Wide-stop-band non-reflection double-frequency filter

Abstract

The invention discloses a wide-stop-band reflection-free double-frequency filter, particularly relates to the technical field of microwave communication, and solves the problems that in the prior art, a double-frequency-band filter usually has signal reflection outside a working frequency band, and a small number of reflection-free double-frequency-band or multi-frequency-band filters are often complex in structure and low in cost. The technical problems of large size, poor absorption effect and poor high-stop-band effect of a non-reflection dual-band filter in the prior art, and certain out-of-band rejection performance and insertion loss are sacrificed while the non-reflection dual-band filter pursues the non-reflection characteristic, and particularly, harmonic suppression is poor in a transition area of two frequency bands and a high-stop-band area are solved. According to the technical scheme, a quarter-wavelength coupling microstrip line MCL1 and a quarter-wavelength microstrip line ML2 are connected in series, and a three-quarter-wavelength microstrip line ML1 and a three-quarter-wavelength microstrip line ML2 are introduced and connected in parallel to form a dual-frequency band-pass filtering response; according to the invention, a good full-band absorption effect is achieved, and the frequency selectivity of in-band signals is also enhanced.

Description

Technical Field

[0001] The invention relates to the technical field of microwave communications, and in particular to a wide stopband non-reflection dual-frequency filter. Background Art

[0002] In modern wireless communication systems, filters are key passive components, and their performance is directly related to the quality and transmission efficiency of signals. With the continuous development of wireless communication technology, especially the rise of new generation communication technologies such as 5G and 6G, the performance requirements for filters are increasing. Traditional filters usually produce reflections when processing signals outside the passband, which may not only cause signal distortion, but also cause unnecessary interference within the system. In order to optimize system performance and reduce signal interference, academia and industry have begun to widely study reflectionless filters. This type of filter can absorb frequency signals outside the passband by adding additional absorption circuits, thereby significantly reducing reflections and improving the quality of signal transmission. At present, although the research on reflectionless filters has made significant progress, most research still focuses on a single frequency band, and the stopband and horizontal width are limited. However, with the continuous advancement of wireless communication technology, single-band filters can no longer meet the complex and changing communication needs, and the research on dual-band or even multi-band filters has gradually become a hot topic. On the other hand, wide stopband filters have a wider stopband range and can effectively suppress unwanted signals or interference in a wider frequency range, which helps modern communication systems to flexibly adjust their passband and stopband ranges, optimize the utilization of spectrum resources, improve the spectrum efficiency of communication systems, enhance the electromagnetic compatibility of equipment and reduce the impact of mutual interference.

[0003] Although some studies have involved dual-band or multi-band filters, there are still many challenges in achieving wide stopband and non-reflection performance at the same time. First, the design complexity of dual-band filters is much higher than that of single-band filters. It is necessary to accurately control the frequency response of the two passbands while ensuring that the stopband has sufficient width and attenuation. Secondly, to achieve the non-reflection characteristics of dual-band filters, it is necessary to achieve good matching in multiple passband ranges to reduce reflection and return loss. This requires designers to adopt appropriate matching circuits and structural designs to ensure that the filter can achieve no reflection or low reflection outside multiple wide stopbands and passbands, which undoubtedly greatly increases the complexity and difficulty of the main circuit and the absorption circuit. In addition, under the condition of ensuring the matching of the complex absorption circuit with the dual-band main circuit, achieving effective signal suppression in a wider frequency range and obtaining a wider stopband bandwidth also further increases the design difficulty of the overall circuit.

[0004] Existing dual-band filters usually have reflected signals outside the working band, and a small number of dual-band or multi-band filters with non-reflection often have complex structures, large volumes, poor absorption effects, and poor high-stopband effects. In addition, while pursuing non-reflection characteristics, non-reflection dual-band filters often sacrifice certain out-of-band suppression performance and insertion loss, especially in the transition area between the two bands and the high-stopband area, and have poor harmonic suppression. Summary of the invention

[0005] Therefore, the present invention solves the problems in the prior art that dual-band filters usually have reflected signals outside the working band, and a small number of dual-band or multi-band filters with non-reflection type often have complex structures, large volumes, poor absorption effects, and poor high-stopband effects. In addition, while pursuing non-reflection characteristics, non-reflection dual-band filters often sacrifice certain out-of-band suppression performance and insertion losses, especially in the transition region between the two frequency bands and the high-stopband region, and have poor harmonic suppression. The present invention provides a wide-stopband non-reflection dual-band filter, the circuit of which not only has the characteristics of simple structure, planarization, and easy integration in terms of structure, but also has the advantages of multi-band, full-band non-reflection, and wide stopband, providing a practical solution for reducing system size, improving the integration of RF components, and improving the overall performance of wireless communication systems.

