Ka-band waveguide sealing system with high-order mode suppression and its implementation method

Abstract

The invention relates to a Ka-band waveguide sealing system loaded with high-order mode suppression and an implementation method thereof, comprising a planar circuit E-plane microstrip probe, a probe substrate sealing structure, a reduced-height rectangular waveguide and a waveguide E-bend; the planar circuit E-plane microstrip probe is located on an E-plane perpendicular to the waveguide transmission direction to convert the electromagnetic wave signal in the waveguide to a planar strip line; the probe substrate sealing structure completely covers the waveguide mouth surface, and the excess part is designed with a metallized via and a complete pad to contact the metal on the periphery of the waveguide; the main mode TE10 mode is transmitted in the reduced-height rectangular waveguide, and the size is reduced and the cut-off frequency is increased by reducing the wide side and narrow side of the rectangular waveguide; the input direction of the waveguide port of the reduced-height rectangular waveguide is consistent with the direction of the planar circuit, and an E-plane turn is performed. By designing a waveguide conversion circuit form, the signal in the waveguide is converted into a planar circuit signal, and the cavity part in the waveguide is sealed to the device inside the circuit module to achieve high-order mode suppression.

Description

Technical Field

[0001] The invention belongs to the technical field of waveguide sealing, and in particular relates to a Ka-band waveguide sealing system loaded with high-order mode suppression and a realization method thereof. Background Art

[0002] Most devices in electronic products are precision devices and have high requirements for the external environment. Especially for bare chip devices, since there are a large number of tiny strip lines, air bridges, micro-channels and other structures made by photolithography on the surface of the device, the structural size is on the order of 0.1mm. When contaminated by impurity particles in the air, excess metal in circuit welding, moisture, etc., it will cause performance degradation or even device failure. The solution to the above problems is to seal the precision electronic devices. In high-frequency circuit design, due to the increasing circuit loss of planar circuits with the increase of operating frequency, especially in the millimeter wave band, waveguide circuits are widely used as a good carrier for transmitting signals. Waveguide is a hollow metal enclosed structure. When cascaded and integrated with electronic devices, there will be a situation where the external air is connected to the internal devices of the circuit module.

[0003] Existing waveguide seals are usually designed using glass insulator probes or sealing windows, which have the problems of complex structure, difficult integration, and inducing high-order modes.

[0004] Therefore, how to improve the existing waveguide seal to solve the problems of high structural complexity, difficulty in integration and induction of high-order modes in the existing waveguide seal is a technical problem that urgently needs to be solved. Summary of the invention

[0005] The purpose of the present invention is to provide a Ka-band waveguide sealing system loaded with high-order mode suppression and an implementation method thereof, so as to improve the existing waveguide sealing to solve the problems of high structural complexity, difficulty in integration and inducing high-order modes of the existing waveguide sealing.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0007] In the first aspect, a Ka-band waveguide sealing system with loaded high-order mode suppression is provided, including a planar circuit E-plane microstrip probe, a probe substrate sealing structure, a reduced-height rectangular waveguide, and a waveguide E-bend;

[0008] The planar circuit E-plane microstrip probe is located on the E-plane perpendicular to the waveguide transmission direction, and is used to convert the electromagnetic wave signal in the waveguide to the planar strip line;

[0009] The probe substrate sealing structure completely covers the waveguide opening, and the portion beyond the opening is designed with metallized vias and complete pads to contact the metal on the periphery of the waveguide;

[0010] The main mode TE10 mode is transmitted in the reduced height rectangular waveguide, the cutoff frequency is increased by reducing the wide side size of the reduced height rectangular waveguide, and the size of the waveguide port is reduced by reducing the narrow side;

[0011] The input direction of the waveguide port of the reduced height rectangular waveguide is consistent with the direction of the planar circuit, and an E-plane turn is performed to form an E-plane turn structure, and the E-plane turn structure is a waveguide E-bend.

[0012] Preferably, the planar circuit E-plane microstrip probe includes a probe conversion circuit, which is equivalent to a monopole antenna. The part inside the waveguide is parallel to the electric field inside the waveguide, excites the field structure on both sides of the antenna, and totally reflects the electromagnetic waves by setting a quarter-wavelength short-circuit surface on one side.

[0013] Preferably, a high-impedance line with a smaller width is used for impedance matching between the planar circuit E-surface microstrip probe and the planar circuit strip line.

[0014] Preferably, the planar circuit strip line has a characteristic impedance of 50 ohms.

