WO2024007717A1

WO2024007717A1 - Strong coupling striplines and microwave element comprising same

Info

Publication number: WO2024007717A1
Application number: PCT/CN2023/092498
Authority: WO
Inventors: 李梓萌; 斯莱德科夫·亚历山大德维奇·维克多; 奥斯塔朋科·亚历山大
Original assignee: 广州司南技术有限公司
Priority date: 2022-07-07
Filing date: 2023-05-06
Publication date: 2024-01-11
Also published as: CN115207591A

Abstract

The present application provides two coupling striplines, comprising: a first strip-shaped conductor arranged on the top surface of a dielectric substrate and a second strip-shaped conductor arranged on the bottom surface of the dielectric substrate, the first strip-shaped conductor and the second strip-shaped conductor being located at an opening of a conductive layer covering the bottom surface of the dielectric substrate, wherein the conductive layer and the second strip-shaped conductor are separated by a gap, and at least part of the first strip-shaped conductor is arranged on a part of the second strip-shaped conductor; and at least one additional conductor arranged on the top surface of the dielectric substrate, separated from the first strip-shaped conductor by a gap, and connected to the conductive layer by means of metal-plated holes of the dielectric substrate.

Description

Strongly coupled striplines and microwave components containing strongly coupled striplines

Technical field

This application relates to microwave transmission lines and microwave components manufactured using conventional printed circuit board technology.

Background technique

The modern mobile communications market requires complex antennas that form narrow beams and operate in multiple frequency bands. This type of antenna consists of radiating elements and a beamforming network that contains many passive components, including directional couplers, differential phase shifters, and filters. Modern antennas for mobile communications must provide very low levels of passive intermodulation, so the elements of the beamforming network are connected to each other via special coaxial cables soldered directly to the passive elements. The dimensions of the passive components must be as small as possible so that they can be installed in a confined space within the radome to protect the antenna from harsh weather conditions.

Most broadband and compact directional couplers and phase shifters contain coupled striplines. A directional coupler with a coupling level between 30dB and 10dB contains two coupling lines that are set on the surface of a dielectric substrate and separated by a gap, but this design cannot produce coupling between 10dB and 2dB because provided The gaps between striplines for this level of coupling must be very narrow and cannot be manufactured with industrial PCB technology. Therefore, engineers used another design to increase the coupled signal. Patent US 10833388 B2 describes a circuit containing several couplers connected together by a power divider to increase the coupled signal. Four couplers connected together can provide coupling levels up to 3dB, but such a circuit is too large and, therefore, expensive to manufacture.

As shown in CN 108110425 A, coupling striplines that produce coupling levels between 10dB and 2dB must be placed opposite each other on the surface of a thin dielectric substrate. Known circuits including couplers and differential phase shifters contain three dielectric substrates placed on top of each other between two metals, so this design is complex to manufacture. Additionally, connecting coaxial transmission lines to metal plates can create passive intermodulation products.

Other known couplers Lange consist of several parallel thin strip lines connected by bridges arranged over a dielectric substrate and soldered to the strip lines. This design is complex for mass production and is typically applied to strip lines provided on substrates made of expensive ceramic materials.

Another type of directional coupler consists of a substrate consisting of two dielectric layers separated by a conductive layer with windows and two strip lines disposed on the top and bottom surfaces of the dielectric substrate. This design is also complex for mass production.

Since the modern communications industry uses a large number of microwave components, it is necessary to simplify the design of coupling lines and provide coupling levels between 10dB-2dB, which is suitable for manufacturing directional couplers and other microwave components including strongly coupled strip lines.

Contents of the invention

The purpose of this application is to provide a new type of strongly coupled stripline suitable for manufacturing very simple microwave components consisting only of printed circuit boards.

A first object of the present application is to overcome the deficiencies of known coupled striplines and provide a strongly coupled stripline formed on both surfaces of a single dielectric substrate by conventional printed circuit board technology.

A second object of the present application is to provide a simple microwave assembly consisting only of a single dielectric substrate.

