CN114284674B

CN114284674B - Coupling waveguide microstrip transition structure with low insertion loss

Info

Publication number: CN114284674B
Application number: CN202111402397.3A
Authority: CN
Inventors: 王博宁; 杨德强; 赵志钦; 孙凯; 陶婷婷; 刘思豪
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: 2023-07-04
Anticipated expiration: 2041-11-24
Also published as: CN114284674A

Abstract

The invention belongs to the technical field of microwave transmission lines, and particularly provides a coupling waveguide microstrip transition structure with low insertion loss, which is used for meeting the radiation loss reduction requirement of the transition structure. The invention comprises the following steps: the lower rectangular metal waveguide 1, the middle transition layer 2, the grounding metal plate 3, the upper dielectric plate 4 and the rectangular metal patch are sequentially stacked from bottom to top, and the rectangular metal patch is introduced into the upper surface of the upper dielectric plate, so that the coupling energy is greatly improved, the radiation energy is obviously reduced, the transmission coefficient from the waveguide to the microstrip line is further obviously improved, and the good port reflection characteristic is also maintained; meanwhile, the short-circuit probe is skillfully applied, the influence of impedance mismatch brought by the rectangular metal patch is counteracted while the rectangular metal patch is effective, and impedance matching is realized; compared with the prior art, the invention has the advantages of simple structure, low processing difficulty and easy realization of industrial production.

Description

Coupling waveguide microstrip transition structure with low insertion loss

Technical Field

The invention belongs to the technical field of microwave transmission lines, relates to a transition structure for converting a waveguide transmission line into a microstrip transmission line, and particularly provides a coupling waveguide microstrip transition structure with low insertion loss.

Background

With the rapid development of wireless communication technology and demand, antennas play a significant role as key elements for determining the performance of wireless systems; the array antenna has strong demands in some remote communication scenes due to the high gain characteristic of the array antenna; however, in some large antenna arrays, the loss on the feed transmission line is not very small, which limits the gain improvement of the array antenna to a great extent; therefore, the use of a transmission structure with lower loss becomes an extremely effective method for improving the radiation efficiency and gain of the array antenna.

For an array feed network, a single form of feed structure often has unavoidable problems; the waveguide transmission line has extremely low transmission loss, but has larger size due to the limitation of a transmission mode; while for microstrip transmission lines, while having smaller dimensions and more flexible wiring, an increase in line length will bring about a non-negligible loss as the array scale increases. In order to have a compact structure and lower insertion loss, a hybrid network of waveguides and microstrip lines is often adopted in engineering to realize large-scale array feeding; the structure is a multi-layer structure, the waveguide and the microstrip are positioned on different layers, and energy is coupled from the waveguide to the microstrip line through a transition structure; however, since the microstrip line is an open transmission line, a part of energy is inevitably coupled into space in the process of coupling energy from the waveguide to the microstrip line, resulting in certain radiation loss; therefore, it is important to develop a method for reducing the radiation loss of the transition structure as much as possible while ensuring the structural functional integrity.

Disclosure of Invention

The invention aims at solving the demand of reducing radiation loss in the transition structure for converting the waveguide transmission line into the microstrip transmission line, and provides a coupling waveguide microstrip transition structure with low insertion loss, which is used for remarkably reducing radiation loss during energy coupling.

In order to achieve the above purpose, the invention adopts the following technical scheme:

a coupled waveguide microstrip transition structure with low insertion loss, comprising: the lower rectangular metal waveguide 1, the middle transition layer 2, the grounding metal plate 3 and the upper dielectric plate 4 which are sequentially stacked from bottom to top are characterized in that a rectangular coupling slot 5 is formed in the upper surface of the lower rectangular metal waveguide 1, the middle transition layer 2 and the grounding metal layer 3 are provided with coupling slots 6 with the same size at positions corresponding to the rectangular coupling slot 5, a rectangular metal patch 7 is arranged on the upper surface of the upper dielectric plate 4, the center line of the rectangular metal patch is overlapped with the center line of the coupling slot, and four corners of the rectangular metal patch 7 are connected to the grounding metal plate 3 through grounding short-circuit through holes 8.

Further, the long sides of the rectangular metal patch 7 are parallel to the long sides of the coupling slit 5, and the length of the rectangular metal patch 7 is smaller than the length of the coupling slit 5.

In terms of working principle:

the invention provides a coupling waveguide microstrip transition structure with low insertion loss, which is divided into three layers: a lower layer where the rectangular waveguide is located, a middle transition layer and an upper layer (an upper dielectric plate) where the microstrip line is located; the upper surface of the end of the rectangular waveguide adopts a wide-edge longitudinal joint technology, and a metal grounding plate and a middle transition layer are slotted (coupling grooves) at the same position so as to realize energy coupling; the rectangular metal patch is adopted to replace a microstrip line right above the coupling slot, and then the rectangular metal patch is connected with the microstrip line, so that the width of the microstrip line is widened greatly, the waveguide slot coupling is mainly magnetic coupling, and when the width of the microstrip line right above the coupling slot is increased, the contact area between a magnetic field and the metal patch is increased, so that the coupling coefficient is improved, and the energy coupled to the microstrip line is increased; meanwhile, the rectangular metal patch partially covers the coupling gap, so that the radiation energy is reduced, and the effect of improving the transmission coefficient and reducing the radiation loss is realized. In addition, because the width of the microstrip line is widened, according to the transmission line theory, the capacitance which is connected in parallel to the ground is additionally introduced into the circuit, in order to reduce the influence on the reflection coefficient caused by the change, the four corners of the rectangular patch are introduced with the grounded short circuit through holes, and the four short circuit through holes are equivalent to the inductance which is connected in parallel to the ground and offset with the parallel capacitance which is introduced by the rectangular metal patch, so that the matching is realized.

