CN108493529A - Double frequency filter - Google Patents
Double frequency filter Download PDFInfo
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- CN108493529A CN108493529A CN201810200005.7A CN201810200005A CN108493529A CN 108493529 A CN108493529 A CN 108493529A CN 201810200005 A CN201810200005 A CN 201810200005A CN 108493529 A CN108493529 A CN 108493529A
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- microstrip line
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
- H01P1/00—Auxiliary devices
- H01P1/20—Frequency-selective devices, e.g. filters
- H01P1/201—Filters for transverse electromagnetic waves
- H01P1/203—Strip line filters
- H01P1/20327—Electromagnetic interstage coupling
- H01P1/20336—Comb or interdigital filters
- H01P1/20345—Multilayer filters
Abstract
The invention discloses a kind of double frequency filters, are set as multilayer circuit, including：First resonant element, be set to multilayer circuit third layer and the 4th layer；Second resonant element is set to the second layer and third layer of multilayer circuit；And third resonant element, be set to multilayer circuit third layer and the 4th layer, wherein the first resonant element is identical with the topological structure of third resonant element, and it is arranged into left and right mirror symmetry, and the second resonant element grade is coupled between the first resonant element and third resonant element.The present invention has many advantages, such as that small, insertion loss is small, working frequency range Independent adjustable, can realize the extraction of multiple frequency range signal and inhibit interference.
Description
Technical field
The present invention relates to technical field of micro communication more particularly to a kind of double frequency filters.
Background technology
Filter to signal have frequency selectivity, can in a communications system by or block, separate or synthesize certain
The signal of frequency.Since electromagnetic spectrum resource is more and more limited, it is necessary to be distributed according to application, institute is for use as separation/group
Closing the filter of signal just seems that ever more important, performance characteristics directly affect whole system index.Double frequency filter can be same
When be operated in two different frequency ranges, often apply in front end microwave radio module and multiplex communication.
In recent years, MEMS (MEMS) technology, high temperature superconductor technology, low-temperature co-fired ceramics (LTCC) technology, photon
Emerging in large numbers for the new materials such as bandgap structure, microwave monolithic integrated circuit and technology, has pushed filter from performance to volume
Continuous improvement.With the sustainable development of wireless communication system and microwave and millimeter wave component, smaller volume, lighter weight,
Lower cost, higher performance have become inexorable trend and the requirement of filter development.
In addition, with wireless telecommunication system fast development, various terminal equipment supported extensively such as 2G, 3G,
The various communications protocols such as LTE, Wi-Fi, GPS.The wireless communication system of single frequency band and single communication standard is not only applicable to it not
Current demand can be met, thus the double frequency wireless communication system that can cover two frequency ranges simultaneously is flourished.And as double
One of the core component of multiband wireless communications system, the high performance double frequency filter design of small size already become the research of industry
Emphasis has broad application prospects.
In the prior art, document 1 (patent No. 201210116440.4) discloses a kind of based on asymmetric stepped impedance
The ultra-narrow band double frequency filter of resonator, helically shaped step impedance resonator and input/output are folded using two sections
Coupled transmission line obtains required resonant frequency to constitute filter main body by changing the impedance ratio of its resonator, from
And it is respectively that 2% and 1.3% ultra-narrow band double frequency filter designs to realize relative bandwidth.The filter construction is relatively easy, band
It is outer to inhibit higher.But due to the transmission characteristic of step impedance resonator, the working frequency of the filter influences each other, two frequency ranges
It can not independent control.Further, since its bandwidth of operation is very narrow, this just proposes very high requirement to processing technology, once
There is deviation in precision controlling, and working frequency is easy to shift.Document 2 (patent No. 201410019016.7) discloses one kind
The square ring bimodulus double frequency filter of minor matters load, four are diagonally extended inwardly by four interior angles in a Q-RING
The inner wall of major branch nodel line, the parallel Q-RING in end of every major branch nodel line extends an open stub, can introduce new
Perturbed structure has encouraged two degenerate modes, to realize the response characteristic of bimodulus double frequency filter.Two passbands of the filter
Centre frequency can be adjusted by changing the length of minor matters line in Fang Huan, but Insertion Loss is higher in passband, and whole occupies
Area is larger, it is difficult to meet growing highly integrated wireless communication terminal to the RF Components such as filter low cost, corpusculum
Product, light weight and high performance requirement.
