阅读说明：本技术 工作频段可调的4通带滤波器 (4-passband filter with adjustable working frequency band ) 是由 王韧 于 2021-11-23 设计创作，主要内容包括：本发明公开了一种工作频段可调的4通带滤波器,包括中间微带线和位于中间微带线两侧的两个阶跃阻抗谐振器,阶跃阻抗谐振器均为E型微带结构；所述中间微带线中间断开,E型微带结构的中部微带线两侧分别设有竖直微带线,E型微带结构的开口朝向中间微带线,E型微带结构的中部微带线位于中间微带线中间的断开处。本发明提供了一种可实现4个通带的带通微带滤波器,分别由两个位于输入和输出端两侧的尺寸不同的E型SIR构成,每个E型SIR和同侧的交叉耦合线均可组成两个通带,因此该结构可以实现2组低频和高频的4个通带,通带频段由谐振环尺寸和交叉耦合线尺寸共同决定。(The invention discloses a 4-passband filter with an adjustable working frequency band, which comprises a middle microstrip line and two step impedance resonators positioned at two sides of the middle microstrip line, wherein the step impedance resonators are all E-shaped microstrip structures; the middle of the middle microstrip line is disconnected, vertical microstrip lines are arranged on two sides of the middle microstrip line of the E-shaped microstrip structure respectively, an opening of the E-shaped microstrip structure faces the middle microstrip line, and the middle microstrip line of the E-shaped microstrip structure is located at the disconnection position in the middle of the middle microstrip line. The invention provides a band-pass microstrip filter capable of realizing 4 pass bands, which is respectively composed of two E-shaped SIRs with different sizes positioned at two sides of an input end and an output end, wherein each E-shaped SIR and a cross coupling line at the same side can form two pass bands, so that the structure can realize 4 pass bands with 2 groups of low frequencies and high frequencies, and the pass band is jointly determined by the size of a resonance ring and the size of the cross coupling line.)

1. The 4-passband filter with the adjustable working frequency band is characterized by comprising a middle microstrip line and two step impedance resonators positioned on two sides of the middle microstrip line, wherein the step impedance resonators are all of an E-shaped microstrip structure; the middle of the middle microstrip line is disconnected, vertical microstrip lines are arranged on two sides of the middle microstrip line of the E-shaped microstrip structure respectively, an opening of the E-shaped microstrip structure faces the middle microstrip line, and the middle microstrip line of the E-shaped microstrip structure is located at the disconnection position in the middle of the middle microstrip line;

two ends of the middle microstrip line are respectively used as a common input end and an output end of the two step impedance resonators; the vertical microstrip line is used as a cross-coupling microstrip line, one end of the vertical microstrip line, which is close to the middle microstrip line, is provided with an opening, the openings are respectively positioned at two ports at the middle break-off position of the middle microstrip line, and the cross-coupling microstrip line is connected with or disconnected from the middle microstrip line through the openings.

2. The 4-passband filter with the adjustable operating frequency band according to claim 1, wherein the two E-shaped microstrip structures have different sizes; when the cross-coupling microstrip line of the large E-shaped microstrip structure is connected with the middle microstrip line and the cross-coupling microstrip line of the small E-shaped microstrip structure is disconnected with the middle microstrip line, two pass bands of a low frequency band are formed; otherwise, two pass bands of a high frequency band are formed; or the cross coupling line microstrip line of the E-shaped microstrip structure is simultaneously connected with the middle microstrip line, so that 4 pass bands can work simultaneously.

Technical Field

The invention relates to a 4-passband filter with an adjustable working frequency band.

Background

With the continuous development of communication systems, the requirements on microstrip filters are higher and higher, and the performance of the microstrip filters can directly affect the quality of the whole communication system. In a general dual-band or multi-band wireless communication system, each band uses a set of independent electronic components such as an antenna, a filter, an amplifier and the like. The design of the current dual-band or multi-band filter mainly comprises the following five methods:

1. the filters are combined in parallel, namely two band-pass filters with different main frequencies are connected in parallel, and the two band-pass filters respectively have own input ports and output ports.

2. The prototype filter conversion, i.e. the known values of the prototype circuit parameters, obtains the required circuit parameters by conversion between them.

3. The parasitic pass band of the coupled resonator is exploited.

4. The zero point and the pole point are integrated, and two methods are mainly used, namely a method for generating a transmission zero point in a circuit by utilizing the characteristic of a band stop structure; the other is a systematic functional synthesis method in which the response curves of a given filter are synthesized by the zero-pole position of the filter.

5. Two filter circuits are integrated together by using LTCC (Low-Temperature Co-fired Ceramics) technology to manufacture a three-dimensional circuit substrate, and an IC and an active device can be integrated on the surface of the three-dimensional circuit substrate.

