CN108376821B - Ka-band substrate integrated waveguide magic T - Google Patents

Abstract

The invention relates to microwave devices and transmission line technology, in particular to a Ka-band substrate integrated waveguide magic T. According to the invention, the H-T branches are matched by adopting the circular wedge-shaped metal through hole through the SIW magic T lower layer main waveguide, and the influence of parasitic capacitance generated by the circular wedge-shaped metal through hole is eliminated by using the inductive metal diaphragm, so that the return loss of the H-arm port is reduced. And the upper layer E-T branch generates parasitic capacitance at the coupling seam due to the electric coupling, so that the influence is eliminated by using an inductive metal block, and the return loss of the E-arm port is reduced. Finally, the working bandwidth of the SIW magic T is increased to 2GHz, and the amplitude unbalance degree is reduced to 0.1 dB.

Description

Ka-band substrate integrated waveguide magic T

Technical Field

The invention relates to microwave devices and transmission line technology, in particular to a Ka-band substrate integrated waveguide magic T.

Background

As a commonly used microwave bridge, the magic T plays a very important role in the design of microwave circuits. It is very widely used in impedance measurement, E-H tuners, duplexers and sum and difference networks required for radar systems. For the traditional rectangular waveguide magic T, the magic T is realized by combining ET and HT joints of a common symmetrical plane, has the advantages of high power capacity, good port characteristics and the like, but has the defects of larger size, difficult tuning and the like.

With the development of modern microwave circuits, integration and miniaturization of electronic devices have become extremely important, and thus a planar integrated waveguide technology, Substrate Integrated Waveguide (SIW), has been proposed. The method is realized by periodically arranging the metallized through holes on the low-loss dielectric substrate, and integrates the advantages of the traditional metal waveguide and microstrip circuit, such as: high Q value, high power capacity, smaller size, easy integration and the like, and simultaneously, because the whole structure is formed by forming metallized through holes on a medium substrate, the preparation can be accurately realized through a PCB (printed Circuit Board) or an LTCC (Low temperature Co-fired ceramic), and the microwave circuit is very suitable for being applied to the design of a microwave circuit.

In recent years, due to the advantages of the SIW technology, the SIW technology has been widely applied to the design of filters, couplers, circulators, power splitters, and the like, and the development of the substrate integrated waveguide technology has been greatly promoted. The magic T is designed by utilizing the substrate integrated waveguide technology, so that the size of the magic T can be reduced, the device is lighter and more convenient, and the magic T is more favorable for being integrated with other circuits. However, for the substrate integrated waveguide structure magic T, the E-plane junction is difficult to implement, and mismatch occurs due to discontinuity at the junction of the junction, which affects performance, so that implementation of the E-T junction and impedance matching at the junction become core problems to be solved by the SIW magic T.

Disclosure of Invention

Aiming at the problems or defects, the invention provides a Ka-band substrate integrated waveguide magic T to solve the problems that an E-T joint of the SIW magic T is difficult to realize and the impedance of a connecting part is matched, so that the designed magic T has better performance in a frequency band of 28.0GHz-30.0 GHz.

The specific technical scheme is as follows:

the Ka-band substrate integrated waveguide magic T comprises an upper layer of medium substrate and a lower layer of medium substrate, wherein the upper layer of medium substrate and the lower layer of medium substrate are provided with coupling slits.

The lower medium substrate is an H-T branch of the magic T, the upper medium substrate realizes an E-T branch in an electric coupling mode, the two medium substrates are overlapped in parallel, the transverse edges and the longitudinal edges of the upper medium substrate and the lower medium substrate are respectively correspondingly parallel, and the waveguide is formed by metal through holes which are periodically arranged on the medium substrates.

The lower medium substrate is provided with a main waveguide and a branch waveguide to form an axisymmetric H-T branch, the central line of the branch waveguide is vertical to the central line of the main waveguide, and the coupling seam is arranged along the symmetric axis of the H-T branch waveguide; the main waveguide adopts a circular wedge-shaped metal through hole to match the H-T branches, the circular wedge-shaped metal through hole generates a parasitic capacitor, the coupling seam of the lower layer substrate is arranged at the tip of the circular wedge, and the coupling seams of the upper layer medium substrate and the lower layer medium substrate are corresponding in position. A blending metal membrane penetrating through the lower-layer dielectric substrate is arranged on the H arm of the lower-layer dielectric substrate to eliminate the influence of parasitic capacitance generated by the circular wedge-shaped metal through hole (the position is shown in figure 12), so that the return loss of the port of the H arm is reduced; the thickness of the prepared metal diaphragm is the same as that of the substrate integrated waveguide, and the upper edge and the lower edge of the prepared metal diaphragm are respectively arranged on the upper plane and the lower plane of the waveguide.

The E arm of the upper dielectric substrate is provided with a blending metal block (the position is shown in fig. 13) penetrating through the upper dielectric substrate, so that the influence of parasitic capacitance generated at the coupling seam due to electric coupling of the upper E-T branch is eliminated, and the return loss of the E arm port is reduced; the width of the adjusting metal block is the same as the thickness of the substrate integrated waveguide, and the upper edge and the lower edge of the adjusting metal block are respectively arranged on the upper plane and the lower plane of the waveguide.