A coupled stripline intended for the purposes of this application includes a first strip conductor disposed on a top surface of a dielectric substrate, and a second strip conductor disposed along the first strip conductor at an opening located at A conductive layer covering the underside of a dielectric substrate. The conductive layer covering the bottom surface of the dielectric substrate is separated from the second strip conductor by a gap. Two additional conductors disposed on the top surface of the dielectric substrate are separated from the first strip conductor by a gap and connected to the conductive layer through metal plated holes in the dielectric substrate. At least a portion of the first strip conductor is disposed over a portion of the second strip conductor.

The couple mode of this stripline has a larger wave impedance Ze than the couple mode of a conventional stripline disposed opposite the conductive layer because the conductive layer is removed from the opening and disposed only at the opposite edge of the strip conductor. The wide sides of the strip conductor are disposed opposite to each other on the top and bottom surfaces of the dielectric substrate, so that the wave impedance Zo of its odd mode is smaller than that of a conventional strip line, which contains a strip conductor disposed on the dielectric substrate. top surfaces of the substrates and are coupled only through their edges. Due to the coupling coefficient, this arrangement of the openings of the conductive layer and the strip conductors increases the coupling between the two strip lines compared to a conventional strip line formed on a single substrate.

Openings in the conductive layer and additional conductors disposed on the top surface of the dielectric substrate provide electrical symmetry for the coupled stripline. The gaps separating the strip conductors from the conductive layers and additional conductors have a shape that provides equal electrical lengths for both modes, so strip lines are preferred to provide directional coupling. The conductive layer of the coupled stripline and the two additional conductors that provide a large coupling coefficient K include edge cuts that are spaced apart from the edges of the first and second strip conductors by a gap to provide equal electrical lengths for both modes.

Description of the drawings

Some embodiments of the present application are described by the following drawings, in which:

Figures 1a, 1b and 1c show top and bottom surfaces and cross-sections of a dielectric substrate containing a coupled stripline of the present application, forming a 3dB directional coupler operating in the 690-960MHz frequency band.

Figures 2a and 2b are measured frequency characteristics of a fabricated sample of the directional coupler shown in Figures 1a-1c.

Figure 3 shows a perspective view of the bottom surface of a dielectric substrate containing the coupling stripline of the present application and a metal plate disposed adjacent to the dielectric substrate, forming a 3dB directional coupler operating in the 1600-2700 MHz frequency band.

Figures 4a and 4b are measured frequency characteristics of the fabricated sample of the directional coupler shown in Figure 3.

Figures 5a and 5b show respectively top and bottom views of a dielectric substrate containing coupled striplines forming a phase shifter.

Figure 6 and Table 1 show the simulated frequency characteristics of the phase shifter shown in Figures 5a and 5b.

Detailed ways

It should be understood that the present application is not limited to the specific forms disclosed in the above drawings. This application is intended to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the application as defined by the appended claims.

The coupling line must meet the following conditions to match the four transmission lines connected to it and provide directional coupling. When Z=50Ohm of the four transmission lines, the impedances of the even and odd modes of the coupling line must satisfy the equation Ohm, and the electrical lengths Le and Lo of their even and odd modes must be equal. This means that when the four transmission lines have equal impedance, the two coupling lines must be electrically equal. Placing a traditional coupled stripline on the same surface of the dielectric substrate can provide the above conditions and produce directional coupling, but it cannot provide strong coupling because traditional printed circuit board technology cannot make its edges smaller than 0.05mm.

The strip conductor of the coupled strip line according to the present application provides a greater wave impedance Ze because the capacitance between the strip conductor and the conductive layer containing the opening arranged opposite to the strip conductor is smaller than that of the strip conductor of a conventional strip line. capacitance to a conductive layer without openings. The strip conductors of the coupled strip line according to the present application are disposed opposite each other on the top and bottom surfaces of the dielectric substrate, providing smaller odd mode wave impedance than a conventional coupled strip line disposed on one side of the dielectric substrate. , because the capacitance between strip conductors stacked on top of each other is greater than that between conventional coupled striplines, which lie on the same surface and couple only through their edges. Therefore, the coupled stripline of the present application provides a larger coupling coefficient.