[0015] Preferably, the planar circuit E-surface microstrip probe is made on the probe substrate sealing structure, which is a low-loss dielectric substrate. The outer dimensions of the probe substrate sealing structure are larger than the rectangular waveguide boundary. The outer dimensions of the probe substrate sealing structure exceed the dimensions of the rectangular waveguide boundary by a range of [0.5mm~1mm], so that it completely covers the waveguide mouth surface.

[0016] Preferably, the wide side dimension range of the reduced height rectangular waveguide is 6±0.1 mm, and the narrow side dimension range of the reduced height rectangular waveguide is 3±0.1 mm.

[0017] In a second aspect, a method for implementing a Ka-band waveguide sealing system loaded with high-order mode suppression is provided, which is based on the implementation of the Ka-band waveguide sealing system loaded with high-order mode suppression, and includes the following processes:

[0018] S1: inputting an electromagnetic wave signal into a waveguide, and turning the transmission direction of the electromagnetic wave signal in the waveguide by 90° through a waveguide E-bend of the waveguide;

[0019] S2: The TE10 mode in the waveguide is converted into a quasi-TEM mode of the planar circuit through the probe conversion circuit of the planar circuit E-plane microstrip probe.

[0020] Preferably, the waveguide E-bend in step S1 is cut at a right angle at the bend to perform impedance matching in the waveguide.

[0021] The beneficial effects of the present invention include:

[0022] The Ka-band waveguide sealing system and implementation method thereof provided by the present invention for loading high-order mode suppression include a planar circuit E-plane microstrip probe, a probe substrate sealing structure, a reduced-height rectangular waveguide and a waveguide E-bend; the planar circuit E-plane microstrip probe is located on the E-plane perpendicular to the waveguide transmission direction to convert the electromagnetic wave signal in the waveguide to a planar strip line; the probe substrate sealing structure completely covers the waveguide mouth surface, and the excess part is designed with metallized vias and complete pads to contact the metal outside the waveguide; the main mode TE10 mode is transmitted in the reduced-height rectangular waveguide, and the size is reduced and the cut-off frequency is increased by reducing the wide side and narrow side of the rectangular waveguide; the input direction of the waveguide port of the reduced-height rectangular waveguide is consistent with the direction of the planar circuit, and an E-plane turn is performed. By designing the waveguide conversion circuit form, the signal in the waveguide is converted into a planar circuit signal, and the cavity part in the waveguide is sealed to the device inside the circuit module to achieve high-order mode suppression.

[0023] First, by designing a planar circuit E-plane microstrip probe on the E-plane perpendicular to the waveguide transmission direction, the electromagnetic wave signal in the waveguide is converted to the planar strip line. The probe conversion circuit is equivalent to a monopole antenna, whose part in the waveguide is parallel to the electric field in the waveguide, and excites the field structure on both sides of the antenna. By setting a quarter-wavelength short-circuit surface on one side, the electromagnetic wave is fully reflected, and good transmission characteristics are formed on the other side. Between the microstrip probe and the planar circuit strip line, a high-impedance line with a smaller width is used for impedance matching. Through reasonable design, the above circuit can achieve good performance within the full rectangular waveguide bandwidth.

[0024] Secondly, through the probe substrate sealing structure, the microstrip probe is made on a low-loss dielectric substrate. The outer dimensions of the substrate are larger than the rectangular waveguide boundary [0.5 mm ~1 mm] and completely cover the waveguide mouth. The excess part is designed with metallized vias and complete pads to contact the metal outside the waveguide. The metal surface treatment of the waveguide periphery adopts gold plating process. When assembling the circuit substrate, welding assembly is adopted to achieve a good sealing effect.

[0025] Finally, a height-reduced rectangular waveguide and waveguide E-bend are set. The main mode TE10 mode is transmitted in the rectangular waveguide, and the cutoff frequency of the main mode is determined by the wide side. Reducing the narrow side does not affect the transmission state in the waveguide, and the purpose of reducing the size of the waveguide port is achieved. Reducing the wide side increases the cutoff frequency. The input direction of the waveguide port is designed to be consistent with the direction of the planar circuit, and an E-surface turn is made. The above two structural designs of reducing the wide side and narrow side and the waveguide E-bend have a significant inhibitory effect on high-order modes due to the change of the structural size of the rectangular waveguide. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a schematic structural diagram of the Ka-band waveguide sealing system with loaded high-order mode suppression according to the present invention.

[0027] Figure 2 It is a schematic diagram of the rectangular waveguide turning simulation optimization results of the present invention.

[0028] Figure 3 It is a schematic diagram of the combined simulation optimization results of the rectangular turn and microstrip probe of the present invention.

