CN105226351A - A kind of adjustable differential double-passband filter and resonator - Google Patents

Abstract

The invention discloses a kind of adjustable differential double-passband filter and resonator, described adjustable differential double-passband filter comprises: the first party ring on described medium substrate upper strata, second party ring and micro-band connecting line, and is etched in a DGS unit and the 2nd DGS unit of described medium substrate lower floor; Also comprise the first input/output end port and the second input/output end port that are coupled in described first ring periphery, and be coupled in the 3rd input/output end port and the 4th input/output end port of described second ring periphery.Wherein first and the 3rd input/output end port form a pair difference port, second and the 4th input/output end port form another to difference port.Enforcement the invention has the beneficial effects as follows, has an adjustable low-frequency passband and a fixing high frequency pass band; DGS unit is etched directly the below at resonator, can suppress the common-mode noise in two passbands on the basis not increasing circuit size.

Description

A kind of adjustable differential double-passband filter and resonator

Technical field

The present invention relates to microwave technical field, more particularly, relate to a kind of adjustable differential double-passband filter and resonator.

Background technology

Due to self distinctive superelevation signal to noise ratio and the hyperimmunity to ambient noise and electromagnetic interference, difference channel receives increasing concern.As microwave send receive the band pass filter of significant components and also develop towards differential configuration.

Adjustable differential double-passband filter based on frequency-adjustable and dual-passband design can meet the communicating requirement of many standards multiple spectra, becomes development trend.

In prior art, adjustable differential filter is single passband design, and difference double-passband filter many employings step impedance resonator, by changing its impedance ratio and electrical length ratio realizes dual-passband.But the method independently cannot control the centre frequency of two passbands.

Therefore, prior art existing defects and deficiency, need to improve.

Summary of the invention

The technical problem to be solved in the present invention is, for the above-mentioned defect of prior art, provides a kind of adjustable differential double-passband filter and resonator.

The technical solution adopted for the present invention to solve the technical problems is:

On the one hand, a kind of adjustable differential double-passband filter is provided, comprise medium substrate, also comprise: the first party ring on described medium substrate upper strata, second party ring and micro-band connecting line, and be etched in a DGS unit and the 2nd DGS unit of described medium substrate lower floor;

Described first party ring is identical with second party ring; Described first party ring comprises four edges, from above square ring, be respectively the first limit, Second Edge, the 3rd limit and the 4th limit according to clockwise direction; Described second party ring comprises four edges, from above square ring, be respectively the first limit, Second Edge, the 3rd limit and the 4th limit according to clockwise direction;

3rd limit of described first party ring is connected by first limit of described microstrip line with described second party ring;

The middle part on the first limit of described first party ring connects short circuit minor matters;

The each open circuit minor matters being connected with varactor in parallel of the Second Edge of described first party ring and the middle part on the 4th limit;

The middle part on the 3rd limit of described second party ring connects short circuit minor matters;

The each open circuit minor matters being connected with varactor in parallel of the Second Edge of described second party ring and the middle part on the 4th limit;

A described DGS unit and the 2nd DGS unit etch under the 3rd limit of described first ring and the first limit of described second ring;

Also comprise:

Be coupled in the first input/output end port and second input/output end port of described first ring periphery, and be coupled in the 3rd input/output end port and the 4th input/output end port of described second ring periphery; Wherein, the first input/output end port and the 3rd input/output end port are a pair difference port, and the second input/output end port and the 4th input/output end port are that another is to difference port.

In one embodiment, described adjustable differential double-passband filter comprises four modes of resonance;

Wherein, two Low-frequency Modes form adjustable low-frequency passband, and two high frequency moulds form fixing high frequency pass band.

In one embodiment, the length of described short circuit minor matters can control the bandwidth of described adjustable low-frequency passband and described fixing high frequency pass band.

In one embodiment, the ratio of the initial centre frequencies of described adjustable low-frequency passband and described fixing high frequency pass band is determined by described open circuit minor matters.

In one embodiment, described low frequency pass band can be made to move down by increasing described varactor capacitance, and keep described high frequency pass band constant.

In one embodiment, described first input/output end port comprises feeder line and coupling arm, and wherein, described coupling arm comprises a horizontal sides and a vertical edges, wherein horizontal sides is parallel with the first limit of described first party ring, and vertical edges is parallel with the 4th limit of described first party ring.

In one embodiment, described second input/output end port comprises feeder line and coupling arm, and wherein, described coupling arm comprises a horizontal sides and a vertical edges, wherein horizontal sides is parallel with the first limit of described first party ring, and vertical edges is parallel with the Second Edge of described first party ring.

In one embodiment, described 3rd input/output end port comprises feeder line and coupling arm, and wherein, described coupling arm comprises a horizontal sides and a vertical edges, wherein horizontal sides is parallel with the 3rd limit of described second party ring, and vertical edges is parallel with the 4th limit of described second party ring.

