing through the metal outer wall of the rectangular waveguide and using microstrip lines as the output interface. It has the characteristics of a compact overall circuit structure.

[0021] In one optional embodiment, a rectangular metal circuit, independent of the output circuit, is provided on the upper and lower surfaces of the dielectric substrate. The rectangular metal circuit is used to coordinate and optimize the design of the distance between the dielectric substrate and the short road surface.

[0022] In one alternative implementation, the circuit extending to the outside of the narrow metal sidewall is configured as a 50-ohm standard output microstrip line for outputting the narrowband output signal.

[0023] In one alternative implementation, the circuit corresponding to the narrow metal sidewall is configured as an impedance matching circuit, which is connected to the output microstrip line and the second metal strip line respectively.

[0024] In one alternative embodiment, opening slots are respectively formed on the two opposite narrow metal sidewalls of the rectangular waveguide, corresponding to the position through which the output circuit passes. Attached Figure Description

[0025] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram of a compact waveguide-microstrip duplexer according to an embodiment of the present invention;

[0027] Figure 2 This is a schematic diagram of the circuit on the upper surface of the dielectric substrate in an embodiment of the present invention;

[0028] Figure 3 This is a schematic diagram of the circuit on the lower surface of the dielectric substrate in an embodiment of the present invention;

[0029] Figure 4The insertion loss (S) of the two channels of the Ka-band duplexer in this embodiment of the invention is... 21 S 31 ) and input return loss (S 11 Simulation results;

[0030] Figure 5 The simulation results show the isolation index of the two channels of the Ka-band duplexer in this embodiment of the invention.

[0031] Explanation of reference numerals in the attached figures:

[0032] 1. First rectangular waveguide; 2. Dielectric substrate; 3. Second rectangular waveguide; 4. Short surface; 5. Upper surface; 6. Lower surface; 7. Internal region; 8. Narrow-sided metal sidewall; 9. Outer region; 10. Grounded metal strip; 11. First metal strip; 12. Second metal strip; 13. Metal-free region; 14. Rectangular metal circuit; 15. Impedance matching circuit; 16. Output microstrip line; 17. Opening slot. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] The following is combined Figures 1 to 5 The following describes embodiments of the present invention.

[0035] According to an embodiment of the present invention, a compact waveguide-microstrip duplexer is provided, comprising a first rectangular waveguide 1, a second rectangular waveguide 3, and a dielectric substrate 2. The first rectangular waveguide 1 constitutes an input channel for electromagnetic wave signals. The terminal of the second rectangular waveguide 3 is sealed with metal to form a short-circuit surface 4. The dielectric substrate 2 is located between the end cross-section of the first rectangular waveguide 1 and the beginning cross-section of the second rectangular waveguide 3. The dielectric substrate 2 includes an opposing upper surface 5 and a lower surface 6. A first output circuit is disposed on the upper surface 5, and a second output circuit is disposed on the lower surface 6.

[0036] The dielectric substrate 2 uses Rogers RT / duroid 5880 material with a thickness of 0.254 mm.

[0037] In this embodiment, the present invention adopts a three-segment basic architecture of a first rectangular waveguide 1, a dielectric substrate 2, and a second rectangular waveguide 3, and sets the dual-output circuits on the upper surface 5 and the lower surface 6 of the dielectric substrate 2 respectively. On the dielectric substrate located in the inner region of the rectangular waveguide, circuits with narrow-band frequency excitation coupling output characteristics for the input signal are fabricated on both sides of the substrate, and bandpass filters with corresponding passbands are fabricated on the transmission line of the excited signal. This fundamentally changes the traditional design mode of separate cascading of filters and common port networks in duplexers. This allows the two excitation signals of the duplexer to complete the coupling and filtering of the input signal in the inner rectangular waveguide before passing through the metal outer wall of the rectangular waveguide and using microstrip lines as the output interface. It has the characteristics of compact overall circuit structure.

