Sealed rectangular waveguide-to-microstrip transition structure

Abstract

The utility model discloses a sealed rectangular waveguide-to-microstrip transition structure, and mainly relates to the field of millimeter wave signal transmission. Comprising an input waveguide, the top of the input waveguide is provided with a sealing substrate, the top of the sealing substrate is provided with an air matching cavity, the top of the air matching cavity is provided with a waveguide short-circuit cavity, a probe is arranged in the air matching cavity and extends into the waveguide short-circuit cavity from a wide-edge opening of the air matching cavity, one side of the air matching cavity is provided with a microstrip, and the other side of the waveguide short-circuit cavity is provided with a micro-strip. A main microstrip section is arranged in the microstrip, and the main microstrip section is connected with the probe through an impedance matching microstrip section. The beneficial effects of the utility model are that: not only have good sealing effect and easy assembly, but also have good low reflection performance and good low loss performance when required signals are transmitted therein.

Description

Technical Field

[0001] The utility model relates to the field of millimeter-wave signal transmission, in particular to a sealed rectangular waveguide to microstrip transition structure. Background Technique

[0002] In recent years, with the rapid development of communication systems, millimeter waves, which have the characteristics of high information carrying rate, narrow beam width, high resolution, etc., have gradually become the focus in the field of radio frequency. Their stability and reliability in practical circuits and systems have attracted extensive attention in military, civilian and other fields. Due to the particularity of the frequency band, waveguide and microstrip are often used in millimeter-wave circuits and systems. The conversion and transmission of electromagnetic signals between different media rely on the transition structure, and the performance of which directly affects the working state of the system. In an actual system, a rectangular waveguide is often used as the input and output interface of the signal for convenient testing. The hollow form of the waveguide makes the system communicate with the outside world and is vulnerable to environmental changes. Moreover, even when these interfaces are used for a long time in an indoor environment, such as in a human body security scanner in the W-band, their performance will be affected due to the intrusion and accumulation of moisture and dust. Therefore, achieving good sealing of the transition structure can support the normal operation of the system in a complex environment and further ensure the performance stability and application reliability of the system.

[0003] Classic transition structures include waveguide-ridge waveguide-microstrip transition, waveguide-opposite finline-microstrip transition, and waveguide-probe-microstrip transition. Among them, the probe transition has the advantages of low loss, compact structure, convenient processing, etc., and is a relatively common transition structure in millimeter-wave systems.

[0004] Although the existing transition structure based on glass bead coaxial probe can achieve the sealing of the transition structure, its standing wave characteristics are not good, it is not easy to assemble, the consistency is poor, and the assembly error has a great influence on the performance, so it is mostly used in circuits with lower frequencies; while at higher frequencies, there are great difficulties in processing and assembly. The multi-layer board transition structure can also achieve sealing, but the multi-layer process is costly and difficult to assemble. Therefore, on the basis of comprehensively considering the complexity of the processing technology and the assembly accuracy, how to realize a transition structure with good sealing effect while ensuring low-loss transmission of the required signal is the research focus of this utility model patent. Content of the Utility Model

[0005] The purpose of the utility model is to provide a sealed rectangular waveguide to microstrip transition structure, which not only has a good sealing effect, is easy to assemble, but also has good low-reflection performance and good low-loss performance for the transmission of the required signal therein.

[0006] The utility model realizes the above purpose through the following technical solutions:

[0007] A sealed rectangular waveguide to microstrip transition structure includes an input waveguide. A sealed substrate is provided on the top of the input waveguide. An air matching cavity is provided on the top of the sealed substrate. A waveguide short - circuit cavity is provided on the top of the air matching cavity. A probe is provided in the air matching cavity, and the probe extends into the air matching cavity from the wide - side opening. A microstrip is provided on one side of the air matching cavity, and a main microstrip section is provided in the microstrip. The main microstrip section is connected to the probe through an impedance - matching microstrip section.

[0008] Further, on the basis of completely covering the top of the input waveguide, the sealed substrate extends outward all around to provide a stable sealing ring.

