CN114284666A

CN114284666A - SIW transmission line capable of loading direct current electric field bias

Info

Publication number: CN114284666A
Application number: CN202111400773.5A
Authority: CN
Inventors: 汪晓光; 林铮; 赵晓琴
Original assignee: University of Electronic Science and Technology of China
Current assignee: University of Electronic Science and Technology of China
Priority date: 2021-11-24
Filing date: 2021-11-24
Publication date: 2022-04-05
Anticipated expiration: 2041-11-24
Also published as: CN114284666B

Abstract

The invention relates to a microwave technology, in particular to a SIW transmission line capable of loading direct current electric field bias. The invention changes the metal through hole structure into the blocking structure on the basis of the substrate integrated waveguide, and adds a row of inverted same blocking structures to reduce the radiation loss and increase the equivalent capacitance to make the equivalent capacitance approach the transmission performance of the traditional SIW transmission line. The electrical schematic diagram of the blocking structure is equivalent to that a parallel capacitor is periodically loaded on the basis of the traditional SIW, and the capacitance value needs to be increased as much as possible on the premise of meeting the size requirement, namely, the distance is reduced and the capacitor area is increased. Compared with a single-row structure, the double-row structure reduces radiation loss on one hand, and is equivalent to additionally adding a parallel capacitor on the other hand, so that the capacitance value is further increased, and the whole DC-blocking transmission line has the performance close to that of a SIW transmission line. The invention satisfies the function of loading the DC bias electric field, but the loss is far lower than the existing strip line and coplanar waveguide structure.

Description

SIW transmission line capable of loading direct current electric field bias

Technical Field

The invention relates to a microwave technology, in particular to a SIW transmission line capable of loading direct current electric field bias.

Background

With the development and progress of science and technology, the microwave technology gradually develops towards miniaturization and integration. The SIW structure has the advantages of low radiation, low insertion loss, higher Q value, high power capacity, miniaturization, easy connection and the like. The ferroelectric material has the characteristic of changing the dielectric constant of the ferroelectric material by changing the electric field applied to the ferroelectric material, has the advantages of high power capacity, high polarization speed and the like, and can be applied to the design of various microwave devices.

The existing ferroelectric material is mostly applied to structures such as strip lines, coplanar waveguides and the like, the loss caused by a transmission line is large, and the insertion loss is below-0.1 dB; and by adopting the rectangular waveguide, the traditional single conductor wave guide structures such as SIW and the like can not meet the requirement that the ferroelectric body needs direct current electric field bias.

Disclosure of Invention

Aiming at the problems or the defects, the problems that the existing guided wave structure cannot load direct current electric field bias or is loaded on transmission line structures such as strip lines, coplanar waveguides and the like, and the loss is high and the Q value is low are solved; the invention provides a SIW transmission line capable of loading DC electric field bias, which is characterized in that a DC blocking structure designed by the invention is formed by improving metal through holes on the basis of a substrate integrated waveguide structure, and a row of the DC blocking structures are additionally arranged to reduce the radiation loss of the SIW, so that the function of isolating the DC electric field is realized under low loss.

The technical scheme of the invention is as follows:

a SIW transmission line capable of loading direct current electric field bias changes two rows of metallized through holes into a single-side double-row DC blocking structure on the basis of the traditional substrate integrated waveguide.

The straight-blocking structure is formed by connecting a bottom metal plate with a metal cylinder and not contacting with an upper metal plate, the distance is h1, h1 is smaller than half of the height t of the middle medium layer, and the upper metal plate is connected with a metal pipe; the inner diameter d1 of the metal tube is larger than the diameter d2 of the metal cylinder of the bottom metal plate, and the metal cylinders of the bottom metal plate correspond to the metal tubes of the upper metal plate one by one; the metal tube is sleeved outside the corresponding metal cylinder, is not in contact with the bottom metal plate and the metal cylinder, and is coaxial with the corresponding metal cylinder to isolate direct current.

The distance between the metal tube and the bottom metal plate is also h1, h1 and b are as small as possible, but the requirements of dielectric breakdown field strength and ferroelectric direct current bias electric field strength are required to be met.

The single-side double-row blocking structure is characterized in that after the original metalized through hole of the SIW transmission line is replaced by the blocking structure, a row of same blocking structures parallel to the blocking structure is loaded on the outer side of each row of blocking structures on the basis of the two rows of blocking structures; however, the two loaded rows of straight-blocking structures are changed into the structure that the upper layer metal plate is connected with the metal cylinder, the bottom layer metal plate is connected with the metal pipe, and the radiation loss is further reduced by adopting the symmetrical structure. The center line distance of the two rows of straight-separating structures on the same side is L, and L is more than or equal to 0.46mm and less than or equal to 0.68 mm.

And drawing a perpendicular line from the center of each outer row of straight-separating structure to the line segment of the corresponding inner row of straight-separating structure, or drawing a perpendicular line from the center of each inner row of straight-separating structure to the line segment of the corresponding outer row of straight-separating structure, wherein the vertical feet of the vertical feet are all located on the corresponding line segments, the horizontal offset of 0-0.16 mm exists between the vertical feet and the midpoint of the connecting line of the centers of the two adjacent straight-separating structures of the nearest inner/outer row, d is more than s-d +0.16mm, d is the outer diameter of the metal pipe, and s is the center distance of the adjacent straight-separating structures.

