CN116454573A - Compact double-end absorption band-pass filter - Google Patents
Compact double-end absorption band-pass filter Download PDFInfo
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- CN116454573A CN116454573A CN202310494401.6A CN202310494401A CN116454573A CN 116454573 A CN116454573 A CN 116454573A CN 202310494401 A CN202310494401 A CN 202310494401A CN 116454573 A CN116454573 A CN 116454573A
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- 230000005540 biological transmission Effects 0.000 claims abstract description 16
- 230000002745 absorbent Effects 0.000 claims description 7
- 239000002250 absorbent Substances 0.000 claims description 7
- 239000006096 absorbing agent Substances 0.000 claims description 5
- 238000001914 filtration Methods 0.000 abstract description 2
- 230000008878 coupling Effects 0.000 description 7
- 238000010168 coupling process Methods 0.000 description 7
- 238000005859 coupling reaction Methods 0.000 description 7
- 238000004891 communication Methods 0.000 description 2
- 238000013461 design Methods 0.000 description 2
- 239000011159 matrix material Substances 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 238000000034 method Methods 0.000 description 2
- 238000004088 simulation Methods 0.000 description 2
- 230000003044 adaptive effect Effects 0.000 description 1
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- 230000001419 dependent effect Effects 0.000 description 1
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- 239000000758 substrate Substances 0.000 description 1
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Classifications
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- 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
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
- Y02E40/40—Arrangements for reducing harmonics
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Abstract
The invention discloses a compact double-end absorption band-pass filter, which is applied to the technical field of filtering and comprises the following components: a band pass section and an absorption section; the band-pass part consists of two parallel microstrip lines; the microstrip line is respectively used as an input end and an output end; the two ends of the microstrip line are connected with the absorption part; the absorbing portion includes: resistance and quarter wavelength transmission lines; each end of the microstrip line is sequentially connected with one end of a resistor and one quarter wavelength transmission line; the quarter wavelength the other end of the transmission line is grounded. The absorption type BPF provided by the invention has the characteristics of small size, flat whole frequency, low group delay, high out-of-band absorption ratio, good in-band symmetry and no reflection performance, and the like, and has wide application prospects.
Description
Technical Field
The invention relates to the technical field of filtering, in particular to a compact double-end absorption band-pass filter.
Background
Filters are an essential component of almost all modern radio frequency/microwave systems, and multifunctional, high performance Band Pass Filters (BPFs) are highly required in radar systems and next generation wireless communication systems. Conventional microwave filters reflect unwanted signals in the stop band back to the source by providing reactive impedance, i.e. the filter has a reflection in the stop band. In practice, the reflective nature of these filters may present system level problems when connected to nonlinear circuits (such as power amplifiers and mixers), the performance of which in many cases is sensitive to out-of-band impedance, particularly those harmonics. Thus, the use of reflective filters may result in unpredictable system performance degradation, such as efficiency loss, excessive spurious signal levels, and dynamic range loss. With conventional bandpass filters, an isolator is typically required at the rf front end to avoid the effect of stop band echo on circuit performance, which increases the system size.
In recent years, an absorption-type or reflection-free radio frequency BPF has become a popular device in a radio frequency front-end chain to prevent inter-block signal interference caused by unwanted radio frequency signal power reflection and to improve the stability of adjacent radio frequency active circuits. Unlike conventional reflective filters, the non-transmitted RF input signal energy is absorbed by the circuit within its stop band rather than being reflected back to the source, avoiding deterioration of the adjacent stage operating conditions. Because the power echo can absorb the out-of-band interference signals reflected back to the source, the harmful influence of the cascade connection of the power echo of the radio frequency signal on the whole radio frequency front end can be effectively reduced, and the operation robustness of the power echo of the radio frequency signal is improved.