In one embodiment, described 4th input/output end port comprises feeder line and coupling arm, and wherein, described coupling arm comprises a horizontal sides and a vertical edges, wherein horizontal sides is parallel with the 3rd limit of described second party ring, and vertical edges is parallel with the Second Edge of described second party ring.

Second aspect, provides a kind of resonator, comprising: described medium substrate, also comprises: the first party ring on described medium substrate upper strata, second party ring and micro-band connecting line, and is etched in a DGS unit and the 2nd DGS unit of described medium substrate lower floor;

Described first party ring is identical with second party ring; Described first party ring comprises four edges, from above square ring, be respectively the first limit, Second Edge, the 3rd limit and the 4th limit according to clockwise direction; Described second party ring comprises four edges, from above square ring, be respectively the first limit, Second Edge, the 3rd limit and the 4th limit according to clockwise direction;

3rd limit of described first party ring is connected by first limit of described microstrip line with described second party ring;

The middle part on the first limit of described first party ring connects short circuit minor matters;

The each open circuit minor matters being connected with varactor in parallel of the Second Edge of described first party ring and the middle part on the 4th limit;

The middle part on the 3rd limit of described second party ring connects short circuit minor matters;

The each open circuit minor matters being connected with varactor in parallel of the Second Edge of described second party ring and the middle part on the 4th limit;

A described DGS unit and the 2nd DGS unit etch under the 3rd limit of described first ring and the first limit of described second ring.

Implement adjustable differential double-passband filter of the present invention and resonator, there is following beneficial effect: have an adjustable low-frequency passband and a fixing high frequency pass band; The initial centre frequencies of two passbands and bandwidth are respectively by open circuit and the decision of short circuit minor matters of resonator; DGS unit is etched directly in the below of resonator to suppress the common-mode noise in two passbands, simultaneously not extra circuits size; Common mode inhibition method in low frequency pass band and high frequency pass band, and can independent design respectively based on slow wave and the band gap effect of DGS.

Accompanying drawing explanation

Below in conjunction with drawings and Examples, the invention will be further described, in accompanying drawing:

Fig. 1 is the structural representation of the resonator of the embodiment of the present invention;

Fig. 2 is the differential mode circuit diagram of the resonator of the embodiment of the present invention;

Fig. 3 (a) is the even moding circuit schematic diagram of the idol of resonator under differential mode of the embodiment of the present invention;

Fig. 3 (b) is the parity mode electrical schematic of resonator under differential mode of the embodiment of the present invention;

Fig. 3 (c) is the even strange moding circuit schematic diagram of resonator under differential mode of the embodiment of the present invention;

Fig. 3 (d) is the Chi Chi moding circuit schematic diagram of resonator under differential mode of the embodiment of the present invention;

Fig. 4 is that the resonator of the embodiment of the present invention is in Different L ₃and C _vlower corresponding differential mode frequency response;

Fig. 5 (a) is the common mode equivalent circuit of the resonator of the embodiment of the present invention;

Fig. 5 (b) is the strange moding circuit of resonator under common mode of the embodiment of the present invention;

Fig. 5 (c) is the even moding circuit of resonator under common mode of the embodiment of the present invention;

Fig. 6 is the different C of the resonator of the embodiment of the present invention _vunder three common mode resonance frequency responses;

Fig. 7 is the structural representation of the adjustable single-ended filter of one embodiment of the invention;

Fig. 8 is the coupling scheme schematic diagram of the filter of the embodiment of the present invention;

Fig. 9 is filter of the invention process with L _trelation;

Figure 10 is the common-mode rejection filters be made up of two DGS unit of the embodiment of the present invention;

Figure 11 is the scale diagrams of the DGS unit of the embodiment of the present invention;

Figure 12 is differential mode and the common mode frequency response of filter after the DGS unit loading varying number in the embodiment of the present invention;

Figure 13 is that the embodiment of the present invention simulates at traditional λ _g/ 4 resonators load the situation of DGS unit to study the impact of DGS position on resonance frequency;

Figure 14 is f _c1and f _c3with the curve chart that d changes;

Figure 15 is the structural representation of the adjustable differential filter of the present invention's instantiation;

Figure 16 (a) is that the adjustable differential filter of the embodiment of the present invention is at different C _vdifferential Mode insertion loss in situation;

Figure 16 (b) is return loss and the common mode inhibition parameters simulation of the adjustable differential filter of the embodiment of the present invention;

Figure 17 (a) is the adjustable differential filter of one embodiment of the invention test result;

Figure 17 (b) is the adjustable differential filter of one embodiment of the invention with test result.

Embodiment

In order to there be understanding clearly to technical characteristic of the present invention, object and effect, now contrast accompanying drawing and describe the specific embodiment of the present invention in detail.

Embodiment 1

It is the structural representation of the resonator of the embodiment of the present invention see Fig. 1.

