CN103296346B - A kind of micro-band balance filter - Google Patents
A kind of micro-band balance filter Download PDFInfo
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- CN103296346B CN103296346B CN201310201088.9A CN201310201088A CN103296346B CN 103296346 B CN103296346 B CN 103296346B CN 201310201088 A CN201310201088 A CN 201310201088A CN 103296346 B CN103296346 B CN 103296346B
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Abstract
The invention provides a kind of micro-band balance filter.By two structures, identical and symmetrical connected microstrip bandpass filter is formed described filter.Under difference mode signal excitation, source-load coupling structure produces transmission zero in passband edge and stopband, improves the frequency selectivity in passband and deepens stopband; The stepped impedance open circuit minor matters of center loaded produce two common-mode signal transmission zeros with the folded dipole loading on feeder line in differential mode passband, thus improve common mode inhibition power.It is high that described balance filter has frequency selectivity, and insertion loss is low, and stopband is wide, compact conformation feature.
Description
Technical field
The invention belongs to electronic technology field, especially relate to a kind of micro-band balance filter.
Background technology
The noise that balancing circuitry can efficiently suppress ambient noise and internal system active device to produce, is thus widely used in Modern Communication System.Balance filter requires to have filtering characteristic when difference mode signal inputs, and has higher common mode inhibition capacity.Conventional balanced filter is consisted of a single port filter and two barron structures, and so not only circuit area is huge, and common mode noise immunity is poor.
Adopt two-sided parallel strips to improve common mode inhibition capacity, but this can cause system dimension to become huge; Have the pectinate line structure that scholar adopts tap to input, this effectively can suppress common-mode noise, but the balance filter isolation obtained is low, and complex circuit designs, is not easy to processing.
Summary of the invention
Technical problem to be solved by this invention is to overcome the deficiencies in the prior art, proposes a kind of micro-band balance filter.This filter has two common-mode signal transmission zeros in differential mode passband, effectively suppresses common-mode noise, and has very low insertion loss and wider stopband, and circuit is simple, is easy to processing.
For solving the problems of the technologies described above, the technical solution adopted in the present invention is:
A kind of micro-band balance filter, be made up of the first filter and the second filter, the first filter is identical with the second filter construction;
Described first filter comprises: the first feeder line, the second feeder line, the first open circuit branch line, the second open circuit branch line, the first resonator, the second resonator, the first folded dipole and the first stepped impedance minor matters; Described first feeder line becomes a word distribution with the second feeder line, spacing is designated value; Described first open circuit branch line and the second open circuit branch line are Z-type structure, be connected to one end of the first feeder line and the second feeder line, the first open circuit branch line and the second open circuit branch line are forming the first source-load coupling structure close to the first feeder line end respectively together with the bending part of the second feeder line end; Described first resonator and the second resonator are U-shaped structure, intercouple respectively, and intercouple between the first resonator and the second resonator with the first open circuit branch line and the second open circuit branch line; Described first folded dipole loads on the middle part of the second feeder line; Described first stepped impedance minor matters load on the end of the first resonator, are connected by the first resonator by high impedance line with low-impedance line;
Described second filter comprises: the 3rd feeder line, the 4th feeder line, the 3rd open circuit branch line, the 4th open circuit branch line, the 3rd resonator, the 4th resonator, the second folded dipole and the second stepped impedance minor matters; Described 3rd feeder line becomes a word distribution with the 4th feeder line, spacing is designated value; Described 3rd open circuit branch line and the 4th open circuit branch line are Z-type structure, be connected to one end of the 3rd feeder line and the 4th feeder line, the 3rd open circuit branch line and the 4th open circuit branch line are forming the second source-load coupling structure close to the 3rd feeder line end respectively together with the bending part of the 4th feeder line end; Described 3rd resonator and the 4th resonator are U-shaped structure, intercouple respectively, and intercouple between the 3rd resonator and the 4th resonator with the 3rd open circuit branch line and the 4th open circuit branch line; Described second folded dipole loads on the middle part of the 4th feeder line; Described second stepped impedance minor matters load on the end of the 3rd resonator, are connected by the 3rd resonator by high impedance line with low-impedance line;
Described first filter is connected with the second filter symmetry, wherein the first resonator is connected with the 3rd resonator, second resonator is connected with the 4th resonator, and the first stepped impedance minor matters are connected with the second stepped impedance minor matters, and the first folded dipole is connected with the second folded dipole; The other end of described first feeder line and the 3rd feeder line is respectively as the output port of described micro-band balance filter or input port; The other end of described second feeder line and the 4th feeder line is respectively as the input port of described micro-band balance filter or output port.
