A broadband slot gap waveguide to microstrip transition structure

Abstract

The application discloses a broadband slot-gap waveguide to microstrip transition structure, and electromagnetic wave transmission is realized through a ridge-gap waveguide and an inverted microstrip line structure between the slot-gap waveguide and the microstrip line, the inverted microstrip line structure comprises an inverted microstrip line dielectric substrate, a gold ball one and a gold ball two which are respectively arranged on a metal ridge of the ridge-gap waveguide and a microstrip line, the inverted microstrip line dielectric substrate is inverted and buckled on the gold ball one and the gold ball two, so that the inverted microstrip line on the inverted microstrip line dielectric substrate is connected with the metal ridge and the microstrip line through the gold ball one and the gold ball two. The application is applied to a millimeter wave frequency band, electromagnetic wave is fed in from the slot-gap waveguide, and finally transmitted to the microstrip line through the ridge-gap waveguide and the inverted microstrip line structure, and the application has the advantages of small loss, high structural stability and the like, is easy to be integrated with other active / passive devices, and is suitable for small unmanned aerial application fields with high requirements on size and weight.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electromagnetic field and microwave technology, in particular to a wideband groove gap waveguide to microstrip transition structure. BACKGROUND

[0002] When the groove gap waveguide (GGW) is converted to the microstrip line, a transition structure is usually needed to transmit the electromagnetic wave to the microstrip line completely. The microstrip line is easy to integrate with active devices due to its good planar characteristics. However, when the microstrip line is used as a transition structure, the radiation loss of the microstrip line increases significantly as the operating frequency rises to the millimeter wave band.

[0003] Since the ridge gap waveguide (RGW) and the microstrip line are both quasi-transverse electromagnetic modes, the mode conversion between them is relatively easy, and the loss in the conversion process is small. Therefore, the ridge gap waveguide can be introduced as an intermediate transition structure between the microstrip line and the groove gap waveguide to reduce the loss.

[0004] However, even if the ridge gap waveguide is used as a transition structure, the conversion from the ridge gap waveguide to the microstrip line still needs to be completed. Currently, the gold wire bonding technology is mostly used to realize the connection between the ridge gap waveguide and the microstrip line, but this method mostly relies on manual welding, which is prone to problems such as too low or too high gold wire height, poor structural stability, and thus affects the performance of the device. Therefore, it is necessary to research a wideband groove gap waveguide to microstrip transition structure with small radiation loss and dielectric loss, high structural stability, and easy integration with active devices to realize efficient transmission of electromagnetic waves. SUMMARY

[0005] The purpose of the present application is to provide a wideband groove gap waveguide to microstrip transition structure with small radiation loss and dielectric loss, high structural stability, and easy integration with active devices.

[0006] Technical solution: To achieve the above purpose, the wideband groove gap waveguide to microstrip transition structure according to the present application, the groove gap waveguide and the microstrip line are connected through the ridge gap waveguide and the inverted microstrip line structure to realize the transmission of electromagnetic waves. The inverted microstrip line structure includes an inverted microstrip line dielectric substrate, gold balls one and two placed on the metal ridge of the ridge gap waveguide and the microstrip line respectively, and the inverted microstrip line dielectric substrate is inverted on the gold balls one and two, so that the inverted microstrip line on the inverted microstrip line dielectric substrate is connected to the metal ridge and the microstrip line through the gold balls one and two.

[0007] Preferably, the inverted microstrip line is a tapered structure, wherein the line width near one end of the metal ridge is smaller than the line width near one end of the microstrip line.

[0008] Preferably, the slot-gap waveguide comprises a first upper metal plate and a first lower metal plate arranged in parallel, and a plurality of first pins arranged between the first upper metal plate and the first lower metal plate; the ridge-gap waveguide comprises a second upper metal plate and a second lower metal plate arranged in parallel, and a plurality of second pins arranged between the second upper metal plate and the second lower metal plate.

[0009] Preferably, the side surfaces of the first upper metal plate and the first lower metal plate of the slot-gap waveguide are connected to the lower surface of the second lower metal plate of the ridge-gap waveguide, and the second lower metal plate of the ridge-gap waveguide is provided with an opening which is coincident with the air slot of the slot-gap waveguide.

[0010] Preferably, one end of the metal ridge is a probe structure, the end of the probe structure corresponds to the center region of the air slot of the slot-gap waveguide, and the other end of the metal ridge is provided with a gold ball.