[0029] Figure numerals: 1 is a sealing ring, 2 is a metallized ground via, 3 is a waveguide boundary, 4 is a planar circuit E-surface microstrip probe, 5 is a high-impedance matching, and 6 is a 50-ohm characteristic impedance transmission line. DETAILED DESCRIPTION

[0030] The following is combined with Figure 1~Figure 3 The present invention is further described in detail:

[0031] Example 1

[0032] See attached Figure 1 As shown, a Ka-band waveguide sealing system loaded with high-order mode suppression includes a planar circuit E-plane microstrip probe, a probe substrate sealing structure, a reduced-height rectangular waveguide, and a waveguide E-bend. The planar circuit E-plane microstrip probe is located on the E-plane perpendicular to the waveguide transmission direction, and is used to convert the electromagnetic wave signal in the waveguide to the planar strip line; the probe substrate sealing structure completely covers the waveguide mouth surface, and the excess part is designed with metallized vias and complete pads to contact the metal on the periphery of the waveguide; the main mode TE10 mode is transmitted in the reduced-height rectangular waveguide, and the cutoff frequency is increased by reducing the wide side size of the reduced-height rectangular waveguide, and the waveguide mouth size is reduced by reducing the narrow side; the input direction of the waveguide port of the reduced-height rectangular waveguide is consistent with the direction of the planar circuit, and an E-plane turn is made to form an E-plane turn structure, and the E-plane turn structure is the waveguide E-bend.

[0033] Since the existing waveguide seal is usually designed by glass insulator probe or sealing window, the existing waveguide seal has a complex structure, is difficult to integrate, and is prone to induce high-order modes. Therefore, the present invention changes the structure of the waveguide seal in the prior art to reduce the structural complexity of the existing waveguide seal, improve the integration, and suppress the high-order mode.

[0034] Therefore, in this embodiment, a planar circuit E-plane microstrip probe is designed on the E-plane perpendicular to the waveguide transmission direction to convert the electromagnetic wave signal in the waveguide to the planar strip line. The probe conversion circuit is equivalent to a monopole antenna, the part of which in the waveguide is parallel to the electric field in the waveguide, and excites the field structure on both sides of the antenna. By setting a quarter-wavelength short-circuit surface on one side, the electromagnetic wave is fully reflected, and good transmission characteristics are formed on the other side. Between the microstrip probe and the planar circuit strip line, a high-impedance line with a smaller width is used for impedance matching. Through reasonable design, the above circuit can achieve good performance within the full rectangular waveguide bandwidth.

[0035] Through the probe substrate sealing structure, the microstrip probe is made on a low-loss dielectric substrate to form a substrate-sealed waveguide structure. The outer dimensions of the substrate are larger than the rectangular waveguide boundary [0.5 mm ~1mm] and completely cover the waveguide mouth. The excess part is designed with metallized vias and complete pads to contact the metal on the periphery of the waveguide. By setting the height-reduced rectangular waveguide and waveguide E-bend. The main mode TE10 mode is transmitted in the rectangular waveguide, and the cutoff frequency of the main mode is determined by the wide side. Reducing the narrow side does not affect the transmission state in the waveguide, achieving the purpose of reducing the size of the waveguide mouth, and reducing the wide side to increase the cutoff frequency. The input direction of the waveguide port is designed to be consistent with the direction of the planar circuit, and an E-surface turn is made. The above two structural designs of reducing the wide side and narrow side and the waveguide E-bend have a significant inhibitory effect on high-order modes due to the change of the structural size of the rectangular waveguide. The substrate sealed waveguide structure includes a sealing ring 1, a metallized grounding via 2, a waveguide boundary 3, a planar circuit E-surface microstrip probe 4, a high impedance matching 5, and a 50 ohm characteristic impedance transmission line 6.

[0036] Example 2

[0037] On the basis of Example 1, the planar circuit E-plane microstrip probe includes a probe conversion circuit, which is equivalent to a monopole antenna. The part in the waveguide is parallel to the electric field in the waveguide, excites the field structure on both sides of the antenna, and sets a quarter-wavelength short-circuit surface on one side to fully reflect the electromagnetic wave. A high-impedance line with a smaller width is used for impedance matching between the planar circuit E-plane microstrip probe and the planar circuit strip line. Preferably, the planar circuit strip line has a characteristic impedance of 50 ohms.