[0038] In one embodiment, both the first rectangular waveguide 1 and the second rectangular waveguide 3 include metal sidewalls, and the metal sidewalls of the first rectangular waveguide 1 and the metal sidewalls of the second rectangular waveguide 3 are correspondingly arranged. The metal sidewalls include a pair of opposing narrow metal sidewalls 8 and a pair of opposing wide metal sidewalls. The length and width dimensions of the waveguide openings of the first rectangular waveguide 1 and the second rectangular waveguide 3 are the same.

[0039] The first output circuit and the second output circuit both include a circuit located in the inner region 7 of the rectangular waveguide, a circuit corresponding to the narrow side metal wall 8, and a circuit extending to the outer region 9 of the narrow side metal wall 8.

[0040] In this embodiment, a circuit structure is adopted in which the dielectric substrate 2 is placed at a precisely and tightly aligned cross-sectional position between the waveguide openings of the first rectangular waveguide 1 and the second rectangular waveguide 3. The two circuits on the dielectric substrate 2 are clearly divided into three continuous circuits: one located inside the rectangular waveguide, one corresponding to the narrow metal sidewall 8, and one extending to the outside of the rectangular waveguide. This design clearly defines the complete physical path of the generation, transmission, and final extraction of the output signal inside the waveguide after the input signal enters the rectangular waveguide, at the positions of the input signal on both surfaces of the dielectric substrate 2. This structural division ensures efficient spatial connection between the coupling excitation and signal output functions, enabling the entire circuit to fully utilize the internal space of the rectangular waveguide and penetrate its walls to achieve output. This is key to achieving highly integrated hybrid circuit design.

[0041] In one embodiment, the circuit located in the internal region 7 of the rectangular waveguide includes a ground metal strip 10, a first metal strip 11, and a second metal strip 12. The ground metal strip 10 is perpendicular to the wide side of the rectangular waveguide and extends to the metal sidewall. The first metal strip 11 is perpendicular to the ground metal strip 10 and is spaced apart from it. The second metal strip 12 is connected to the first metal strip 11.

[0042] Among them, the grounded metal strip 10, the first metal strip 11 and the second metal strip 12 together constitute a circuit structure that excites a narrowband signal from the input master mode signal in an electrically coupled manner and then outputs the signal to the outside of the rectangular waveguide.

[0043] In this embodiment, by employing a circuit structure consisting of a grounded metal strip 10 and a first metal strip 11 arranged perpendicularly and spaced apart to form a basic coupling unit, and then connecting it to a second metal strip 12, this scheme establishes an efficient electric field coupling mechanism within the rectangular waveguide. The gap between the grounded metal strip 10 and the first metal strip 11 can effectively couple the electromagnetic energy in the waveguide's main mode, thereby exciting the desired narrowband signal. The second metal strip 12 is then used for the transmission of the excited narrowband signal. This structure is the core of transmitting broadband signals that can be transmitted within the waveguide, and its structural dimensions and the spacing between them directly determine the center frequency of the duplexer's output channel.

[0044] In one embodiment, the second metal strip 12 is perpendicularly directed to one of the narrow metal sidewalls 8 of the rectangular waveguide for transmitting the excited narrowband output signal.

[0045] In this embodiment, by vertically guiding the second metal strip 12 to the narrow metal sidewall 8 of the waveguide, this design provides a transmission path solely for the narrowband signal generated from the rectangular waveguide. It directs the signal to the region near the narrow sidewall of the waveguide, creating the necessary conditions for the signal to subsequently penetrate the waveguide wall and be output to external circuitry.

[0046] In one embodiment, the width dimensions of the first metal strip 11 and the second metal strip 12 are different.

[0047] It should be noted that the width and length of the grounding metal strip 10 on the upper surface 5 are 0.84 mm and 1.31 mm, respectively. The width and length of the first metal strip 11, which is adjacent to and perpendicular to it, are 0.85 mm and 1.54 mm, respectively. The perpendicular distance between the end edge of the grounding metal strip 10 and the adjacent edge of the first metal strip 11 is 0.16 mm. The width and length of the second metal strip 12 are 0.48 mm and 1.68 mm, respectively. The distance between the crescent-shaped metal-free region 13 on the second metal strip 12 and the narrow sidewall of the waveguide is approximately 0.83 mm, and the area of ​​the crescent-shaped metal-free region 13 is approximately 0.06 mm². 2 The independent rectangular metal circuit 14 on the other side of the grounding metal strip 10 has a length and width of 2.14 mm and 1.25 mm, respectively. The second metal strip 12 is connected to the narrow sidewall and the impedance matching circuit 15 on the outside of the sidewall and the output microstrip line 16, and outputs a signal at a center frequency f1 of 28.7 GHz.

