CN104882650A - Balanced filter adopting coupling branch knot to load resonator - Google Patents
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- CN104882650A CN104882650A CN201510275815.5A CN201510275815A CN104882650A CN 104882650 A CN104882650 A CN 104882650A CN 201510275815 A CN201510275815 A CN 201510275815A CN 104882650 A CN104882650 A CN 104882650A
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Abstract
The invention discloses a balanced filter adopting a coupling branch knot to load a resonator. The balanced filter comprises a first filter unit and a second filter unit which are symmetrically distributed. The first filter unit comprises a first coupling branch knot loading resonator, a first input and output port and a second input and output port. The first coupling branch knot loading resonator is formed by a first coupling branch knot and first and second transmission lines of a cascade. The first input and output port is connected to a third transmission line and is loaded with a first branch knot, a second branch knot and a third branch knot. The second input and output port is connected to a fourth transmission line and is loaded with a fourth branch knot. The second filter unit comprises a second coupling branch knot loading resonator, a third input and output port and a fourth input and output port. The second coupling branch knot loading resonator is formed by a second coupling branch knot and fifth and sixth transmission lines of the cascade. The third input and output port is connected to a seventh transmission line and is loaded with a fifth branch knot. The fourth input and output port is connected to a eighth transmission line and is connected to the fourth branch knot too. The invention discloses the design of the balanced filter with high selectivity and high common mode rejection.
Description
Technical field
The present invention relates to the technical field of microwave communication, refer in particular to a kind of balance filter adopting coupling minor matters to load resonator.
Background technology
Balance filter has obtained people and more and more pays close attention to since proposition, and existing different structure meets the different needs at present.Based on the comprehensive designing method of band stop filter and band pass filter, although can broadband be realized, design more complicated, be difficult to realize high selectivity.Some other balanced structure from height common mode inhibition, such as slot line structure, signal disturbing structure etc. are owing to introducing transmission zero in band outer being difficult to, and passband selectivity ratios is milder.Method based on multimode resonator is an effective way in design broadband, can improve filter order, realize high selectivity and miniaturization.But the multimode resonator design be applied in balance filter is relatively less, therefore, research multimode broadband balance filter, the high precipitous type balance filter of design RF/Microwave communications band has extremely important theory significance, greatly economic benefit and wide application prospect.
The most basic implementation of balance filter is for representative with minor matters loading structure.Realize wider bandwidth by increasing minor matters number, shortcoming is that the selectivity of differential mode passband is poor, common mode bandwidth of rejection is limited, size is larger.For this reason, some modified model schemes are suggested, what such as Chu Qing sunrise team of South China Science & Engineering University in 2013 delivered at IEEE Microwave and Wireless Components Letters is entitled as in " DifferentialWideband Bandpass Filter With High-Selectivity and Common-ModeSuppression " article, as shown in Figure 7.By adopting coupling minor matters line and coupling minor matters loading technique, the size of filter reduces greatly, and selectivity improves greatly.But this structure common mode inhibition still needs to improve.
Principle based on the anti-phase suppression of two path signal in-phase stacking can realize good common mode inhibition equally, as the article being entitled as " ANovel Ultra-Wideband Differential Filter Based on Double-SidedParallel-Strip Line " that Q Xue delivers at IEEE Microwave and Wireless Components Letters, as shown in Figure 8.When the Signal averaging of two paths, if the θ that satisfies condition
path1(f
0)=θ
path2(f
0) ± 2n π and θ
path1(f
0)=θ
path2(f
0) ± n π, (n=1,2,3 ...) time, a passband and stopband will be produced respectively.Based on the balance filter of the method design, in whole frequency range, its common-mode signal can be suppressed, but its differential mode passband is not owing to having transmission zero sideband characteristic poor.
The method that another kind realizes balance filter uses multimode micro-strip resonantor, what such as W Q Che. in 2012 delivered at IEEE Transactions on Microwave Theory and Techniques is entitled as " NovelWideband Differential Bandpass Filters Based on T-Shaped Structure " article, as shown in Figure 9.Three modes of resonance of T-shaped resonator define differential mode passband, introduce transmission zero simultaneously, realize common mode inhibition during common mode at centre frequency place.The advantage of this structure is that common mode inhibition scope covers whole frequency band, and size is less.But selectivity still needs to improve.