Described first feeder line, the second feeder line, the 3rd feeder line, the 4th feed line impedance are all 50 ohm.
The invention has the beneficial effects as follows: the invention provides a kind of micro-band balance filter, described filter can produce two common-mode signal transmission zeros in difference mode signal passband, there is higher common mode inhibition power, and produce multiple transmission zero in difference mode signal passband edge thus make passband edge more precipitous, improve the frequency selectivity of passband.Described balance filter insertion loss is low, and stopband is wide, compact conformation, is easy to carry out integrated with other circuit.
Accompanying drawing explanation
Fig. 1 is the schematic diagram of single-layer printed circuit plate.
Fig. 2 is balance filter schematic diagram.
Fig. 3 is the equivalent electric circuit under common-mode signal excitation.
Fig. 4 is the equivalent electric circuit under difference mode signal excitation.
Fig. 5 is the difference mode signal insertion loss curve S of balance filter
dd21and difference mode signal return loss plot S
dd11emulation and measurement result.
Fig. 6 is the common-mode signal insertion loss curve S of balance filter
cc21emulation and measurement result.
Fig. 7 is by the difference mode signal insertion loss of balance filter and return loss and common-mode signal insertion loss partial enlarged drawing in differential mode passband, can characteristic in clearer display differential mode passband.
In description of reference numerals: Fig. 1 to Fig. 4,
1: the first filter; 2: the second filters;
3: the first feeder lines; 3 ': the three feeder line; 4: the second feeder lines; 4 ': the four feeder line;
5: the first open circuit branch lines; 5 ': the three open circuit branch line; 6: the second open circuit branch lines; 6 ': the four open circuit branch line;
7: the first resonators; 7 ': the three resonator; 8: the second resonators; 8 ': the four resonator;
9: the first stepped impedance minor matters; 9 ': the second stepped impedance minor matters; 10: the first folded dipoles; 10 ': the second folded dipole;
11: upper metal patch; 12: dielectric substrate; 13: lower metal patch;
P1: input port 1; P1 ', input port 1 '; P2: output port 1; P2 ': output port 1 '; Or using P2, P2 ' as input port, P1, P1 ' as output port;
Z: the first source-load coupling structure; Z ': the second source-load coupling structure.
Embodiment
Below in conjunction with accompanying drawing, the micro-band balance filter of one that the present invention proposes is described in detail:
The output port of balance filter of the present invention and input port with the welding of SMA head, are tested or practical devices to access respectively.
The present embodiment adopt relative dielectric constant be 2.2, thickness be the pcb board of 0.508mm as substrate, the pcb board of other specifications also can be adopted as substrate.As shown in Figure 1, metal patch 11 and lower metal patch 13 is coated with respectively on the upper and lower surface of the dielectric substrate 12 of pcb board.
As shown in Figure 2, balance filter of the present invention, is formed on pcb board, is made up of two microstrip filters, is the first filter 1 and the second filter 2 respectively; First filter 1 and the second filter 2 are connected at dotted line AA ' place and along dotted line AA ' axial symmetry.Described first filter 1 comprises: the first feeder line 3 and the first open circuit branch line 5, second feeder line 4 and the second open circuit branch line 6, first resonator 7, second resonator 8, first folded dipole 10, first stepped impedance minor matters 9; Described second filter comprises: the 3rd feeder line 3 ' and the 3rd open circuit branch line 5 ', the 4th feeder line 4 ' and the 4th open circuit branch line 6 ', the 3rd resonator 7 ', the 4th resonator 8 ', the second folded dipole 10 ', the second stepped impedance minor matters 9 '.Illustrate for the first filter 1, due to the full symmetric of structure, be equally applicable to the second filter 2.In first filter 1, the first open circuit branch line 5 is connected with the first feeder line 3, second open circuit branch line 6 is connected with the second feeder line 4, first open circuit branch line 5 and the second open circuit branch line 6 form the first source-load coupling structure Z on length d, first stepped impedance minor matters 9 are connected with the first resonator 7, first resonator 7 and the first open circuit branch line 5 intercouple on length L2, second resonator 8 and the second open circuit branch line 6 intercouple on length L2, first resonator 7 and the second resonator 8 intercouple, coupling length is L1, first folded dipole 10 is connected to the middle part of the second feeder line 4.
