CN118676560B - A microstrip bandpass filter with quasi-absorption and arbitrary frequency-variable coupling structure - Google Patents
A microstrip bandpass filter with quasi-absorption and arbitrary frequency-variable coupling structure Download PDFInfo
- Publication number
- CN118676560B CN118676560B CN202410941714.6A CN202410941714A CN118676560B CN 118676560 B CN118676560 B CN 118676560B CN 202410941714 A CN202410941714 A CN 202410941714A CN 118676560 B CN118676560 B CN 118676560B
- Authority
- CN
- China
- Prior art keywords
- microstrip line
- absorption
- quasi
- band
- arbitrary frequency
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
- 230000008878 coupling Effects 0.000 title claims description 66
- 238000010168 coupling process Methods 0.000 title claims description 66
- 238000005859 coupling reaction Methods 0.000 title claims description 66
- 238000010521 absorption reaction Methods 0.000 title claims description 41
- 230000004044 response Effects 0.000 claims description 4
- 230000005540 biological transmission Effects 0.000 description 11
- 210000002445 nipple Anatomy 0.000 description 11
- 238000010586 diagram Methods 0.000 description 8
- 238000013461 design Methods 0.000 description 6
- 230000000052 comparative effect Effects 0.000 description 4
- 230000002238 attenuated effect Effects 0.000 description 3
- 238000004088 simulation Methods 0.000 description 3
- 230000002411 adverse Effects 0.000 description 2
- 230000015556 catabolic process Effects 0.000 description 2
- 238000004891 communication Methods 0.000 description 2
- 238000006731 degradation reaction Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000003780 insertion Methods 0.000 description 2
- 230000037431 insertion Effects 0.000 description 2
- 230000010354 integration Effects 0.000 description 2
- 239000011159 matrix material Substances 0.000 description 2
- 238000012546 transfer Methods 0.000 description 2
- 239000002250 absorbent Substances 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 239000003989 dielectric material Substances 0.000 description 1
- 230000008030 elimination Effects 0.000 description 1
- 238000003379 elimination reaction Methods 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 230000007274 generation of a signal involved in cell-cell signaling Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 230000035699 permeability Effects 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
- H01P1/00—Auxiliary devices
- H01P1/20—Frequency-selective devices, e.g. filters
- H01P1/201—Filters for transverse electromagnetic waves
- H01P1/203—Strip line filters
Landscapes
- Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- Control Of Motors That Do Not Use Commutators (AREA)
Abstract
The invention belongs to the field of microwave filters, and particularly relates to a microstrip line band-pass filter with a quasi-absorption and arbitrary frequency-dependent coupling structure. According to the invention, the filter network with complex transfer functions is formed by commonly coupling the plurality of resonant cavities of the main body parallel coupling microstrip line between the input port and the output port. Each resonant cavity in the parallel coupling structure contributes one transmission extremum, and the quality factor of the filter is improved by superposition of a plurality of extremums. When the signal passes through any frequency-changing structure, the 1/4 wavelength open-circuit microstrip line with two characteristic frequencies f1 and f2 introduces an extra transmission zero point, the attenuation efficiency of the signal out of band is quickened by adjusting f1 and f2, and the passband bandwidth of the invention can be adjusted by changing the coupling coefficient of the parallel coupling microstrip line. The invention has the advantages of both out-of-band reflection absorption and out-of-band attenuation rate, suitability for 5G communication frequency bands, simple design and easy integration.
Description
Technical Field
The invention belongs to the technical field of microwave filters, and particularly relates to a microstrip line band-pass filter with a quasi-absorption and arbitrary frequency-variable coupling structure.
Background
Conventional reflective filters filter unwanted signals in the stop band by providing reactive impedance (the signals to be filtered are reflected back at the reactive impedance to achieve the filtering function), but the reflective nature of the filter may present system level problems in non-linear circuits such as power amplifiers, mixers, etc. to affect the performance of the overall circuit. The reflective nature of the filter may present a system level problem in nonlinear circuits because nonlinear circuits are sensitive to out-of-band impedance, especially at harmonics, so reflective filters may lead to unpredictable system performance degradation (e.g., increased efficiency loss, excessive spurious signal generation, increased dynamic range loss, etc.) due to their reflective nature. Conventional solutions to this problem include the use of attenuators or non-reciprocal components, such as isolators and circulators, to reduce unwanted spurious signal reflections, but such approaches are significantly costly at relatively large signal losses, high costs, difficult volumes to control, and weight of the system.
