CN101599564A - Controllable Electromagnetic Coupling Microstrip Split Ring Resonator Filter - Google Patents

Abstract

The invention relates to a controllable electromagnetic coupling microstrip split ring resonator filter, which comprises an input microstrip line, an output microstrip line and a microstrip resonator group, wherein the microstrip resonator group is one or more controllable electromagnetic coupling filter units; the controllable electromagnetic coupling filtering unit consists of two resonators coupled with each other, and the effective length of each resonator is half of the working wavelength of the controllable electromagnetic coupling microstrip split ring resonator filter; in the same controllable electromagnetic coupling filtering unit, the top or the bottom of one side of each resonator is provided with an opening, the positions of the openings on the two resonators are simultaneously positioned at the top or the bottom of the resonator, the side where the opening is positioned is adjacent to the coupling sides of the two resonators, the positions of the two openings are centrosymmetric relative to the center lines of the two coupling sides, and the two coupling sides are formed by high-impedance lines. The filter can realize the filtering characteristic of a quasi-elliptic function, and has the advantages of compact structure, small volume, low cost and good characteristic.

Description

Controllable Electromagnetic Coupling Microstrip Split Ring Resonator Filter

technical field

The invention relates to a microstrip filter, in particular to a microstrip split ring resonator filter with controllable electromagnetic coupling.

Background technique

Microwave filters play a very important role in wireless signal processing, which can filter out interference signals and pass useful signals. Due to the advantages of small size, light weight, easy processing, and easy integration, microstrip filters with quasi-elliptic function responses are widely used in circuit modules of various wireless communication systems. The high-temperature superconducting film has a surface resistance close to zero and has a very high quality factor (Q value). The quasi-elliptic function microstrip filter made of the high-temperature superconducting film has extremely low passband loss and is suitable for mobile Communication base station system. After the mobile communication base station uses high-temperature superconducting filters, it can increase the system capacity, reduce adjacent frequency interference, improve the quality of mobile calls, reduce the transmission power of base stations and mobile phones, and reduce electromagnetic radiation and electromagnetic pollution in space.

A quasi-elliptic function response is a filter response with finite frequency transmission zeros that can appear on one or both sides of the filter passband to improve out-of-band rejection and produce a symmetrical or asymmetrical filter response. The characteristics obtained by the low-order quasi-elliptic function filter are equal to or even better than those of the high-order Chebyshev filter by using the transmission zero. However, in the filter synthesis design under the current technical conditions, the microstrip filter with only the main coupling path can only realize the common Chebyshev function filter response but cannot realize the quasi-elliptic function filter response with transmission zero. The most common way to achieve transmission nulls is to use cross-coupling techniques. The cross-coupling technology means that the electromagnetic signal not only passes through the main coupling path but also passes through the cross-coupling path from the input end to the output end of the filter. The main coupling means that the resonant units between the input end and the output end of the filter are coupled in sequence, and each resonant unit only has a coupling relationship with the resonant units adjacent to it in sequence; cross coupling refers to non-adjacent resonant units There is a coupling relationship between units, and a filter with a cross-coupling setting is called a cross-coupling filter. At present, most of the quasi-elliptic function filtering characteristics are realized by cross-coupled filters, but the order of traditional cross-coupled filters is still high, the size is still large, and the transmission zero position is very sensitive to the coupling between resonators. The disadvantage of high design difficulty. Moreover, in the existing microstrip filter, there is only a single controllable electrical coupling or magnetic coupling between all adjacent or non-adjacent resonant units, and there is no controllable electromagnetic hybrid coupling. Therefore, it is necessary to propose a controllable electromagnetic hybrid coupling main coupling filter that can realize quasi-elliptic function filtering characteristics.

A typical microstrip split ring half-wavelength resonator filter with quasi-elliptic function filtering response shown in the data is shown in Figure 1, please refer to Jia-Sheng Hong and Michael J. Lancaster, "Couplings of microstrip square open-loop resonators for cross-coupled planar microwave filters,” IEEE Transactions on Microwave Theory and Techniques, vol.44, no.12, pp.2099-2109, (December 1996). The design includes four square split ring resonators 11 with openings 12 , input microstrip lines 13 , and output microstrip lines 14 . In this design, the effective length of each resonator is half a wavelength, the coupling between the input resonator and the output resonator is cross-coupling, and the coupling polarity is electrical coupling. The other couplings are all main couplings, and their polarity is magnetic coupling. Electromagnetic signals produce phase differences through different coupling paths, so that the response of the filter presents quasi-elliptic function characteristics with transmission zeros. The two transmission zeros of this design are symmetrical. The size of the cross-coupling between the input resonator and the output resonator determines the positions of the two transmission zeros at the same time. Changing the cross-coupling will change the positions of the two transmission zeros at the same time, so the two transmission zeros cannot be independently controlled, and the position of the zero point is very sensitive to changes in the magnitude of the cross-coupling, making it difficult to design applications.