The resonator of the embodiment of the present invention comprises: comprise medium substrate, the first party ring 10 on medium substrate upper strata, second party ring 20 and micro-band connecting line 50, and is etched in a DGS unit 30 and the 2nd DGS unit 40 of medium substrate lower floor.

First party ring 10 comprises four edges, and from above square ring, be respectively the first limit, Second Edge, the 3rd limit and the 4th limit according to clockwise direction, wherein the first limit is relative limit with the 3rd limit, and Second Edge is relative limit with the 4th limit.

Second party ring 20 comprises four edges, and from above square ring, be respectively the first limit, Second Edge, the 3rd limit and the 4th limit according to clockwise direction, wherein the first limit is relative limit with the 3rd limit, and Second Edge is relative limit with the 4th limit.

3rd limit of first party ring 10 is connected with the first limit of second party ring 20 by microstrip line 50.

The middle part on the first limit of first party ring 10 connects short circuit minor matters 101.

The each open circuit minor matters 102 being connected with varactor in parallel of the Second Edge of first party ring 10 and the middle part on the 4th limit.

The middle part on the 3rd limit of second party ring 20 connects short circuit minor matters 201.

The each open circuit minor matters 202 being connected with varactor in parallel of the Second Edge of second party ring 20 and the middle part on the 4th limit.

One DGS unit 30 and the 2nd DGS unit 40 etch under the 3rd limit of first ring 10 and the first limit of the second ring 20.

First party ring 10 and second party ring 20 are two identical varactors and minor matters loaded ring.The girth of first party ring 10 is 4L ₁, the length of open circuit minor matters 102 is L ₂, the length of short circuit minor matters 101 is L ₃.Same, the girth of second party ring 20 is 4L ₁, the length of open circuit minor matters 202 is L ₂, the length of short circuit minor matters 201 is L ₃.

The characteristic admittance of first party ring 10 and second party ring 20 is Y ₀.The characteristic admittance of micro-band connecting line 50 is 2Y ₀.

Below with reference to Fig. 2-Fig. 6, differential mode and Common mode analysis are carried out to the resonator of the embodiment of the present invention.

(1) Differential mode analysis

Under differential mode, cut-off rule (dotted line of the micro-band connecting line of the crosscut in Fig. 1) presents virtually, and the resonator of the embodiment of the present invention forms an independently resonator.This resonator comprises the open circuit minor matters and two short circuit minor matters that are connected to varactor for a pair as shown in Figure 2.Line of symmetry 1 and 2 shown in Fig. 1 and 2 represents auxiliary line of symmetry of advocating peace respectively.Utilize twice even and odd mode analysis, four difference equivalent electric circuits are as shown in Fig. 3 (a)-(d).Fig. 3 (a) and (b) even mould and parity mode input impedance can be obtained by formula (1) and (2) respectively.

$Y_{ee}^d=\frac{{\mathrm{j\ωC}}_v}{2}-\frac{{\mathrm{jY}}_0}{tan\mathrm{\β}(L_1+L_2+L_3)}---\left(1\right)$

$Y_{oe}^d=\frac{{\mathrm{j\ωC}}_v}{2}-\frac{{\mathrm{jY}}_0}{tan\mathrm{\β}(L_1+L_2)}---\left(2\right)$

According to condition of resonance, with imaginary part be 0.Even mould and parity mode resonance frequency f _d1, f _d2can be represented by formula (3) and (4).

$f_{d1}=\frac{c}{2\mathrm{\π}(L_1+L_2+L_3)\sqrt{{\mathrm{\ϵ}}_{eff}}}\·arctan\frac{Y_0}{2{\mathrm{\π\ωC}}_v}---\left(3\right)$

$f_{d2}=\frac{c}{2\mathrm{\π}(L_1+L_2)\sqrt{{\mathrm{\ϵ}}_{eff}}}\·arctan\frac{Y_0}{2{\mathrm{\π\ωC}}_v}---\left(4\right)$

In like manner according to Fig. 3 (c) and (d), even strange mould f _d3with Chi Chi mould f _d4can be expressed as:

$f_{d3}=\frac{c}{2(L_1+L_3)\sqrt{{\mathrm{\ϵ}}_{eff}}}---\left(5\right)$

$f_{d4}=\frac{c}{2L_1\sqrt{{\mathrm{\ϵ}}_{eff}}}---\left(6\right)$

Fig. 4 is depicted in Different L ₃and C _vlower corresponding differential mode frequency response.Thus, the resonator of the embodiment of the present invention has following characteristics:

Two Low-frequency Modes f _d1and f _d2the varactor derived from as shown in Fig. 3 (a) He (b) loads λ _g/ 4 resonators.Terminal short circuit λ as shown in Fig. 3 (c) He (d) _g/ 2 resonators produce two high frequency mould f _d3and f _d4; Four resonant modes are divided into two groups, f _d1and f _d2constitute centre frequency to exist adjustable low-frequency passband; And f _d3and f _d4combination define centre frequency and exist fixing high frequency pass band; Do not affecting when, improve C _vcan make move down; Change length L ₃make f _d1and f _d3away from f _d2and f _d4, this parameter is used for the bandwidth of control two passbands.