[0048] The grounding metal strip 10 on the lower surface 6 has a width of 0.56 mm and a length of 1.01 mm. The adjacent and perpendicular first metal strip 11 has a width of 0.85 mm and a length of 1.54 mm. The perpendicular distance between the end edge of the grounding metal strip 10 and the adjacent edge of the first metal strip 11 is 0.08 mm. The second metal strip 12 has a width of 0.48 mm and a length of 1.68 mm. The crescent-shaped metal-free region 13 on the second metal strip 12 is approximately 1.1 mm away from the narrow sidewall, and its area is approximately 0.04 mm². 2 The rectangular metal circuit 14 on the other side of the grounding metal strip 10 has a length and width of 1.25 mm and 1.14 mm, respectively. The second metal strip 12 outputs a signal at a center frequency f2 of 36.1 GHz after being connected to the narrow sidewall and the impedance matching circuit 15 on the outside of the sidewall and the output microstrip line 16.

[0049] In this embodiment, by making the first metal strip 11 and the second metal strip 12 have different width dimensions, a discontinuous structure is formed on the signal transmission path. By using this structure and cooperating with the impedance matching circuit 15 at the back end, it is easier to achieve the impedance matching design purpose of the output channel signal transmission when using a 50-ohm standard microstrip line as the final output port.

[0050] In one embodiment, the circuit dimensions of the ground metal strip 10 and the first metal strip 11, as well as their relative positions, are adjusted to obtain the desired narrowband output signals in different frequency bands.

[0051] In one embodiment, a crescent-shaped metal-free region 13 is formed on the second metal strip 12, constituting a filter circuit structure for improving frequency selectivity.

[0052] In this embodiment, by creating a crescent-shaped metal-free region 13 on the second metal strip 12, a built-in filter is formed again on the signal transmission path, which can perform secondary frequency filtering on the narrowband signal passing through the second metal strip 12, further suppressing out-of-band spurious signals and improving the frequency selection performance of the duplexer.

[0053] In one embodiment, a rectangular metal circuit 14, independent of the output circuit, is provided on the upper surface 5 and lower surface 6 of the dielectric substrate 2. The rectangular metal circuit 14 is used to coordinate and optimize the design of the distance between the dielectric substrate 2 and the short surface 4.

[0054] In this embodiment, by setting a rectangular metal circuit 14 independent of the main output circuit on the surface of the dielectric substrate 2, this design provides an additional tuning means. By adjusting the size and position of this independent metal block, the transmission characteristics of both outputs of the duplexer can be compensated for and improved under the same waveguide terminal short-circuit surface 4 size.

[0055] In one embodiment, the circuit extending to the outside of the narrow metal sidewall 8 is configured as a standard 50-ohm output microstrip line 16 for outputting a narrowband output signal.

[0056] An external bandpass filter corresponding to the passband frequency band can be cascaded on the two output microstrip lines 16. This hybrid design, combining built-in frequency-selective coupling with external high-performance filtering, can achieve a steeper out-of-band rejection roll-off and a higher stopband rejection level by utilizing external filters while maintaining a highly compact core, thus meeting diverse engineering application requirements.

[0057] In one embodiment, the circuit corresponding to the narrow metal sidewall 8 is configured as an impedance matching circuit 15, which is connected to the output microstrip line 16 and the second metal strip line 12 respectively.

[0058] In one embodiment, opening slots 17 are respectively provided on the two opposite narrow metal sidewalls 8 of the rectangular waveguide, corresponding to the positions through which the output circuit passes.