The first embodiment of the present application is shown in Figures 1a-1c. The strip conductor and the conductive layer form a 3dB directional coupler operating in the 690-960 MHz frequency band, and the strip conductor and the conductive layer are arranged on the surface of the dielectric substrate 1 . The top surface of the dielectric substrate 1 contains a first strip conductor 2a and two additional conductors 3a and 3b, which are separated from the first strip conductor 2a by gaps 4a and 4b. The additional conductors 3a and 3b are connected through metal plated holes 6 to the Conductive layer 5 on the bottom surface of the electrical substrate 1 . The edges of the additional conductors 3a and 3b contain cutouts 7, which include a narrow portion 7a and a wide portion 7b. The end portion of the strip conductor 2a is connected to the strip conductors 8a and 8b.

The bottom surface of the dielectric substrate 1 contains the second strip conductor 2 b and the conductive layer 5 , and the conductive layer 5 and the second strip conductor 2 b are separated by a gap 11 . The ends of the strip conductor 2b are connected to the strip conductors 9a and 9b through metal plated holes 10a and 10b.

The conductive layer 5 contains a cutout 12 including a narrow portion 12a and a wide portion 12b. Cross-section A-A of the dielectric substrate across the stripline and conductive layer is shown in Figure 1c.

The other ends of the strip conductors 8a, 8b, 9a and 9b are connected to the inner conductor of the coaxial cable (not shown). The outer conductor of the coaxial cable is connected to the conductors 5a-5d provided near the edge of the dielectric substrate 1 and connected to the conductive layer 5 through the metal plated hole 6.

The odd-mode electromagnetic field of the coupling strip line is concentrated between the coupling lines provided with the dielectric substrate. Therefore, the dielectric substrate can effectively delay the electromagnetic wave. The even-mode electromagnetic field of the coupled stripline is concentrated between the edge of the coupling line and the edge of the conductive layer and additional conductor. Therefore, a part of the electromagnetic wave propagates through the air region adjacent to the dielectric substrate, so the delay of the even mode is smaller than that of the odd mode. The cutout 12 significantly increases the even-mode wave impedance, but has little effect on the odd-mode wave impedance. The cutouts 12 form a periodic structure, connecting multiple transmission lines with different wave impedances in series. This periodic structure increases the delay of even modes and allows the electrical lengths of even and odd modes to be equal.

Therefore, the coupling line provides directional coupling, and splits the electromagnetic wave exciting strip line 8a between strip lines 8b and 9a. A very small part of the electromagnetic wave that excites strip line 8a penetrates strip line 9b. Figures 2a and 2b depict the measured frequency characteristics of the fabricated sample of the directional coupler shown in Figures 1a-1c. In Figure 1a, stripline 8a corresponds to port 1, stripline 8b corresponds to port 2, stripline 9a corresponds to port 3, and stripline 9b corresponds to port 4. The directional coupler including the coupled stripline according to the present application provides S11 ≤ -31.7dB, S41 ≤ -31dB and coupling -3.4±0.2dB in the 690-960MHz frequency band.

Another embodiment of the present application is a 3dB directional coupler operating at frequencies above 1 GHz, as shown in Figure 3 from a perspective view of the underside of dielectric substrate 13. The metal plate 14 disposed opposite the coupling line 15 is connected to the conductive layer 16 through bent portions 17a-17d. The metal plate 14 reduces radiation from the coupling line 15 and therefore a directional coupler including the metal plate 14 provides smaller insertion loss than a directional coupler without the metal plate 14 .

When the second metal plate is disposed on the top surface of the dielectric substrate 13, the radiation from the coupling line will be smaller. Figures 4a and 4b depict the measured frequency characteristics of the directional coupler fabricated sample shown in Figure 3. Directional couplers containing coupled striplines and metal plates provide S11 ≤ -28.3dB, S41 ≤ -23.2dB and coupling -3.6±0.2dB in the 1700-2800MHz band.

Another embodiment of the present application is a phase shifter. Figures 5a and 5b respectively show a coupled strip containing a phase shifter. Top and bottom views of the wire's dielectric substrate.