[0011] Preferably, the two sides of the air slot are a first electromagnetic bandgap structure composed of the first pins, the first upper metal plate and the first lower metal plate, in the first electromagnetic bandgap structure, the first pins, the part of the first upper metal plate directly above the first pins, the part of the first lower metal plate directly below the first pins, and the first air gap together constitute a first pin periodic unit; wherein the part is a square region with the center of the first pin as the center point.

[0012] Preferably, the side length of the first pin is less than 0.5p1, p1 is the period of the first pin periodic unit, and the period of the first pin periodic unit is less than half of the wavelength of the maximum frequency in the working frequency band.

[0013] Preferably, the two sides of the metal ridge are a second electromagnetic bandgap structure composed of the second pins, the second upper metal plate and the second lower metal plate, in the second electromagnetic bandgap structure, the second pins, the part of the second upper metal plate directly above the second pins, the part of the second lower metal plate directly below the second pins, and the second air gap together constitute a second pin periodic unit; wherein the part is a square region with the center of the second pin as the center point.

[0014] Preferably, the side length of the second pin is less than 0.5p2, p2 is the period of the second pin periodic unit, and the period of the second pin periodic unit is less than half of the wavelength of the maximum frequency in the working frequency band.

[0015] Preferably, the microstrip line dielectric substrate material of the microstrip line is gallium nitride, and the inverted microstrip line dielectric substrate material is alumina ceramic.

[0016] Beneficial effects: the transition conversion structure has the following advantages: 1, the transition conversion structure realizes the signal transmission between the slot gap waveguide and the microstrip line through the ridge gap waveguide and the inverted microstrip line structure, and the radiation loss and the dielectric loss in the electromagnetic wave transmission process are small; 2, the inverted microstrip line structure can realize good impedance matching and signal transition between the ridge gap waveguide and the microstrip line, and also improves the stability and reliability of the structure; 3, compared with the existing mechanical processing or three-dimensional printing technology, the structure of the application can use the existing CNC processing method, is easy to prepare, and is also easy to be integrated with other active / passive devices; 4, can be widely applied to millimeter wave frequency band, has the characteristics of small size, light weight, stable performance, etc., and is suitable for small unmanned aerial application fields with high requirements on size and weight. BRIEF DESCRIPTION OF DRAWINGS

[0017] Fig. 1 is a perspective view of the slot gap waveguide to ridge gap waveguide transition structure;

[0018] Fig. 2 is a top view of the slot gap waveguide to ridge gap waveguide transition structure;

[0019] Fig. 3 is a front view of the slot gap waveguide to ridge gap waveguide transition structure along the electromagnetic wave transmission direction;

[0020] Fig. 4 is a perspective view of the transition conversion structure;

[0021] Fig. 5 is a top view of the transition conversion structure;

[0022] Fig. 6 is a front view of the transition conversion structure along the electromagnetic wave transmission direction;

[0023] Fig. 7 is a side view of the transition conversion structure;

[0024] Fig. 8 is the electromagnetic wave transmission performance simulation result of the transition conversion structure. DETAILED DESCRIPTION

[0025] The technical solutions of the application will be described in detail below in combination with the embodiments and the drawings.

[0026] The transition structure works in the millimeter wave frequency band, and is connected between the slot-gap waveguide and the microstrip line through the ridge-gap waveguide and the inverted microstrip line structure. The inverted microstrip line structure comprises an inverted microstrip line dielectric substrate 12 and gold balls arranged on the metal ridge 6 of the ridge-gap waveguide and the microstrip line 16 respectively, and the two gold balls are synchronously welded on the inverted microstrip line dielectric substrate 12. Electromagnetic waves are fed into the slot-gap waveguide, transmitted through the ridge-gap waveguide and the inverted microstrip line structure, and finally transmitted to the microstrip line. The microstrip line in the transition structure is replaced by other active chips, such as power amplifier chips, so that the integration with active devices can be realized, and the integration with other passive full dielectric can also be realized.

[0027] As shown in Figs. 1~3 The slot-gap waveguide comprises a first upper metal plate 4 and a first lower metal plate 5 arranged in parallel, and a plurality of pin one 2 is arranged between the first upper metal plate 4 and the first lower metal plate 5. The ridge-gap waveguide comprises a second upper metal plate 9 and a second lower metal plate 10 arranged in parallel, and a plurality of pin two 7 is arranged between the second upper metal plate 9 and the second lower metal plate 10.

[0028] The side surfaces of the first upper metal plate 4 and the first lower metal plate 5 of the slot-gap waveguide are connected with the lower surface of the second lower metal plate 10 of the ridge-gap waveguide, and the second lower metal plate 10 of the ridge-gap waveguide is provided with an opening, and the position of the opening coincides with the air slot 1 of the slot-gap waveguide (the opening size is consistent with the air slot). The air slot 1 is flanked by the first electromagnetic bandgap structure composed of the pin one 2, the first upper metal plate 4 and the first lower metal plate 5.