[0009] Further, the upper part of the impedance - matching microstrip section includes a constraint cavity, and the upper part of the main microstrip section includes a fixed cavity. The constraint cavity is located on the top of the air matching cavity.

[0010] Further, the sealed substrate is a ceramic component with no water absorption rate and good airtight properties, with a relative dielectric constant of 9.8 and a thickness of 0.127 mm.

[0011] Further, the input waveguide adopts a standard rectangular waveguide BJ900 covering the W - band, with its main - mode frequency range of 75 GHz - 110 GHz and a cross - sectional size of 2.54 mm×1.27 mm.

[0012] Compared with the prior art, the beneficial effects of the present utility model are as follows:

[0013] This patent realizes the transition between the waveguide and the microstrip through the connection between the probe, the impedance - matching microstrip section and the main microstrip section. The sealed substrate makes this patent have a good sealing effect and is easy to assemble. After simulation of this patent, the frequency band range with a return loss better than 20 dB is 89.56 GHz - 96.58 GHz, that is, within an absolute bandwidth of 7.02 GHz and a relative bandwidth of 7.54%, it has good low - reflection performance; within 89.50 GHz - 96.95 GHz, the insertion loss is less than 0.2 dB, having good low - loss performance, and can ensure low - loss transmission of the required signal therein. Description of the Drawings

[0014] Attached Figure 1 is a schematic structural diagram of the present utility model.

[0015] Attached Figure 2 is a schematic top - view structural diagram of the present utility model.

[0016] Attached Figure 3 is a schematic front - view structural diagram of the present utility model.

[0017] Attached Figure 4 is the return - loss value of the present utility model within the frequency band of 88 GHz - 100 GHz.

[0018] Attached Figure 5 is the insertion loss value of the present utility model within the frequency band of 88 GHz - 100 GHz.

[0019] Reference numerals shown in the attached drawings:

[0020] 1. Input waveguide; 2. Sealing substrate; 3. Probe; 4. Air matching cavity; 5. Waveguide short - circuit cavity; 6. Microstrip; 61. Impedance - matching microstrip section; 62. Main microstrip section; 63. Constraint cavity; 64. Fixed cavity. Specific embodiments

[0021] The following further elaborates the present utility model in combination with specific embodiments. It should be understood that these embodiments are only used to illustrate the present utility model and not to limit the scope of the present utility model. In addition, it should be understood that after reading the content taught by the present utility model, those skilled in the art can make various changes or modifications to the present utility model, and these equivalent forms also fall within the scope defined by this application.

[0022] The present utility model relates to a sealed rectangular waveguide - to - microstrip transition structure. The main structure includes an input waveguide 1 with a rectangular structure. A sealing substrate 2 is provided on the top of the input waveguide 1. An air matching cavity 4 is provided on the top of the sealing substrate 2. The air matching cavity 4 has the same cross - sectional dimensions as the sealing substrate 2, which is 3.94 mm × 2.98 mm, and a height of 0.17 mm, eliminating the resonance formed by the sealing substrate 2 contacting the electric wall and improving the discontinuity in the signal transmission process from the waveguide to the microstrip. A waveguide short - circuit cavity 5 is provided on the top of the air matching cavity 4. The short - circuit cavity 5 has the same cross - section as the input waveguide 1 and a height of 0.4 mm. A probe 3 is provided in the air matching cavity 4. The probe 3 extends into the air matching cavity 4 from the wide - side opening. The length of the probe 3 extending into the air matching cavity 4 is 0.66 mm, and the width is 0.11 mm, electrically coupling the energy of the main TE10 mode of the waveguide to be transmitted in the microstrip 6. A microstrip 6 is provided on one side of the air matching cavity 4. The microstrip 6 has the same substrate material as the sealing substrate 2 and is in the same plane, making the two approximately in a T - shape. The metal thicknesses of both the probe 3 and the microstrip 6 are 17 μm. A main microstrip section 62 is provided in the microstrip 6. The width of the main microstrip section is 0.09 mm, and the characteristic impedance is 50 ohms. The main microstrip section 62 is connected to the probe 3 through an impedance - matching microstrip section 61. The impedance - matching microstrip section 61 starts from the end of the probe 3 and is a high - impedance line with a length of 0.24 mm and a width of 0.02 mm.