[0006] The present invention provides a wide stopband non-reflection dual-frequency filter, comprising a dual-band filter network, wherein two ends of the dual-band filter network are respectively connected with fan-shaped resonance structures, and one end of the two fan-shaped resonance structures away from the dual-band filter network is respectively connected with an input port and an output port; an absorption network 2 is connected in parallel at the connection between the fan-shaped resonance structure and the dual-band filter network; two groups of absorption networks 1 are connected in parallel inside the dual-band filter network; and the entire dual-band filter circuit with wide stopband and non-reflection characteristics is completely symmetrically distributed on the left and right sides.

[0007] Furthermore, the dual-band filtering network includes a pair of quarter-wavelength coupled microstrip lines MCL1, a quarter-wavelength microstrip line ML2 and a three-quarter-wavelength microstrip line ML1; one end of the first coupled line MCL1a of the coupled microstrip line MCL1 is open, and the other end is connected to the microstrip line ML2; one end of the second coupled line MCL1b of the two groups of coupled microstrip lines MCL1 is respectively connected to the input port and the output port, and the other end is connected to the absorption network 1.

[0008] Furthermore, the absorption network 1 includes a resistor R2, a quarter-wavelength microstrip line ML3 and a half-wavelength microstrip line ML4 which are sequentially connected in series.

[0009] Furthermore, the absorption network 2 includes quarter-wavelength microstrip lines ML5, ML6, ML7 and ML8, and a resistor R1; the microstrip line ML5, the resistor R1 and the microstrip line ML7 are connected in series in sequence, and the end of the microstrip line ML7 away from the resistor R1 is grounded; the microstrip line ML5 is connected to the resistor R1 at a connection point connected to the microstrip line ML6 in parallel, and the microstrip line ML7 is connected to the resistor R1 at a connection point connected to the microstrip line ML8 in parallel.

[0010] Furthermore, the fan-shaped resonant structure includes a first fan-shaped patch pair structure, a third fan-shaped patch pair structure, and a second fan-shaped patch pair structure that are symmetrical in the upper and lower parts; the first fan-shaped patch pair structure and the second fan-shaped patch pair structure are connected at their respective symmetry points; the third fan-shaped patch pair structure is connected through a first microstrip line structure; the first fan-shaped patch pair structure, the second fan-shaped patch pair structure, and the third fan-shaped patch pair structure are connected in series through a second microstrip line structure; and the second microstrip line structure is connected to the third microstrip line structure at both ends. The entire structure is completely symmetrically distributed about the horizontal and vertical axes.

[0011] Furthermore, one terminal of the absorption network is open.

[0012] Furthermore, the filter as a whole includes an upper metal structure, a dielectric substrate, and a lower metal grounding structure arranged up and down in the thickness direction.

[0013] Furthermore, the dielectric substrate is made of RO4003C plate with a relative dielectric constant ε r is 3.55, and the thickness H is 1.524mm.

[0014] Furthermore, the thickness of the upper metal structure and the lower metal grounding structure are both 0.017 mm.

[0015] In the above technical solution, the technical effects and advantages provided by the present invention are:

[0016] 1. A wide stopband non-reflection dual-frequency filter provided by the present invention adopts a pair of quarter-wavelength coupled microstrip lines MCL1 and a quarter-wavelength microstrip line ML2 connected in series, and introduces a three-quarter-wavelength microstrip line ML1 and a microstrip line ML2 in parallel. After the lateral signal interference with an electrical length difference of half a wavelength, in addition to forming a stopband at the center frequency, two transmission zeros can be generated, thereby constructing a dual-band bandpass filter response with good frequency selection characteristics.

[0017] 2. The present invention provides a wide stopband non-reflection dual-frequency filter, which adds two complementary absorption networks 1 and 2 to the circuit, forming three non-reflection areas in three out-of-band signal areas, and ultimately achieving full-band non-reflection characteristics.