Therefore, it is necessary to it is a kind of it is small, insertion loss is small, Out-of-band rejection degree is high, working frequency range Independent adjustable double frequency filter
Wave device extracts multi-band signal and inhibits to interfere.
Invention content
In order to solve the above technical problems, the present invention provides a kind of double frequency filter, there is multilayer circuit structure, can adjust
Transmission zero and separately adjustable working frequency have the characteristics that miniaturization, filter with low insertion loss, high inhibition.
Double frequency filter provided by the invention is set as multilayer circuit, including：First resonant element, is set to multilayer circuit
Third layer and the 4th layer；Second resonant element is set to the second layer of multilayer circuit, third layer and the 4th layer；And third
Resonant element, be set to multilayer circuit third layer and the 4th layer, wherein the topology of the first resonant element and third resonant element
Structure is identical, and is arranged into left and right mirror symmetry, and the second resonant element grade is coupled to the first resonant element and third resonance list
Between member.
Optionally, the first resonant element includes the first resonance microstrip line being located in third layer, the first pole plate and positioned at the
The second resonance microstrip line, the second pole plate on four layers, the first pole plate and the second pole plate layer coupling constitute the equivalent electricity of the first micro-strip
Hold；Third resonant element include be located at third layer on third resonance microstrip line, third pole plate and on the 4th layer the 4th
Resonance microstrip line, quadripolar plate, third pole plate and quadripolar plate layer coupling constitute the second micro-strip equivalent capacity.
Optionally, one end of the second resonance microstrip line is connected via the second via with one end of the first resonance microstrip line, the
The other end of one resonance microstrip line is connected with the first pole plate；One end of 4th resonance microstrip line is via the 6th via and third resonance
One end of microstrip line is connected, and the other end of third resonance microstrip line is connected with third pole plate.
Optionally, the second resonant element includes the 5th resonance microstrip line positioned at third layer, the 6th resonance microstrip line, the 7th
Resonance microstrip line, the 5th pole plate positioned at the second layer and the sextupole plate on the 4th layer, the 5th pole plate and the 7th resonance are micro-
Band line and sextupole plate layer coupling constitute third micro-strip equivalent capacity, and the both ends of the 6th resonance microstrip line are humorous with the 5th respectively
Shake one end of microstrip line is connected with one end of the 7th resonance microstrip line.
Optionally, the other end of the 5th resonance microstrip line is connected via the 9th via with one end of the 5th pole plate, and the 7th is humorous
Shake the other end and the 5th pole plate and sextupole plate layer coupling of microstrip line.
Optionally, which further includes：Input terminal is set to the first layer of multilayer circuit, the first resonance micro-strip
One end of line is connected via the tenth via with input terminal；And output end, it is set to the first layer of multilayer circuit, third resonance is micro-
One end with line is connected via the 11st via with output end.
Optionally, input terminal uses coplanar waveguide transmission line with output end.
Optionally, the characteristic impedance of coplanar waveguide transmission line is 50 ohm.
Optionally, which further includes：Ground plane is set to the layer 5 of multilayer circuit, the second resonance micro-strip
The other end of line is connected via the first via with ground plane, and the other end of the 4th resonance microstrip line is via the 5th via and ground plane
It is connected, the second pole plate is connected via third via and the 4th via with ground plane, and quadripolar plate is via the 7th via and the 8th mistake
Hole is connected with ground plane.
Optionally, each layer circuit topological structure of multilayer circuit or so mirror symmetry.
Optionally, the 4th spacing of the first spacing of first layer and the second layer and the 4th layer and layer 5 is more than the second layer
With the second spacing and third layer and the 4th layer of third spacing of third layer.
Optionally, multilayer circuit is manufactured based on LTCC Technology；And/or multilayer circuit uses interior
It is silver to bury metal material；And/or the dielectric constant of the baseplate material of multilayer circuit is 5.9；And/or multilayer circuit
The dielectric loss tangent angle of baseplate material is 0.002.
Optionally, the transmission zero of the first resonant element is adjusted by changing the capacitance of the first micro-strip equivalent capacity；It is logical
Cross the transmission zero for the capacitance adjusting third resonant element for changing the second micro-strip equivalent capacity；And by changing third micro-strip
The capacitance of equivalent capacity adjusts the transmission zero of the second resonant element.