[0038] Example 3

[0039] Based on Example 1 or Example 2, the planar circuit E-surface microstrip probe is made on the probe substrate sealing structure, which is a low-loss dielectric substrate. The outer dimensions of the probe substrate sealing structure are larger than the rectangular waveguide boundary, and the outer dimensions of the probe substrate sealing structure exceed the dimensions of the rectangular waveguide boundary by [0.5 mm ~1 mm], so that it completely covers the waveguide mouth surface. The metal surface treatment of the waveguide periphery adopts a gold plating process, and when assembling the circuit substrate, a welding assembly method is adopted to achieve a good sealing effect.

[0040] In this embodiment, the wide side dimension range of the reduced height rectangular waveguide is 6±0.1 mm, and the narrow side dimension range of the reduced height rectangular waveguide is 3±0.1 mm.

[0041] The method for implementing the Ka-band waveguide sealing system loaded with high-order mode suppression is based on the Ka-band waveguide sealing system loaded with high-order mode suppression, and includes the following processes:

[0042] S1: Input an electromagnetic wave signal into a waveguide, and turn the transmission direction of the electromagnetic wave signal in the waveguide by 90° through the waveguide E-bend of the waveguide. The waveguide E-bend in step S1 uses a right angle cut at the bend to perform impedance matching in the waveguide.

[0043] S2: The TE10 mode in the waveguide is converted into a quasi-TEM mode of the planar circuit through the probe conversion circuit of the planar circuit E-plane microstrip probe.

[0044] Through the waveguide turning structure, the electromagnetic wave signal transmission direction in the waveguide is turned 90 degrees, and then the TE10 mode in the waveguide is converted into the quasi-TEM mode of the planar circuit through the probe conversion circuit. For the waveguide turning, the impedance matching in the waveguide is carried out by cutting the right angle at the corner. Through simulation optimization and selecting the appropriate cutting angle parameters, better matching can be achieved in the entire waveguide frequency band.

[0045] After the signal direction transmitted in the waveguide is perpendicular to the plane of the microstrip probe circuit, the width, length, size of the high-resistance line, and the distance between the short-circuit surface and the probe are reasonably selected and optimized to achieve good results. The design of this part needs to be jointly simulated with the waveguide bend to eliminate the standing wave deterioration caused by cascading and affect the performance. It should be noted that in the above design, the airtight substrate will also affect the matching of the microstrip conversion to 50 ohm characteristic impedance, and it needs to be considered as a component in the three-dimensional model.

[0046] See also Figure 2 and Figure 3 The results of the joint simulation are compared with the simulation results of the single waveguide turn, and it can be seen that its transmission bandwidth has been reduced. In fact, in addition to the main propagation mode TE10 mode in the waveguide, there are also higher-order modes, whose lowest cutoff frequency is around 44GHz in the rectangular waveguide of the Ka band. On the one hand, by reducing the height of the waveguide when the waveguide turns, the size of the waveguide is reduced, which increases the lowest cutoff frequency of the high-order mode; on the other hand, in the design of waveguide to microstrip, the microstrip probe, as an antenna array element in the waveguide, can only excite the field structure consistent with the direction of the TE10 mode electric field, while the field structure of the high-order mode is inconsistent with the TE10 mode. Through the above two design factors, the high-order mode is significantly suppressed.

[0047] In summary, the Ka-band waveguide sealing system and implementation method thereof provided by the present invention with high-order mode suppression loading include a planar circuit E-surface microstrip probe, a probe substrate sealing structure, a reduced rectangular waveguide and a waveguide E-bend; the planar circuit E-surface microstrip probe is located on the E-surface perpendicular to the waveguide transmission direction to convert the electromagnetic wave signal in the waveguide to a planar stripline; the probe substrate sealing structure completely covers the waveguide mouth, and the excess part is designed with metallized vias and complete pads to contact the metal on the periphery of the waveguide; the main mode TE10 mode is transmitted in the reduced rectangular waveguide, and the size is reduced and the cut-off frequency is increased by reducing the wide side and narrow side of the rectangular waveguide; the input direction of the waveguide port of the reduced rectangular waveguide is consistent with the direction of the planar circuit, and an E-surface turn is performed. By designing a waveguide conversion circuit form, the signal in the waveguide is converted into a planar circuit signal, and the cavity part in the waveguide is sealed to the device inside the circuit module to achieve high-order mode suppression. By designing a planar circuit E-surface microstrip probe on the E-surface perpendicular to the waveguide transmission direction, the electromagnetic wave signal in the waveguide is converted to a planar stripline. The probe conversion circuit is equivalent to a monopole antenna, whose part in the waveguide is parallel to the electric field in the waveguide, and excites the field structure on both sides of the antenna. By setting a quarter-wavelength short-circuit on one side, the electromagnetic wave is fully reflected, and good transmission characteristics are formed on the other side. Between the microstrip probe and the planar circuit strip line, a high-impedance line with a smaller width is used for impedance matching. Through reasonable design, the above circuit can achieve good performance within the full rectangular waveguide bandwidth.