An absorption filter is adopted to solve the problem that the performance degradation of the whole system can be avoided to the greatest extent. In an absorption filter, the port impedance is well matched both in-band and out-of-band. When the in-band signal passes through the filter with minimal insertion loss, the out-of-band signal is not reflected inside the filter, but is attenuated and may be approximately fully absorbed. Many structures exist for absorption filters, such as the quasi-absorption structure shown in fig. 3, to achieve a better level of reflection properties. The quasi-absorbing structure is described here because its reflected signal, although very small, is not zero, which we consider to be negligible.
While quasi-absorptive structures can avoid the effects of system performance caused by out-of-band reflection, but can result in slow attenuation of the out-of-band of the filter, the prior art mostly reduces such adverse effects by cascading multiple filter units, or mixing other structures such as cavity filters, but it increases adverse factors such as filter area and power consumption while improving out-of-band rejection capability.
Disclosure of Invention
Aiming at the problems or the shortcomings, the invention provides the microstrip line band-pass filter with the quasi-absorption and arbitrary frequency-variable coupling structure, which can meet the higher requirements of 5G communication on the noise elimination in the system and the out-of-band rejection rate of the filter, has simple design and high integration level.
The technical scheme adopted by the invention is as follows:
A microstrip line band-pass filter with quasi-absorption and arbitrary frequency-variation coupling structure comprises an input quasi-absorption microstrip line structure, an output quasi-absorption microstrip line structure, an arbitrary frequency-variation microstrip line structure and a main body parallel coupling microstrip line structure.
The quasi-absorption microstrip line structure is provided with two absorption pup joints for absorbing out-of-band reflection. Each absorption nipple is formed by connecting a matched load resistor and matched impedance, one end of each of the 2 matched load resistors is respectively connected with the left and right ports of the microstrip line on the same side of the parallel coupling microstrip line, the other end of each absorption nipple is connected with the corresponding matched impedance, and the other end of each matched impedance is grounded.
Furthermore, the matching impedance is realized by adopting a microstrip line so as to improve the integration level of the whole device.
The main body parallel coupling microstrip line structure is divided into two identical parts, each part is a cascade n-level parallel coupling microstrip line and is respectively connected with the two ends of any frequency-variable microstrip line structure and the input and output end quasi-absorption microstrip line structure, the n-level parallel coupling microstrip lines cascade from the any frequency-variable microstrip line structure to the two ends are counted, the structural parameters of the two parallel coupling microstrip lines of each level are identical, and therefore the symmetry of the whole structure is met, and n is more than or equal to 2.
Furthermore, the number of the main body parallel coupling microstrip line series n is adjusted according to the performance requirement of the filter, more parallel coupling microstrip lines (the larger the number of the parallel coupling microstrip lines is) are cascaded when the performance requirement is higher, and the cascade number n is calculated by a chebyshev frequency response curve.
The arbitrary frequency type microstrip line structure comprises two 1/4 wavelength microstrip lines (corresponding to two series resonators), two open microstrip line pup joints and an input/output microstrip line coupling part realized by parallel coupling microstrip lines. The input end parallel coupling microstrip line is connected with one port of the first 1/4 wavelength microstrip line, the other port of the first 1/4 wavelength microstrip line is connected with two open microstrip line pup joints and one port of the second 1/4 wavelength microstrip line, the other ends of the two open microstrip line pup joints are open, and the other port of the second 1/4 wavelength microstrip line is connected with the output end parallel coupling microstrip line.
Furthermore, the two open microstrip line pups adopt open 1/4 wavelength microstrip lines, the characteristic frequencies of the two open microstrip line pups are f1 and f2, and the characteristic frequencies are determined by the passband width and the out-of-band attenuation requirements of the filter.