Optionally, by changing the impedance value of the first resonance microstrip line and third resonance microstrip line, double frequency filter is adjusted
The first working frequency range；And the impedance value by changing the 5th resonance microstrip line and the 7th resonance microstrip line, adjust double frequency filter
Second working frequency range of wave device.
Double frequency filter provided by the invention, by integrating three resonant elements in five conductor layers of multilayer circuit,
By using vertical coupled mode, larger capacitance can be realized in smaller size smaller.Compared with conventional dual band bandpass filter, this hair
The technical solution of bright embodiment has following technological merit：
(1) small.Based on low-temperature co-fired ceramics (LTCC) technology, keep filter construction compact, favorable repeatability is applicable in
In wireless communication terminal and radio-frequency front-end that such as mobile phone, data card etc. are stringent to volume requirement.(2) band connection frequency and transmission zero
Facilitate control.Based on the horizontal mirror image symmetrical structure feature of the double frequency filter, even and odd mode analysis can be carried out to its resonant element,
To carry out independent setting to passband resonant frequency and transmission zero location, facilitate filter under different demands environment in wideband
Switch between band and high inhibition.(3) insertion loss is small.(4) highly selective.Filter realizes higher in smaller volume
Out-of-band rejection can effectively filter out various garbage signals and noise signal, reduce the signal interference between each communication channel.
Description of the drawings
Disclosure illustrative embodiments are described in more detail in conjunction with the accompanying drawings, the disclosure above-mentioned and its
Its purpose, feature and advantage will be apparent, wherein in disclosure illustrative embodiments, identical reference label
Typically represent same parts.
Fig. 1 is the double frequency filter three dimensional structure diagram of the embodiment of the present invention.
Fig. 2 is the equivalent schematic diagram of the double frequency filter of the embodiment of the present invention.
Fig. 3 is the first layer schematic top plan view of the double frequency filter of the embodiment of the present invention.
Fig. 4 is the second layer schematic top plan view of the double frequency filter of the embodiment of the present invention.
Fig. 5 is the third layer schematic top plan view of the double frequency filter of the embodiment of the present invention.
Fig. 6 is the 4th layer of schematic top plan view of the double frequency filter of the embodiment of the present invention.
Fig. 7 is the layer 5 schematic top plan view of the double frequency filter of the embodiment of the present invention.
Fig. 8 is the impedance of the first resonance microstrip line of the double frequency filter of the embodiment of the present invention to 5.2GHz passbands resonance frequency
The influence schematic diagram of rate.
Fig. 9 is the schematic frequency resonse characteristic figure of the double frequency filter of the embodiment of the present invention.
Reference sign：
1 first layer；2 second layers；3 third layer；4 the 4th layers；5 layer 5s；6 input terminals；7 output ends；8,11,8 ' thirds are micro-
Band equivalent capacity；9 the 5th resonance microstrip lines；10 the 6th resonance microstrip lines；11 the 7th resonance microstrip lines；12 first resonance micro-strips
Line；13 third resonance microstrip lines；14,14 ' first micro-strip equivalent capacity；15,15 ' second micro-strip equivalent capacity；16 second resonance
Microstrip line；17 the 4th resonance microstrip lines；18 the tenth vias；19 the 11st vias；20 the 9th vias；21 second vias；21 ' the 6th
Via；22 first vias；23 the 5th vias；24 third vias and the 4th via；25 the 7th vias and the 8th via.
Specific implementation mode
The preferred embodiment of the disclosure is more fully described below with reference to accompanying drawings.Although showing the disclosure in attached drawing
Preferred embodiment, however, it is to be appreciated that may be realized in various forms the disclosure without the embodiment party that should be illustrated here
Formula is limited.On the contrary, these embodiments are provided so that the disclosure is more thorough and complete, and can be by the disclosure
Range is completely communicated to those skilled in the art.
The design method of traditional double frequency filter includes：It (1), will by introducing transmission zero in single-pass band filter
Single-pass band is divided into dual-passband, and the filter construction is complicated, and design difficulty is big；(2) stepped impedance bimodulus characteristic is used to design bilateral
Band filter, each passband of the filter are difficult to individually control；(3) it is realized by pass filter and stop-band filter cascade double
Pass filter, the filter construction is complicated, size is big；(4) two single-pass band filter parallel connections is used to realize dual-passband filtering
Device, it is complicated, volume is big although the filter can individually control each passband.It is filtered for traditional double frequency
Device, the present invention set double frequency filter to multilayer circuit.