Conventional solutions include the use of attenuators or non-reciprocal components, such as isolators and circulators, to reduce reflection of spurious signals, but at the cost of significant signal loss, cost, size, and system weight; novel fully absorbing adaptive radio frequency filters based on complementary diplexers, which have no reflection behavior only at the input (i.e., not at both ports); the distributed quasi-absorption band-pass filter adopts a resistor load-carrying resonant cavity as a first resonant cavity, and only absorbs one side of reflection; based on a symmetrical circuit, the even mode and the odd mode of the symmetrical circuit have the same amplitude reflection coefficient at all frequencies, and lumped element symmetrical double-port absorption filters with opposite signs; the band-pass part (reflective coupling line filter) and the absorption part (a matched resistor is connected in series with a short-circuit stub) are used for realizing the higher-order and symmetrical full-band quasi-absorption BPF, and the structure is complex and the size is large.
Therefore, it is a need for a solution to the problem of providing a compact double-ended absorption band-pass filter with miniaturized circuit dimensions without degrading in-band echo loss performance.
Disclosure of Invention
In view of the above, the present invention provides a compact double-ended absorption band-pass filter to solve the technical problems mentioned in the background art.
In order to achieve the above purpose, the present invention adopts the following technical scheme:
a compact double ended absorption band pass filter comprising: a band pass section and an absorption section; the band-pass part consists of two parallel microstrip lines; the microstrip line is respectively used as an input end and an output end; the two ends of the microstrip line are connected with the absorption part; the absorbing portion includes: resistance and quarter wavelength transmission lines; each end of the microstrip line is sequentially connected with one end of a resistor and one quarter wavelength transmission line; the other end of the quarter-wavelength transmission line is grounded.
Preferably, in a compact double-ended absorption band-pass filter as described above, the output is connected to a matching load.
Preferably, in the above-mentioned compact double-ended absorption band-pass filter, the input and output impedance matrices are:
wherein: z is Z 1,1, Z 1,2, Z 2,1, Z 2,2, Respectively, the port impedance.
Preferably, in the above-described compact double-ended absorption band-pass filter, the port impedance expression is as follows:
in (2 a) and (2 b), N 1 ，N 2 ，N 3 ，N 4 Is that
Wherein Z is 0e And Z 0o The characteristic impedance of the even mode and the odd mode of the transmission line respectively; θ is the corresponding electrical length; z is Z A Is the input impedance of the absorbent structure.
Preferably, in the above-described compact double-ended absorption band-pass filter, the input impedance of the absorption section:
Z A ＝R+jZ a tanθ a (4)；
Z a for the characteristic impedance of the absorbent structure, θ a The corresponding electric length is as follows; r is the absorption resistance.
Preferably, in the above-mentioned compact double-ended absorption band-pass filter, the output port is connected to a matching load, and the input impedance of the input port is obtained:
wherein,,
Z B ＝Z A //Z 0 (6)；
Z in1 is the parameter Z 0e 、Z 0o 、Z a 、θ a And a frequency function of R.
Preferably, in a compact double-ended absorption band-pass filter as described above, when Z A →infinity, i.e. θ a Pi/2, Z at the center frequency in Represented as
As can be seen from the above technical solution, compared with the prior art, the present disclosure provides a compact dual-port absorption microstrip coupling line bandpass filter, in which four unmatched absorption portions and resistors are combined to generate dual-port absorption, and the bandpass response of the proposed filter structure is implemented by parallel coupling line portions, similar to the conventional coupling line filter; the absorption part is composed of a resistor and a grounded quarter-wavelength transmission line. In order to realize dual-port absorption of all frequencies, the open ports of the coupling lines are connected in series to the absorption branches, and the input/output ports are connected in parallel to the absorption branches. Within a certain range from the center frequency, these ends exhibit an Open Circuit (OC) characteristic, so that the structure exhibits a coupled line filter characteristic. Outside the passband, the absorbing branches appear as matching loads to ground, helping to absorb out-of-band signals. The band pass section is composed of only one quarter-wavelength coupled line, has a miniaturized circuit size, and does not degrade in-band echo loss performance. The proposed absorption type BPF has the characteristics of small size, flat full frequency, low group delay, high out-of-band absorption ratio, good in-band symmetry and no reflection performance, and the like, and has wide application prospect.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are required to be used in the embodiments or the description of the prior art will be briefly described below, and it is obvious that the drawings in the following description are only embodiments of the present invention, and that other drawings can be obtained according to the provided drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of a structure provided by the present invention;
FIG. 2 (a) is a graph showing the input impedance of the absorber of the present invention;
fig. 2 (b) is an s-parameter curve of the coupled line filter without the absorber according to the present invention;
FIG. 3 (a) is a physical layout of the present invention;
FIG. 3 (b) is a group delay profile of the present invention;
FIG. 3 (c) s-parameter curve of the absorbent BPF of the present invention;
FIG. 3 (d) shows the absorption ratio curve of the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The embodiment of the invention discloses a compact double-end absorption band-pass filter, as shown in fig. 1, comprising: a band pass section and an absorption section; the band-pass part consists of two parallel microstrip lines; the microstrip line is respectively used as an input end and an output end; the two ends of the microstrip line are connected with the absorption part; the absorbing portion includes: resistance and quarter wavelength transmission lines; each end of the microstrip line is sequentially connected with one end of a resistor and one quarter wavelength transmission line; the other end of the quarter-wavelength transmission line is grounded.
