Cavity filtering coupler

Abstract

The invention discloses a cavity filtering coupler, particularly relates to the technical field of wireless communication, and solves the technical problem that a coupler in the prior art cannot give consideration to the performance index of a microwave circuit while reducing the size of a system. According to the technical scheme, a coupler and a filter are fused into one device, so that the coupler and the filter share the same resonator. The coupler does not need to be cascaded with a filter, so that the cascading loss between the coupler and the filter is eliminated, and the system size is remarkably reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of wireless communication, and particularly relates to a cavity filter coupler. Background Art

[0002] The finiteness of spectrum resources is an important challenge faced by wireless communication technologies. With the continuous growth of communication demands, the spectrum has become increasingly crowded. As a core device for frequency selection and signal conditioning, filters are widely used in systems. At the same time, in a dense urban networking environment, it is necessary to suppress spurs, harmonics, and external interference sources, which poses higher requirements for the frequency selectivity and stopband suppression of filters.

[0003] A coupler is an important passive device, especially having an irreplaceable role in small-signal sampling and monitoring. The coupler extracts a small part of the energy (coupling end) from the main transmission path (input end to through end) through electromagnetic energy coupling to achieve non-invasive sampling. This characteristic hardly affects the main signal transmission and can effectively ensure the power monitoring and calibration of the transmitter.

[0004] In a radio frequency system, cavity filters and cavity couplers often cascade with each other to achieve the two functions of filtering and directional coupling. However, the cascade loss will cause an increase in the insertion loss of the system. The cascade of the two types of cavity devices requires a large volume, which is not conducive to the miniaturization of the system. Summary of the Invention

[0005] Therefore, the present invention solves the technical problems in the prior art that in a radio frequency system, cavity filters and cavity couplers often cascade with each other to achieve the two functions of filtering and directional coupling; however, the cascade loss will cause an increase in the insertion loss of the system; the cascade of the two types of cavity devices requires a large volume, which is not conducive to the miniaturization of the system. The cavity filter coupler provided by the present invention integrates the coupler and the filter into one device, enables the coupler and the filter to share the same resonator, and the coupler no longer needs to cascade with the filter, thereby eliminating the cascade loss between the two and significantly reducing the system volume. This overall system-level optimization solution not only reduces the design cost but also takes into account the performance indicators of microwave circuits, meeting the development requirements of communication systems for high performance, miniaturization, and low cost.

[0006] The present invention provides a cavity filter coupler, which includes a dielectric cavity, two identical double-headed fork-shaped coupling probes embedded inside the cavity, and a feeding probe inserted into four ports of the dielectric cavity (the port connectors are pressed on the cavity surface). The dielectric cavity contains four octagonal (non-regular octagon) dielectric resonators of the same size, and each octagonal dielectric resonator is obtained by cutting off four corners of a square dielectric resonator (each corner is cut off an isosceles triangle). The four octagonal dielectric resonators are arranged in a 2×2 array, and are coupled to each other through rectangular dielectric sheets, and the widths of the dielectric sheets in the x-axis and y-axis directions are different.

[0007] Further, the four ports are respectively port 1, port 2, port 3, and port 4; port 1 and port 2 are close to each other (biased towards the first double-headed fork-shaped coupling probe side), that is, deviated from the center positions of their respective resonators. Similarly, port 3 and port 4 are biased towards the second double-headed fork-shaped coupling probe side. As Figure 1 、 Figure 2 shown, starting from the upper left corner and rotating clockwise, the port order is that the input end is port 1, the through end is port 2, the coupling end is port 3, and the isolation end is port 4. The input end and the through end are on the same side and are coupled through the first double-headed fork-shaped coupling probe. The coupling end and the isolation end are on the same side and are coupled through the second double-headed fork-shaped coupling probe.

[0008] Further, the contact surface between the dielectric cavity and the feeding port is not silver-plated, and the rest of the surfaces are silver-plated (the contact surfaces between the cavity and the air are silver-plated). The plane where the "double-headed fork" type coupling probe is embedded inside the cavity is parallel to the bottom of the dielectric cavity and is placed at half the height of the dielectric cavity.