Contents of the invention

The purpose of the present invention is to overcome the problem that the existing main coupling filter cannot realize the quasi-elliptic function filtering characteristics, overcome the problem that the existing cross-coupling filter is still large and the transmission zero point cannot be independently controlled, and provide a controllable electromagnetic coupling The microstrip split-ring filter uses a main coupling filter to realize quasi-elliptic function filtering characteristics, and has a compact structure, small volume, low cost, and good characteristics, and is suitable for various wireless communication needs.

The technical solution adopted for the purpose of realizing the present invention: a controllable electromagnetic coupling microstrip split ring resonator filter, including input microstrip line, output microstrip line and microstrip resonator group, it is characterized in that the microstrip The band resonator group refers to one or more controllable electromagnetic coupling filter units; the controllable electromagnetic coupling filter unit is composed of two mutually coupled resonators, and the effective length of each resonator is the controllable electromagnetic coupling filter unit. Coupling the half working wavelength of the microstrip split ring resonator filter; in the same controllable electromagnetic coupling filter unit, there is an opening at the top or bottom of one side of each resonator, and the opening positions on the two resonators are located at the same time The top of the resonator or at the bottom of the resonator at the same time, the side where the opening is located is adjacent to the coupling sides of the two resonators, and the positions of the two openings are symmetrical to the center line of the two coupling sides, the two The coupled edges consist of high-impedance lines.

As a simple structure, the microstrip resonator group refers to a controllable electromagnetic coupling filter unit; the controllable electromagnetic coupling filter unit is composed of two mutually coupled resonators, and the effective The length is half of the operating wavelength of the controllable electromagnetic coupling microstrip split ring resonator filter, and an opening is provided on the top or bottom of one side of each resonator, and the positions of the openings on the two resonators are located at the top of the resonator at the same time Or at the bottom of the resonator at the same time, the side where the opening is located is adjacent to the coupling sides of the two resonators, and the positions of the two openings are symmetrical to the center line of the two coupling sides, and the two coupling sides are composed of high-impedance lines.

More specifically, the resonators in the microstrip resonator group are rectangular resonators or triangular resonators.

The resonators in the microstrip resonator group are arranged in a straight line, and this structure is more suitable for duplex and multiplexer applications than cross-coupled filters.

The main working principle of the present invention is: the filter of the present invention can form a strong electric field distribution near the opening by opening at the top or bottom of one side of each resonator, and the two coupling sides of two adjacent resonators are formed by The high-impedance line structure can form a strong magnetic field distribution in the area near the high-impedance line. Such a structure facilitates strong electromagnetic coupling between two adjacent resonators. Adjusting the positions of the two openings on the sides of the two mutually coupled resonators, that is, adjusting the relative distance between the two openings can change the ratio of electrical coupling to magnetic coupling: the closer the two openings are, the The greater the electrical coupling is relative to the magnetic coupling, and vice versa the greater the magnetic coupling is relative to the electrical coupling. Therefore, two adjacent resonators constitute a single controllable electromagnetic coupling filter unit through electromagnetic hybrid coupling. When the electromagnetic signal passes through any electromagnetic coupling filter unit, a transmission zero point will be generated, and the relative distance between the two opening positions can be controlled to control the electromagnetic coupling ratio between the two mutually coupled resonators, and the electromagnetic coupling filter unit can be controlled. The position of the transmission zero to achieve the required quasi-elliptic function filtering characteristics. When the relative distance between the two openings is large, the magnetic coupling is greater than the electrical coupling, and the controllable electromagnetic coupling filter unit can realize a transmission zero on the left side of the passband; when the relative distance between the two openings is small, the magnetic coupling is less than When electrically coupled, the controllable electromagnetic coupling filter unit can realize a transmission zero on the right side of the passband.

Each controllable electromagnetic coupling filter unit can work independently to form a second-order quasi-elliptic function filter with a single transmission zero, and can also be coupled with other hybrid coupling units or resonant units and work together to form a high-frequency filter with multiple transmission zeros. order quasi-elliptic function filter.