Impedance matrix based on traditional four-port parallel coupled line structure, its matrix of 1 'and 2' port voltages and currents can be expressed as
Wherein:
in (2 a) and (2 b), N 1 ，N 2 ，N 3 ，N 4 Is that
Wherein Z is 0e And Z 0o The characteristic impedances of the even and odd modes of the coupled transmission line, respectively. θ is the corresponding electrical length. Z is Z A As shown in FIG. 1, is represented as the input impedance of the absorbent structure
Z A ＝R+jZ a tanθ a (4)；
Z a For the characteristic impedance of the absorbent structure, θ a For its corresponding electrical length. R is the absorption resistance.
When the output port is connected with impedance Z 0 In this case, set to 50Ω, 1 is obtained from fig. 1, and the Z parameter of the input impedance of the port is:
here:
Z B ＝Z A //Z 0 (6)；
from the above, Z in1 Is the parameter Z 0e 、Z 0o 、Z a 、θ a And a frequency dependent function of R. The parameters contained therein are too many to be used for direct design.
When Z is A →infinity, i.e. θ a Pi/2, Z at the center frequency in Can be expressed as:
as can be seen from (8), the structure in fig. 1 is identical to a conventional coupled line circuit at the center frequency. In practical application, Z A Can be kept large enough in a certain frequency range from the center, as shown in fig. 2 (a), ensuring the bandpass characteristics of the coupled line filter. Z A I varies with Z a And R is as shown in FIG. 2 (a). Notably, the bandwidth of such a structure is limited by the excessively small high impedance frequency range.
To ensure good characteristics of the bandpass segment, the loading at the end is Z 0 When =50Ω and there are no four absorption roots, Z is designed based on formula (8) 0e And Z 0o 157.66 Ω and 57.1 Ω, respectively, the S-parameters of the coupled line filter are as shown in fig. 2 (b).
Design, manufacturing, simulation and test results:
based on the absorption type BPF model in fig. 1, a dual-port absorption type microstrip coupling line band-pass filter with 50 omega input/output impedance and 2.4GHz center frequency is designed. A filter layout using a Rogers RO3003 substrate with a thickness of 0.762mm is shown in fig. 3 (a).
The physical dimensions of the absorption filter were simulated and optimized by ANSYS HFSS as shown in fig. 3 (a). The optimal circuit parameters of the absorption filter are Z 0e ＝157.66Ω，Z 0e ＝157.66Ω，Z a ＝50.59Ω,R＝100Ω。
To demonstrate the performance of the proposed absorption band pass filter, a circuit was implemented and fabricated on a microstrip. Fig. 3 (b) is a photograph of the prepared absorptive BPF with a circuit size of 0.27λ 0.28λ, and fig. 3 (b) - (c) are scattering parameters and GDs measured using an Agilent vector network analyzer. In addition, the power absorption ratio is
AR＝(1-|S 11 | 2 -|S 21 | 2 )×100％ (9)；
Calculated and plotted using MATLAB as shown in fig. 3 (d). The experimental result shows that the measurement result of the prepared absorptive BPF is very consistent with the simulation result.