(2) Common mode analysis

Fig. 5 (a) shows the common mode equivalent circuit of the resonator of the embodiment of the present invention, and the parity mode circuit of its common mode is as shown in Fig. 5 (b) He (c).Can see that its strange mould equivalent electric circuit can be decomposed into structure shown in Fig. 3 (b) and (d) further.Therefore, two common mode resonance frequency f _c1and f _c2with differential-mode response f _d2and f _d4identical.The even mould input impedance expression formula of common mode shown in Fig. 5 (c) is:

$Y_e^c=Y_0\frac{Y_L+{\mathrm{jY}}_{0}tan({\mathrm{\θ}}_1+{\mathrm{\θ}}_3)}{Y_0+{\mathrm{jY}}_{L}tan({\mathrm{\θ}}_1+{\mathrm{\θ}}_3)}---\left(7\right)$

$Y_L={\mathrm{jY}}_{0}tan({\mathrm{\θ}}_1+{\mathrm{\θ}}_3)+2{\mathrm{jY}}_0\frac{{\mathrm{\ωC}}_v+2Y_0{\mathrm{tan\θ}}_2}{2Y_0-{\mathrm{\ωC}}_v{\mathrm{tan\θ}}_2}---\left(8\right)$

According to condition of resonance 3rd common mode resonance frequency f _c3can obtain:

${\tan }^2({\mathrm{\θ}}_1+{\mathrm{\θ}}_3)+2\frac{{\mathrm{\ωC}}_v+2Y_0{\mathrm{tan\θ}}_2}{2Y_0-{\mathrm{\ωC}}_v{\mathrm{tan\θ}}_2}\·tan({\mathrm{\θ}}_1+{\mathrm{\θ}}_3)=1---\left(9\right)$

Fig. 6 shows different C _vunder three common mode resonance frequency response (wherein, L ₁=27.4mm, L ₂=2mm and L ₃=1.6mm).According to Fig. 3 (a) He Fig. 5 (c), two common mode frequency f _c1and f _c3all derive from varactor and load λ _g/ 4 wave resonator.Therefore, f _c1and f _c3along with C _vincrease and diminish.

There is multiple common-mode signal in the resonator of the embodiment of the present invention, simultaneously f _c1and f _c2with differential mode frequency f _d2and f _d4overlap.Thus, the common mode inhibition method of the embodiment of the present invention needs on the basis not affecting differential-mode response, suppress common-mode noise automatically to adapt to adjustable low-frequency passband simultaneously.The resonator of the embodiment of the present invention, DGS unit is etched below the differential signal line (the 3rd limit of first party ring and the first limit of second party ring) of a pair vicinity, due to the loop that ground is only common-mode signal, therefore common-mode noise can be suppressed on the basis not affecting difference mode signal.

Thus, the varactor of the embodiment of the present invention and minor matters load dumbbell shape resonator, can produce two groups of four resonance frequencys, and wherein two low-frequency resonant moulds can move along with varactor change.The DGS unit simultaneously etched can suppress common-mode noise and automatically adapt to adjustable low-frequency resonant mode.

Embodiment 2

In order to reduce repetition, based on symmetrical structure, adjustable differential filter can be divided into two according to cut-off rule, forms two identical adjustable single-end circuits.It is the structural representation of the adjustable single-ended filter of one embodiment of the invention see Fig. 7.The adjustable differential filter of the embodiment of the present invention comprises the resonator described in above-described embodiment 1, and four comprise feeder line and coupling arm composition input/output end port.Wherein, the first input/output end port and the second input/output end port are positioned at the ground floor on medium floor, and and first ring periphery coupling.3rd input/output end port and the 4th input/output end port are positioned at the upper strata of medium substrate, and and the second ring periphery coupling.

First input/output end port and the 3rd input/output end port are a pair difference port, and the second input/output end port and the 4th input/output end port are that another is to difference port

Should be understood that Fig. 7 illustrate only the half of adjustable differential filter circuit, namely not shown in the input/output end port of the opposing party's ring and correspondence thereof, two DGS unit Fig. 7.

See Fig. 7,51 as output port, and 52 as input port; Or 51 as input port, 52 as output port.

First input/output end port comprises feeder line 502 and coupling arm 501, and wherein, coupling arm 501 comprises a horizontal sides and a vertical edges, and wherein horizontal sides is parallel with the first limit of first party ring 10, and vertical edges is parallel with the 4th limit of first party ring 10.