[0048] Through the probe substrate sealing structure, the microstrip probe is made on a low-loss dielectric substrate. The outer dimensions of the substrate are larger than the rectangular waveguide boundary [0.5 mm ~1mm] and completely cover the waveguide mouth surface. The part beyond is designed with metallized vias and complete pads to contact the metal on the periphery of the waveguide. The metal surface treatment of the waveguide periphery adopts the gold plating process. When assembling the circuit substrate, the welding assembly method is adopted to achieve a good sealing effect. Set up a reduced rectangular waveguide and a waveguide E-bend. The main mode TE10 mode is transmitted in the rectangular waveguide, and the cutoff frequency of the main mode is determined by the wide side. Reducing the narrow side does not affect the transmission state in the waveguide, so as to achieve the purpose of reducing the size of the waveguide mouth. Reducing the wide side increases the cutoff frequency. The input direction of the waveguide port is designed to be consistent with the direction of the planar circuit, and an E-surface turn is made. The above two structural designs of reducing the wide side and narrow side and the waveguide E-bend have a significant inhibitory effect on the high-order mode due to the change of the structural size of the rectangular waveguide.

Claims

1. Ka-band waveguide sealing system with high-order mode suppression, characterized in that: It includes a planar circuit E-surface microstrip probe, a probe substrate sealing structure, a reduced-height rectangular waveguide and a waveguide E-bend; The planar circuit E-plane microstrip probe is located on the E-plane perpendicular to the waveguide transmission direction, and is used to convert the electromagnetic wave signal in the waveguide to the planar strip line; The probe substrate sealing structure completely covers the waveguide opening, and the portion beyond the opening is designed with metallized vias and complete pads to contact the metal on the periphery of the waveguide; The main mode TE10 mode is transmitted in the reduced height rectangular waveguide, and the cutoff frequency is increased by reducing the wide side size of the reduced height rectangular waveguide, and the size of the waveguide port is reduced by reducing the narrow side; The input direction of the waveguide port of the height-reduced rectangular waveguide is consistent with the direction of the planar circuit, and an E-plane turn is performed to form an E-plane turn structure, and the E-plane turn structure is a waveguide E-bend; The planar circuit E-plane microstrip probe includes a probe conversion circuit, which is equivalent to a monopole antenna. The part in the waveguide is parallel to the electric field in the waveguide, excites the field structure on both sides of the antenna, and completely reflects the electromagnetic wave by setting a quarter-wavelength short-circuit surface on one side; The planar circuit E-plane microstrip probe is made on the probe substrate sealing structure, which is a low-loss dielectric substrate. The outer dimensions of the probe substrate sealing structure are larger than the rectangular waveguide boundary. The outer dimensions of the probe substrate sealing structure exceed the dimensions of the rectangular waveguide boundary by a range of [0.5 mm ~1 mm], so that it completely covers the waveguide mouth surface; A method for realizing a Ka-band waveguide sealing system loaded with high-order mode suppression based on the Ka-band waveguide sealing system loaded with high-order mode suppression includes the following process: S1: inputting an electromagnetic wave signal into a waveguide, and turning the transmission direction of the electromagnetic wave signal in the waveguide by 90° through a waveguide E-bend of the waveguide; S2: The TE10 mode in the waveguide is converted into a quasi-TEM mode of the planar circuit through the probe conversion circuit of the planar circuit E-plane microstrip probe.

2. The Ka-band waveguide sealing system with loaded high-order mode suppression according to claim 1 is characterized in that: A high impedance line with a specified width is used to perform impedance matching between the planar circuit E-surface microstrip probe and the planar circuit strip line.

3. The Ka-band waveguide sealing system with loaded high-order mode suppression according to claim 2 is characterized in that: The planar circuit strip line has a characteristic impedance of 50 ohms.

4. The Ka-band waveguide sealing system with loaded high-order mode suppression according to claim 1, characterized in that: The wide side dimension range of the reduced height rectangular waveguide is 6±0.1 mm, and the narrow side dimension range of the reduced height rectangular waveguide is 3±0.1 mm.

5. The method for implementing the Ka-band waveguide sealing system with loaded high-order mode suppression according to claim 1 is characterized in that: The waveguide E bend in step S1 is cut at a right angle at the bend corner to perform impedance matching in the waveguide.

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