From the measurement results, the group delay is less than 0.74ns at 0.5-4GHz, f 0 Maximum at=2.4 GHz and a gentle trend, as shown in fig. 3 (b). As shown in FIG. 3 (c), the measured 3-dB FBW (DeltaS 21-3 dB) of the prepared filter was 28.1%, at f 0 Insertion Loss (IL) at =2.4 GHz is 0.22dB, at f 0 Experimental input and output return losses at=2.4 GHz were 22.75dB and 22.77dB, respectively. Meanwhile, the measured return loss in the passband and outside the passband are respectively greater than 19.2dB and 20.5dB. Further, as shown in fig. 3 (d), from 0 to 4GHz (i.e., regardless of the passband range), the minimum stopband power absorption ratio is 98.5%, and the minimum passband absorption ratio is 2.58%.
In summary, the present embodiment discloses a compact dual-port absorption microstrip coupling line bandpass filter. A combination of four mismatched absorbers is utilized to create a dual port absorber. The band pass section is composed of only 1/4 wavelength coupled lines, avoiding an increase in circuit size, and not reducing in-band echo loss. The absorption type BPF has the characteristics of compact structure, full frequency flatness, low GD, high out-of-band absorption ratio, good full-band reflection-free performance and the like, and has wide application prospects in radar and 5G communication systems.
In the present specification, each embodiment is described in a progressive manner, and each embodiment is mainly described in a different point from other embodiments, and identical and similar parts between the embodiments are all enough to refer to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant points refer to the description of the method section.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (7)
1. A compact double ended absorption bandpass filter comprising: a band-pass section and an absorber section; the band-pass part consists of two parallel microstrip lines; the microstrip line is respectively used as an input end and an output end; the two ends of the microstrip line are connected with the absorption part; the absorbing portion includes: resistance and quarter wavelength transmission lines; each end of the microstrip line is sequentially connected with one end of a resistor and one quarter wavelength transmission line; the other end of the quarter-wavelength transmission line is grounded.
2. A compact double ended absorption bandpass filter according to claim 1 wherein the output is connected to a matched load.
3. The compact, double ended, absorbing bandpass filter of claim 1 wherein the input and output impedance matrices are:
wherein: z is Z 1,1 ,Z 1,2 ,Z 2,1 ,Z 2,2 Respectively, the port impedance.
4. A compact double ended absorption bandpass filter according to claim 3 wherein the port impedance expression is as follows:
in (2 a) and (2 b), N 1 ，N 2 ，N 3 ，N 4 Is that
Wherein Z is 0e And Z 0o The characteristic impedance of the even mode and the odd mode of the transmission line respectively; θ is the corresponding electrical length; z is Z A Is the input impedance of the absorbent structure.
5. The compact double ended absorption band pass filter of claim 4, wherein the input impedance of the absorption section:
Z A ＝R+jZ a tanθ a (4)；
Z a for the characteristic impedance of the absorbent structure, θ a The corresponding electric length is as follows; r is the absorption resistance.
6. The compact, double ended, absorbing bandpass filter of claim 5 wherein the output port is coupled to a matched load to obtain the input impedance of the input port:
wherein,,
Z B ＝Z A //Z 0 (6)；
Z in1 is the parameter Z 0e 、Z 0o 、Z a 、θ a And a frequency function of R.
7. A compact dual-end absorption bandpass filter according to claim 6 wherein when Z A →infinity, i.e. θ a Pi/2, Z at the center frequency in Expressed as:
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| CN202310494401.6A CN116454573A (en) | 2023-05-05 | 2023-05-05 | Compact double-end absorption band-pass filter |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116937093A (en) * | 2023-09-15 | 2023-10-24 | 南京邮电大学 | Novel broadband reflection-free band-pass filter |
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2023
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116937093A (en) * | 2023-09-15 | 2023-10-24 | 南京邮电大学 | Novel broadband reflection-free band-pass filter |
| CN116937093B (en) * | 2023-09-15 | 2023-11-21 | 南京邮电大学 | Broadband reflection-free band-pass filter |
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Application publication date: 20230718 |