Second input/output end port comprises feeder line 502 and coupling arm 501, and wherein, coupling arm 501 comprises a horizontal sides and a vertical edges, and wherein horizontal sides is parallel with the first limit of first party ring 10, and vertical edges is parallel with the Second Edge of first party ring 10.

3rd input/output end port comprises feeder line 502 and coupling arm 501, and wherein, coupling arm 501 comprises a horizontal sides and a vertical edges, and wherein horizontal sides is parallel with the 3rd limit of second party ring 20, and vertical edges is parallel with the 4th limit of second party ring 20.

4th input/output end port comprises feeder line 502 and coupling arm 501, and wherein, coupling arm 501 comprises a horizontal sides and a vertical edges, and wherein horizontal sides is parallel with the 3rd limit of second party ring 20, and vertical edges is parallel with the Second Edge of second party ring 20.

The band-pass behavior of the adjustable differential filter of the embodiment of the present invention can be obtained by this single-ended topology of research.External sort factor and coupling coefficient are most important two parameters of designing filter, and the former and stiffness of coupling are inversely proportional to, and the latter determines pass band width.

As shown in Figure 8, its interior joint S and L represents input/output end port to the coupling scheme of this filter respectively, and node 1 to 4 represents four difference mould (f _d1to f _d4).Wherein two groups is asynchronous mould, this is because L ₃only change f _d1and f _d3and f _d2and f _d4remain unchanged, the coupling coefficient between two patterns therefore between each group is 0.Coupling between input/output end port and differential mode circuit is defined as M _siand M _iL, i=1,2,3,4.Coupling between the load of source can improve passband selectivity.

(1) initial condition

At initial condition (C _v=0), the detailed design index of differential mode passband is as shown in table 1.

Table 1

	Centre frequency	Absolute bandwidth	Relative bandwidth	Return loss
					Passband I	1540MHz	120MHz	7.8％	15dB
Passband II	3560MHz	290MHz	8％	10dB

The physical size of this resonator is: L ₁=27.4mm, L ₂=2mm, L ₃=1.6mm, these parameters can be passed through computing formula (3)-(6) and obtain.According to coupling matrix analytical technology, coupling matrix can be provided

$M^L=\left[\begin{array}{cccc}0& M_{S1}& M_{S2}& 0\\ M_{S1}& M_{11}& 0& M_{1L}\\ M_{S2}& 0& -M_{22}& -M_{2L}\\ 0& M_{1L}& -M_{2L}& 0\end{array}\right]=\left[\begin{array}{cccc}0& 0.6447& 0.6447& 0\\ 0.6447& 1.0218& 0& 0.6447\\ 0.6447& 0& -1.0218& -0.6447\\ 0& 0.6447& -0.6447& 0\end{array}\right]---\left(10\right)$

$M^U=\left[\begin{array}{cccc}0& M_{S3}& M_{S4}& 0\\ M_{S3}& M_{33}& 0& M_{3L}\\ M_{S4}& 0& -M_{44}& -M_{4L}\\ 0& M_{3L}& -M_{4L}& 0\end{array}\right]=\left[\begin{array}{cccc}0& 0.6213& 0.6213& 0\\ 0.6213& 1.0434& 0& 0.6213\\ 0.6213& 0& -1.0434& -0.6213\\ 0& 0.6213& -0.6213& 0\end{array}\right]---\left(11\right)$

Wherein, M ^land M ^urepresent the bimodulus matrix of the low and high frequency pass band of difference respectively.Ideally, M _s1=M _s2, M _s3=M _s4and M _si=M _iL.Diagonal M in coupling matrix _iifor:

$M_{ii}=\frac{f_0^2-f_i^2}{\mathrm{\Δ}f\·f_i}---\left(12\right)$

Wherein, f ₀centre frequency and absolute bandwidth is represented respectively with Δ f.Live width w shown in Fig. 7 ₀, w and gap g affects simultaneously but these parameters are difficult to independent control two passband responses.In addition, the link position L of the feeder line of Fig. 7 mark _talso can control adjustment L _tinput/output terminal coupling can be treated with a certain discrimination to meet the performance requirement of two difference passbands. can according to element M in matrix _sicalculate

$Q_{ex}^{L/U}\·FBW\·M_{Si}^2=1---\left(13\right)$

The low frequency pass band quality factor calculated high frequency pass band quality factor fig. 9 draws with L _trelation.Show according to Fig. 9, feed position selects L _tmeet design requirement during=9mm.And work as L _twhen becoming large, diminish simultaneously slight change is large.This phenomenon shows by regulating L _tbalance can be realized to meet requirement.

In initial condition, the bandwidth of two passbands is by L ₃determine.By the length L of appropriate change coupling arm _t1, the frequency response with superperformance can be optimized and obtains.