Further, the interval b between the inner diameter d1 of the metal tube and the diameter d2 of the metal cylinder is (d1-d2) × 0.5.

Further, the vertical foot is superposed with the midpoint of the connecting line of the centers of the two adjacent straight-blocking structures, namely the left offset and the right offset are 0. The offset from the center causes a certain jitter in the insertion loss curve and increases the radiation loss, so that the effect is best when the left-right offset is 0.

Furthermore, the SIW transmission line capable of being loaded with the dc electric field bias is applied to an X-band.

The electrical schematic diagram of the blocking structure is equivalent to that a parallel capacitor is periodically loaded on the basis of the traditional SIW, and the capacitance value needs to be increased as much as possible on the premise of meeting the size requirement, namely, the distance is reduced and the capacitor area is increased. Compared with a single-row structure, the double-row structure reduces radiation loss on one hand, and is equivalent to additionally adding a parallel capacitor on the other hand, so that the capacitance value is further increased, and the whole DC-blocking transmission line has the performance close to that of a SIW transmission line.

The design method of the SIW transmission line capable of loading the DC electric field bias comprises the following steps:

step 1, according to the equivalent formula of the substrate integrated waveguide and the traditional rectangular waveguide, meeting the requirement of a radiation loss stripDesign of the substrate integrated waveguide in the case of the piece: selecting a dielectric substrate, the thickness t and the relative dielectric constant of the dielectric substrate, and determining the width w, the length and the diameter d of the metallized through hole of the substrate integrated waveguide¹And a via center spacing s.

Step 2, metallizing the diameter d of the through hole¹The outer diameter d of the metal tube as the blocking structure is determined according to the breakdown field intensity of the dielectric substrate and the bias field intensity of the ferroelectric material, wherein the inner diameter d1 of the metal tube of the blocking structure, the diameter d2 of the metal cylinder, the distance b and the h1 of the metal cylinder are determined according to the breakdown field intensity of the dielectric substrate and the bias field intensity of the ferroelectric material.

And 3, selecting the relative positions of the outer row of straight-blocking structures and the inner row of straight-blocking structures, wherein L is more than or equal to 0.46mm and less than or equal to 0.68mm, d is more than s-d +0.16mm, d is the outer diameter of the metal pipe, and s is the center distance of the adjacent straight-blocking structures.

Furthermore, the transmission performance of the antenna in a required frequency band is further improved by adjusting the value of L.

In summary, the invention changes the metal via structure into the blocking structure on the basis of the substrate integrated waveguide, and adds a row of inverted blocking structures with the same shape to reduce the radiation loss, and increase the equivalent capacitance to make the equivalent capacitance approach the transmission performance of the traditional SIW transmission line. The invention satisfies the function of loading the DC bias electric field, but the loss is far lower than the existing strip line and coplanar waveguide structure.

Drawings

FIG. 1 is a schematic structural view of a substrate-integrated waveguide according to an embodiment;

FIG. 2 is a drawing showing S of the substrate integrated waveguide in the embodiment₁₁Graph of parameters

FIG. 3 is S of a substrate integrated waveguide in the embodiment₂₁A parameter curve graph;

FIG. 4 is a schematic side perspective view of a DC blocking structure according to the present invention;

FIG. 5 is a schematic top view of a DC blocking structure according to the present invention;

FIG. 6 is a schematic diagram of a structure of a SIW transmission line biased by a loadable DC electric field according to the present invention;

FIG. 7 is a top view of the loadable DC electric field biased SIW transmission line of the present invention;

FIG. 8 is an embodiment of the inventionS carrying DC electric field bias SIW transmission line₁₁A parameter curve graph;

FIG. 9 is a diagram illustrating an embodiment of an S-shaped transmission line biased by a DC electric field₂₁A parametric curve.

Detailed Description

The present invention will be described in further detail below with reference to the accompanying drawings and a specific embodiment applied to the X-band.

A design method of an X-waveband loadable direct-current electric field biased SIW transmission line comprises the following steps:

step 1, designing a substrate integrated waveguide under the condition of meeting a radiation loss condition according to an equivalent formula of the substrate integrated waveguide and a traditional rectangular waveguide, selecting a polytetrafluoroethylene material as a medium, wherein the thickness t of the medium substrate is 0.80mm, and the relative dielectric constant epsilon is_r2.1, determining the width w of the substrate integrated waveguide to be 17.5mm, the diameter d of the metallized through hole to be 0.4mm and the center-to-center distance s of the through hole to be 0.45 mm; the transmission performance of the substrate integrated waveguide is modeled and analyzed in HFSS, so that the return loss of the substrate integrated waveguide in the whole X-wave band (8-12GHz) is less than-51.39 dB, the insertion loss is less than-0.015 dB, and the transmission performance is good; the structure is shown in figure 1, and the S parameter graph is shown in figures 2 and 3.

Step 2, determining the outer diameter d and the height parameter t of the blocking structure according to the parameters of the substrate integrated waveguide determined in the step 1: the outer diameter of the metal pipe with the blocking structure is 0.4mm, and the height of the metal pipe is 0.8 mm. The breakdown field strength of a polytetrafluoroethylene dielectric material is 200kv/mm, the breakdown field strength is increased along with the decrease of the thickness, the dielectric constant of a ferroelectric material is decreased along with the increase of an electric field, generally, under the bias of a direct current electric field of 8kv/mm, the change of the dielectric constant is not obvious any more, and under the condition of meeting the processing technology requirement, h1 is 0.05mm, b is 0.05mm, d1 is 0.2mm, and d2 is 0.3 mm. The structure is shown in figures 4 and 5.

And 3, building a loadable direct current electric field bias SIW transmission line according to the parameters obtained in the

steps

1 and 2, wherein the distance between two rows is L which is 0.55 mm. The structure is shown in figures 6 and 7, and the S parameter graph is shown in figures 8 and 9.

As can be seen from fig. 8 and 9, in the embodiment, the substrate integrated waveguide can be biased by the dc electric field to obtain a return loss of less than-33.16 dB in the entire X-band (8-12GHz), and when the frequency efficiency is 8.8GHz, the return loss is less than-40 dB; the whole insertion loss is less than-0.046 dB and can reach more than-0.025 dB at 10-12 GHz.

The embodiments can see that, on the basis of the traditional substrate integrated waveguide, the invention improves the metal through hole structure into a special blocking structure, and adopts a double-row structure, so that on one hand, the radiation loss is reduced, on the other hand, a parallel capacitor is additionally added, the capacitance value is further increased, and the performance of the whole blocking transmission line is close to that of a SIW transmission line. The transmission performance is good, the loss is far lower than that of a strip line, the coplanar waveguide structure is adopted, and the function of loading a direct current bias electric field is met.

Claims

1. A kind of SIW transmission line that can load the bias of direct current electric field, characterized by that: two rows of metallized through holes are changed into a single-side double-row blocking structure on the basis of the traditional substrate integrated waveguide;

the straight-blocking structure is formed by connecting a bottom metal plate with a metal cylinder and not contacting with an upper metal plate, the distance is h1, h1 is smaller than half of the height t of the middle medium layer, and the upper metal plate is connected with a metal pipe; the inner diameter d1 of the metal tube is larger than the diameter d2 of the metal cylinder of the bottom metal plate, and the metal cylinders of the bottom metal plate correspond to the metal tubes of the upper metal plate one by one; the metal pipe is sleeved outside the corresponding metal cylinder, is not in contact with the bottom metal plate and the metal cylinder, and is coaxial with the corresponding metal cylinder to isolate direct current;

the distance between the metal tube and the bottom metal plate is also h1, and h1 and b meet the requirements of dielectric breakdown field strength and ferroelectric direct-current bias electric field strength;

the single-side double-row blocking structure is characterized in that after the original metalized through hole of the SIW transmission line is replaced by the blocking structure, a row of same blocking structures parallel to the blocking structure is loaded on the outer side of each row of blocking structures on the basis of the two rows of blocking structures; but the loaded two rows of straight-separating structures are changed into that the upper layer metal plate is connected with the metal cylinder, and the bottom layer metal plate is connected with the metal pipe; the center line distance of the two rows of straight-separating structures on the same side is L, and L is more than or equal to 0.46mm and less than or equal to 0.68 mm;

2. The SIW transmission line that can be loaded with a dc electric field bias of claim 1, wherein: the interval b between the inner diameter d1 of the metal tube and the diameter d2 of the metal cylinder is (d1-d2) multiplied by 0.5.

3. The SIW transmission line that can be loaded with a dc electric field bias of claim 1, wherein: the vertical foot is superposed with the midpoint of the connecting line of the centers of the two adjacent straight-blocking structures, namely the left offset and the right offset are 0.

4. The SIW transmission line that can be loaded with a dc electric field bias of claim 1, wherein: is applied to the X wave band.

5. The method for designing the SIW transmission line capable of being loaded with the dc electric field bias according to claim 1, comprising the steps of:

step 1, designing a substrate integrated waveguide under the condition of meeting a radiation loss condition according to an equivalent formula of the substrate integrated waveguide and a traditional rectangular waveguide: selecting a dielectric substrate, the thickness t and the relative dielectric constant of the dielectric substrate, and determining the width w, the length and the diameter d of the metallized through hole of the substrate integrated waveguide¹And a through hole center spacing s;

step 2, metallizing the diameter d of the through hole¹Determining the outer diameter d of the metal tube as a blocking structure, the inner diameter d1 of the metal tube of the blocking structure, the diameter d2 of a metal cylinder, the distance b and h1 according to the breakdown field intensity of the dielectric substrate and the bias field intensity of the ferroelectric material;

6. The method for designing a SIW transmission line that can be loaded with a dc electric field bias as claimed in claim 5, wherein: and the L is adjusted to further improve the transmission performance of the antenna in a required frequency band.