Compared with the prior art, the present invention has the following advantages:

1. The traditional main-coupled microstrip filter can only realize the common Chebyshev filter response, but the present invention can realize the quasi-elliptic with better performance by controlling the electromagnetic hybrid coupling in the main coupling between adjacent microstrip resonators The function filter reduces the number of required resonance units, thereby reducing the size of the filter and reducing the production cost.

2. Compared with the existing cross-coupling filter, the present invention has lower order, smaller volume and more flexible transmission zero setting. A traditional cross-coupling filter needs at least three resonant units to generate a transmission zero; while the present invention only needs one electromagnetic coupling filter unit including two resonant units to generate a transmission zero. The transmission zeros of the cross-coupling filter require an overall design, wherein changes in the position of each transmission zero will cause changes in other transmission zeros, and the position of the transmission zeros is very sensitive to changes in the cross-coupling magnitude; and in the present invention, each transmission The zero points are independently created by a single controllable electromagnetic hybrid coupling unit, so in a high-order hybrid coupling filter, the change of a single transmission zero point will not cause changes in other transmission zero points, and it is easy to achieve an asymmetric filter response.

3. In the present invention, since the resonators are arranged in a straight line, the present invention is more suitable for duplex and multiplexer applications than cross-coupling filters.

4. The present invention can be combined with the existing cross-coupling technology to create a quasi-elliptic function filter with smaller volume and better performance.

5. The present invention can not only be used for traditional planar ordinary metal microstrip filters, but also suitable for manufacturing high-temperature superconducting filters with high quality factors.

Description of drawings

Fig. 1 is the structural representation of a kind of typical microstrip split-ring half-wavelength resonator filter with quasi-elliptic function filtering response in the prior art;

Fig. 2 a is the structural representation of the second-order controllable electromagnetic coupling rectangular microstrip split ring resonator filter adopted in embodiment 1;

Fig. 2 b is the structural representation of the second-order controllable electromagnetic coupling triangular microstrip split ring resonator filter adopted in embodiment 1;

Fig. 3 is the structural representation of the fourth-order controllable electromagnetic coupling rectangular microstrip split ring resonator filter adopted in embodiment 2;

Fig. 4 is the third-order controllable electromagnetic coupling triangular microstrip split-ring resonator filter formed by the second-order controllable electromagnetic coupling triangular microstrip split-ring resonator filter and a stepped impedance microstrip resonator unit used in embodiment 3;

Fig. 5 is a schematic diagram of the electromagnetic simulation curve of the frequency response of the second-order controllable electromagnetic coupling triangular microstrip split-ring resonator filter shown in Fig. 2b, which has a controllable transmission zero point;

Figure 6 is a schematic diagram of the electromagnetic simulation curve and the experimental test curve of the frequency response of the fourth-order controllable electromagnetic coupling rectangular microstrip split-ring resonator filter shown in Figure 3, which has a low-stop band transmission zero point and a high-stop band transmission zero point;

Fig. 7 is a schematic diagram of the electromagnetic simulation curve and the experimental test curve of the frequency response of the third-order controllable electromagnetic coupling triangular microstrip split ring resonator filter shown in Fig. 4, which has a controllable high-stop band transmission zero.

Detailed ways

The present invention will be further described in detail below in conjunction with the embodiments and accompanying drawings.