[0009] In the above technical solution, the technical effects and advantages provided by the present invention are as follows:

[0010] 1. A cavity filter coupler provided by the present invention integrates the coupler and the filter into one device, enables the coupler and the filter to share the same resonator, and the coupler no longer needs to be cascaded with a filter, thereby eliminating the cascading loss between the two and significantly reducing the system volume.

[0011] 2. A cavity filter coupler provided by the present invention, while reducing the design cost with the overall optimization scheme, takes into account the performance indicators of the microwave circuit, meeting the development requirements of the communication system for high performance, miniaturization, and low cost.

[0012] 3. A cavity filter coupler provided by the present invention, due to the adoption of the "double-headed fork" type coupling probe, the cross-coupling between the two ports on both sides of the coupling probe is enhanced, so that S 21 and S 31 each generate a transmission zero point in the upper stopband, enhancing the out-of-band rejection ability of the device to a certain extent. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required in the embodiments. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings.

[0014] Figure 1 Schematic diagram of the overall structure of the present invention;

[0015] Figure 2 Top view of the present invention;

[0016] Figure 3 Amplitude-frequency response diagram of the cavity filter coupler of the present invention.

[0017] Description of reference numerals:

[0018] 1. Dielectric cavity; 2. First double-headed fork-shaped coupling probe; 3. Second double-headed fork-shaped coupling probe; 4. Input end; 5. Through end; 6. Coupling end; 7. Isolation end; 8. Feeding probe. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0019] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the following will further introduce the present invention in detail with reference to the drawings.

[0020] Embodiment 1:

[0021] This embodiment provides a cavity filter coupler, as shown in Figure 1 and Figure 2 , which includes a dielectric cavity 1, two identical double-headed fork-shaped coupling probes embedded inside the cavity, and a feeding probe 8 inserted into four ports of the dielectric cavity 1 (the port connectors are pressed on the cavity surface). The dielectric cavity 1 contains four octagonal (non-regular octagon) dielectric resonators of the same size. Each octagonal dielectric resonator is obtained by cutting off four corners of a square dielectric resonator (each corner is cut off an isosceles triangle). The four octagonal dielectric resonators are arranged in a 2×2 array, and are coupled to each other through rectangular dielectric sheets, and the widths of the dielectric sheets in the x-axis and y-axis directions are different.

[0022] In this embodiment, the four ports are port 1, port 2, port 3, and port 4 respectively; port 1 and port 2 are close to each other (biased towards the first double-headed fork-shaped coupling probe 2), that is, deviated from the center positions of their respective resonators. Similarly, port 3 and port 4 are biased towards the second double-headed fork-shaped coupling probe 3. As shown in Figure 1 , Figure 2As shown, starting from the upper left corner and rotating clockwise, the port order is: the input end 4 is port 1, the through end 5 is port 2, the coupling end 6 is port 3, and the isolation end 7 is port 4. The input end 4 and the through end 5 are on the same side and are coupled by the first double-headed fork-shaped coupling probe 2. The coupling end 6 and the isolation end 7 are on the same side and are coupled by the second double-headed fork-shaped coupling probe 3.

[0023] In this embodiment, the contact surface between the dielectric cavity 1 and the feed port is not silver-plated, and the rest of the surfaces are silver-plated (the contact surfaces between the cavity and the air are all silver-plated). The plane where the "double-headed fork" shaped coupling probe embedded inside the cavity is parallel to the bottom of the dielectric cavity 1 and is placed at half the height of the dielectric cavity 1.

[0024] In the specific circuit design process, the dielectric constant of the dielectric cavity 1 is 32. The contact surface between the port and the cavity is not silver-plated, and the rest of the surfaces of the dielectric cavity 1 are silver-plated. Each resonator in the dielectric cavity 1 operates in the TE 110 , and by adjusting the size of the chamfers around the cavity, its resonant frequency can be finely tuned. Since the inclined surfaces of the chamfers are not large, it is convenient for subsequent polishing and adjustment of the device.

[0025] Embodiment 2:

[0026] This embodiment provides a cavity filter coupler optimized based on the device provided in the above Embodiment 1. Its size parameters are shown in Table 1. All the chamfered edges (the length of the waist of the cut isosceles triangle) in the dielectric cavity 1 are 4 mm, and the height of the dielectric cavity is 4 mm. The diameter of all the feed probes 8 is 1.3 mm, the depth inserted into the dielectric cavity 1 is 2.1 mm, the diameter of the embedded double-headed fork-shaped coupling probe is 0.6 mm, 2 mm away from the bottom of the dielectric cavity 1, and the angle α of the arcs at both ends of the double-headed fork-shaped coupling probe takes a value of 180°, that is, a semi-circular arc.