Equally, multimode line of rabbet joint resonator also may be used for the design of balance filter, what such as Chen C J delivered at IEEEMicrowave and Wireless Components Letters is entitled as " Band-notchedbalanced UWB BPF with stepped-impedance slotline multi-mode resonator " article, as shown in Figure 10.Multimode ultra broadband characteristic can be realized by line of rabbet joint step electric impedance resonator.Because during common mode, the plane of symmetry place line of rabbet joint can not transmit common-mode signal, whole frequency band common mode all reaches fine suppression.In addition by source-load coupling, can produce two transmission zeros outside passband, selectivity is necessarily improved.
Summary of the invention
The object of the invention is to overcome the deficiencies in the prior art, a kind of balance filter adopting coupling minor matters to load resonator is provided, overcome the problem that existing multimode resonator difficulty realizes transmission zero, propose a kind of multimode resonator, when making differential mode, multimode resonator produces multiple transmission zero band is outer, and transmission zero is controlled, and when common mode, this multimode resonator can produce transmission zero in passband; Overcome the problem of height differential loss when existing multistage balance filter realizes, a kind of design adopting multimode resonator is provided; Overcome balance filter common mode inhibition and realize difficult point, apply a kind of common mode inhibition feed structure, make the design of filter concentrate in the realization of differential mode passband; Overcome the difficult point realized compared with high selectivity, a kind of implementation of high abruptness high common mode inhibition balance filter is provided.
For achieving the above object, technical scheme provided by the present invention is: a kind of balance filter adopting coupling minor matters to load resonator, include the first filter cell and second filter cell of specular distribution, wherein, described first filter cell includes the first coupling minor matters and loads resonator, first input/output port, second input/output port, described first coupling minor matters load resonator and are made up of the first coupling minor matters and the first transmission line of cascade and the second transmission line, described first transmission line and the second transmission line are parallel to the symmetry axis of the first filter cell and the second filter cell, described first coupling minor matters are perpendicular to this symmetry axis, and be connected with the first transmission line and the second transmission line respectively, described first input/output port is connected with the 3rd transmission line, 3rd transmission line and the first transmission line form input/output terminal coupling feed, and this coupling feed is loaded with the first minor matters, second minor matters, 3rd minor matters, described second input/output port is connected with the 4th transmission line, 4th transmission line and the second transmission line form input/output terminal coupling feed, and this coupling feed is loaded with the 4th minor matters, described second filter cell includes the second coupling minor matters and loads resonator, 3rd input/output port, 4th input/output port, described second coupling minor matters load resonator and are made up of the second coupling minor matters and the 5th transmission line of cascade and the 6th transmission line, described 5th transmission line and the 6th transmission line are parallel to the symmetry axis of the first filter cell and the second filter cell, described second coupling minor matters are perpendicular to this symmetry axis, its one end is connected with the 5th transmission line and the 6th transmission line respectively, its other end and above-mentioned first minor matters that are coupled are connected, described 3rd input/output port is connected with the 7th transmission line, 7th transmission line and the 5th transmission line form input/output terminal coupling feed, and this coupling feed is loaded with the 5th minor matters, one end of described 5th minor matters is connected with the 7th transmission line, its other end respectively with above-mentioned first minor matters, one end of second minor matters connects, the other end of these the first minor matters is connected to the 3rd transmission line, the other end of these the second minor matters is connected to the center of above-mentioned 3rd minor matters, described first minor matters and the 5th minor matters specular, and with the first filter cell and the same symmetry axis of the second filter cell, described second minor matters extend on this symmetry axis, described 3rd minor matters are perpendicular to this symmetry axis, described 4th input/output port is connected with the 8th transmission line, 8th transmission line and the 6th transmission line form input/output terminal coupling feed, and this coupling feed is connected with above-mentioned 4th minor matters.
Described 4th minor matters are formed by connecting by the transmission line of two sections of specular, and these two sections of transmission lines and the first filter cell and the same symmetry axis of the second filter cell.
Described first coupling minor matters and the second coupling minor matters are short circuit coupling minor matters or open circuit coupling minor matters.
Described first minor matters, the second minor matters, the 3rd minor matters, the 4th minor matters, the 5th minor matters are short circuit minor matters or open circuit minor matters.