Because the development trend of wireless communication systems is miniaturization, low power consumption and high stability, in a dual-band or multi-band wireless communication system, the volume, weight and power consumption of the whole communication system can be greatly increased by using a set of independent electronic components such as an antenna, a filter and an amplifier on each frequency band, and the stability of the whole system operation can be reduced by a plurality of elements such as the antenna, the filter and the amplifier. However, the 5 methods commonly used at present have certain disadvantages, for example, two filters operating at a single frequency are connected in parallel, two bandpass filters have their own input port and output port respectively, and the system needs input and output of a single port, so that the two filters need to share the input and output ports, which causes the problem of port impedance mismatch, and an input impedance matching circuit needs to be added at the input end, which increases the size of the filter and causes excessive loss. Although the prototype filter transform is simpler in design, when the distance between two pass bands is close, the rejection capability of the stop band is poor. The center frequency of the parasitic passband of the coupling resonator is usually two to three times of the center frequency of the main frequency passband, so the method is more suitable for the occasions with larger difference of the two passband frequencies. In the zero and pole synthesis method, the transmission zero is generated inside the pass band, and the same is true for the zero and pole position synthesis method, so the zero and pole synthesis method is more suitable for the situation that the difference of the main frequencies of two or more required pass bands is small. LTCC technology, however, can increase design and processing difficulties.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provides a band-pass microstrip filter capable of realizing 4 pass bands, which is respectively composed of two E-shaped SIRs with different sizes positioned at two sides of an input end and an output end, wherein each E-shaped SIR and a cross coupling line at the same side can form two pass bands, so that the structure can realize 4 pass bands with 2 groups of low frequencies and high frequencies, and the pass band is jointly determined by the size of a resonance ring and the size of the cross coupling line.

The purpose of the invention is realized by the following technical scheme: the 4-passband filter with the adjustable working frequency band comprises a middle microstrip line and two step impedance resonators which are positioned on two sides of the middle microstrip line, wherein the step impedance resonators are all of an E-shaped microstrip structure; the middle of the middle microstrip line is disconnected, vertical microstrip lines are arranged on two sides of the middle microstrip line of the E-shaped microstrip structure respectively, an opening of the E-shaped microstrip structure faces the middle microstrip line, and the middle microstrip line of the E-shaped microstrip structure is located at the disconnection position in the middle of the middle microstrip line;

two ends of the middle microstrip line are respectively used as a common input end and an output end of the two step impedance resonators; the vertical microstrip line is used as a cross-coupling microstrip line, one end of the vertical microstrip line, which is close to the middle microstrip line, is provided with an opening, the openings are respectively positioned at two ports at the middle break-off position of the middle microstrip line, and the cross-coupling microstrip line is connected with or disconnected from the middle microstrip line through the openings.

Further, the two E-shaped microstrip structures have different sizes; when the cross-coupling microstrip line of the large E-shaped microstrip structure is connected with the middle microstrip line and the cross-coupling microstrip line of the small E-shaped microstrip structure is disconnected with the middle microstrip line, two pass bands of a low frequency band are formed; otherwise, two pass bands of a high frequency band are formed; or the cross coupling line microstrip line of the E-shaped microstrip structure is simultaneously connected with the middle microstrip line, so that 4 pass bands can work simultaneously.

The invention has the beneficial effects that: the invention provides a band-pass microstrip filter capable of realizing 4 passbands, wherein the 4 passbands can be divided into two groups of low frequency and high frequency, and respectively consist of two E-type Step Impedance Resonators (SIRs) with different sizes positioned at two sides of an input end and an output end. The two SIR structures use the same input and output port, and cross-coupled microstrip lines are loaded on two sides of the input and output ports and are coupled with the two E-shaped SIR structures. The cross coupling microstrip line is provided with openings, the coupling with the E-shaped SIR structure with different sizes at two sides can be realized by selectively connecting or disconnecting the openings at two sides, the selection between two groups of working frequency bands of low frequency and high frequency is realized, the openings at two ends on the cross coupling line can be simultaneously connected, and the simultaneous working of 4 passbands is realized.

Drawings

FIG. 1 is a schematic diagram of a 4-pass band filter according to the present invention;

FIG. 2 is a schematic view of an E-type microstrip structure according to the present invention;

fig. 3 is a schematic diagram of a common input/output microstrip line and cross-coupled lines on both sides according to the present invention;

FIG. 4 is a side view of a 4-pass band filter of the present invention;

fig. 5 is a graph of S-parameter of 4 pass bands formed in the present embodiment.

Description of reference numerals: 1, 2-shared input end and output end, 3,4-E type microstrip structure, 5-middle microstrip line, 6, 8-cross coupling line, 7, 9-cross coupling line opening, 10-dielectric plate and 11-metal grounding plate.

Detailed Description

The technical scheme of the invention is further explained by combining the attached drawings.