[0023] Preferably, on the basis of completely covering the top of the input waveguide 1, the sealing substrate 2 extends 0.71 mm outward in the direction of the signal transmission of the microstrip 6, 1 mm outward in the direction opposite to the signal transmission of the microstrip 6, and 0.7 mm outward in both directions perpendicular to the signal transmission direction of the microstrip 6 to provide a stable sealing ring. The sealing substrate 2 is a ceramic component with no water absorption rate and good airtight properties, with a relative dielectric constant of 9.8 and a thickness of 0.127 mm to ensure good sealing effect.

[0024] Preferably, the upper part of the impedance matching microstrip section 61 includes a constraint cavity 63, and the upper part of the main microstrip section 62 includes a fixing cavity 64. The constraint cavity 63 is located on the top of the air matching cavity 4, and the size of the constraint cavity 63 is 1 mm × 0.56 mm × 0.5 mm, and the size of the fixing cavity 64 is 1 mm × 1.68 mm × 1 mm.

[0025] Preferably, the input waveguide 1 adopts a standard rectangular waveguide BJ900 covering the W band, with a dominant mode frequency range of 75 GHz - 110 GHz and a cross-sectional size of 2.54 mm × 1.27 mm.

[0026] Appendix Figure 4 、Appendix Figure 5 respectively give the S-parameter curve graphs when the present patent works specifically. Figure 4 represents the return loss value of the present patent in the frequency band of 88 GHz - 100 GHz. The frequency band range with a return loss better than 20 dB is marked in the figure as 89.56 GHz - 96.58 GHz, that is, within the absolute bandwidth of 7.02 GHz and the relative bandwidth of 7.54%, it has good low-reflection performance. Figure 5 represents the insertion loss value of the present patent in the frequency band of 88 GHz - 100 GHz. It is marked in the figure that within 89.50 GHz to 96.95 GHz, the insertion loss is less than 0.2 dB, having good low-loss performance.

[0027] In summary, the present patent realizes the transition between the waveguide and the microstrip through the connection between the probe, the impedance matching microstrip section and the main microstrip section. The present patent has a good sealing effect through the sealing substrate and is easy to assemble. After simulation verification, the present patent has good low-reflection performance and good low-loss performance, and can ensure the low-loss transmission of the required signal therein.

Claims

1. A sealed rectangular waveguide to microstrip transition structure, characterized in that: It includes an input waveguide (1), on the top of which there is a sealing substrate (2), on the top of the sealing substrate (2) there is an air matching cavity (4), on the top of the air matching cavity (4) there is a waveguide short - circuit cavity (5), a probe (3) is arranged in the air matching cavity (4), the probe (3) extends in from the wide - side opening of the air matching cavity (4), a microstrip (6) is arranged on one side of the air matching cavity (4), a main microstrip section (62) is arranged in the microstrip (6), and the main microstrip section (62) is connected to the probe (3) through an impedance - matching microstrip section (61).

2. The sealed rectangular waveguide to microstrip transition structure according to claim 1, characterized in that: On the basis of completely covering the top of the input waveguide (1), the sealing substrate (2) extends outwards all around to provide a stable sealing ring.

3. A sealed rectangular waveguide to microstrip transition structure according to claim 1, characterized in that: The upper part of the impedance - matching microstrip section (61) includes a constraint cavity (63), the upper part of the main microstrip section (62) includes a fixing cavity (64), and the constraint cavity (63) is located on the top of the air matching cavity (4).

4. A sealed rectangular waveguide to microstrip transition structure according to claim 1, characterized in that: The sealing substrate (2) is a ceramic component with no water absorption rate and good air - tight properties, with a relative dielectric constant of 9.8 and a thickness of 0.127 mm.

5. A sealed rectangular waveguide to microstrip transition structure according to claim 1, characterized in that: The input waveguide (1) adopts a standard rectangular waveguide BJ900 covering the W - band, with its dominant - mode frequency range of 75 GHz - 110 GHz and a cross - sectional size of 2.54 mm × 1.27 mm.

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