Described first input/output port, the second input/output port, the 3rd input/output port, the 4th input/output port are the transmission line of impedance 50 Ω.
Compared with prior art, tool has the following advantages and beneficial effect in the present invention:
1, compared with existing multimode resonator structure, coupling minor matters of the present invention load resonator, can produce outward multiple transmission zero, and transmission zero are controlled at differential mode band.And when common mode, this multimode resonator can produce transmission zero in passband.
2, compared with existing multistage balance filter implementation method, coupling minor matters of the present invention load resonator design scheme, can obviously improve passband differential loss.
3, compared with existing feed structure, the coupling feed minor matters loading structure of employing can introduce two transmission poles in differential mode band, realizes multistage broadband.This structure can introduce multiple transmission zero in common mode simultaneously, obviously improves common mode inhibition effect.
4, compared with existing balance filter high selectivity implementation method, the coupling minor matters that the present invention adopts load resonator, achieve high abruptness differential mode passband.
5, because balance filter of the present invention adopts planar horizontal symmetrical structure, cost is low, and characteristic is good, easy of integration, and therefore the present invention is relatively applicable to being integrated in mobile terminal device system.
Accompanying drawing explanation
Fig. 1 is that the present invention adopts coupling minor matters to load the structural representation of the balance filter of resonator.
Fig. 2 is medium substrate schematic diagram used in the present invention.
Fig. 3 a is the differential mode equivalent circuit figure of balance filter of the present invention.
Fig. 3 b is the common mode equivalent circuit figure of balance filter of the present invention.
Fig. 4 a is balance filter of the present invention curve chart on the impact of differential mode passband when difference loads.
Fig. 4 b is parameter K
1and K
2on the curve chart of differential mode passband impact.
Fig. 5 a is balance filter of the present invention curve chart to common-mode influence when difference loads.
Fig. 5 b is the change curve of balance filter common mode equivalent circuit of the present invention response.
Fig. 6 a is balance filter differential-mode response simulated measurement result figure of the present invention.
Fig. 6 b is balance filter common-mode response simulated measurement result figure of the present invention.
Fig. 7 is the coupling minor matters wideband balance filter circuit figure of Chu Qing sunrise team of South China Science & Engineering University in background technology.
Fig. 8 is the balancing band bandpass filter circuit figure based on multipath of Q Xue in background technology.
Fig. 9 is the balanced filter circuit figure based on multimode resonator of W Q Che in background technology.
Figure 10 is the balanced filter circuit figure based on line of rabbet joint multimode resonator of Chen C J in background technology.
Embodiment
Below in conjunction with specific embodiment, the invention will be further described.
As shown in Figure 1, employing coupling minor matters described in the present embodiment load the balance filter of resonator, include the first filter cell and the second filter cell that distribute for symmetry axis specular with trunnion axis OO ', wherein, described first filter cell includes the first coupling minor matters and loads resonator, first input/output port A1, second input/output port A2, described first coupling minor matters load resonator and are made up of the first coupling minor matters A7 and the first transmission line A3 of cascade and the second transmission line A4, described first transmission line A3 and the second transmission line A4 is parallel to the symmetry axis of the first filter cell and the second filter cell, described first coupling minor matters A7 is perpendicular to this symmetry axis, and be connected with the first transmission line A3 and the second transmission line A4 respectively, described first input/output port A1 is connected with the 3rd transmission line A5, 3rd transmission line A5 and the first transmission line A3 forms input/output terminal coupling feed, and this coupling feed is loaded with the first minor matters A8, second minor matters C2, 3rd minor matters C3, described second input/output port A2 is connected with the 4th transmission line A6, 4th transmission line A6 and the second transmission line A4 forms input/output terminal coupling feed, and this coupling feed is loaded with the 4th minor matters C1, described second filter cell includes the second coupling minor matters and loads resonator, 3rd input/output port B1, 4th input/output port B2, described second coupling minor matters load resonator and are made up of the second coupling