Fig. 1 is the three dimensional structure diagram of the double frequency filter of the embodiment of the present invention.As shown in Figure 1, double frequency filter is set
It is set to multilayer circuit, including five layers of conductor layer：Input terminal 6, output end 7 are located at the first layer of multilayer circuit, the first resonant element
(12,16,14,14 '), the second resonant element (8,8 ', 9,10,11) and third resonant element (13,17,15,15 ') are located at more
The layer second layer of circuit, third layer and the 4th layer, constitute the main body of double frequency filter, layer 5 is ground plane, each conductor layer
Between be connected by metallic vias, can be through-hole type via or buried type via.
Wherein, which can be based on low-temperature co-fired ceramics (LTCC) technique by various passive devices
It is buried in ceramic dielectric, is realized on three-dimensional circuit substrate active and passive integrated, make circuit miniaturization and densification.
The metal material of high conductivity can be used, such as silver, copper is conducive to the quality factor for improving circuit system as conductor material.
Such as may be used in silver conduct and bury metal material, it will not be aoxidized in sintering process, may not need plating protection.LTCC materials
Dielectric constant can change in very large range, the length of resonant element is with the square root of the dielectric constant of LTCC materials at anti-
Than the needs of to meet high frequency and high speed, the dielectric constant that ceramic substrate material may be used is 5.9, dielectric loss tangent angle
It is 0.002.
As shown in Figure 1, input terminal 6 and output end 7 are located at the first layer 1 of multilayer circuit, input terminal 6 is for microwave signal
Feed-in, output end 7 are used for the output of microwave signal, wherein microwave signal refers to the electromagnetic wave that frequency is 300MHz~300GHz
Signal.
Input terminal 6 is set to the first layer 1 of multilayer circuit, and the first resonance for being located at the first resonant element of third layer 3 is micro-
One end with line 12 is connected via the tenth via 18 with input terminal 6.
Output end 7 is set to the first layer 1 of multilayer circuit, and the third resonance for being located at the third resonant element of third layer 3 is micro-
One end with line 13 is connected via the 11st via 19 with output end 7.
Fig. 3 is the double frequency filter first layer schematic top plan view of the embodiment of the present invention.Input terminal 6 can be adopted with output end 7
It is that counterpoise grounding and center conductor band are placed in same plane using coplanar waveguide transmission line with the form of coplanar waveguide transmission line
And constitute, it is connect since co-planar waveguide not only has ground plane and be also dispersed in top of media signal transmssion line both sides in medium bottom surface
Ground, therefore its contact area with bigger.Co-planar waveguide may be implemented in such a way that counterpoise grounding surrounds center conductor band
The stabilization of electric property.Compared to microstrip line, there is broader effective bandwidth, the impedance ranges of bigger and the suppression of better pattern
System.
The transmission characteristic of coplanar waveguide transmission line can be characterized with characteristic impedance and effective dielectric constant, wherein characteristic
When impedance is that transmission line is in traveling wave state, the voltage and current ratio of same point.The characteristic impedance of coplanar waveguide transmission line can
It is the compromise for considering the balance of minimal losses and maximum power and being done to be set as 50 ohm.
First resonant element (such as shown in FIG. 1 12,14,14', 16), be set to the third layer 3 and the 4th of multilayer circuit
Layer 4；Second resonant element (such as shown in FIG. 18,8', 9,10,11) is set to the second layer 2,3 and of third layer of multilayer circuit
4th layer 4；And third resonant element (such as shown in FIG. 1 13,15,15', 17), be set to 3 He of third layer of multilayer circuit
4th layer 4.
First resonant element is identical with the topological structure of third resonant element, and is arranged into left and right mirror symmetry.Second is humorous
It shakes unit cascaded between the first resonant element and third resonant element.
Here, resonant element can be the passive port network comprising inductance, capacitance, resistance, when the voltage of circuit port
Resonance occurs when there is same-phase with electric current.Topological structure in each conductor layer can be disposed as left and right mirror symmetry, with
Just parity mode emi analysis is carried out.
Fig. 5 is the double frequency filter third layer schematic top plan view of the embodiment of the present invention.Fig. 6 is the double frequency of the embodiment of the present invention
The 4th layer of schematic top plan view of filter.