(2) frequency adjustment

In embodiments of the present invention, by increasing C _vlow frequency pass band can move down and high frequency pass band remains unchanged.In order to the band-pass behavior realized in low frequency pass band frequency adjustment procedure, it is inversely prroportional relationship that the change of external sort factor and coupling coefficient should correspond to operating frequency.As Fig. 3 (a) and (b), at increase C _vin process, λ _gthe electrical length of/4 resonators is extended, and feeder line is moved and keeps away terminal, obtains and becomes large simultaneously remain unchanged, as shown in Figure 9.On the other hand, in frequency adjustment procedure, the bandwidth change of low frequency pass band cannot from fixing L ₃obtain with in null value coupling coefficient.But by bimodulus matrix being converted into the coupling coefficient m that second order direct-coupling matrix can obtain non-zero ₁₂,

$m_{12}=\frac{f_{d2}^2-f_{d1}^2}{f_{d2}^2+f_{d1}^2}=\frac{1-{(f_{d1}/f_{d2})}^2}{1+{(f_{d1}/f_{d2})}^2}---\left(14\right)$

According to formula (3) and (4), f _d2to C _vchange more responsive.Increase C _vmake f _d1/ f _d2become large, the m diminished gradually ₁₂.Table 2 lists different C _vunder and m ₁₂.As shown in Table 2, when resonance frequency regulates downwards, increase m ₁₂decline.Required by therefore, in the frequency adjustment procedure of low frequency pass band and m ₁₂between inversely prroportional relationship can be satisfied the passband that realizes.

Table 2

In one embodiment, the embodiment of the present invention utilizes band gap effect to suppress the common-mode signal in high frequency pass band, and utilizes Slow-wave effect to suppress the common mode under adjustable low-frequency passband.

(1) band gap effect is utilized to suppress the common-mode signal in high frequency pass band

See Fig. 1, the adjustable differential filter of the embodiment of the present invention, etches two DGS unit below the differential signal line (the 3rd limit of first party ring and the first limit of second party ring) of a pair vicinity.Due to the loop that ground is only common-mode signal, therefore common-mode noise can be suppressed on the basis not affecting difference mode signal.See Fig. 1, the limit that two rings are adjacent can be approximated to be adjacent differential lines pair, and a DGS unit and the 2nd DGS unit are arranged on the differential signal line of this pair vicinity, also can avoid increasing circuit size.

Utilize the band gap effect of DGS unit, common-mode noise can be eliminated at stopband.Figure 10 shows a common-mode rejection filters be made up of two DGS unit, and change the size of DGS unit, its differential mode and common mode simulation result are plotted.

With square simulated line in Figure 10, DGS unit is of a size of l ₁× l ₂=5.2mm ².The simulated line that band is circular, DGS unit is of a size of l ₁× l ₂=39.4mm ².With the simulated line of triangle, DGS unit is of a size of l ₁× l ₂=18.4mm ².l ₃＝5.6mm,l ₄＝1.6mm,l ₅＝l ₆＝0.2mm,w _c＝1.8mm。

See Figure 11, parameter 1 ₁, l ₂, l ₃, l ₄, l ₅, l ₆, in w, w _cfor the width of medium substrate upper strata microstrip line, l ₄be the spacing of two contiguous microstrip lines, all the other are DGS cellular construction size.

The common-mode rejection filters be made up of small size DGS unit presents good common-mode rejection properties at stopband.The embodiment of the present invention is by selecting the DGS of suitable dimension, f _c2can be eliminated and not affect

See Fig. 9, by common mode resonance frequency f _c1and f _c3the region A formed can control and move to the corresponding position of differential mode low frequency pass band, then can obtain certain common mode inhibition degree.Can along with C with time domain A _vincrease move down.Therefore, can realize for adaptive common mode inhibition adjustable low-frequency passband.

(2) utilize Slow-wave effect to the common mode inhibition under adjustable low-frequency passband

When embedded DGS unit is etched in below resonator time, based on the Slow-wave effect of DGS, the disturbed and current path of the CURRENT DISTRIBUTION of common mode equivalent circuit is extended.On the basis not affecting difference mode signal, common mode resonance frequency is dragged down, the differential mode that can separately overlap thus and common mode.Figure 12 compares differential mode and the common mode frequency response of the resonator after the DGS unit loading varying number.The size of embedded DGS unit resonator is respectively: l ₁× l ₂=5.2mm ², l ₃=4mm, l ₄=2.4mm, l ₅=l ₆=0.2mm, L ₁=27.4mm, L ₂=2mm, L ₃=1.6mm, C _v=0.4pF.

When loading embedded DGS unit, f _c1and f _c3be moved downward based on Slow-wave effect.Simultaneously along with DGS unit loads increasing number, Slow-wave effect strengthens.When use two DGS unit, the trap of common-mode signal just in time mates with low frequency pass band.

In addition, because the intensity of Slow-wave effect is relevant to the amplitude of distributed current on resonator, therefore the position of DGS is for control f _c1and f _c3also extremely important.As shown in Fig. 5 (b) He (c), f _c1and f _c3all derive from λ _g/ 4 resonators.