[0027] Table 1: Size parameter table of this embodiment

[0028] Parameter <![CDATA[l1]]> <![CDATA[d1]]> <![CDATA[d2]]> <![CDATA[d3]]> Value (mm) 20 7.6 2 4 Parameter <![CDATA[d4]]> <![CDATA[d5]]> <![CDATA[d6]]> R Value (mm) 2 14 6.1 5

[0029] The amplitude-frequency response of the cavity filter coupler is as Figure 3As shown, its center frequency is 1.8 GHz. The in-band insertion loss of the through-end signal is better than 0.49 dB, the return loss of the input-end signal is better than 20 dB, and the coupling degree is 20 ± 1 dB. After the signal enters the input end 4, the energy is mainly output from the through end 5, a small part is output from the coupling end 6, and very little energy is output from the isolation end 7. Since the input end 4 (port 1) and the through end 5 (port 2) approach each other while deviating from the center positions of their respective resonators (the coupling end 6 (port 3) and the isolation end 7 (port 4) also synchronously deviate from the centers of their respective resonators), and a double-headed fork-shaped coupling probe is introduced between the resonators. Under the action of the above two aspects, the cross-coupling between the two ports on both sides of the double-headed fork-shaped coupling probe is enhanced, and a transmission zero point is generated at 2.3 GHz, improving the out-of-band rejection performance of this filter coupler.

[0030] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. Any equivalent structural or equivalent process transformation made by using the content of the specification and drawings of the present invention, or directly or indirectly applied to other related technical fields, shall be equally included in the patent protection scope of the present invention.

Claims

1. A cavity filter coupler, characterized in that, Comprising a dielectric cavity (1), two sets of double-headed fork-shaped coupling probes are arranged in the dielectric cavity (1), namely a first double-headed fork-shaped coupling probe (2) and a second double-headed fork-shaped coupling probe (3); ports are arranged in the areas of the dielectric cavity (1) on both sides of the first double-headed fork-shaped coupling probe (2) and the second double-headed fork-shaped coupling probe (3), and feeding probes (8) are arranged in the ports.

2. The cavity filter coupler according to claim 1, wherein, The dielectric cavity (1) comprises four octagonal dielectric resonators, and each octagonal dielectric resonator is obtained by cutting off four corners of a square dielectric resonator; the four octagonal dielectric resonators are arranged in a 2×2 array, and are coupled to each other by rectangular dielectric sheets, and the widths of the dielectric sheets in the x-axis and y-axis directions are different.

3. The cavity filter coupler according to claim 2, wherein, Ports are arranged on each of the octagonal dielectric resonators, and the four ports are respectively an input end (4), a through end (5), a coupling end (6) and an isolation end (7).

4. The cavity filter coupler according to claim 3, characterized in that, The input end (4) and the through end (5) are on the same side and are coupled by the first double-headed fork-shaped coupling probe (2); the coupling end (6) and the isolation end (7) are on the same side and are coupled by the second double-headed fork-shaped coupling probe (3).

5. The cavity filter coupler according to claim 4, wherein, The surfaces of the dielectric cavity (1) in contact with air are all silver-plated.

6. The cavity filter coupler according to claim 5, wherein The plane where the first double-headed fork-shaped coupling probe (2) and the second double-headed fork-shaped coupling probe (3) are arranged in the dielectric cavity (1) is parallel to the bottom of the dielectric cavity (1).

7. The cavity filter coupler according to claim 6, wherein, The first double-headed fork-shaped coupling probe (2) and the second double-headed fork-shaped coupling probe (3) are at the position of half the height in the dielectric cavity (1).

8. The cavity filter coupler according to claim 7, wherein, The four octagonal dielectric resonators are of the same size.

9. The cavity filter coupler according to claim 8, wherein The input end (4) and the through end (5) are close to each other, that is, they deviate from the center positions of their respective octagonal resonators.

10. The cavity filter coupler according to claim 8, wherein The coupling end (6) and the isolation end (7) are close to each other, that is, they deviate from the center positions of their respective octagonal resonators.

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