As shown in Fig. 5-Fig. 6, the first resonant element includes the first resonance microstrip line 12 being located in third layer 3, the first pole
Plate and the second resonance microstrip line 16, the second pole plate on the 4th layer 4, the first pole plate and the second pole plate layer coupling constitute the
One micro-strip equivalent capacity 14,14'.Third resonant element and the first resonant element or so mirror symmetry, including be located in third layer 3
Third resonance microstrip line 13, third pole plate and the 4th resonance microstrip line 17, quadripolar plate on the 4th layer 4, third pole
Plate and quadripolar plate layer coupling constitute the second micro-strip equivalent capacity 15,15'.
As shown in Fig. 1 or Fig. 5-Fig. 6, one end of the second resonance microstrip line 16 is via the second via 21 and the first resonance micro-strip
One end of line 12 is connected, and the other end of the first resonance microstrip line 12 is connected with the first pole plate.One end of 4th resonance microstrip line 17
It is connected with one end of third resonance microstrip line 13 via the 6th via 21', the other end and the third pole of third resonance microstrip line 13
Plate is connected.
As shown in figure 5, can also include two in third layer 3 is used for cascade conducting wire, and can be microstrip line, it is humorous with first
Shake unit, the second resonant element and third resonant element is electrically connected.
Fig. 4 is the double frequency filter second layer schematic top plan view of the embodiment of the present invention.
As shown in fig. 4-5, the second resonant element include positioned at third layer 3 the 5th resonance microstrip line 9, the 6th resonance it is micro-
With line 10, the 7th resonance microstrip line 11, the 5th pole plate positioned at the second layer 2 and the sextupole plate on the 4th layer, the 5th pole
Plate and the 7th resonance microstrip line and sextupole plate layer coupling constitute third micro-strip equivalent capacity, the 6th resonance microstrip line 10
Both ends are connected with one end of one end of the 5th resonance microstrip line 9 and the 7th resonance microstrip line 11 respectively.5th resonance microstrip line 9
The other end is connected via the 9th via 20 with one end of the 5th pole plate, the 7th resonance microstrip line 11 of the 5th pole plate and third layer 3
Sextupole plate layer coupling with the 4th layer together constitutes multi-layer capacity C2, i.e. third micro-strip equivalent capacity, in smaller size smaller
Inside realize C2Required larger capacitance.Wherein, the 7th resonance microstrip line 11 can be plain conductor of the branch on dielectric substrate
With the microwave transmission line constituted, general dielectric substrate selects the material that dielectric constant is high, lossy microwave is low.Multi-layer capacity C2Knot
Structure may include three parts：Ceramic dielectric, metal inner electrode, metal external electrode can be regarded as multiple simple parallel plate capacitances
The doublet of device.
Double frequency filter can also include ground plane, be set to the layer 55 of multilayer circuit.
Fig. 7 is double frequency filter layer 5 schematic top plan view of the present invention.
As shown in fig. 7, ground plane is provided with the first via 22, third via and the 4th via 24, the 5th via the 23, the 7th
Via and the 8th via 25.As shown in Figure 1, the other end of the second resonance microstrip line 16 is via the first via 22 and ground plane phase
Even, the other end of the 4th resonance microstrip line 17 is connected via the 5th via 23 with ground plane, the second pole plate via third via with
4th via 24 is connected with ground plane, and quadripolar plate is connected via the 7th via and the 8th via 25 with ground plane.In order to implement
The one side of ground plane, Mulitilayer circuit board can be manufactured by Continuous Copper, and as ground.
Above-described to be connected to electrical connection, each layer circuit topological structure of multilayer circuit could be provided as left and right mirror
As symmetrical.
In one embodiment, between the 4th of the first spacing of first layer 1 and the second layer 2 and the 4th layer 4 and layer 55
Away from more than the second layer 2 and the second spacing and third layer 3 of third layer 3 and the 4th layer 4 of third spacing.
For example, the 4th spacing of first layer 1 and the first spacing of the second layer 2 and the 4th layer 4 and layer 55 could be provided as
Identical, such as 0.3mm, the second spacing and third layer 3 of the second layer 2 and third layer 3 could be provided as with the 4th layer 4 of third spacing
It is identical, such as 0.03mm.
Equivalent circuit method can be utilized to calculate the value of each element in filter, then be obtained by circuit transformations actually required
The circuit structure and component value of filter.
Fig. 2 is the equivalent schematic diagram of the double frequency filter of the embodiment of the present invention.
As shown in Fig. 2, double frequency filter can be equivalent to the cascade of three resonant elements.Cascade is usually same unit device
Part joins end to end, and forms new logic unit.