Figure 13 simulates at λ _g/ 4 resonators load the situation of DGS unit to study the impact of its position on resonance frequency.Corresponding simulation result is listed in table 3, and L is shorter, and the resonance frequency obtained is less.This is because mobile DGS unit can strengthen Slow-wave effect to the short dot with maximum distribution electric current.This mechanism can be used to regulate common mode inhibition degree.

Table 3

Distance (mm)	L＝10	L＝8	L＝6	L＝4
					Resonance frequency (GHz)	1.58	1.38	1.31	1.21

As shown in Figure 1, the position of embedded DGS unit is defined as d, and it is the distance between DGS and line of symmetry 1.DGS unit is arranged in common mode equivalent circuit minor matters L shown in Fig. 5 (b) and (c) after decomposing ₂left side.For the strange moding circuit of Fig. 5 (a), when d reduces, DGS unit is near short dot, f _c1move down shown in table 3 result.The contrary d that reduces for even moding circuit is equivalent to mobile DGS to open end, and the now impact of DGS on resonator is weakened, therefore f _c3move up.F _c1and f _c3the curve that adjoint d changes as shown in figure 14.Widen f _c1and f _c3between interval make region A create darker common mode trap.Therefore by regulating the quantity of embedded DGS unit and the position of region A, common mode inhibition position and suppression level can be optimised.

In one embodiment, the adjustable differential double-passband filter of the embodiment of the present invention has an adjustable low-frequency passband, it works in multiple gps system (1.2-1.5GHz) and a fixing high frequency pass band, and it is applied to 802.16WiMAX (3.6GHz).

See Figure 15, in an instantiation, each parameter of adjustable differential filter is w=0.4mm, w ₁=g=s=0.2mm, L ₁=27mm, L ₂=2mm, L ₃=1.6mm, L ₄=7.2mm, L ₅=8.2mm, L ₆=5.8mm, L ₇=1.2mm, L ₈=3mm, L ₉=3.2mm, L ₁₀=3mm, L ₁₁=8.4mm, L ₁₂=1mm, L ₁₃=6.2mm, L ₁₄=3mm, d=1.4mm.

In the adjustable differential filter shown in Figure 15, in order to save area, Second Edge and the 4th limit of first ring and the second ring fold, and the coupling arm of the first input/output end port, the second input/output end port, the 3rd input/output end port and the 4th input/output end port folds.Concrete folding mode can be determined according to actual conditions.

Tunable capacitor C _vcan be expressed as:

$C_v=\frac{C_{vc}{C}_b}{C_{vc}+C_b}---\left(15\right)$

Wherein, C _vcfor the capacitance of varactor, C _bfor capacitance.Figure 16 (a) simulates at different C _vdifferential Mode insertion loss in situation.Work as C _vwhen s is increased to 0.8pF from 0.4pF, drop to 1.27GHz from 1.51GHz and be held in 3.68GHz.Figure 16 (b) shows DGS unit and inhibit common-mode signal in two difference passband, and suppression level reaches 18dB.Meanwhile, as increase C _vtime, differential mode low frequency pass band and common mode inhibition can move down simultaneously.Add man-hour at material object, varactor and capacitance (3pF) series connection are to represent C _v.Reverse bias voltage V _biasconnect a 50-k Ω resistance.Whole circuit size is that 52mm × 18mm namely exists electricity is of a size of 0.424 λ _g× 0.147 λ _g.Figure 17 (a) is it test result; Figure 17 (b) is it with test result.See Figure 17 (a) as bias voltage V _biaswhen dropping to 5V from 27, the centre frequency of low frequency pass band drops to 1.24GHz from 1.54, and the centre frequency of high frequency pass band maintains 3.76GHz simultaneously.Now count the loss of SMA connector in, the Insertion Loss of low frequency pass band is increased to 5.1dB from 1.92, and 1-dB relative bandwidth changes to 5.6% by 5.8%.The minimum Insertion Loss of high frequency pass band is 1.84dB.Common mode inhibition degree in whole adjustment process medium and low frequency passband and high frequency pass band is greater than 16dB and 18dB respectively.

The adjustable differential double-passband filter of the embodiment of the present invention has an adjustable low-frequency passband and a fixing high frequency pass band; The initial centre frequencies of two passbands and bandwidth are respectively by open circuit and the decision of short circuit minor matters of resonator; DGS unit is etched directly in the below of resonator to suppress the common-mode noise in two passbands; Common mode inhibition method in low frequency pass band and high frequency pass band, and can independent design respectively based on slow wave and the band gap effect of DGS.

By reference to the accompanying drawings embodiments of the invention are described above; but the present invention is not limited to above-mentioned embodiment; above-mentioned embodiment is only schematic; instead of it is restrictive; those of ordinary skill in the art is under enlightenment of the present invention; do not departing under the ambit that present inventive concept and claim protect, also can make a lot of form, these all belong within protection of the present invention.