[0029] The metal ridge 6 is arranged directly below the second upper metal plate 9 of the ridge-gap waveguide, and the lower surface of the metal ridge 6 is connected with the upper surface of the second lower metal plate 10 of the ridge-gap waveguide. One end of the metal ridge 6 is a probe type structure, and the probe end corresponds to the center region of the air slot 1 of the slot-gap waveguide. The metal ridge 6 is flanked by the second electromagnetic bandgap structure composed of the pin two 7, the second upper metal plate 9 and the second lower metal plate 10.

[0030] The first electromagnetic bandgap structure and the second electromagnetic bandgap structure are composed of pin periodic units arranged in a periodic manner, wherein the air slot 1 and the metal ridge 6 are electromagnetic conductive bands, and electromagnetic waves are transmitted along the electromagnetic conductive bands. In the first electromagnetic bandgap structure, the pin one 2, the part of the first upper metal plate 4 above the pin one and the part of the first lower metal plate 5 below the pin one, and the first air gap 3 together constitute a pin one periodic unit. Wherein, the part of the metal plate is: taking the center of the pin one 2 as the center of the whole pin one periodic unit, extending 0.5p1 in +Z, -Z, +Y and -Y directions as the edge length of the part of the metal plate. P1 is the period of the pin one periodic unit.

[0031] In the second magnetic band gap structure, the partial second upper layer metal plate 9 above the pin two 7 and the partial second lower layer metal plate 10 below the pin two 7, and the second air gap 8 jointly constitute a pin two periodic unit. The partial metal plate is specifically: taking the center of the pin two 7 as the center of the entire pin two periodic unit, extending 0.5p2 in the +X, -X, +Y and -Y directions as the edge length of the partial metal plate. P2 is the period of the pin two periodic unit.

[0032] In the above-mentioned electromagnetic band gap structure, the lower layer metal plate and the pin jointly constitute a PMC structure (ideal magnetic conductor), and the upper layer metal plate is a PEC structure (ideal electric conductor), and a stop band is formed between the PMC structure and the PEC structure, and the stop band range can be adjusted by adjusting the pin size and the pin unit period.

[0033] In order to avoid Bragg scattering, the period of the pin one periodic unit and the pin two periodic unit is less than half of the wavelength of the maximum frequency in the working frequency band.

[0034] In order to maintain the safety gap of the pin one periodic unit and the pin two periodic unit and facilitate processing, the edge length of the pin one 2 and the pin two 7 is not greater than 0.5p1 and 0.5p2.

[0035] As shown in Figs. 4~7 The microstrip line 16 is located on the microstrip line dielectric substrate 11, and the microstrip line dielectric substrate 11 is located on the tray loaded at the end of the second lower layer metal plate 10, so that the microstrip line 16 and the end of the metal ridge 6 (the other end corresponding to the probe) are kept in the same horizontal plane. At the end of the second lower layer metal plate 10, the length of the second upper layer metal plate 9 is shorter than that of the second lower layer metal plate 10, which facilitates the assembly of the microstrip line dielectric substrate 11 and the inverted microstrip line structure.

[0036] The end of the microstrip line 16 and the end of the metal ridge 6 are respectively welded with the gold ball two 21 and the gold ball one 20. The gold ball two 21 and the gold ball one 20 are both cylindrical, and the inverted microstrip line dielectric substrate 12 is placed above the gold ball two 21 and the gold ball one 20. The gold ball two 21 and the gold ball one 20 are respectively welded with the inverted microstrip line 17 on the inverted microstrip line dielectric substrate 12, thereby forming a structure in which the metal ridge 6 is connected with the inverted microstrip line 17 through the gold ball one 20, and the inverted microstrip line 17 is connected with the microstrip line 16 through the gold ball two 21. The inverted microstrip line 17 is a tapered structure, in which the line width near the end of the metal ridge 6 is smaller, and the line width near the end of the microstrip line 16 is larger, so as to facilitate the transmission of electromagnetic waves.