When common-mode signal enters system from input port P1 and input port P1 ', this balance filter is equivalent to open circuit on symmetry axis AA ', and its equivalent electric circuit as shown in Figure 3.Now, first resonator 7, second resonator the 8, three resonator 7 ', 4th resonator 8 ' length is the open circuit end that the 1/2nd, first stepped impedance minor matters 9 of operation wavelength and the second stepped impedance minor matters 9 ' load on the first resonator 7 and the 3rd resonator 7 ' respectively./ 2nd wavelength oscillators being loaded with stepped impedance minor matters and feeder line being coupled between minor matters of opening a way produces a transmission zero, and the position of transmission zero can be changed by the length of adjustment stepped impedance minor matters, therefore, transmission zero can be made to be positioned within difference mode signal passband to the suitable value of the length of stepped impedance minor matters, thus improve the suppression to common-mode signal.In addition, the folded dipole loaded on 50 ohm of feeder lines also can produce a new transmission zero in the passband of difference mode signal.So there is the transmission zero of two common-mode signals in difference mode signal passband, substantially increase common mode inhibition level.
When difference mode signal enters system from input port P1 and input port P1 ', this balance filter is equivalent to short circuit on symmetry axis AA ', and as shown in Figure 4, now stepped impedance minor matters work its equivalent electric circuit hardly.Under difference mode signal excitation, the first resonator 7, second resonator the 8, three resonator 7 ', the 4th resonator 8 ' length is 1/4th of operation wavelength.First filter and the second filter are second order, illustrate, without loss of generality for the first filter.Adopt the first source-load coupling structure Z that input 50 ohm of first feeder line 3 and output 50 ohm of second feeder line 4 are formed, a transmission zero can be produced respectively in passband top edge and stopband, thus increase the frequency selectivity of passband top edge and deepen stopband, the harmonic wave simultaneously produced by quarter-wave resonance device also can be suppressed.By the spacing g1 of suitable adjustment source-load coupling structure, and length d shown in Fig. 2 or Fig. 4, the precipitous filter of a Wide stop bands and edge just can be obtained.In addition, load on 50 ohm and export the folded dipole of the second feeder lines 4, can produce two new transmission zeros in differential mode stopband, more widen and deepened difference mode signal stopband, raising selectivity.
Fig. 5 is the difference mode signal insertion loss curve S of balance filter
dd21and difference mode signal return loss plot S
dd11emulation and measurement result.As seen from the figure, simulation result and measured value coincide good, and slight shift and the error of centre frequency come from foozle.The 2dB relative bandwidth of difference mode signal insertion loss is 7.3%, and measuring the minimum insertion loss value of gained is-0.9dB, and return loss value is all less than-10dB in differential mode passband.Two transmission zeros produced at upper stopband make frequency selectivity improve, and widen and deepened stopband.
Fig. 6 is the common-mode signal insertion loss curve S of balance filter
cc21emulation and measurement result, as seen from the figure, the two is substantially identical.In differential mode passband, be positioned at two common mode transmission zero points of 2.39GHz and 2.58GHz, decay reaches-68.5dB, inhibit the transmission of common-mode signal greatly, in whole differential mode passband, common-mode signal insertion loss is all below-51dB, this has absolutely proved that balance filter of the present invention has very high common mode inhibition level, can also be seen by figure, to common-mode signal under the suppression level of-14.5dB, its stopband can reach 11GHz.
Can clearlyer see in difference mode signal passband from Fig. 7, the value of the insertion loss of difference mode signal and return loss and common-mode signal insertion loss, by Tu Ke get, in whole difference mode signal passage, common-mode signal insertion loss value is less than-51dB, illustrates that balance filter of the present invention has very high common mode inhibition level.