Claims (10)

1. an adjustable differential double-passband filter, comprise medium substrate, it is characterized in that, also comprise: the first party ring on described medium substrate upper strata, second party ring and micro-band connecting line, and be etched in a DGS unit and the 2nd DGS unit of described medium substrate lower floor;

Described first party ring is identical with second party ring; Described first party ring comprises four edges, from above square ring, be respectively the first limit, Second Edge, the 3rd limit and the 4th limit according to clockwise direction; Described second party ring comprises four edges, from above square ring, be respectively the first limit, Second Edge, the 3rd limit and the 4th limit according to clockwise direction;

3rd limit of described first party ring is connected by first limit of described microstrip line with described second party ring;

The middle part on the first limit of described first party ring connects short circuit minor matters;

The each open circuit minor matters being connected with varactor in parallel of the Second Edge of described first party ring and the middle part on the 4th limit;

The middle part on the 3rd limit of described second party ring connects short circuit minor matters;

The each open circuit minor matters being connected with varactor in parallel of the Second Edge of described second party ring and the middle part on the 4th limit;

A described DGS unit and the 2nd DGS unit etch under the 3rd limit of described first ring and the first limit of described second ring;

Also comprise:

Be coupled in the first input/output end port and second input/output end port of described first ring periphery, and be coupled in the 3rd input/output end port and the 4th input/output end port of described second ring periphery; Wherein, the first input/output end port and the 3rd input/output end port are a pair difference port, and the second input/output end port and the 4th input/output end port are that another is to difference port.

2. adjustable differential double-passband filter according to claim 1, is characterized in that, described adjustable differential double-passband filter comprises four modes of resonance;

Wherein, two Low-frequency Modes form adjustable low-frequency passband, and two high frequency moulds form fixing high frequency pass band.

3. adjustable differential double-passband filter according to claim 2, is characterized in that, the length of described short circuit minor matters can control the bandwidth of described adjustable low-frequency passband and described fixing high frequency pass band.

4. adjustable differential double-passband filter according to claim 2, is characterized in that, the ratio of the initial centre frequencies of described adjustable low-frequency passband and described fixing high frequency pass band is determined by described open circuit minor matters.

5. adjustable differential double-passband filter according to claim 2, is characterized in that, described low frequency pass band can be made to move down, and keep described high frequency pass band constant by increasing described varactor capacitance.

6. adjustable differential double-passband filter according to claim 1, it is characterized in that, described first input/output end port comprises feeder line and coupling arm, wherein, described coupling arm comprises a horizontal sides and a vertical edges, wherein horizontal sides is parallel with the first limit of described first party ring, and vertical edges is parallel with the 4th limit of described first party ring.

7. adjustable differential double-passband filter according to claim 1, it is characterized in that, described second input/output end port comprises feeder line and coupling arm, wherein, described coupling arm comprises a horizontal sides and a vertical edges, wherein horizontal sides is parallel with the first limit of described first party ring, and vertical edges is parallel with the Second Edge of described first party ring.

8. adjustable differential double-passband filter according to claim 1, it is characterized in that, described 3rd input/output end port comprises feeder line and coupling arm, wherein, described coupling arm comprises a horizontal sides and a vertical edges, wherein horizontal sides is parallel with the 3rd limit of described second party ring, and vertical edges is parallel with the 4th limit of described second party ring.

9. adjustable differential double-passband filter according to claim 1, it is characterized in that, described 4th input/output end port comprises feeder line and coupling arm, wherein, described coupling arm comprises a horizontal sides and a vertical edges, wherein horizontal sides is parallel with the 3rd limit of described second party ring, and vertical edges is parallel with the Second Edge of described second party ring.

10. a resonator, comprising: described medium substrate, is characterized in that, also comprises: the first party ring on described medium substrate upper strata, second party ring and micro-band connecting line, and is etched in a DGS unit and the 2nd DGS unit of described medium substrate lower floor;

Described first party ring is identical with second party ring; Described first party ring comprises four edges, from above square ring, be respectively the first limit, Second Edge, the 3rd limit and the 4th limit according to clockwise direction; Described second party ring comprises four edges, from above square ring, be respectively the first limit, Second Edge, the 3rd limit and the 4th limit according to clockwise direction;

3rd limit of described first party ring is connected by first limit of described microstrip line with described second party ring;

The middle part on the first limit of described first party ring connects short circuit minor matters;

The each open circuit minor matters being connected with varactor in parallel of the Second Edge of described first party ring and the middle part on the 4th limit;

The middle part on the 3rd limit of described second party ring connects short circuit minor matters;

The each open circuit minor matters being connected with varactor in parallel of the Second Edge of described second party ring and the middle part on the 4th limit;

A described DGS unit and the 2nd DGS unit etch under the 3rd limit of described first ring and the first limit of described second ring.