The top surface of the dielectric substrate 18 contains a first strip conductor 19a, and an additional conductor 20 separated from the first strip conductor 19a by a gap 21. Additional conductors 20 are connected to the conductive layer 22 through metal plated holes 23 . The edge of the additional conductor 20 located opposite the strip conductor 19 a contains a cutout 24 . The left end of the coupling strip conductor 19a is connected to the strip conductor 25 to form a transmission line connected to the phase shifter input port.

The bottom surface of the dielectric substrate 18 includes the conductive layer 22 and the second strip conductor 19 b disposed in the opening 30 . The left end of the strip conductor 19b is connected to the strip conductor 26 through the metal plated hole 27. Strip conductor 26 forms a transmission line connected to the output port of the phase shifter. The right ends of strip conductors 19a and 19b are connected together by metal plated holes 28a and 28b. The edge of the conductive layer 22 disposed opposite the strip conductor 19 b contains a cutout 29 .

The dimensions of strip conductors 19a and 19b, additional conductor 20, gap 21 and opening 30 are calculated to provide coupling lines matching the transmission lines of strip conductors 25 and 26. Figure 6 shows a simulation S11 of the phase shifter shown in Figures 5a and 5b. Table 1 shows the simulated phases of the phase shifters shown in Figures 5a and 5b. The phase shifter provides S11 = -30.76dB and a phase shift of 90+/-2.5 degrees compared to a transmission line having an electrical length of 3/4 wavelength at the mid-frequency of the 1710-2690MHz operating band.

Table 1

Claims

Two coupled striplines, including:

The first strip conductor disposed on the top surface of the dielectric substrate and the second strip conductor disposed on the bottom surface of the dielectric substrate are located at the opening of the conductive layer covering the bottom surface of the dielectric substrate, and the conductive layer is connected to the third strip conductor. The two strip conductors are separated by a gap, wherein at least a part of the first strip conductor is disposed on a part of the second strip conductor;

At least one additional conductor is disposed on the top surface of the dielectric substrate, separated by a gap from the first strip conductor, and connected to the conductive layer through a metal plated hole in the dielectric substrate.
2. Two coupled strip lines according to claim 1, characterized in that the conductive layer and the two additional conductors contain cuts spaced from the edges of the first strip conductor and the second strip conductor. on the edge of a gap.
2. Two coupled strip lines according to claim 2, characterized in that at least one cutout has a narrow portion and a wide portion.
The two coupled strip lines according to any one of claims 1 to 3, characterized in that a metal plate is disposed below the dielectric substrate and connected to the conductive layer through a metal strip.
A directional coupler comprising two coupled strip lines according to any one of claims 1 to 3, characterized in that four strip transmission lines are connected to the ends of the first strip conductor and the second strip conductor .
A directional coupler comprising two coupling strip lines according to any one of claims 1 to 3, characterized in that the third strip conductor and the fourth strip conductor are disposed on the top surface of the dielectric substrate , its end is connected to the end of the second strip conductor through a metal plated hole in the dielectric substrate, and its other end is connected to a coaxial cable or coaxial connector.
A differential phase shifter comprising two coupled strip lines according to any one of claims 1 to 3, characterized in that the first end of the first strip conductor and the second strip conductor The first end is connected to the coaxial cable or coaxial connector, and the other ends of the first strip conductor and the second strip conductor are connected together through metal plated holes in the dielectric substrate.
A differential phase shifter, comprising two coupled strip lines according to claim 6, characterized in that the third strip conductor is disposed on the top surface of the dielectric substrate, and its first end passes through the dielectric substrate Plated metal holes on the The first end of the two strip conductors is connected to the other end of the coaxial cable or coaxial connector.
A beamforming network comprising two coupled striplines according to any one of claims 1-3, forming a directional coupler and a differential phase shifter.
The beamforming network according to claim 9, characterized by comprising a 3dB directional coupler and a 90-degree phase shifter forming a 0/180-degree directional coupler.
The beamforming network according to claim 9, characterized by comprising a 3db directional coupler and a 90 degree phase shifter, connected by strip lines, to distribute the RF signal from any one of the two inputs to the three outputs.