Further, the characteristic frequency of the 1/4 wavelength microstrip line is adjusted by microstrip line dimension parameters.
The principle of the invention is that the parallel coupling microstrip line structure forms a filter network with complex transfer function by commonly coupling a plurality of resonant cavities (main body parallel coupling microstrip lines) between an input port and an output port. Each resonant cavity in the parallel coupling structure contributes one transmission extremum, and superposition of a plurality of extremums improves the quality factor of the filter. The signal is input from the input port of the first-stage parallel coupling microstrip line, and the signal to be filtered usually generates reflection at the port. Similarly, the reflection generated by the signal as it passes through the output port is also attenuated by the absorption nipple. The signals are processed by the main body parallel coupling microstrip line structure in the filter main body, when the signals pass through any frequency-changing structure, additional transmission zero points are introduced by two 1/4 wavelength open-circuit microstrip lines with characteristic frequencies f1 and f2, and the attenuation efficiency of the signals outside the band can be accelerated by adjusting f1 and f2 to proper positions outside the passband (generally arranged in band-stop areas at two sides of the passband and specifically determined by the passband frequency). The characteristic frequency can be adjusted through the width and the length of the open-circuit microstrip line, so that the characteristic of adjustable arbitrary frequency is achieved. And the passband bandwidth of the invention can also be adjusted by changing the coupling coefficient of the parallel coupling microstrip line.
Compared with the traditional microstrip filter, the parallel coupling microstrip filter has the advantages that not only can the higher quality factor and narrower passband and stopband width be realized, but also the self-adaptive adjustment and multi-mode selection can be realized by changing the parameters such as the width, the length, the shape and the like of the microstrip, and the characteristic impedance of the microstrip filter can be adjusted and controlled by the geometric dimension of the microstrip and the dielectric constant of a dielectric material. The quasi-absorption structure can avoid the influence of system performance caused by out-of-band reflection by absorbing noise signals in the system instead of reflection, but can lead to slow out-of-band attenuation of the filter, so that any frequency-variable coupling structure is introduced to accelerate the out-of-band attenuation rate, thereby not only absorbing out-of-band reflection, avoiding the influence of out-of-band reflection, but also rapidly attenuating out-of-band signals outside the passband.
In summary, the invention has the advantages of (1) absorbing most out-of-band reflection signals, avoiding system problems caused by out-of-band reflection, improving out-of-band attenuation rate obviously while improving out-of-band reflection absorption capacity, (2) being adjustable in out-of-band transmission zero point, having design flexibility, being applicable to different bandwidth ranges and being applied to most 5G communication frequency bands, and (3) being good in circuit structure symmetry, small in size, good in compatibility, easy to integrate, simple in design and easy to manufacture.
Drawings
FIG. 1 is a schematic diagram of a parallel coupled microstrip filter according to a comparative example;
FIG. 2 is a graph of simulation results for a comparative example filter;
FIG. 3 is a schematic diagram of a quasi-absorptive microstrip line structure according to the present invention;
FIG. 4 is a schematic diagram of an arbitrary frequency-variant microstrip line structure according to the present invention;
FIG. 5 is a practical structure diagram of an arbitrary frequency type microstrip line structure of the present invention;
FIG. 6 is a schematic diagram of a filter according to an embodiment;
Fig. 7 is a diagram showing simulation results of the filter according to the embodiment.
Detailed Description
The invention is described in further detail below with reference to the drawings and examples.
The parallel coupling microstrip line structure in this embodiment has symmetry, and the specific structure is shown in fig. 6, and considering that the filter formed by the single-stage parallel coupling microstrip line has insufficient performance, a multi-stage parallel coupling microstrip line structure is adopted, and the parameter calculation theory is as follows:
normalized frequency:
The parallel coupling microstrip line order which is actually needed can be obtained by combining the equation with the Chebyshev frequency response curve. In the formula, omega is a normalized frequency, f 0 is a center frequency, f H is a passband high-frequency cutoff frequency, and f L is a passband low-frequency cutoff frequency.