Claims (2)
1. a micro-band balance filter, is characterized in that, be made up of the first filter and the second filter, the first filter is identical with the second filter construction;
Described first filter comprises: the first feeder line, the second feeder line, the first open circuit branch line, the second open circuit branch line, the first resonator, the second resonator, the first folded dipole and the first stepped impedance minor matters; Described first feeder line becomes a word distribution with the second feeder line, spacing is designated value; Described first open circuit branch line and the second open circuit branch line are Z-type structure, be connected to one end of the first feeder line and the second feeder line, the first open circuit branch line and the second open circuit branch line are forming the first source-load coupling structure close to the first feeder line end respectively together with the bending part of the second feeder line end; Described first resonator and the second resonator are U-shaped structure, intercouple respectively, and intercouple between the first resonator and the second resonator with the first open circuit branch line and the second open circuit branch line; Described first folded dipole loads on the middle part of the second feeder line; Described first stepped impedance minor matters load on the end of the first resonator, are connected by the first resonator by high impedance line with low-impedance line;
Described second filter comprises: the 3rd feeder line, the 4th feeder line, the 3rd open circuit branch line, the 4th open circuit branch line, the 3rd resonator, the 4th resonator, the second folded dipole and the second stepped impedance minor matters; Described 3rd feeder line becomes a word distribution with the 4th feeder line, spacing is designated value; Described 3rd open circuit branch line and the 4th open circuit branch line are Z-type structure, be connected to one end of the 3rd feeder line and the 4th feeder line, the 3rd open circuit branch line and the 4th open circuit branch line are forming the second source-load coupling structure close to the 3rd feeder line end respectively together with the bending part of the 4th feeder line end; Described 3rd resonator and the 4th resonator are U-shaped structure, intercouple respectively, and intercouple between the 3rd resonator and the 4th resonator with the 3rd open circuit branch line and the 4th open circuit branch line; Described second folded dipole loads on the middle part of the 4th feeder line; Described second stepped impedance minor matters load on the end of the 3rd resonator, are connected by the 3rd resonator by high impedance line with low-impedance line;
Described first filter is connected with the second filter symmetry, wherein the first resonator is connected with the 3rd resonator, second resonator is connected with the 4th resonator, and the first stepped impedance minor matters are connected with the second stepped impedance minor matters, and the first folded dipole is connected with the second folded dipole; The other end of described first feeder line and the 3rd feeder line is respectively as the output port of described micro-band balance filter or input port; The other end of described second feeder line and the 4th feeder line is respectively as the input port of described micro-band balance filter or output port.
2. a kind of micro-band balance filter as claimed in claim 1, is characterized in that, described first feeder line, the second feeder line, the 3rd feeder line and the 4th feed line impedance are all 50 ohm.
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| CN103904389B (en) * | 2014-03-13 | 2016-05-04 | 南京航空航天大学 | The micro-band balance filter of a kind of compact based on slotted line structure |
| CN103915665B (en) * | 2014-03-28 | 2015-12-02 | 南京航空航天大学 | The balancing band bandpass filter that a kind of compact ultra broadband biobelt falls into |
| SG11201807715UA (en) * | 2016-03-09 | 2018-10-30 | Peerbridge Health Inc | System and method for monitoring conditions of a subject based on wireless sensor data |
| CN105762471B (en) * | 2016-05-06 | 2019-03-08 | 上海海事大学 | I-shaped differential bandpass filter based on transversal filter theory |
| CN109524748B (en) * | 2018-11-09 | 2020-06-23 | 南京航空航天大学 | Frequency-tunable microstrip balance band-pass filter |
| CN111276777A (en) * | 2020-02-04 | 2020-06-12 | 电子科技大学 | Balun filter with balanced port free of reflection |
| CN117613529B (en) * | 2024-01-23 | 2024-04-16 | 南京典格通信科技有限公司 | 5G balance filter with high common mode rejection |
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| CN202076392U (en) * | 2011-04-26 | 2011-12-14 | 南京航空航天大学 | Ultra wideband filter |
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| CN103107390A (en) * | 2013-01-23 | 2013-05-15 | 南京理工大学 | Balance type radio frequency electronically-controlled band-pass filter with bandwidth control |
| CN203300774U (en) * | 2013-05-24 | 2013-11-20 | 南京航空航天大学 | Microstrip balance filter |
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