In summary, the invention has the following beneficial effects:

the invention provides a coupling waveguide microstrip transition structure with low insertion loss, which is based on the principle of radiation coupling, and a rectangular metal patch is introduced into the upper surface of an upper dielectric plate, so that the coupling energy is greatly improved, the radiation energy is obviously reduced, the transmission coefficient from a waveguide to a microstrip line is further obviously improved, and good port reflection characteristics are also maintained; meanwhile, the short-circuit probe is skillfully applied, the influence of impedance mismatch brought by the rectangular metal patch is counteracted while the rectangular metal patch is effective, and impedance matching is realized; compared with the prior art, the invention has the advantages of simple structure, low processing difficulty and easy realization of industrial production.

Drawings

FIG. 1 is a cross-sectional view of a coupled waveguide microstrip transition structure with low insertion loss provided by the present invention;

FIG. 2 is a top view of a coupled waveguide microstrip transition structure with low insertion loss provided by the present invention;

wherein, 1 is lower metal waveguide, 2 is the transition layer, 3 is the metal ground plate, 4 is upper dielectric plate, 5 is the coupling seam, 6 is the coupling groove, 7 is rectangular metal paster, 8 is ground short circuit through hole, 9 is microstrip transmission line.

FIG. 3 shows a port S with a low insertion loss coupled waveguide microstrip transition structure according to the present invention ₁₁ Insertion loss.

Detailed Description

The present invention will be described in further detail with reference to examples and drawings.

The present embodiment provides a coupling waveguide microstrip transition structure with low insertion loss, the structure of which is shown in fig. 1 and 2, and specifically includes: the upper surface of the upper dielectric plate 4 is provided with a rectangular metal patch 7, the center line of the rectangular metal patch is overlapped with the center line of the coupling slot, and four corners of the rectangular metal patch 7 are connected with the grounding metal plate 3 through grounding short-circuit through holes 8; the two ends of the rectangular metal patch are connected with a 100 ohm microstrip transmission line 9 through an impedance transformation line, so that energy transmission is realized.

More specifically, in this embodiment, as shown in fig. 1, the total height of the transition structure is 11.108mm; wherein, the upper dielectric plate adopts a Tacouc RF-35 plate with the thickness of 0.508mm and the dielectric constant of 3.5, and the lower surface is a metal plating layer, namely a metal grounding plate; the intermediate transition layer adopts an FR-4 dielectric plate with the thickness of 3.6mm, the upper surface, the lower surface and the surface of an opened coupling groove are subjected to metallization treatment, and the transition layer is not only used for improving matching, but also used for realizing a cavity antenna of microstrip feed; the overall thickness of the lower metal waveguide is 7mm, and the lower metal waveguide is realized by screwing a layer of aluminum plate with the thickness of 5mm and milled into a waveguide cavity and a layer of planar metal cover plate with the thickness of 2mm, and can also be directly realized by 3D printing and metal coating; as shown in fig. 2, the width of the rectangular waveguide is 19mm, and the rectangular waveguide is used for realizing the transmission of a main mode under the working frequency, the coupling slot 6 is a rectangular longitudinal slot, and the center position of the slot is positioned at the position of about one quarter wavelength at the tail end of the waveguide and is transversely deviated from the center of the waveguide; the length of the rectangular coupling gap is 10.1mm, the width is 1.2mm, the length of the rectangular metal patch is 6.5mm, the width is 5.5mm, and the four corners are grounded through the metallized via holes.

As shown in FIG. 3, the S-shaped coupling waveguide microstrip transition structure is ₁₁ Curves and insertion loss curves, the curves exhibiting good reflection coefficients and excellent insertion loss, achieving losses of less than 0.25dB at the center frequency; compared with the traditional coupling type transition structure, the structure has the characteristic of obviously improving the insertion loss.

While the invention has been described in terms of specific embodiments, any feature disclosed in this specification may be replaced by alternative features serving the equivalent or similar purpose, unless expressly stated otherwise; all of the features disclosed, or all of the steps in a method or process, except for mutually exclusive features and/or steps, may be combined in any manner.

Claims

1. A coupled waveguide microstrip transition structure with low insertion loss, comprising: the low-level rectangular metal waveguide (1), the middle transition layer (2), the grounding metal plate (3) and the upper-level dielectric plate (4) which are sequentially stacked from bottom to top are characterized in that rectangular coupling slots (5) are formed in the upper surface of the low-level rectangular metal waveguide (1), coupling grooves (6) with the same size are formed in positions, corresponding to the rectangular coupling slots (5), of the middle transition layer (2) and the grounding metal plate (3), of the grounding metal plate (3), rectangular metal patches (7) are arranged on the upper surface of the upper-level dielectric plate (4), the center lines of the rectangular metal patches are overlapped with the center lines of the coupling slots, and four corners of the rectangular metal patches (7) are connected to the grounding metal plate (3) through grounding short-circuit through holes (8); the long sides of the rectangular metal patches (7) are parallel to the long sides of the coupling slits (5), and the length of the rectangular metal patches (7) is smaller than that of the coupling slits (5).