Normalized bandwidth:
microstrip line odd-even mode impedance:
Zo|i,i+1＝Z0[1-Z0Ji,i+1+(Z0Ji,i+1)2]
ZE|i,i+1＝Z0[1+Z0Ji,i+1+(Z0Ji,i+1)2]
The odd-even mode impedance of each stage of parallel coupling microstrip line can be calculated through the above formula, and then the actual size parameter of each stage of microstrip line can be calculated according to LINECALE in the ADS tool. In the formula, omega H is an upper limit frequency, omega L is a lower limit frequency, omega 0 is a center frequency, Z o is an odd mode characteristic impedance, Z E is an even mode characteristic impedance, Z 0 is a characteristic impedance of a microstrip line, and J i,i+1 is a coupling coefficient between adjacent microstrip lines.
The quasi-absorption microstrip line structure adopted in this embodiment is shown in fig. 3, each quasi-absorption structure contains two absorption nipple segments, each absorption nipple segment is formed by connecting a load resistor with a microstrip line, the two nipple segments are respectively loaded at two ends of a parallel coupling microstrip line, and the load resistor and microstrip line parameters are mainly calculated by the following formula:
the parameters involved in the formula include: is the four-port S parameter of a quasi-absorbent structure, For the equivalent impedance of the absorption nipple, M, N is an intermediate variable related to the coupling microstrip line parameter, R is the load resistance on the nipple, Z s is the microstrip line characteristic impedance, and θ is the absorption nipple electrical length.
The principle diagram of any frequency-variable coupling microstrip line structure in this embodiment is shown in fig. 4, the basic core is the relationship between the zero and the pole of the short-circuit admittance or scattering parameter of the filter network and the characteristic values of the coupling matrix and the two main matrices thereof, and the two parallel impedances in the principle diagram of fig. 4 can be realized as a distributed element circuit network composed of the following elements by the coupling matrix parameter, as shown in fig. 5, two 1/4 wavelength open transmission lines correspond to two series resonators, two open microstrip line pup joints, and an input/output microstrip line coupling part realized by parallel coupling microstrip lines. The two 1/4 wavelength microstrip lines can generate transmission zero points at the characteristic frequencies f1 and f2 respectively, and can correspond to left and right zero points required in the design of the band-pass microstrip line filter. The impedance is calculated by the following formula:
The complete circuit structure of the embodiment is shown in figure 6, wherein the two sides of a parallel coupling microstrip line of a first stage of a main body parallel coupling microstrip line are connected with quasi-absorption microstrip line pup joints of an input end, the two sides of a microstrip line of a last stage of the main body parallel coupling microstrip line are connected with quasi-absorption microstrip line pup joints of an output end, each absorption pup joint is formed by connecting a matched load resistor and a microstrip line, one end of each absorption pup joint is connected with the side of the parallel coupling microstrip line, the other end of each absorption pup joint is grounded, the parallel coupling line of the input end and the output end of a distributed element of any frequency-changing structure can be equivalently two stages of parallel coupling microstrip lines in the main body, the parallel coupling microstrip line of the input end is described from left to right, the parallel coupling microstrip line of the input end is connected with a left port of a first 1/4 wavelength microstrip line, the right port of the first 1/4 wavelength microstrip line is connected with the left port of two open microstrip line pup joints and a second 1/4 wavelength microstrip line, the other end of the two open microstrip line pup joints is opened, and the right port of the second 1/4 wavelength microstrip line is connected with the microstrip line of the output end. The parallel coupling microstrip line of the input end and the output end of the part is the middle two stages of the parallel coupling microstrip line of the main body.
In the method, signals are input through an input port of a first-stage parallel coupling microstrip line, frequency components in a passband are coupled to a next-stage microstrip line, most of the frequency components outside the passband are blocked, partial reflection signals enter a quasi-absorption nipple of the input end and are absorbed through matching load and microstrip line impedance consumption, the entered signals are further filtered in a subsequent parallel coupling microstrip line, when the signals reach an arbitrary frequency-changing structure, out-of-band signals are further accelerated to attenuate through two transmission zero points introduced by the arbitrary frequency-changing structure, when the signals reach an output port, the frequency components in the passband are output through an output port of the last-stage parallel coupling microstrip line, and residual reflection signals are absorbed by the quasi-absorption nipple connected with the output end.