[0018] 3. The present invention provides a wide stopband non-reflection dual-frequency filter, in which a complementary absorption network 1 composed of a resistor R2, a microstrip line ML3 and an open branch ML4 is embedded inside the dual-band filter network, so that the reflected signal between the two passbands can be effectively absorbed; and the absorption network 1 can generate a reflection zero point to improve the band-stop characteristics between the two passbands.

[0019] 4. The present invention provides a wide stopband non-reflection dual-frequency filter, in which a complementary absorption network 2 is loaded in parallel at the input / output section of the dual-band filter network N, and can effectively absorb the reflected signals in the low-frequency and high-frequency bands of the two passbands; the absorption network 2 is composed of a quarter-wavelength ML5, a resistor R1 and a quarter-wavelength short-circuit branch M7 connected in series, and a quarter-wavelength open-circuit branch ML6 and ML4 are respectively connected in parallel at both ends of the resistor R1; the absorption network 2 can generate four reflection zeros, which not only achieves good out-of-band signal absorption performance, but also increases the frequency selection characteristics of the two passbands.

[0020] 5. The present invention provides a wide stopband non-reflection dual-frequency filter. The proposed fan-shaped resonant structure is composed of three pairs of fan-shaped patch pairs and a high-impedance microstrip line connected in series. The required cut-off frequency can be achieved by adjusting the angle and radius of the fan-shaped load, the length of the load branch and the distance between the two. While not affecting the reflection-free dual-frequency bandpass filtering characteristics of the main circuit, a good high stopband response is achieved, and the structure is simple, compact and easy to integrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can also be obtained based on these drawings.

[0022] Figure 1 It is a schematic diagram of the circuit framework of the present invention;

[0023] Figure 2 It is a schematic diagram of the circuit structure of the present invention;

[0024] Figure 3 It is a schematic diagram of the fan-shaped resonance structure of the present invention;

[0025] Figure 4 The working principle diagram of the present invention for generating a reflection-free filtering response by loading the absorption network 1 and the absorption network 2, wherein (a) is a schematic diagram of a dual-frequency bandpass filter, (b) is an effect diagram of loading the absorption network 1, and (c) is a response curve diagram of loading the absorption network 1 and the absorption network 2 at the same time;

[0026] Figure 5It is a schematic diagram of circuit parameters of the reflectionless dual-band bandpass filter of the present invention;

[0027] Figure 6 It is a schematic diagram of the dimensions of the fan-shaped resonant structure of the present invention;

[0028] Figure 7 It is a schematic diagram of the layout size of the upper metal structure of the wide stopband non-reflection dual-frequency filter of the present invention;

[0029] Figure 8 A schematic diagram of the cross-sectional structure and dimensions of the wide stopband non-reflection dual-frequency filter of the present invention;

[0030] Fig. 9 The frequency response curve of the dual-frequency bandpass filter with full-band non-reflection function of the present invention;

[0031] Fig.10 It is a comparison diagram of transmission response before and after the fan-shaped resonant structure of the present invention;

[0032] Fig.11 The figure is a frequency response curve diagram of the dual-frequency bandpass filter with full-band non-reflection and wide stopband functions according to the present invention.

[0033] Description of reference numerals:

[0034] 1. Dual-band filtering network; 2. Fan-shaped resonant structure; 3. Absorption network 1; 4. Absorption network 2; 5. Input port; 6. Output port; 10. Upper metal structure; 20. Dielectric substrate; 30. Lower metal grounding structure; 101. First fan-shaped patch pair structure; 102. Second fan-shaped patch pair structure; 103. Third fan-shaped patch pair structure; 104. First microstrip line structure; 105. Second microstrip line structure; 106. Third microstrip line structure. DETAILED DESCRIPTION