Example 1

The structure of the second-order controllable electromagnetic coupling microstrip split-ring resonator filter of the present invention is shown in Figure 2a to Figure 2b, wherein Figure 2a is a structural schematic diagram of the second-order controllable electromagnetic coupling rectangular microstrip split-ring resonator filter , FIG. 2b is a schematic structural diagram of a second-order controllable electromagnetic coupling triangular microstrip split ring resonator filter, including two resonators 21, 26, a signal input microstrip line 24 and a signal output microstrip line 25. The effective length of the resonators 21, 26 is half the operating wavelength of the second-order controllable electromagnetic coupling microstrip split ring resonator filter, and an opening 22 is provided at the top of the side adjacent to the coupling side 23 in the resonator 21 , the top of one side adjacent to the coupling side 28 in the resonator 26 is provided with an opening 27, and the positions of the openings 22 and 27 can be adjusted on its side according to the electric and magnetic coupling ratio required by the filter; The positions of 22 and 27 are symmetrical (or approximately symmetrical) relative to the center line of the two coupling sides 23 and 28, and the coupling sides 23 and 28 are composed of high-impedance lines, which is convenient for realizing strong electromagnetic coupling. The shape of the resonators 21, 26 can be rectangular, as shown in Figure 2a, or triangular, as shown in Figure 2b. The two resonators 21 and 26 coupled to each other through controllable electromagnetic coupling constitute a single controllable electromagnetic coupling filter unit, referred to as the electromagnetic coupling filter unit. When the electromagnetic signal passes through any electromagnetic coupling filter unit, a transmission zero point will be generated, and the position of the transmission zero point can be controlled by controlling the proportion of the electromagnetic coupling. At the operating frequency, since there is a strong electric field distribution E near the openings 22 and 27 at the top of the resonators 21, 26, the area between the top openings 22 and 27 of two adjacent resonators 21, 26 forms a strong electric field coupling ; Since the coupling sides 23, 28 of the two resonators 21, 26 are made of high-impedance lines, the area near the high-impedance lines has a stronger magnetic field distribution H, so the coupling sides of the adjacent two resonators 21, 26 The area on one side of 23 and 28 forms a strong magnetic field coupling. Adjusting the positions of the two openings 22 and 27 on their sides, that is, adjusting the relative distance between the two openings can change the ratio of electric coupling and magnetic coupling. The closer the two openings are, the greater the electrical coupling is relative to the magnetic coupling, and vice versa, the greater the magnetic coupling is relative to the electrical coupling. By controlling the electromagnetic coupling ratio between the two resonators 21, 26, the transmission zero point position generated by the electromagnetic coupling filter unit can be controlled to achieve the required quasi-elliptic function filter characteristics. When the relative distance between the two openings is large, the magnetic coupling is greater than the electrical coupling, and the controllable electromagnetic coupling filter unit can realize a transmission zero on the left side of the passband; when the relative distance between the two openings is small, the magnetic coupling is less than When electrically coupled, the controllable electromagnetic coupling filter unit can realize a transmission zero on the right side of the passband.

Using the second-order controllable electromagnetic coupling triangular microstrip split ring resonator filter shown in Figure 2b, when the relative distance between the two openings 22 and 27 is greater than the width of a single resonator, the magnetic coupling is greater than the electrical coupling, The simulated response curve of the controllable electromagnetic coupling filter unit formed by it is shown in the curve 51 in Fig. 5, the controllable electromagnetic coupling filter unit can realize a transmission zero point 52 on the left side of the passband; when two openings 22 and 27 When the relative distance is less than the width of a single resonator, the magnetic coupling is smaller than the electrical coupling, and the simulation response curve of the controllable electromagnetic coupling filter unit formed by it is shown in curve 53 in Figure 5, and the controllable electromagnetic coupling filter unit can be Realize a transmission zero 54 on the right side of the passband; it can be seen that the filter can realize a transmission zero with controllable position.

Example 2

The fourth-order controllable electromagnetic coupling rectangular microstrip split ring resonator filter including two controllable electromagnetic coupling filter units is shown in Figure 3, including four resonators 31-34, signal input microstrip line 24 and signal output microstrip line The strip line 25, the resonators 31 and 32 form a controllable electromagnetic coupling filter unit, the resonators 33 and 34 form another controllable electromagnetic coupling filter unit, and the four resonators 31-34 are arranged in a straight line. The effective lengths of the resonators 31 to 34 are half the working wavelength of the filter, the top of the resonator 31 adjacent to the coupling side 35 is provided with an opening 39, and the side of the resonator 32 adjacent to the coupling side 36 An opening 40 is provided at the top of the top, and the positions of the openings 39 and 40 can be adjusted on the side where the openings 39 and 40 are located according to the electric and magnetic coupling ratios required by the filter. Central symmetry (or approximately symmetry); similarly, an opening 41 is provided at the bottom of the side adjacent to the resonator 33 and the coupling side 37, and an opening is provided at the bottom of the side of the resonator 34 adjacent to the coupling side 38 42. The positions of the openings 41 and 42 can be adjusted on the side where they are located according to the electrical and magnetic coupling ratio required by the filter. The openings 41 and 42 are symmetrical (or approximately symmetrical) to the center line of the two coupling sides 37 and 38 Just); the coupling sides 35-38 are composed of high-impedance lines, which is convenient for realizing strong electromagnetic coupling.

The resonators 31-34 are rectangular in shape, and the simulated and measured response curves of the filter are shown in FIG. 6 . In FIG. 6 , S11 represents the reflection coefficient between the filter input end and the output end, and S21 represents the transmission coefficient between the filter input end and the output end. When the distance between the openings 39 and 40 on the resonators 31 and 32 is approximately greater than the width of a single resonator, the magnetic coupling is greater than the electrical coupling, and the controllable electromagnetic coupling filter unit formed by it realizes the controllable transmission on the left side of the passband Zero point 61; when the distance between the openings 41, 42 on the resonators 33, 34 was approximately less than the width of a single resonator, the magnetic coupling was smaller than the electrical coupling, and the controllable electromagnetic coupling filter unit formed by it realized the right side of the passband Controllable transmission zero point 62. Therefore, the filter has two controllable transmission zeros, one left and one right.