First resonant element and third resonant element mirror symmetry, respectively by two sections of resonance lines and a microstrip capacitor
Equivalent composition.Resonance microstrip line can be equivalent to LC resonance circuits in parallel or series, and frequency selectivity and impedance operator can
It is explained using equivalent LC resonance circuit.
Impedance Z1、Z1' the first resonance microstrip line 12, the third resonance microstrip line 13 being equivalent in Fig. 1, is set as with phase
Same impedance value Z1With electrical length θ1。
Impedance Z2、Z2' the second resonance microstrip line 16, the 4th resonance microstrip line 17 being equivalent in Fig. 1, is set as with phase
Same impedance value Z2With electrical length θ2。
Capacitance C1、C1' be equivalent to the first micro-strip equivalent capacity (14,14 ') in Fig. 1, the second micro-strip equivalent capacity (15,
15 '), it is set as capacitance C having the same1。
Second resonant element is between the first resonant element and third resonant element, by three sections of resonance lines and one
The equivalent composition of microstrip capacitor.
Impedance Z3、Z3' the 5th resonance microstrip line 9, the 7th resonance microstrip line 11 being equivalent in Fig. 1, is set as having identical
Impedance value Z3With electrical length θ3。
Impedance Z4The 6th resonance microstrip line 10 being equivalent in Fig. 1.
Capacitance C2The third micro-strip equivalent capacity (8,11,8 ') being equivalent in Fig. 1.
One signal can be decomposed into the superposition of Qi Mo and even mould, and odd mode analysis, which is equivalent between two sections of lines, has added one
Ground, even mould analysis is exactly that two lines are parallel, and the analysis of circuit, field can be carried out with one section of line.The core of even and odd mode analysis is solution
Coupling can carry out even and odd mode analysis by equivalent circuit to Tunable dual band filter of the present invention according to Fig.2,.
The return loss S of filter can be obtained11With transmission loss S21As follows：
S21=Y0(Yodd-Yeven)/[(Y0+Yeven)(Y0+Yodd)] (2)
Wherein Y0It is characterized admittance, YoddFor strange mould admittance, YevenFor even mould admittance, there is following equalities establishment：
Wherein, θ1、θ2、θ3、θ4Respectively impedance Z1、Z2、Z3、Z4Electrical length, by the way that equation (3) and (4) are substituted into equation
(1) and (2), and assume S21=0, and Z3=Z4(to simplify the calculation), transmission zero location can be obtained to be determined by following equalities：
1-ω1C1Z1tanθ1=0 (5)
1-ω2C2Z3sin(2θ3+θ4)=0 (6)
Wherein ω1Indicate the position of the first resonant element and third resonant element transmission zero, ω2Indicate the second resonance list
The position of first transmission zero.I.e. transmission zero refers to the position that the transfer function of filter is zero, the energy on this frequency point
Cannot be by network, thus play the role of isolation frequency.By equation (5) and (6) it is found that ω1Position by equivalent capacity C1、
C1' and equiva lent impedance Z1、Z1' determine, ω2Position by equivalent capacity C2With equiva lent impedance Z3、Z3′、Z4It determines.In other words, two
The transmission zero of a passband can independently be regulated and controled by its corresponding resonant element equivalence element respectively, be independent of each other.It can be by changing
The capacitance for becoming the first micro-strip equivalent capacity adjusts the transmission zero of the first resonant element, by changing the second micro-strip equivalent capacity
Capacitance adjust the transmission zero of third resonant element, the capacitance by changing third micro-strip equivalent capacity adjusts second humorous
It shakes the transmission zero of unit.
The LTCC miniaturization Tunable dual bands filter of the present invention can also carry out its band connection frequency separately adjustable.It can pass through
The impedance value for changing the first resonance microstrip line and third resonance microstrip line adjusts the first working frequency range of double frequency filter, passes through
The impedance value for changing the 5th resonance microstrip line and the 7th resonance microstrip line adjusts the second working frequency range of double frequency filter.
Below by taking the tuning of 5.2GHz band connection frequencies as an example, the tuning of 2.4GHz band connection frequencies is similar, and this will not be repeated here.Fig. 8
Show equivalent impedance Z in the embodiment of the present invention1To the influence schematic diagram of 5.2GHz passband resonant frequencies.As shown in figure 8, working as it
His component value is constant, impedance Z1Impedance value when being changed to 40 Ω from 20 Ω, the centre frequency of high frequency pass band is dropped from 6.5GHz
To 5.2GHz, tuning range is up to 1.3G, and low frequency pass band is barely affected.This is also provided for the flexible design of filter
Great convenience.