minor matters B7 and the 5th transmission line B3 of cascade and the 6th transmission line B4, described 5th transmission line B3 and the 6th transmission line B4 is parallel to the symmetry axis of the first filter cell and the second filter cell, described second coupling minor matters B7 is perpendicular to this symmetry axis, its one end is connected with the 5th transmission line B3 and the 6th transmission line B4 respectively, its other end and above-mentioned first minor matters A7 that is coupled is connected, described 3rd input/output port B1 is connected with the 7th transmission line B5, 7th transmission line B5 and the 5th transmission line B3 forms input/output terminal coupling feed, and this coupling feed is loaded with the 5th minor matters B8, one end of described 5th minor matters B8 is connected with the 7th transmission line B5, its other end respectively with above-mentioned first minor matters A8, one end of second minor matters C2 connects, the other end of this first minor matters A8 is connected to the 3rd transmission line A5, the other end of this second minor matters C2 is connected to the center of above-mentioned 3rd minor matters C3, described first minor matters A8 and the 5th minor matters B8 specular, and with the first filter cell and the same symmetry axis of the second filter cell, described second minor matters C2 extends on this symmetry axis, described 3rd minor matters C3 is perpendicular to this symmetry axis, described 4th input/output port B2 is connected with the 8th transmission line B6, 8th transmission line B6 and the 6th transmission line B4 forms input/output terminal coupling feed, and this coupling feed is connected with above-mentioned 4th minor matters C1, described 4th minor matters C1 is formed by connecting by the transmission line of two sections of specular, and these two sections of transmission lines and the first filter cell and the same symmetry axis of the second filter cell.Described first input/output port, the second input/output port, the 3rd input/output port, the 4th input/output port are the transmission line of impedance 50 Ω; Described first coupling minor matters A7 and second coupling minor matters B7 is short circuit coupling minor matters or open circuit coupling minor matters; Described first minor matters A8, the second minor matters C2, the 3rd minor matters C3, the 4th minor matters C1, the 5th minor matters B8 are short circuit minor matters or open circuit minor matters.The coupling coefficient of definition feeder line is K
1=(Z
oe1-Z
oo1)/(Z
oe1+ Z
oo1), the coupling coefficient of the coupling minor matters that definition resonator loads is K
2=(Z
oe2-Z
oo2)/(Z
oe2+ Z
oo2).
Because structure level of the present invention is symmetrical, when differential mode and common mode operation, the plane of symmetry OO ' of filter is equivalent to a desirable electric wall and Ci Bi respectively, and the plane of symmetry is equivalent to short circuit and open circuit respectively, and its differential mode and common mode equivalent circuit are as shown in Figure 3 a and Figure 3 b shows.
When the die worker that is on duty does, as shown in Figure 3 a, the coupling feed cascade that filter loads resonator and the loading of short circuit minor matters by short circuit coupling minor matters forms.Short circuit coupling minor matters load the passband that resonator can form three transmission poles and dual transfer zero, as shown in fig. 4 a.After coupling feed loads short circuit minor matters, in band, add two extra transmission poles.And the impedance Z s loading short circuit minor matters diminishes, abruptness improves, and band is outer also better to be suppressed.Fig. 4 b depicts differential mode pass-band performance and coupling coefficient K
1, K
2relation curve.Visible K
2larger, pass band width is wider.Meanwhile, K is worked as
2constant, feeder line coupling parameter K
1then can be used to the ripple level in accommodation zone.
When common mode operation, as shown in Figure 3 b, the coupling feed cascade that filter loads resonator and two open circuit minor matters loaded by coupling minor matters of opening a way forms.The resonator loaded due to open circuit coupling minor matters can at centre frequency f
odd1produce resonance and transmission zero, as shown in Figure 5 a, its common mode inhibition limited efficiency.When coupling feed all loads the open circuit minor matters of four/wavelength, coupling feed is also at f
odd1place produces transmission zero, and common mode inhibition level is improved.When coupling feed loads four/wavelength and half-wavelength open circuit minor matters respectively, common mode can at 0-2f
odd1two transmission zeros that interior increase is extra, make common mode inhibition better effects if.Fig. 5 b depicts the relation curve of coupling feed to common-mode response of circuit simulation.Transmission zero can be seen not by coupling feed odd mode impedance Z
oo1with loading minor matters impedance Z
simpact, Z
sless or Z
oo1larger, common mode inhibition effect is better.