As shown in fig. 1, 2 and 3, the 4-passband filter with adjustable operating frequency band of the present invention includes a middle microstrip line 5 and two Stepped-Impedance resonators (SIR) 3 and 4 located at two sides of the middle microstrip line, where the Stepped-Impedance resonators are all E-type microstrip structures; the middle of the middle microstrip line is disconnected, vertical microstrip lines 6 and 7 are respectively arranged on two sides of the middle microstrip line of the E-shaped microstrip structure, the opening of the E-shaped microstrip structure faces the middle microstrip line, and the middle microstrip line of the E-shaped microstrip structure is positioned at the disconnection position in the middle of the middle microstrip line;

two ends 1 and 2 of the middle microstrip line are respectively used as a common input end and an output end of the two step impedance resonators; the vertical microstrip line is used as a cross-coupling microstrip line, one end of the vertical microstrip line, which is close to the middle microstrip line, is provided with openings 8 and 9, the openings are respectively positioned at two ports at the middle break-off position of the middle microstrip line, and the cross-coupling microstrip line is connected with or disconnected from the middle microstrip line through the openings.

The 4-passband filter is positioned above the dielectric plate 10, and the back of the dielectric plate 10 is provided with a metal grounding plate 11.

The two E-shaped microstrip structures have different sizes; when the cross-coupling microstrip line of the large E-shaped microstrip structure is connected with the middle microstrip line and the cross-coupling microstrip line of the small E-shaped microstrip structure is disconnected with the middle microstrip line, two pass bands of a low frequency band are formed; otherwise, two pass bands of a high frequency band are formed; the opening on the two sides can be selectively disconnected or connected to select which group of band-pass filters to work, or the cross-coupled line microstrip line of the E-type microstrip structure is simultaneously connected with the middle microstrip line, so that 4 pass bands can work simultaneously.

The two E-shaped microstrip structures are formed by connecting a plurality of microstrip lines with different characteristic impedances in series, and an equivalent diagram is shown in fig. 4. The middle microstrip line is equivalent to the middle transverse microstrip line of the E-shaped microstrip structure, and the corresponding electrical length is 2 theta₁The corresponding characteristic impedance is Z₁(ii) a The microstrip lines at two ends are respectively equivalent to the microstrip lines at two vertical ends of the microstrip structure, and the corresponding electrical lengths are respectively theta₂Corresponding to a characteristic impedance of Z₂(ii) a The microstrip line in the middle of the E-shaped microstrip structure is an additional structure, and the purpose is to form a coupling effect with the vertical microstrip lines on the two sides; impedance ratio of K ═ Z₂/Z₁The E-type microstrip structure is considered to be three two-port network cascades, and the input end admittance is as follows:

Y₂is theta₂Admittance of microstrip lines, i.e. Z₂The reciprocal of (a);

when Y is_inWhen 0, the resonance condition is obtained: obtaining K ═ tan theta according to formula (1)₁·tanθ₂；

Let θ₁＝θ₂Then the length of the two end portions of the E-type microstrip structure should be equal to θThe middle portion length is 2 theta; and at this time the input admittance of equation (1) becomes:

each cross-coupling structure and the structure formed by the middle microstrip line can provide 3 transmission zeros: the middle microstrip line is connected with any upward or downward cross-coupled line, for example, the middle microstrip line is connected with two upward cross-coupled lines, when the rest structures (including an upper E-shaped microstrip structure and a lower E-shaped microstrip structure) are completely removed, the 1-port input and the 2-port output can form the phenomenon that 3 frequency points have no output, and 3 transmission zero points are formed. The two cross-coupled wires are equivalent to loading branch wires and play an inductive role. The gaps between the coupling lines are equivalent to capacitors, and jointly form a parallel inductance-capacitance structure, so that the filtering function of 3 frequency points is realized, and the corresponding three resonances are f₂、f₃And f₄。

Let the fundamental resonance frequency of the E-type microstrip structure be f₁The first three higher order resonances are f₂、f₃And f₄Corresponding electrical lengths are respectively theta₂、θ₃And theta₄When the resonance condition Y is satisfied_inWhen 0, obtained from formula (2):

Ktanθ₂＝∞

tan²θ₃-K＝0 (3)

tanθ₄＝0

obtained by the formula (3):

then there are:

according to the equation (5), the position of the high-order resonance frequency of the SIR structure depends on the impedance ratio K, and the impedance ratio K can be adjusted by adjusting the sizes of the two ends and the middle of the SIR structure shown in fig. 1, so that the adjustment of the resonance frequency point can be realized by adjusting the size of the SIR structure.

Fig. 5 is a graph of S-parameters of 4 pass bands formed in the present embodiment, wherein (a) is a graph of S-parameters of two low-frequency pass bands formed when only the large E-type microstrip structure connected with the upper cross coupling is formed; (b) in order to connect only the cross coupling at the lower part, when the small E-shaped microstrip structure, the S parameter curve graphs of two high-frequency pass bands are formed.

It will be appreciated by those of ordinary skill in the art that the embodiments described herein are intended to assist the reader in understanding the principles of the invention and are to be construed as being without limitation to such specifically recited embodiments and examples. Those skilled in the art can make various other specific changes and combinations based on the teachings of the present invention without departing from the spirit of the invention, and these changes and combinations are within the scope of the invention.