In one embodiment, parameters setting can be as follows shown in Fig. 3~7：W1=0.6mm, W2=0.4mm,
W3=0.58mm, W4=0.6mm, W5=0.2mm, W6=0.34mm, W7=0.45mm, W8=0.58mm, W9=0.3mm, W10
=0.45mm, W11=4.6mm, L1=0.8mm, L2=0.7mm, L3=3.8mm, L4=1.7mm, L5=4.3mm, L6=
0.8mm, L7=0.7mm, L8=4.1mm, L9=0.8mm, L10=5.1mm.
The dielectric constant of LTCC materials can be 5.9, and dielectric loss tangent value can be 0.002.By low temperature co-fired
Ceramic process manufactures, and the volume of entire double frequency filter can be only 5.1mm × 4.6mm × 0.7mm.
Fig. 9 is the schematic frequency resonse characteristic figure of double frequency filter in the embodiment of the present invention.Test result such as Fig. 9
Shown, which is 0.75dB in the insertion loss of 2.4G frequency ranges, and relative bandwidth 4.6% is damaged in the insertion of 5.2G frequency ranges
Consumption is 0.72dB, and relative bandwidth 4.1% effectively covers entire working frequency range.As it can be seen that filter is damaged in the insertion of height frequency range
Consumption can realize dual-passband response within 0.8dB in the common 2.4GHz and 5.2GHz frequency ranges of WLAN.In addition, two
Return loss in a passband is all higher than 20dB, embodies good transmission characteristic.The presence of transmission zero makes filter
Selectivity is very good, and at least 10GHz since 6GHz, the Out-of-band rejection realized more than 23dB is horizontal.It can be seen that the filter
In addition to small, Insertion Loss is low, also has good selectivity and broad stop-band.
In conclusion the present invention provides a kind of miniaturization Tunable dual band filter based on LTCC multilayer circuits.It can root
According to the resonant frequency and transmission zero location of two frequency ranges of demand independent tuning, flexible design, tuning is convenient.With it is small,
Insertion loss is small, with excellent properties such as outer high inhibition, Wide stop bands, is easy to be integrated with other circuit modules, in nothing of new generation
Line communication field has broad application prospects.
Those skilled in the art will also understand is that, various illustrative logical blocks, mould in conjunction with described in disclosure herein
Block, circuit and algorithm steps may be implemented as the combination of electronic hardware, computer software or both.
Flow chart and block diagram in attached drawing show that the possibility of the system and method for multiple embodiments according to the present invention is real
Existing architecture, function and operation.In this regard, each box in flowchart or block diagram can represent module, a journey
A part for sequence section or code, the part of the module, section or code include one or more for realizing defined
The executable instruction of logic function.It should also be noted that in some implementations as replacements, the function of being marked in box also may be used
With to occur different from the sequence marked in attached drawing.For example, two continuous boxes can essentially be basically executed in parallel,
They can also be executed in the opposite order sometimes, this is depended on the functions involved.It is also noted that block diagram and/or stream
The combination of each box in journey figure and the box in block diagram and or flow chart can use functions or operations as defined in executing
Dedicated hardware based system realize, or can realize using a combination of dedicated hardware and computer instructions.
Various embodiments of the present invention are described above, above description is exemplary, and non-exclusive, and
It is not limited to disclosed each embodiment.Without departing from the scope and spirit of illustrated each embodiment, for this skill
Many modifications and changes will be apparent from for the those of ordinary skill in art field.The selection of term used herein, purport
In the principle, practical application or improvement to the technology in market for best explaining each embodiment, or make the art
Other those of ordinary skill can understand each embodiment disclosed herein.
Claims (14)
1. a kind of double frequency filter is set as multilayer circuit, including：
First resonant element, be set to the multilayer circuit third layer and the 4th layer；
Second resonant element is set to the second layer of the multilayer circuit, third layer and the 4th layer；And
Third resonant element, be set to the multilayer circuit third layer and the 4th layer,
Wherein, first resonant element is identical with the topological structure of the third resonant element, and is arranged into left and right mirror image pair
Claim, and
The second resonant element grade is coupled between first resonant element and the third resonant element.