This structure implements to have generality, and in such as Fig. 1 structure, transmission line can use the structure such as microstrip line, strip line, and the coupled transmission line such as shown in A7, A8 can use two-wire, three lines or multi-thread coupled transmission line to realize.The structure that microstrip structure, three wire configuration adopt when being the present embodiment specific implementation.Example structure as shown in Figure 1, micro-band medium substrate of employing as shown in Figure 2, D
1for using the upper strata metal patch of dielectric-slab, D
2for dielectric layer (its relative dielectric constant is 2.55, and thickness is 0.8mm, and loss angle tangent is 0.029), D
3for dielectric-slab lower floor grounded metal paster.
During this design of filter, first determine operating frequency f
0=f
odd1, make θ simultaneously
1=90 ° of f
0.K can be determined according to bandwidth requirement
2.According to return loss, parameter K
1, Z
oo1and Z
oo2be used for controlling transmission pole in passband and realize more flat ripple level.In order to suppress common mode, determine θ
scarry out controls transfer the Distribution of Zeros, select suitable Z simultaneously
s.
A frequency to be 3.7GHz, 3-dB bandwidth be 30% balance filter be designed.It is of a size of 0.6 λ
g× 0.57 λ
g(λ
gcentered by frequency place guide wavelength), circuit parameter is respectively K
2=0.264, K
1=0.32, Z
oo2=74.4 Ω, Z
oo1=71 Ω, Z
s=88.3 Ω, θ
1=90 °, θ
s=90 °.In order to avoid being coupled between resonator and loading minor matters, have employed foldable structure, resonator uses three interdigital coupling lines simultaneously.Fig. 6 a and Fig. 6 b gives the emulation of this example of balance filter and measures comparing result.During differential mode work, the centre frequency measuring (Electromagnetic Simulation) is 3.65 (3.7) GHz, and 3dB relative bandwidth is 31% (30%), and in band, minimum Insertion Loss is 1.1dB (0.3dB).Recording in frequency is that 3/4.3GHz (3.1/4.28GHz) place produces 2 transmission zeros, makes passband Δ f
3db/ Δ f
20dbreach 0.97 (0.978).Measure and emulate (circuit and electromagnetism) all reaches 20dB (13.5dB) respectively Out-of-band rejection at 4.7-7GHz.Emulation is due to even mould harmonic wave f at the harmonic wave of 7.5GHz
even1impact.Measuring (Electromagnetic Simulation) during common mode operation is that 2.27/3.73/6.3/7.22GHz (2.29/3.7/6.03/7.3GHz) place produces 4 transmission zeros in frequency, and common mode all achieves the suppression level of more than 20dB in 1-6.9GHz.There is a small amount of deviation in measurement and Electromagnetic Simulation, mainly because the coupling of coupling feed resonator minor matters causes, machining accuracy, medium and SMA loss also can produce error in addition.
Can see from above-mentioned example, the employing coupling minor matters that the present invention proposes load the balance filter of resonator, have very high precipitous type, are suitable for the design of high selectivity high common mode inhibition balance filter, there is important research and engineering practical value, be worthy to be popularized.
The examples of implementation of the above are only the preferred embodiment of the present invention, not limit practical range of the present invention with this, therefore the change that all shapes according to the present invention, principle are done, all should be encompassed in protection scope of the present invention.