[0035] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0036] This embodiment provides a wide stopband non-reflection dual-frequency filter, such as Figure 1As shown. It is mainly composed of a dual-band filter network 1, a pair of absorption networks 1 3, a pair of absorption networks 2 4, a pair of fan-shaped resonant structures 2, an input port 5 and an output port 6. The dual-band filter network 1, a pair of absorption networks 1 3, and a pair of absorption networks 2 4 together form a non-reflective dual-band bandpass filter circuit. The two ends of the non-reflective dual-band bandpass filter circuit are respectively connected to a pair of fan-shaped resonant structures 2, and the other end connected to the fan-shaped resonant structure 2 is respectively connected to the input port 5 and the output port 6 for energy feeding and output. Specifically, the input port 5 is connected to the fan-shaped resonant structure 2, the dual-band filter network 1, the fan-shaped resonant structure 2 and the output port 6 are connected in series in sequence, the fan-shaped resonant structure 2 is connected in parallel with the absorption network 1 3 at the connection between the fan-shaped resonant structure 2 and the input / output port 6, and the dual-band filter network 1 circuit is connected in parallel with two branches, which are connected to the absorption network 1 3. The entire dual-band filter circuit with wide stopband and non-reflective characteristics is completely symmetrically distributed on the left and right.

[0037] Figure 2 for Figure 1 Schematic diagram of the structure of the reflectionless dual-band bandpass filter circuit described in FIG. Figure 2 As shown, the dual-band filtering network 1 is composed of a pair of quarter-wavelength coupled microstrip lines MCL1, a quarter-wavelength microstrip line ML2 and a three-quarter-wavelength microstrip line ML1. The left end of the first coupled line MCL1a of the coupled microstrip line MCL1 is open, and the right end is connected to the microstrip line ML2. The left end of the second coupled line MCL1b of the coupled microstrip line MCL1 is connected to port 1, and the right end of MCL1b is connected to the absorption network 13. The absorption network 13 is composed of a resistor R2, a quarter-wavelength microstrip line ML3 and a half-wavelength microstrip line ML4 connected in series in sequence, and the terminal of the absorption network 13 is open. The absorption network 24 is connected in parallel at the connection between the input port 5 and the coupled microstrip line MCL1. The absorption network 24 is composed of four quarter-wavelength microstrip lines (ML5, ML6, ML7 and ML8) and a resistor R1, wherein the microstrip line ML5, the resistor R1 and the microstrip line ML7 are connected in series in sequence, and the other end of the microstrip line ML7 is grounded. The connection between microstrip line ML5 and resistor R1 is connected in parallel to microstrip line ML6, and the connection between microstrip line ML7 and resistor R1 is connected in parallel to microstrip line ML8. Finally, the above structure is mirrored with the vertical center axis of microstrip line ML2 as the symmetry line to form a completely symmetrical circuit distribution on the left and right, and the input port 5 is mirrored to form the output port 6.

[0038] Figure 3 for Figure 1 Schematic diagram of the fan-shaped resonant structure 2. Figure 3It can be seen that the fan-shaped resonant structure 2 is mainly composed of three pairs of fan-shaped patch pair structures that are symmetrical in the upper and lower parts, namely the first fan-shaped patch pair structure 101, the second fan-shaped patch pair structure 102, and the third fan-shaped patch pair structure 103; the three sections of microstrip line structures are respectively the first microstrip line structure 104, the second microstrip line structure 105, and the third microstrip line structure 106. The first fan-shaped patch pair structure 101 and the second fan-shaped patch pair structure 102 that are symmetrical in the upper and lower parts are connected at the vertex, and the third fan-shaped patch pair structure 103 that is symmetrical in the upper and lower parts is connected through a section of the first microstrip line structure 104. The three pairs of fan-shaped patch pair structures are horizontally distributed along the horizontal symmetry line and are connected in series through the second microstrip line structure 105. The first and last ends of the second microstrip line structure 105 are respectively connected to the third microstrip line structure 106 to form a complete fan-shaped resonant patch pair structure. The entire structure is completely symmetrically distributed about the horizontal and vertical axes.

[0039] Under the condition that the fan-shaped resonant structure 2 is not loaded, the microwave signal is fed from the input port 5, and after the coupled microstrip line passes through the half-wavelength coupled microstrip line MCL1 structure, the signal is divided into two paths, one passing through the microstrip line ML1, and the other passing through the microstrip line structure ML2. Since the electrical lengths of the microstrip line ML1 and the microstrip line ML2 differ by 180°, the high-frequency signal of the center frequency f0 will be offset at the convergence point, so that the bandpass filter response formed by the MWCL1 structure is divided into two, thereby achieving a dual-band filtering effect, and generating two transmission poles in each passband, generating two transmission zeros between the two passbands, and finally outputting from the output.