[0037] The material of the microstrip line dielectric substrate 11 is gallium nitride, the relative dielectric constant = 9, and the material of the inverted microstrip line dielectric substrate 12 is aluminum oxide ceramic, and the dielectric constant = 9.8. The back surface (the other surface relative to the inverted microstrip line 17) and the side surface of the inverted microstrip dielectric substrate 12, the side surface and the back surface of the microstrip dielectric substrate 11 are provided with the metallized layer 13. The metal column one 18 and the metal column two 19 are arranged on both sides of the gold ball two 21 respectively, for connecting the back surface metal layer of the inverted microstrip dielectric substrate 12 and the back surface metal layer of the microstrip dielectric substrate 11, so as to reduce the radiation loss size and improve the overall stability of the inverted microstrip line structure.

[0038] In the transition conversion structure, the electromagnetic wave is transmitted from the air slot 1 of the slot gap waveguide to the second air gap 8 of the ridge gap waveguide, then to the inverted microstrip line 17, and finally to the microstrip line 16. The electromagnetic wave is transmitted from the gold ball one 20 at the end of the metal ridge 6 to the inverted microstrip line 17. Since the inverted microstrip line 17 is too short, the electromagnetic wave does not form a TEM mode completely, and is directly input into the microstrip line 16. Therefore, the inverted microstrip line structure plays a good role in signal connection. At the same time, the height of the gold ball after pressing is fixed, and the gold ball is used to replace the gold wire, so as to improve the stability of the structure.

[0039] The present application is based on the gap waveguide technology (the loss is similar to that of the rectangular waveguide). During the transmission of the electromagnetic wave, there is almost no radiation loss and dielectric loss except at the transition. Therefore, compared with other high-frequency microwave devices, the loss of the structure is smaller. The main part of the structure is processed by full metal, and the existing CNC processing method can be used to realize it. The inverted microstrip line structure only needs to process a separate dielectric substrate, which is buckled on the metal ridge 6 and the microstrip line 16 through two groups of gold balls, so as to reduce the manufacturing difficulty. The impedance matching between the slot gap waveguide and the ridge gap waveguide is realized by the probe type metal ridge 6. The impedance matching between the ridge gap waveguide and the inverted microstrip line 17 is realized by adjusting the width of the inverted microstrip line 17. The matching between the inverted microstrip line 17 and the microstrip line 16 is realized by adjusting the width of each.

[0040] The present application provides a transition conversion structure design embodiment working in the G band, which is as follows:

[0041] The period of the pin one period unit is set as p1 = 0.42 mm, the side length is set as a1 = 0.2 mm, the height is set as h9 = 0.35 mm, and the height of the first air gap 3 is set as h8 = 0.04 mm. The period of the pin two period unit is set as p2 = 0.3 mm, the side length is set as a2 = 0.1 mm, the height is set as h3 = 0.405 mm, and the height of the second air gap 8 is set as h2 = 0.135 mm.

[0042] The air slot 1 of the slot-gap waveguide is set to have a length of g = 1.092 mm, a slot width of h8 + h9 = 0.39 mm, an overall size of the slot-gap waveguide of h4 = 2.94 mm, w1 = 2.552 mm, a thickness of the first upper metal plate 4 and the first lower metal plate 5 of h1 = 0.2 mm, and an overall height of the slot-gap waveguide of 2 x h1 + h9 + h8 = 0.79 mm.

[0043] The length of each part of the metal ridge 6 is set to be l4 = 0.32 mm, l5 = 0.63 mm, l6 = 3.18 mm, the width of each part is set to be w3 = 0.05 mm, w4 = 0.2 mm, w5 = 0.35 mm, and the height is set to be h3 = 0.405 mm, which is the same as the height of the pin 2. The overall size of the ridge-gap waveguide is set to be w1 = 2.552 mm, the height of the second upper metal plate 9 and the second lower metal plate 10 is set to be h1 = 0.2 mm, the length of the second upper metal plate 9 is set to be l1 = 5.104 mm, and the length of the second lower metal plate 10 is set to be l1 + l2 + l3 + l7 = 6.939 mm. The second lower metal plate 10 is loaded with a tray at the end, and the height of the tray is set to be h5 = 0.555 mm, and the length and width are the same as those of the microstrip line dielectric substrate 11.

[0044] The size of the inverted microstrip line 17 is set to be l IMSL = 0.26 mm, w IMSL1 = 0.04 mm, w IMSL2 = 0.07 mm; the size of the microstrip line 16 is set to be l MSL = 1.463 mm, w MSL = 0.03 mm, r MSL = 0.015 mm. The size of the gold ball 1 20 is set to be r1 = 0.02 mm, h ball = 0.09 mm, and the size of the gold ball 2 21 is set to be r2 = 0.023 mm, h ball = 0.09 mm. The metal column 1 18 and the metal column 2 19 have the same size, the radius is set to be r2 = 0.023 mm, and the height is set to be h7 + h ball + h6 = 0.185 mm.