2. double frequency filter according to claim 1, wherein
First resonant element includes the first resonance microstrip line being located in the third layer, the first pole plate and positioned at described the
It is micro- that the second resonance microstrip line, the second pole plate on four layers, first pole plate and the second pole plate layer coupling constitute first
Band equivalent capacity；And
The third resonant element includes the third resonance microstrip line being located in the third layer, third pole plate and positioned at described the
It is micro- that the 4th resonance microstrip line, quadripolar plate on four layers, the third pole plate and the quadripolar plate layer coupling constitute second
Band equivalent capacity.
3. double frequency filter according to claim 2, wherein
One end of the second resonance microstrip line is connected via the second via with one end of the first resonance microstrip line, and described
The other end of one resonance microstrip line is connected with first pole plate；And
One end of the 4th resonance microstrip line is connected via the 6th via with one end of the third resonance microstrip line, and described
The other end of three resonance microstrip lines is connected with the third pole plate.
4. double frequency filter according to claim 3, wherein
Second resonant element includes positioned at the 5th resonance microstrip line of the third layer, the 6th resonance microstrip line, the 7th humorous
Shake microstrip line, the 5th pole plate positioned at the second layer and the sextupole plate on described 4th layer,
5th pole plate and the 7th resonance microstrip line and sextupole plate layer coupling composition third micro-strip are equivalent
Capacitance, and
The both ends of the 6th resonance microstrip line respectively with one end of the 5th resonance microstrip line and the 7th resonance micro-strip
One end of line is connected.
5. double frequency filter according to claim 3, wherein
The other end of the 5th resonance microstrip line is connected via the 9th via with one end of the 5th pole plate, and the described 7th is humorous
It shakes the other end and the 5th pole plate and the sextupole plate layer coupling of microstrip line.
6. double frequency filter according to claim 3, further includes：
Input terminal is set to the first layer of the multilayer circuit, and described one end of the first resonance microstrip line is via the tenth mistake
Hole is connected with the input terminal；And
Output end is set to the first layer of the multilayer circuit, and described one end of the third resonance microstrip line is via the 11st
Via is connected with the output end.
7. double frequency filter according to claim 6, wherein
The input terminal uses coplanar waveguide transmission line with the output end.
8. double frequency filter according to claim 7, wherein the characteristic impedance of the coplanar waveguide transmission line is 50 Europe
Nurse.
9. double frequency filter according to claim 3, further includes：
Ground plane is set to the layer 5 of the multilayer circuit,
The other end of the second resonance microstrip line is connected via the first via with the ground plane,
The other end of the 4th resonance microstrip line is connected via the 5th via with the ground plane,
Second pole plate is connected via third via and the 4th via with the ground plane, and
The quadripolar plate is connected via the 7th via and the 8th via with the ground plane.
10. double frequency filter according to claim 1, wherein each layer circuit topological structure of the multilayer circuit or so
Mirror symmetry.
11. double frequency filter according to claim 1, wherein
First spacing of the first layer and the second layer and described 4th layer are more than with the 4th spacing of the layer 5
The second layer and the second spacing of the third layer and the third layer and the 4th layer of the third spacing.
12. double frequency filter according to claim 11, wherein
The multilayer circuit is manufactured based on LTCC Technology；And/or
The interior metal material that buries that the multilayer circuit uses is silver；And/or
The dielectric constant of the baseplate material of the multilayer circuit is 5.9；And/or
The dielectric loss tangent angle of the baseplate material of the multilayer circuit is 0.002.
13. double frequency filter according to claim 1, wherein
Capacitance by changing the first micro-strip equivalent capacity adjusts the transmission zero of first resonant element；
Capacitance by changing the second micro-strip equivalent capacity adjusts the transmission zero of the third resonant element；And
Capacitance by changing the third micro-strip equivalent capacity adjusts the transmission zero of second resonant element.
14. double frequency filter according to claim 1, wherein
By changing the impedance value of the first resonance microstrip line and the third resonance microstrip line, the double frequency filter is adjusted
The first working frequency range；And
By changing the impedance value of the 5th resonance microstrip line and the 7th resonance microstrip line, the double frequency filter is adjusted
The second working frequency range.
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| CN110556616A (en) * | 2018-05-30 | 2019-12-10 | 罗森伯格技术（昆山）有限公司 | Miniaturized filter |
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