Example 3:

The third-order controllable electromagnetic coupling triangular microstrip split-ring resonator filter comprising a controllable electromagnetic coupling filtering unit is shown in Figure 4, including a ladder impedance resonance unit 43, two triangular split-ring resonators 44, 45, signal The input microstrip line 24 and the signal output microstrip line 25, and two resonators 44, 45 form a controllable electromagnetic coupling filter unit. The effective lengths of the resonators 44 and 45 are half the operating wavelength of the filter, and the top of the adjacent side of the resonator 44 and the coupling side 46 is provided with an opening 48, and the position of the opening 48 can be adjusted according to the electric, The magnetic coupling ratio is adjusted on its side; the top of the resonator 45 adjacent to the coupling side 47 is provided with an opening 49, and the position of the opening 49 can be on its side according to the electric and magnetic coupling ratio required by the filter. Adjustment; the positions of the openings 48 and 49 are symmetrical (or approximately symmetrical) relative to the center line of the coupling sides 46 and 47, and the coupling sides 46 and 47 are composed of high-impedance lines, which is convenient for achieving strong electromagnetic coupling. Resonators 44, 45 are triangular in shape, and the simulation and measured response curves of the filter are shown in Figure 7. In Figure 7, S11 represents the reflection coefficient between the filter input end and the output end, and S21 represents the filter input end The transfer coefficient to the output. When the distance between the openings 48 and 49 of the two resonators 44, 45 is about less than the width of a single resonator, the magnetic coupling is smaller than the electrical coupling, and the controllable electromagnetic coupling filter unit formed by it realizes the controllable transmission zero point on the right side of the passband 71.

The above-described embodiment is a preferred implementation mode of the present invention, but the implementation mode of the present invention is not limited by the above-mentioned embodiment. For example, each controllable electromagnetic coupling filter unit can also interact with a plurality of controllable electromagnetic hybrid coupling filter units. Coupling and working together to form a high-order elliptic function filter with multiple transmission zeros, or coupling with other resonant units and working together to form a high-order elliptic function filter with no less than one transmission zero, etc., Any changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principles of the present invention shall be equivalent replacements and shall be included within the protection scope of the present invention.

Claims (5)

1, a kind of controllable electromagnetic coupling microstrip split-ring resonator filter comprises input microstrip line, output microstrip line and micro-strip resonantor group, it is characterized in that, described micro-strip resonantor group is meant one or more controllable electromagnetic coupling filter units; Described controllable electromagnetic coupling filter unit is made up of two resonators that intercouple, and the effective length of described each resonator is half operation wavelength of described controllable electromagnetic coupling microstrip split-ring resonator filter; In same controllable electromagnetic coupling filter unit, each resonator top or bottom on one side is provided with an opening, aperture position on two resonators is positioned at the top of resonator simultaneously or is positioned at the bottom of resonator simultaneously, the limit at described opening place is adjacent with the coupling edge of two resonators, and the position of two openings is with respect to the center line center symmetry of two coupling edge, and described two coupling edge are made of the high impedance line.

2, controllable electromagnetic coupling microstrip split-ring resonator filter according to claim 1 is characterized in that, described micro-strip resonantor group is meant a controllable electromagnetic coupling filter unit; Described controllable electromagnetic coupling filter unit is made up of two resonators that intercouple, the effective length of described each resonator is half operation wavelength of described controllable electromagnetic coupling microstrip split-ring resonator filter, each resonator top or bottom on one side is provided with an opening, aperture position on two resonators is positioned at the top of resonator simultaneously or is positioned at the bottom of resonator simultaneously, the limit at described opening place is adjacent with the coupling edge of two resonators, and the position of two openings is with respect to the center line center symmetry of two coupling edge, and described two coupling edge are made of the high impedance line.

According to claim 1 or 2 described controllable electromagnetic coupling microstrip split-ring resonator filters, it is characterized in that 3, the resonator in the described micro-strip resonantor group is rectangle resonator or triangle resonator.

According to claim 1 or 2 described controllable electromagnetic coupling microstrip split-ring resonator filters, it is characterized in that 4, the resonator in the described micro-strip resonantor group is along linear array.

According to the described controllable electromagnetic coupling microstrip split-ring resonator filter of claim 3, it is characterized in that 5, the resonator in the described micro-strip resonantor group is along linear array.

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