[0040] To illustrate the working mechanism of the dual-band non-reflection feature, Figure 4 The working principle of generating non-reflection filtering response by loading absorption network 1 3 and absorption network 2 4 is given. Figure 4 a shows the dual-band bandpass filter response when the absorption network 1 3 and the absorption network 2 4 are not loaded. The effect of loading the absorption network 1 3 is shown in Figure 4 As shown in Fig. 2a, the absorption network 3 is a complementary dual stopband structure, and the two transmission zero points are located at (2n+1)f0 (n=0,1,2…), symmetrical about the center frequency f0, conducting outside the center frequency f0 and the upper and lower passbands of the filter, and cutting off at the center frequencies of the upper and lower passbands, and generating a reflection zero point at f0. Therefore, the reflected signal of the stopband part between the two passbands is introduced into the absorption network 3, dissipated by the resistor R2, and a reflection-free characteristic region is formed in the region between the two passbands. Figure 4c is the response curve when the absorption network 13 and the absorption network 24 are loaded at the same time. The loaded complementary absorption network 24 can generate a complementary wide stopband filter with a center frequency of f0, which can introduce the reflected signals of the upper and lower frequency bands of the two passbands into the absorption network 24 circuit to be absorbed by the resistor R1, and finally form two reflection-free areas in the upper and lower frequency bands of the two passbands. And by adjusting the impedance of the microstrip line in the absorption network 24, four reflection zero points can be generated in the full frequency band, two of which are distributed outside the two passbands, effectively improving the out-of-band absorption level, and the other two are distributed at the filtering edge of the large bandwidth filter generated by the coupled microstrip line MWCL1, that is, the left edge of the lower passband and the right edge of the upper passband, which improves the selectivity of signal transmission in the passband. At this point, after passing through the absorption network 13 and the absorption network 24, the reflected signal in the entire frequency band will be completely absorbed, realizing the full-band reflection-free dual-frequency filtering characteristics. Due to the loading of Figure 3 The fan-shaped resonant structure 2 shown has a low-pass response, so it will not affect the full-band reflectionless dual-frequency filtering characteristics of the low-frequency band, but has a good suppression effect on the harmonics of the high-frequency band. Finally, a non-reflective dual-band bandpass filter circuit is loaded between the input / output port as shown in FIG. Figure 3 The fan-shaped resonant structure 2 shown can construct a dual-band filter with wide stopband and non-reflection characteristics.

[0041] The following shows the filter completed according to the above working mechanism and related design guidance, and is simulated and verified. Figure 5 The figure is a parameter diagram of an ideal circuit of a reflectionless dual-band bandpass filter according to the present invention. Its ideal electrical parameters are as follows: θ = 90°, Ze = 113.2Ω, Zo = 59Ω, Z1 = 63.6Ω, Z2 = 64.8Ω, Z3 = 79Ω, Z4 = 47.8Ω, Z5 = 120.7Ω, Z6 = 97.8Ω, Z7 = 34Ω, Z8 = 159Ω, R1 = 68.1Ω, R2 = 127Ω.

[0042] Figure 6 Schematic diagram of fan-shaped resonant structure parameters. The second microstrip line structure 105 has a length of Lss1 and a width of Ws; the radius of the first fan-shaped patch structure 101 is Ls2 and the angle is β; the angle of the third fan-shaped patch structure 103 is θ, the radius is Ls1, and the overlapping length of the third fan-shaped patch structure 103 and the first microstrip line structure 104 is Ws; the length of the first microstrip line structure 104 is Ls4 and the width is WS4; the spacing between the first fan-shaped patch structure 101 and the third fan-shaped patch structure 103 is Lgs12; the width of the third microstrip line structure 106 is W0; the second fan-shaped patch structure 102 is symmetrical to the first fan-shaped patch structure 101.

[0043] Figure 7The schematic diagram of the upper metal structure layout size of a wide stopband non-reflection dual-frequency filter of the present invention. The input feeder and the output feeder have a line width of W0 and a length of Lport; the fan-shaped resonant structure 2 is embedded in the port and is at a distance of IN1 from the starting part of the port; the coupled microstrip line MCL1 has a line width of WCL1, a length of LCL1, and a spacing of S1; the microstrip line ML1 has a line width of W1 and a length of L1; the microstrip line ML2 has a line width of W2 and a length of L2; the microstrip line ML3 has a line width of W3 and a length of L3; the open microstrip line ML4 has a line width of W4 and a length of L4; the microstrip line ML5 has a line width of W5 and a length of L5; the microstrip line ML6 has a line width of W6 and a length of L6; the microstrip line ML7 has a line width of W7 and a length of L7; the microstrip line ML8 has a line width of W8 and a length of L8; and the radius of the metal through hole is Rvia. The specific structural parameters are as follows: W0 = 3.38mm, Lport = 25mm, IN1 = 5mm, IN2 = 1mm, WCL1 = 1.1mm, S1 = 0.66mm, LCL1 = 23.5, W1 = 2.24mm, L1 = 19mm, W2 = 2.16mm, L2 = 72mm, W3 = 1.68mm, L3 = 23mm, W4 = 3.94mm, L4 = 43.1mm, W5 = 0.56mm, L5 = 22.2 mm, W6=0.88mm, L6=24.8mm, W7=6mm, L7=20.2mm, W8=0.17mm, L8=21.8mm, R1=68.1Ω, R2=127Ω; in the fan-shaped resonant structure: WS=0.7mm, β=86°, LS1=4.4mm, Lgs12=6.1mm, θ=48°, LS2=4.1mm, WS4=0.3mm, LS4=1.8mm; LSS1=19mm.

[0044] Figure 8 FIG. 2 is a cross-sectional structural dimension diagram of the filter of the present invention. Figure 8 As shown, in the thickness direction, the overall structure of the filter mainly includes an upper metal structure 10, a lower metal grounding structure 30, a dielectric substrate 20, and a metallized through-hole structure Via opened on the dielectric substrate 20. The dielectric substrate 20 is made of RO4003C sheet material with a relative dielectric constant ε r is 3.55, and the thickness H is 1.524 mm; the thickness of the upper metal structure 10 and the lower metal grounding structure 30 are both 0.017 mm. Dual-band filters with wide stopband and no reflection characteristics in other frequency bands can be obtained by scaling up this embodiment.

[0045] Fig. 9 The frequency response of the non-reflective dual-band bandpass filter without loading the fan-shaped resonator structure 2 is obtained by CST MWS three-dimensional simulation software in this embodiment. And by the formula: Absorption rate AR = 100 × (1-|S 11| 2 -|S 21 | 2 ) obtained the absorption efficiency curve of the absorption network for the signal in the entire frequency band. Fig. 9 It can be seen that the center frequencies of the two frequency bands are 1.45GHz and 2.55GHz, and the corresponding minimum insertion losses in the passbands are 1.52dB and 2.35dB respectively; the reflection coefficient S11 is below -13dB in 0-4.75GHz, and the return losses in the two passbands are 17.1dB and 14.3dB respectively. The four transmission poles in the bands are located at 1.36GHz, 1.49GHz, 2.46GHz and 2.65GHz respectively. Two poles are generated at the left edge of the first passband and the right edge of the second passband, which are located at 1.26GHz and 2.76GHz respectively. Combined with the signal absorption efficiency curve, the signal absorption rates at these two points are 92.4% and 98.7% respectively. In addition, the other two reflection zeros generated by the absorption network 3 are at 0.68GHz and 3.68GHz respectively. The two transmission zeros between the passbands are located at 1.87 GHz and 2.17 GHz, respectively, with signal suppression better than 39.2 dB, and the reflection zero generated by the absorption network 3 is located at 2.25 GHz.

[0046] Fig.10 The figure is a comparison diagram before and after the fan-shaped resonant structure is loaded on the filter of the present invention. It can be seen from the figure that the reflectionless dual-band filter without the fan-shaped resonant structure 2 generates high-order harmonics in the high-frequency band. After the fan-shaped resonant structure 2 is loaded, it has a significant suppression effect on the high-order harmonics. In the range of 4.2GHz to 16GHz, the signal suppression is above 43.3dB, and finally the signal suppression of 6f0 is achieved, and the suppression level is relatively high.

[0047] Fig.11 The S parameter curve and absorption efficiency curve of the filter of the present invention are shown in FIG. Fig.11 It can be seen that the center frequencies of the two passbands are 1.45GHz and 2.55GHz respectively, and the minimum insertion losses in the two passbands are 1.77dB and 2.52dB respectively. The reflection coefficient S11 can be maintained below -12.2dB in the range of 0-4GHz, achieving a reflection-free effect in the full frequency band. In addition, in the three frequency bands of 0-1.27GHz, 1.66-2.36GHz and 2.7-4GHz, the absorption rate of reflected signals exceeds 94%.

[0048] The above description is only by way of illustration of certain exemplary embodiments of the present invention. It is undoubted that those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the above drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A wide stopband non-reflection dual-frequency filter, characterized in that: The invention comprises a dual-band filter network (1), wherein two ends of the dual-band filter network (1) are respectively connected to fan-shaped resonant structures (2), and one end of the two fan-shaped resonant structures (2) away from the dual-band filter network (1) is respectively connected to an input port (5) and an output port (6); an absorption network 2 (4) is connected in parallel at the connection between the fan-shaped resonant structure (2) and the dual-band filter network (1); and two groups of absorption network 1 (3) branches are connected in parallel inside the dual-band filter network (1).

2. The wide stopband non-reflection dual-frequency filter according to claim 1, characterized in that: The dual-band filtering network (1) comprises a pair of quarter-wavelength coupled microstrip lines MCL1, a quarter-wavelength microstrip line ML2 and a three-quarter-wavelength microstrip line ML1; one end of a first coupled line MCL1a of the coupled microstrip line MCL1 is open-circuited, and one end thereof is connected to the microstrip line ML2; one end of a second coupled line MCL1b of the two sets of coupled microstrip lines MCL1 is respectively connected to an input port (5) and an output port (6), and the other end thereof is connected to an absorption network 1 (3).

3. The wide stopband non-reflection dual-frequency filter according to claim 2, characterized in that: The absorption network 1 (3) includes a resistor R2, a quarter-wavelength microstrip line ML3 and a half-wavelength microstrip line ML4 connected in series.

4. The wide stopband non-reflection dual-frequency filter according to claim 3, characterized in that: The absorption network 2 (4) includes a quarter-wavelength microstrip line ML5, a microstrip line ML6, a microstrip line ML7 and a microstrip line ML8, and a resistor R1; the microstrip line ML5, the resistor R1 and the microstrip line ML7 are connected in series in sequence, and the end of the microstrip line ML7 away from the resistor R1 is grounded; the microstrip line ML5 is connected to the resistor R1 at a connection point connected to the microstrip line ML6 in parallel, and the microstrip line ML7 is connected to the resistor R1 at a connection point connected to the microstrip line ML8 in parallel.

5. The wide stopband non-reflection dual-frequency filter according to claim 4, characterized in that: The fan-shaped resonant structure (2) comprises a first fan-shaped patch pair structure (101), a third fan-shaped patch pair structure (103) and a second fan-shaped patch pair structure (102) which are symmetrical in top and bottom; the first fan-shaped patch pair structure (101) and the second fan-shaped patch pair structure (102) are connected at their respective symmetry points; the third fan-shaped patch pair structure (103) is connected via a first microstrip line structure (104); the first fan-shaped patch pair structure (101), the second fan-shaped patch pair structure (102) and the third fan-shaped patch pair structure (103) are connected in series via a second microstrip line structure (105); and the second microstrip line structure (105) is connected to a third microstrip line structure (106) at both ends.

6. The wide stopband non-reflection dual-frequency filter according to claim 5, characterized in that: The fan-shaped resonant structure (2) is symmetrical vertically and horizontally.

7. The wide stopband non-reflection dual-frequency filter according to claim 3, characterized in that: One (3) terminal of the absorption network is open circuit.

8. The wide stopband non-reflection dual-frequency filter according to claim 5, characterized in that: The filter as a whole comprises an upper metal structure (10), a dielectric substrate (20), and a lower metal grounding structure (30) arranged up and down in the thickness direction.

9. The wide stopband non-reflection dual-frequency filter according to claim 8, characterized in that: The dielectric substrate (20) is made of RO4003C plate material, and the relative dielectric constant ε r is 3.55, and the thickness H is 1.524mm.

10. The wide stopband non-reflection dual-frequency filter according to claim 9, characterized in that: The thickness of the upper metal structure (10) and the lower metal grounding structure (30) are both 0.017 mm.

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