Claims (5)
1. the balance filter adopting coupling minor matters to load resonator, it is characterized in that: the first filter cell and the second filter cell that include specular distribution, wherein, described first filter cell includes the first coupling minor matters and loads resonator, first input/output port, second input/output port, described first coupling minor matters load resonator and are made up of the first coupling minor matters and the first transmission line of cascade and the second transmission line, described first transmission line and the second transmission line are parallel to the symmetry axis of the first filter cell and the second filter cell, described first coupling minor matters are perpendicular to this symmetry axis, and be connected with the first transmission line and the second transmission line respectively, described first input/output port is connected with the 3rd transmission line, 3rd transmission line and the first transmission line form input/output terminal coupling feed, and this coupling feed is loaded with the first minor matters, second minor matters, 3rd minor matters, described second input/output port is connected with the 4th transmission line, 4th transmission line and the second transmission line form input/output terminal coupling feed, and this coupling feed is loaded with the 4th minor matters, described second filter cell includes the second coupling minor matters and loads resonator, 3rd input/output port, 4th input/output port, described second coupling minor matters load resonator and are made up of the second coupling minor matters and the 5th transmission line of cascade and the 6th transmission line, described 5th transmission line and the 6th transmission line are parallel to the symmetry axis of the first filter cell and the second filter cell, described second coupling minor matters are perpendicular to this symmetry axis, its one end is connected with the 5th transmission line and the 6th transmission line respectively, its other end and above-mentioned first minor matters that are coupled are connected, described 3rd input/output port is connected with the 7th transmission line, 7th transmission line and the 5th transmission line form input/output terminal coupling feed, and this coupling feed is loaded with the 5th minor matters, one end of described 5th minor matters is connected with the 7th transmission line, its other end respectively with above-mentioned first minor matters, one end of second minor matters connects, the other end of these the first minor matters is connected to the 3rd transmission line, the other end of these the second minor matters is connected to the center of above-mentioned 3rd minor matters, described first minor matters and the 5th minor matters specular, and with the first filter cell and the same symmetry axis of the second filter cell, described second minor matters extend on this symmetry axis, described 3rd minor matters are perpendicular to this symmetry axis, described 4th input/output port is connected with the 8th transmission line, 8th transmission line and the 6th transmission line form input/output terminal coupling feed, and this coupling feed is connected with above-mentioned 4th minor matters.
2. a kind of balance filter adopting coupling minor matters to load resonator according to claim 1, it is characterized in that: described 4th minor matters are formed by connecting by the transmission line of two sections of specular, and these two sections of transmission lines and the first filter cell and the same symmetry axis of the second filter cell.
3. a kind of balance filter adopting coupling minor matters to load resonator according to claim 1, is characterized in that: described first coupling minor matters and the second coupling minor matters are short circuit coupling minor matters or open circuit coupling minor matters.
4. a kind of balance filter adopting coupling minor matters to load resonator according to claim 1, is characterized in that: described first minor matters, the second minor matters, the 3rd minor matters, the 4th minor matters, the 5th minor matters are short circuit minor matters or open circuit minor matters.
5. a kind of coupling minor matters that adopt according to claim 1 load the balance filter of resonator, it is characterized in that: described first input/output port, the second input/output port, the 3rd input/output port, the 4th input/output port are the transmission line of impedance 50 Ω.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN108879043A (en) * | 2018-06-26 | 2018-11-23 | 井冈山大学 | A kind of three modal balancing filters using coupling minor matters load line of rabbet joint resonance structure |
| CN111355019A (en) * | 2018-12-24 | 2020-06-30 | 北京小米移动软件有限公司 | Terminal device |
| CN115425377A (en) * | 2022-09-29 | 2022-12-02 | 河南科技大学 | Double-passband balance filter based on square ring loading |
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| CN102280678A (en) * | 2011-05-27 | 2011-12-14 | 华南理工大学 | Balanced radio frequency electrically tunable bandpass filter with constant relative bandwidth |
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2015
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| CN102280678A (en) * | 2011-05-27 | 2011-12-14 | 华南理工大学 | Balanced radio frequency electrically tunable bandpass filter with constant relative bandwidth |
| CN102324599A (en) * | 2011-05-27 | 2012-01-18 | 华南理工大学 | Balanced type radio frequency voltage tunable bandpass filter with constant absolute bandwidth |
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Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108879043A (en) * | 2018-06-26 | 2018-11-23 | 井冈山大学 | A kind of three modal balancing filters using coupling minor matters load line of rabbet joint resonance structure |
| CN108879043B (en) * | 2018-06-26 | 2024-04-12 | 井冈山大学 | Three-mode balance filter adopting coupling branch loading slot line resonance structure |
| CN111355019A (en) * | 2018-12-24 | 2020-06-30 | 北京小米移动软件有限公司 | Terminal device |
| CN111355019B (en) * | 2018-12-24 | 2023-03-24 | 北京小米移动软件有限公司 | Terminal device |
| CN115425377A (en) * | 2022-09-29 | 2022-12-02 | 河南科技大学 | Double-passband balance filter based on square ring loading |
| CN115425377B (en) * | 2022-09-29 | 2023-09-08 | 河南科技大学 | Double-passband balance filter based on loading of ring resonator |
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|---|---|
| CN104882650B (en) | 2017-08-25 |
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