[0045] The electromagnetic wave transmission performance of the above transition structure is simulated, and the simulation results are shown in FIGS. 6A and 6B. Fig. 8The simulation results of electromagnetic simulation software HFSS are shown. The simulation can be performed by corresponding modeling in HFSS according to the instance size, assigning the material properties mentioned in the instance, and finally setting appropriate boundary conditions and frequency range. It can be seen that in the frequency band range of 200 GHz to 240 GHz, the insertion loss |S 21 |≤1.41 dB, the input return loss |S 11 |、|S 22 |≥15 dB, in this frequency band, the electromagnetic wave can be normally transmitted.

Claims

1. A transition structure from a broadband slot gap waveguide to a microstrip, characterized in that, The slot gap waveguide and the microstrip line are connected by a ridge gap waveguide and an inverted microstrip line structure to realize the transmission of electromagnetic waves. The inverted microstrip line structure includes an inverted microstrip line dielectric substrate (12), gold sphere one (20) and gold sphere two (21) respectively placed on the metal ridge (6) of the ridge gap waveguide and the microstrip line (16). The inverted microstrip line dielectric substrate (12) is upside down on the gold sphere one (20) and gold sphere two (21), so that the inverted microstrip line (17) on the inverted microstrip line dielectric substrate (12) is connected to the metal ridge (6) and the microstrip line (16) through the gold sphere one (20) and gold sphere two (21).

2. The transition structure according to claim 1, characterized in that, The inverted microstrip line (17) has a gradient structure, wherein the linewidth at the end near the metal ridge (6) is smaller than the linewidth at the end near the microstrip line (16).

3. The transition structure according to claim 1, characterized in that, The slot gap waveguide includes a first upper metal plate (4) and a first lower metal plate (5) arranged in parallel, with multiple sets of pins (2) between the first upper metal plate (4) and the first lower metal plate (5); the ridge gap waveguide includes a second upper metal plate (9) and a second lower metal plate (10) arranged in parallel, with multiple sets of pins (7) between the second upper metal plate (9) and the second lower metal plate (10).

4. The transition structure according to claim 3, characterized in that, The side surfaces of the first upper metal plate (4) and the first lower metal plate (5) of the slot gap waveguide are connected to the lower surface of the second lower metal plate (10) of the ridge gap waveguide, and the second lower metal plate (10) of the ridge gap waveguide is provided with an opening, the position of which coincides with the air slot (1) of the slot gap waveguide.

5. The transition structure according to claim 4, characterized in that, One end of the metal ridge (6) is a probe structure, and the end of the probe structure corresponds to the central region of the air slot (1) of the slot gap waveguide. The other end of the metal ridge (6) is where the gold ball (20) is placed.

6. The transition structure according to claim 4, characterized in that, The air slot (1) is a first electromagnetic bandgap structure composed of pin 1 (2), first upper metal plate (4), and first lower metal plate (5) on both sides. In the first electromagnetic bandgap structure, pin 1 (2), part of the first upper metal plate (4) directly above pin 1 (2) and part of the first lower metal plate (5) directly below pin 1 (2), and the first air gap (3) together constitute a pin 1 periodic unit; among which, part of the area is a square area with the center of pin 1 (2) as the center point.

7. The transition structure according to claim 6, characterized in that, The side length of pin 1 (2) is less than 0.5p1, where p1 is the period of the periodic unit of pin 1, and the period of the periodic unit of pin 1 is less than half of the wavelength of the maximum frequency in the working frequency band.

8. The transition structure according to claim 3, characterized in that, The metal ridge (6) is composed of a second electromagnetic bandgap structure on both sides, consisting of pin 2 (7), a second upper metal plate (9), and a second lower metal plate (10). In the second electromagnetic bandgap structure, pin 2 (7), a portion of the second upper metal plate (9) directly above pin 2 (7), a portion of the second lower metal plate (10) directly below pin 2, and the second air gap (8) together constitute a pin 2 periodic unit; among which, a portion of the area is a square area centered on the center of pin 2 (7).

9. The transition structure according to claim 8, characterized in that, The side length of the second pin (7) is less than 0.5p2, where p2 is the period of the second pin periodic unit, and the period of the second pin periodic unit is less than half of the maximum frequency wavelength in the working frequency band.

10. The transition structure according to claim 1, characterized in that, The microstrip line dielectric substrate (11) of the microstrip line (16) is made of gallium nitride, and the inverted microstrip line dielectric substrate (12) is made of alumina ceramic.

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