[0059] A specific Ka-band duplexer design based on the above embodiments, and its simulation results are as follows: Figure 4 and Figure 5 As shown. Figure 4 The input return loss S is shown. 11 And the insertion loss S of the two output ports 21 , S 31 Simulation results show that the insertion loss of both output passbands is less than 0.5dB in the frequency ranges of 28.6-28.8GHz and 36.0-36.2GHz, respectively, and the input return loss is better than -10dB in the passband. Figure 5 This demonstrates the isolation S between the two output ports. 23 It achieved a level of approximately -47dB within the corresponding frequency band, verifying that the compact structure has good transmit / receive isolation performance.

[0060] Although embodiments of the invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A compact waveguide-microstrip duplexer, characterized in that, include: The first rectangular waveguide (1) forms the input channel for electromagnetic wave signals; The second rectangular waveguide (3) has a short road surface (4) formed by metal enclosure at its terminal. The dielectric substrate (2) is located between the end cross-section of the first rectangular waveguide (1) and the beginning cross-section of the second rectangular waveguide (3). The dielectric substrate (2) includes an upper surface (5) and a lower surface (6) opposite to each other. A first output circuit is provided on the upper surface (5) and a second output circuit is provided on the lower surface (6). On the upper surface (5) and / or the lower surface (6) of the dielectric substrate (2), a rectangular metal circuit (14) independent of the output circuit is provided. The rectangular metal circuit (14) is used to coordinate and optimize the design of the distance between the dielectric substrate (2) and the short surface (4).

2. The compact waveguide-microstrip duplexer according to claim 1, characterized in that, The first rectangular waveguide (1) and the second rectangular waveguide (3) both include metal sidewalls, and the metal sidewalls of the first rectangular waveguide (1) and the metal sidewalls of the second rectangular waveguide (3) are correspondingly arranged. The metal sidewalls include a pair of opposing narrow metal sidewalls (8) and a pair of opposing wide metal sidewalls. The length and width dimensions of the waveguide openings of the first rectangular waveguide (1) and the second rectangular waveguide (3) are the same. The first output circuit and the second output circuit each include a circuit located in the inner region (7) of the rectangular waveguide, a circuit corresponding to the narrow side metal wall (8), and a circuit extending to the outer region (9) of the narrow side metal wall (8).

3. The compact waveguide-microstrip duplexer according to claim 2, characterized in that, The circuit located in the internal region (7) of the rectangular waveguide includes: A grounded metal strip (10) is perpendicular to the wide side of the rectangular waveguide and extends to the metal sidewall; The first metal strip (11) is perpendicular to the grounding metal strip (10) and is spaced apart from it; The second metal strip (12) is connected to the first metal strip (11); The grounded metal strip (10), the first metal strip (11), and the second metal strip (12) together constitute a circuit structure that excites a narrowband signal from the input master mode signal in an electrically coupled manner and then outputs the signal to the outside of the rectangular waveguide.

4. The compact waveguide-microstrip duplexer according to claim 3, characterized in that, The second metal strip (12) is directed vertically to one of the narrow metal sidewalls (8) of the rectangular waveguide for transmitting the excited narrowband signal.

5. The compact waveguide-microstrip duplexer according to claim 4, characterized in that, The width dimensions of the first metal strip (11) and the second metal strip (12) are different.

6. The compact waveguide-microstrip duplexer according to claim 3, characterized in that, On the second metal strip (12), one or more circular, rectangular or crescent-shaped metal-free regions (13) are fabricated in the direction of excitation signal transmission to form a filter circuit structure for further improving frequency selection characteristics.

7. The compact waveguide-microstrip duplexer according to claim 3, characterized in that, The circuit extending to the outside of the narrow metal sidewall (8) is configured as a 50-ohm standard output microstrip line (16) for outputting the narrowband signal.

8. The compact waveguide-microstrip duplexer according to claim 7, characterized in that, The circuit corresponding to the narrow metal sidewall (8) is configured as an impedance matching circuit (15), which is connected to the output microstrip line (16) and the second metal strip line (12) respectively.

9. The compact waveguide-microstrip duplexer according to claim 2, characterized in that, On the two opposite narrow metal sidewalls (8) of the rectangular waveguide, opening slots (17) are respectively provided at the positions through which the output circuit passes.

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