According to the invention, the H-T branches are matched by adopting the circular wedge-shaped metal through hole through the SIW magic T lower layer main waveguide, so that the power distribution effect is improved, and the amplitude unbalance degree is reduced; and the influence of parasitic capacitance generated by the round wedge-shaped metal through hole is eliminated by using the inductive metal diaphragm, so that the return loss of the H-arm port is reduced. And the upper layer E-T branch can generate parasitic capacitance at the coupling seam due to the electric coupling, and an inductive metal block is used for eliminating the influence, so that the return loss of the E-arm port is reduced.

The invention adopts the circular wedge-shaped metal through hole to match the H-T branches, thereby improving the power division effect and reducing the amplitude unbalance degree; and the matching of each port is better by allocating the metal diaphragm and allocating the metal block, the use bandwidth is widened, and the amplitude imbalance degree is reduced. Finally, the working bandwidth of the SIW magic T is increased to 2GHz, and the amplitude unbalance degree is reduced to 0.1 dB.

Drawings

FIG. 1 is a schematic diagram of the overall structure of the SIW magic T of the present invention;

FIG. 2 is a top view of the upper layer structure of the SIW magic T of the present invention;

FIG. 3 is a top view of the understructure of the SIW magic T of the present invention;

FIG. 4 is a return loss plot for each port of an embodiment;

FIG. 5 is an isolation view of an embodiment;

FIG. 6 is an inverse power division diagram of an embodiment;

FIG. 7 is a graph of the inverse magnitude imbalance of an embodiment;

FIG. 8 is an in-phase power division diagram of an embodiment;

FIG. 9 is a graph of in-phase amplitude imbalance for an embodiment;

FIG. 10 is a graph of in-phase imbalance for an embodiment;

FIG. 11 is a graph of the inverse phase imbalance of an embodiment;

FIG. 12 is a schematic diagram of an embodiment of a lower substrate, where r is the radius of the wedge match of the lower H-T branch, l is the length of the formulated metal diaphragm, and d is the distance from the formulated metal diaphragm to port 4;

FIG. 13 is a schematic diagram of the positions of the components of the upper substrate of the present invention, wherein oz is the lateral offset, ox is the longitudinal offset, a is the length of the E-arm prepared metal block, h is the thickness of the prepared metal block, u is the distance from the prepared metal block to the center of the coupling hole, r1 is the radius of the SIW metal via, and j is the distance between the centers of two adjacent metal vias;

reference numerals: 1-main waveguide of lower H arm, 2-branch waveguide of lower H arm, 3-coupling gap, 4-matching circular wedge 5-lower allocation metal diaphragm, 6-upper E arm, and 7-upper allocation metal block.

Detailed Description

The invention is explained in further detail with reference to the figures and examples:

the invention relates to a four-port device consisting of an upper layer substrate integrated waveguide structure and a lower layer substrate integrated waveguide structure, which is shown in figure 1. The lower layer structure is an H-T branch of the magic T, and the upper layer structure realizes the function of the E-T branch in an electric coupling mode. The H-T branch of the lower dielectric substrate is in an axisymmetric structure, the H-arm branch is led out from a symmetric axis of the lower substrate (main substrate) integrated waveguide, and the matching is realized by using a circular wedge type (circular wedge-shaped metal through hole) design, and meanwhile, a coupling gap is formed in the center of the H-arm main waveguide to realize the coupling with the E arm. A top view thereof is shown in fig. 3.

The upper E-arm is parallel to the lower H-arm, and is electrically coupled to the main substrate waveguide, unlike the conventional waveguide magic T, and the top view is shown in fig. 2.

The design method comprises the following steps:

firstly, determining the SIW width according to the required working frequency band Ka wave band and the selected structure parameters of the substrate integrated waveguide.

Secondly, according to the structural parameters, the branch substrate integrated waveguide 2 is led out from the central symmetry position of the main substrate integrated waveguide 1 to form an H-T branch based on the substrate integrated waveguide, a circular wedge-shaped metal through hole 4 is designed at the offset position of the central line of the main substrate integrated waveguide to match the H arm, and then the H arm is allocated by an allocation metal diaphragm 5.

Then, a coupling gap 3 is opened at the center of the branch waveguide of the H arm to realize the coupling with the E arm; then, adding a substrate integrated waveguide structure 6 on the upper layer of the H-T branch, wherein the left end of the structure 6 is sealed by a metalized through hole, and a slot gap is formed at the corresponding position in the bottom layer of the structure to realize strong coupling with the lower H-T branch structure;

finally, the return loss of the upper E arm is reduced by using the blending metal block 7, so that the purpose of expanding the bandwidth is achieved, and the performance of the SIW magic T is improved.