The PCB circuit board adopted in the simulation of the embodiment is Rogers5880, the dielectric constant Er is 2.2, the magnetic permeability Mur is 1, the thickness H of the board is 1.6mm, the thickness T of the metal layer is 0.035mm, and the loss angle TanD is 0.0009. Wherein Rogers5880 is a commonly used high frequency circuit board. The comparative example uses the same material. The matching load resistor of this embodiment has a resistance of 40Ω (which can be adjusted according to passband requirements).
The result obtained by simulating the circuit (comparative example) shown in fig. 1 by the radio frequency simulation software ADS is shown in fig. 2, and the result obtained by simulating the circuit shown in fig. 6 is shown in fig. 7. Wherein S11 and S21 are filter characteristic parameters, S11 is filter return loss, and S21 is filter insertion loss. The characteristic curve reflects the in-band and out-of-band performance of the filter.
As can be seen from the S (2, 1) curve in FIG. 2, the single parallel coupling microstrip line band-pass filter has larger in-band ripple and slower out-of-band attenuation, and cannot achieve attenuation of at least 30dB at the center frequency of plus or minus 0.6GHz, so that the performance is poor. As can be seen from the S (2, 1) curves in FIG. 7, the added open-ended microstrip line in the parallel coupled microstrip line successfully generates two transmission zeros at the positions of f1 and f2 on both sides of the center frequency, so that the attenuation of approximately 35dB can be achieved at the positions of plus or minus 0.6GHz of the center frequency, the attenuation is deep at 3.15GHz and 4.35GHz, the attenuation exceeds 200dB, the selectivity is extremely high, the attenuation of 50dB can be maintained in a larger stop band range, the typical design requirement is only more than 30dB, the ripple coefficient is basically not generated in the pass band within a controllable range, and the pass band response is excellent. The S (1, 1) reflection curve shows that the structure of the embodiment of the invention basically has no reflection or smaller reflection (the return loss of most areas is more than 20 dB) in the range of 3.3 GHz-4.2 GHz of the passband, and the S11 curve is close to 0dB outside the passband, so that the out-of-band rejection performance of the filter can be considered as an ideal state.
As can be seen from the above embodiments, the present invention forms a filter network with complex transfer functions by commonly coupling a plurality of resonators of a main body parallel-coupled microstrip line between an input port and an output port. Each resonant cavity in the parallel coupling structure contributes one transmission extremum, and the quality factor of the filter is improved by superposition of a plurality of extremums. The signals are attenuated and filtered to reflect signals through a quasi-absorption microstrip line structure at the input end and the output end; when signals are processed in the filter main body by the main body parallel coupling microstrip line structure and pass through any frequency-changing structure, two 1/4 wavelength open-circuit microstrip lines with characteristic frequencies f1 and f2 introduce additional transmission zero points, the attenuation efficiency of the signals outside the passband can be accelerated by adjusting the f1 and f2 to proper positions outside the passband, and the passband bandwidth of the filter can be adjusted by changing the coupling coefficient of the parallel coupling microstrip lines. The out-of-band transmission zero is adjustable, the design flexibility is high, the out-of-band transmission zero is suitable for different bandwidth ranges, the out-of-band attenuation rate can be obviously improved, and the out-of-band attenuation rate is improved.