The substrate integrated waveguide magic T with the Ka wave band is composed of an upper layer E-T, H-T branch and a lower layer E-T, H-T branch and matching elements, and the structure parameters are as follows:

thickness t of the substrate integrated waveguide: 0.8mm

Substrate integrated waveguide width k: 5.6mm

Through-hole radius r 1: 0.25mm

Through hole pitch j: 0.8mm

Circular wedge-shaped matching radius r: 2.4mm

Radius of metal via in round wedge: 0.07mm

Width g of coupling slit: 0.4mm

And (3) adjusting the thickness of the membrane by using the lower H arm: 0.01mm

The length l of the membrane is adjusted by the lower layer H arm: 0.4mm

The width of the membrane is adjusted by the lower H arm: 0.8mm

Length b of coupling slot: 4.4mm

The length a of the upper layer E arm adjusting metal block: 0.68mm

Adjusting the thickness h of the metal block by the upper layer E arm: 0.09mm

The distance u from the upper layer blending metal block to the center of the coupling hole is 0.95mm

The distance d from the lower layer prepared metal membrane to the port 4 is as follows: 2.4mm

Longitudinal offset of the coupling slot in the E-arm ox: 0.7mm

Lateral offset oz of the coupling slot in the E-arm: 1.45mm

The obtained Ka-band substrate integrated waveguide magic T is made of duroid (tm) (the relative dielectric constant r is 2.2, and the loss tangent tan is 0.0009). When the SIW structure magic T with the parameters is tested at the frequency of 28 GHz-30 GHz, the return loss of each port is less than-20 dB as shown in figure 4, the isolation of the 2 and 3 ports is better than-20 dB as shown in figure 5, the isolation of the E arm H arm is better than-42 dB, the amplitude unbalance of the in-phase output and the anti-phase output is less than 0.10dB as shown in figures 7 and 9, and the in-phase unbalance and the anti-phase unbalance are less than 0.63 degrees as shown in figures 10 and 11.

In conclusion, the magic T has good performance through the adjustment of the structural parameters, and the matching of each port is better through the allocation of the metal diaphragm and the allocation of the metal block, so that the use bandwidth is widened, and the amplitude imbalance is reduced.

Claims (2)

1. The utility model provides a Ka wave band substrate integrated waveguide magic T, includes the upper and lower two-layer medium substrate that is provided with the coupling slit, its characterized in that:

the lower dielectric substrate is an H-T branch of the magic T, the upper dielectric substrate realizes an E-T branch in an electric coupling mode, the two dielectric substrates are overlapped in parallel, the transverse edges and the longitudinal edges of the upper dielectric substrate and the lower dielectric substrate are respectively correspondingly parallel, and the waveguide is formed by metal through holes which are periodically arranged on the dielectric substrates;

the lower medium substrate is provided with a main waveguide and a branch waveguide to form an axisymmetric H-T branch, the central line of the branch waveguide is vertical to the central line of the main waveguide, and the coupling seam is arranged along the symmetric axis of the H-T branch waveguide; the main waveguide adopts a circular wedge-shaped metal through hole to match the H-T branches, the circular wedge-shaped metal through hole generates parasitic capacitance, the coupling seam of the lower layer substrate is arranged at the tip of the circular wedge, and the coupling seams of the upper layer medium substrate and the lower layer medium substrate are corresponding in position;

the arm E of the upper dielectric substrate is provided with a blending metal block penetrating through the upper dielectric substrate so as to eliminate the influence of parasitic capacitance generated at the coupling seam due to electric coupling of the upper E-T branch; the width of the prepared metal block is the same as the thickness of the substrate integrated waveguide, and the upper edge and the lower edge of the prepared metal block are respectively arranged on the upper plane and the lower plane of the waveguide;

the H arm of the lower dielectric substrate is also provided with a prepared metal diaphragm penetrating through the lower dielectric substrate to eliminate the influence of parasitic capacitance generated by the circular wedge-shaped metal through hole, the thickness of the prepared metal diaphragm is the same as that of the substrate integrated waveguide, and the upper edge and the lower edge of the prepared metal diaphragm are respectively arranged on the upper plane and the lower plane of the waveguide.

2. The Ka-band substrate integrated waveguide magic T of claim 1, wherein the structural parameters are as follows:

thickness t of the substrate integrated waveguide: 0.8mm substrate integrated waveguide width k: 5.6mm

Through-hole radius r 1: 0.25mm via spacing j: 0.8mm

Circular wedge-shaped matching radius r: radius of metal through hole in 2.4mm round wedge: 0.07mm

Width g of coupling slit: the thickness of the membrane is adjusted by the lower layer H arm of 0.4 mm: 0.01mm

The length l of the membrane is adjusted by the lower layer H arm: the width of the membrane is adjusted by the lower layer H arm of 0.4 mm: 0.8mm

Length b of coupling slot: 4.4mm length a of upper E arm adjusting metal block: 0.68mm

Adjusting the thickness h of the metal block by the upper layer E arm: 0.09mm

The distance u from the upper layer blending metal block to the center of the coupling hole is 0.95mm

The distance d from the lower layer prepared metal membrane to the port 4 is as follows: 2.4mm

Longitudinal offset of the coupling slot in the E-arm ox: 0.7mm

Lateral offset oz of the coupling slot in the E-arm: 1.45 mm.

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