Claims (5)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202410941714.6A CN118676560B (en) | 2024-07-15 | 2024-07-15 | A microstrip bandpass filter with quasi-absorption and arbitrary frequency-variable coupling structure |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202410941714.6A CN118676560B (en) | 2024-07-15 | 2024-07-15 | A microstrip bandpass filter with quasi-absorption and arbitrary frequency-variable coupling structure |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN118676560A CN118676560A (en) | 2024-09-20 |
| CN118676560B true CN118676560B (en) | 2025-01-24 |
Family
ID=92732421
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202410941714.6A Active CN118676560B (en) | 2024-07-15 | 2024-07-15 | A microstrip bandpass filter with quasi-absorption and arbitrary frequency-variable coupling structure |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN118676560B (en) |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN203039052U (en) * | 2013-01-04 | 2013-07-03 | 成都信息工程学院 | Parallel-coupled microstrip filter |
| CN112909461A (en) * | 2021-01-25 | 2021-06-04 | 北京邮电大学 | Complementary duplex structure full-band absorption dual-frequency band-pass filter |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2008160437A (en) * | 2006-12-22 | 2008-07-10 | Oki Electric Ind Co Ltd | Bandpass filter and its manufacturing method |
| JP4784836B2 (en) * | 2007-06-05 | 2011-10-05 | 独立行政法人情報通信研究機構 | Band pass filter |
| CN105552493B (en) * | 2016-01-26 | 2018-10-26 | 电子科技大学 | The Direct Method of Design of Coupled Miccrostrip Lines bandpass filter |
| CN117712649A (en) * | 2022-09-07 | 2024-03-15 | 南京理工大学 | A microstrip bandpass filter with impedance conversion function |
| CN116487858A (en) * | 2022-12-09 | 2023-07-25 | 大连海事大学 | Broadband filtering power divider with non-reflection input port |
-
2024
- 2024-07-15 CN CN202410941714.6A patent/CN118676560B/en active Active
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN203039052U (en) * | 2013-01-04 | 2013-07-03 | 成都信息工程学院 | Parallel-coupled microstrip filter |
| CN112909461A (en) * | 2021-01-25 | 2021-06-04 | 北京邮电大学 | Complementary duplex structure full-band absorption dual-frequency band-pass filter |
Also Published As
| Publication number | Publication date |
|---|---|
| CN118676560A (en) | 2024-09-20 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN103259501B (en) | A kind of band elimination filter for communication system | |
| CA2178727C (en) | Microwave filter | |
| CN115882813A (en) | Based on surface acoustic wave-lumped element combination syntonizer and band-pass filter | |
| CN118676560B (en) | A microstrip bandpass filter with quasi-absorption and arbitrary frequency-variable coupling structure | |
| CN111740192B (en) | Substrate integrated waveguide filter loaded by interdigital structure | |
| CN113346861B (en) | Bandwidth-adjustable reflection-free filter of full-open branch transmission line | |
| CN113381143B (en) | A kind of microstrip low-pass filter and transmission zero point determination, frequency setting method | |
| CN114826187A (en) | Filter and electronic device | |
| CN113346868A (en) | Surface acoustic wave filter | |
| CN104009271B (en) | Planar band-pass filter based on four cascaded resonators | |
| CN209948009U (en) | Reflection-free band-pass filter and radio frequency communication equipment | |
| CN101217210B (en) | Three-band Filter Based on Parallel Coupled Line Structure | |
| CN111725596A (en) | High-performance three-mode filtering power divider and design method thereof | |
| CN115275545B (en) | A compact absorptive filter power splitter | |
| CN217114739U (en) | Miniaturized ultra wide band pass filter | |
| CN110676543A (en) | A coupled-line externally loaded low-pass and band-reject microwave transmission line filter with reconfigurable transmission response | |
| CN117254228A (en) | Reflection-free waveguide band-pass filter based on 3dB orthogonal coupler | |
| CN113067112B (en) | Ultra-wide stopband high-temperature superconducting low-pass filter with closed-loop cross-coupling microstrip structure | |
| CN110707401B (en) | A coupled line-loaded low-pass or band-stop filter with reconfigurable transmission response | |
| CN222463392U (en) | Broadband terahertz waveguide band-pass filter with high out-of-band rejection | |
| CN112332053A (en) | Wide-stopband filtering power divider | |
| CN203871449U (en) | Planar band pass filter based on concatenation of four resonators | |
| CN221841986U (en) | A topological structure, filter and communication device | |
| CN221508452U (en) | Filter and communication equipment | |
| CN115295992B (en) | Waveguide low-pass filter with high frequency selectivity |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |