CN105789789A - Tunable dual-band bandstop filter based on center loaded coupling structure - Google Patents
Tunable dual-band bandstop filter based on center loaded coupling structure Download PDFInfo
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- CN105789789A CN105789789A CN201610254572.1A CN201610254572A CN105789789A CN 105789789 A CN105789789 A CN 105789789A CN 201610254572 A CN201610254572 A CN 201610254572A CN 105789789 A CN105789789 A CN 105789789A
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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
Abstract
The invention discloses a tunable dual-band bandstop filter based on a center loaded coupling structure. The tunable filter comprises an upper-layer microstrip structure, a middle-layer dielectric substrate and a lower grounding metal layer, wherein the upper-layer microstrip structure is composed of two pairs of coupling lines, two pairs of varactors, two blocking capacitors and three microstrip lines. Due to the two pairs of coupling lines, the transmission characteristics of the dual-band bandstop filter are realized, and through adjusting parameters such as the distance between the coupling lines and the coupling line width, the coupling amount can be effectively controlled, and two different stopband frequencies are thus acquired. Due to the varactors loaded between the coupling lines, the frequency of the first bandstop can be effectively adjusted, and the varactors connected with the tail ends of the coupling lines, the out-of-band transmission characteristics of the dual-band bandstop filter can be improved. The tunable filter has the advantages that good stopband characteristics and multiple out-of-band transmission poles can be realized, the tunable range of the first stopband frequency reaches 18.3%, the absolute bandwidth is constantly unchanged, the structure is simply designed, the electric performance is good, and circuit integration and system packaging are realized easily.
Description
Technical field
The present invention relates to a kind of radio frequency electrically adjusted wave filter based on varactor, particularly a kind of Tunable dual band band elimination filter based on center loaded coupled structure.
Background technology
Along with developing rapidly of radio communication, electrically tunable filter application in communication system is increasingly extensive.Electrically tunable filter is short because of its tuning period, communication system is used widely, it plays the effect of rear class filtering before being positioned at antenna in transmitters, and in receivers as preselection filter between antenna and frequency mixer, its effect is to select useful signal frequency from a large amount of frequency spectrums that antenna receives, suppress harmful interfering frequency, thus improving the signal to noise ratio of receiver.Within 1987, California, USA university proposes MEMS technology, RFMEMS technology uses the components and parts of MEMS technology processing replace traditional microwave parts and significantly improve the performance of Microwave radio frequency system, the Insertion Loss of wave filter can be greatly reduced, so applying when being adapted at narrow-band high frequency, there is a very big advantage, but somewhat expensive and the integrated difficulty of technique.Utilize the electrically tunable filter that YIG designs, there is wider frequency tuning range, the higher linearity and regulate time absolute bandwidth be basically unchanged, owing to receiving the restriction of hysteresis effect, its electric tuning speed is difficult to improve, and there is also the shortcomings such as temperature stability is poor, volume big, control voltage is big simultaneously.Due to the advantage in tuned speed and cost etc. of the electrically tunable filter based on varactor, receive the extensive concern of scientific research personnel in recent years.Double frequency filter, as one of core parts in double frequency band transceiver, is widely used in suppression out-of-band noise.Tunable dual band wave filter is possible not only to meet dual band communication requirement, also can alleviate the problem that single-frequency adjustable extent is limited, and therefore, many scholars are devoted to research high-performance double-frequency adjustable filter.Load varactor by resonator central and can realize that low-frequency band is fixing to be adjusted high frequency band, seldom have article to mention Tunable dual band stop-band filter and high frequency band secured adjusted low-frequency band.The shortcoming that the tunable filter of design existed in the past has: (1) circuit is complicated, and volume is bigger；(2) insertion loss is big, it is necessary to DC source many；(3) when regulating mid frequency, absolute bandwidth changes greatly.
Summary of the invention
It is an object of the invention to provide a kind of Tunable dual band band elimination filter based on center loaded coupled structure.
The technical solution realizing the object of the invention is: a kind of Tunable dual band band elimination filter based on center loaded coupled structure, this tunable filter includes upper-layer micro-strip structure, interlayer substrate and lower floor's grounded metal, this tunable filter generally bilateral symmetry, wherein the first port and the second port are positioned at the upper strata of medium substrate, article two, the microstrip line of 50 ohm is connected with two corresponding ports respectively, this microstrip line of two 50 ohm respectively the first microstrip line and second microstrip line；First port and the second port lay respectively at the left and right sides of medium substrate, and first network port and second network port are located along the same line.
First coupling line and the 3rd microstrip line are all connected with the first microstrip line, and the first capacitance is embedded among the first microstrip line, and the first varactor is positioned at the center of the first coupling line, and the other end of described first coupling line is connected to the second varactor；Second coupling line and the 4th microstrip line are all connected with the second microstrip line, and the 3rd capacitance is embedded among the second microstrip line, and the 3rd varactor is positioned at the center of the second coupling line, and the other end of described second coupling line is connected to the 4th varactor；The other end of described 3rd microstrip line and the other end of the 4th microstrip line are connected by the 5th microstrip line.
The present invention is compared with prior art, its remarkable advantage is: (1) present invention is based on quarter-wave coupling line, the coefficient of coup can be conveniently adjusted by regulating the parameters such as Coupled Line Length of Band, width, coupling space, thus two stop-band frequency needed for obtaining wave filter；(2) method adopting coupling line center loaded varactor, keeps higher frequency constant, and Frequency range of accommodation reaches 18.3%, is maintained with the absolute constancy bandwidth of 460MHz；(3) band is outer can produce multiple transmission pole, and out-of-band harmonics suppresses frequency range to reach three frequencys multiplication.
Below in conjunction with accompanying drawing, the present invention is described in further detail.
Accompanying drawing explanation
Fig. 1 is the present invention schematic diagram based on the Tunable dual band band elimination filter of center loaded coupled structure.
Fig. 2 a is the schematic diagram of the coupled resonators of the center loaded varactor in Fig. 1.
Fig. 2 b is the strange mould equivalent circuit of the coupled resonators of the center loaded varactor in Fig. 1.
Fig. 2 c is the even mould equivalent circuit of the coupled resonators of the center loaded varactor in Fig. 1.
That Fig. 3 is the present invention is constant based on Tunable dual band band elimination filter second stop-band frequency of center loaded coupled structure, the first stop-band frequency regulates transmission characteristic and return loss plot.
Detailed description of the invention
The invention discloses a kind of Tunable dual band band elimination filter based on center loaded coupled structure, including upper-layer micro-strip structure, interlayer substrate and lower floor's grounded metal, this tunable filter generally bilateral symmetry, wherein the first port P1 and the second port P2 is positioned at the upper strata of medium substrate, article two, the microstrip line of 50 ohm is connected with two corresponding ports respectively, and this microstrip line of two 50 ohm is the first microstrip line 1 and the second microstrip line 2 respectively；First port P1 and the second port P2 lays respectively at the left and right sides of medium substrate, and first network port P1 and the second network port P2 is located along the same line.
First coupling line 5 is all connected with the first microstrip line 1 with the 3rd microstrip line 11, first capacitance 3 is embedded among the first microstrip line 1, first varactor 7 is positioned at the center of the first coupling line 5, and the other end of described first coupling line 5 is connected to the second varactor 9；Second coupling line 6 is all connected with the second microstrip line 2 with the 4th microstrip line 12,3rd capacitance 4 is embedded among the second microstrip line 2,3rd varactor 8 is positioned at the center of the second coupling line 6, and the other end of described second coupling line 6 is connected to the 4th varactor 10；The other end of described 3rd microstrip line 11 and the other end of the 4th microstrip line 12 are connected by the 5th microstrip line 13.
The vacant end of above-mentioned varactor both passes through interlayer substrate and is connected with lower floor grounded metal.
Article two, the microstrip line of 50 ohm has equal length and width, and described first coupling line 5 and the second coupling line 6 have identical length, width and coupling space, and described 3rd microstrip line 11 and the 4th microstrip line 12 have identical length and width.
The length of first coupling line the 5, second coupling line the 6, the 3rd microstrip line 11 and the 4th microstrip line 12 is 1/4th of these two stopband center frequency wavelengths of tunable filter, the length of the 5th microstrip line 13 is 1/2nd of these two stopband center frequency wavelengths of tunable filter, the width of described first coupling line the 5, second coupling line the 6, the 3rd microstrip line the 11, the 4th microstrip line 12 and the 5th microstrip line 13 is 0.2mm-4mm, and the capacitance of said two capacitance is identical and be all 100pF.
The width of the first coupling line 5 and the second coupling line 6 is 0.36mm, the width of described 3rd microstrip line 11 and the 4th microstrip line 12 is 1.4mm, the width of described 5th microstrip line 13 is 3.76mm, and the coupling space of described first coupling line 5 and the second coupling line 6 is 0.4mm.
The dielectric constant of medium substrate is 2～16, and the height of medium substrate is 0.1～3mm.
Below in conjunction with embodiment, the present invention will be further described in detail.
Embodiment
The present invention is based on the Tunable dual band stop-band filter of center loaded coupled structure, it adopts in the middle of coupling line and end loads the version of varactor, by changing the coefficient of coup between resonator, change the stop-band frequency of wave filter response, utilize the interaction between coupling line and all the other microstrip lines, create multiple transmission pole, achieve good out of band signal to suppress, the size of whole medium substrate is 85.8mm*42.8mm*1mm, the dielectric constant of medium substrate is 2.65, and medium substrate divides upper and lower double-layer structure.In Fig. 1, the width of coupling line 5,6 is set to 0.36mm, length is 26mm, coupling space is 0.4mm, the width of microstrip line 11,12 is set to 1.4mm, and length is 28mm, and the width of microstrip line 13 is set to 3.76mm, length is 53.1mm, the capacitance of capacitance 3,4 is 100pF, and 50 ohm microstrip 1,2 length are not limit, wide 2.7mm.First varactor the 7, the 3rd varactor 8 selects the SMV2201-040LF of Skyworks company, and the second varactor the 9, the 4th varactor 10 selects the SMV1234-040LF of Skyworks company.
Fig. 2 a is the schematic diagram of the coupled resonators of center loaded varactor, analyzes in order to convenient, it is possible to use the method for parity mode equivalent circuit calculates its resonant frequency.
Fig. 2 b and Fig. 2 c is the parity mode equivalent circuit of the coupled resonators of center loaded varactor respectively, and its parity mode impedance can be expressed as:
Zine=-jZoecot2 θ
Wherein, Zoe and Zoo is the parity mode impedance of coupling line 5,6, and 2 θ are the electrical length of coupling line 5,6, and Cv1 is the capacitance of varactor 7,8.The Z matrix table of whole coupled resonators is shown as:
As Im (Zin)=Im (| Z |)=0, it can be deduced that the variation relation of resonant frequency and varactor capacitance value Cv1.
Fig. 3 is based on the simulation result of the Tunable dual band stop-band filter of center loaded coupled structure, and transverse axis represents frequency, and the longitudinal axis represents transmission characteristic S21With return loss S11, it is seen that the second stop-band frequency of wave filter immobilizes as 2.39GHz, and the first stop-band frequency tuning range, from 1.19GHz to 1.43GHz, has the relative frequency range of accommodation of 18.3%, and absolute bandwidth keeps 460MHz constant.In band, return loss is within 1.5dB, and insertion loss is better than 50dB, can suitably reduce return loss in band by regulating the resistance value of biasing circuit.Have 3 transmission poles outside high frequency band, lay respectively at 3.0GHz, 3.29GHz and 4.11GHz so that Out-of-band rejection from 2.85GHz extend to 4.5GHz (| S11| <-15dB), greatly improve the out-of-band harmonics rejection characteristic of wave filter.
Therefore, the Tunable dual band stop-band filter that the present invention proposes, the coupling between resonator can be changed by regulating the varactor being carried in the middle of coupling line, keep the second stop-band frequency and bandwidth constant, effectively regulate the frequency of the first stopband, range of accommodation reaches 18.3%, and constant absolute bandwidth, the varactor that coupling line end connects can improve the out-of-band transmission characteristic of Double-frequency band elimination filter, additionally this tunable filter is also equipped with being with interior return loss low, required DC source is few, structural design is simple, the advantages such as band Multi-extended is many, good restructural double frequency stop-band filter can be realized.
Claims (6)
1. the Tunable dual band band elimination filter based on center loaded coupled structure, it is characterized in that, including upper-layer micro-strip structure, interlayer substrate and lower floor's grounded metal, this tunable filter generally bilateral symmetry, wherein the first port (P1) and the second port (P2) are positioned at the upper strata of medium substrate, and the microstrip line of two 50 ohm is connected with two corresponding ports respectively, this microstrip line of two 50 ohm respectively the first microstrip line (1) and the second microstrip line (2)；First port (P1) and the second port (P2) lay respectively at the left and right sides of medium substrate, and first network port (P1) and second network port (P2) are located along the same line；
First coupling line (5) is all connected with the first microstrip line (1) with the 3rd microstrip line (11), first capacitance (3) is embedded among the first microstrip line (1), first varactor (7) is positioned at the center of the first coupling line (5), and the other end of described first coupling line (5) is connected to the second varactor (9)；Second coupling line (6) is all connected with the second microstrip line (2) with the 4th microstrip line (12), second capacitance (4) is embedded among the second microstrip line (2), 3rd varactor (8) is positioned at the center of the second coupling line (6), and the other end of described second coupling line (6) is connected to the 4th varactor (10)；The other end of described 3rd microstrip line (11) and the other end of the 4th microstrip line (12) are connected by the 5th microstrip line (13).
2. the Tunable dual band band elimination filter based on center loaded coupled structure according to claim 1, it is characterised in that the vacant end of above-mentioned varactor both passes through interlayer substrate and is connected with lower floor grounded metal.
3. the Tunable dual band band elimination filter based on center loaded coupled structure according to claim 1, it is characterized in that, article two, the microstrip line of 50 ohm has equal length and width, described first coupling line (5) and the second coupling line (6) have identical length, width and coupling space, and described 3rd microstrip line (11) and the 4th microstrip line (12) have identical length and width.
4. the Tunable dual band band elimination filter based on center loaded coupled structure according to claim 1 or 3, it is characterized in that, first coupling line (5), second coupling line (6), the length of the 3rd microstrip line (11) and the 4th microstrip line (12) is 1/4th of these two stopband center frequency wavelengths of tunable filter, the length of the 5th microstrip line (13) is 1/2nd of these two stopband center frequency wavelengths of tunable filter, described first coupling line (5), second coupling line (6), 3rd microstrip line (11), the width of the 4th microstrip line (12) and the 5th microstrip line (13) is 0.2mm-4mm, the capacitance of said two capacitance is identical and be all 100pF.
5. the Tunable dual band band elimination filter based on center loaded coupled structure according to claim 4, it is characterized in that, the width of described first coupling line (5) and the second coupling line (6) is 0.36mm, the width of described 3rd microstrip line (11) and the 4th microstrip line (12) is 1.4mm, the width of described 5th microstrip line (13) is 3.76mm, and the coupling space of described first coupling line (5) and the second coupling line (6) is 0.4mm.
6. the Tunable dual band band elimination filter based on center loaded coupled structure according to claim 1, it is characterised in that the dielectric constant of medium substrate is 2～16, and the height of medium substrate is 0.1～3mm.
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Cited By (2)
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| CN110148817A (en) * | 2019-06-11 | 2019-08-20 | 上海海事大学 | The four transmission zero Double-frequency band elimination filters based on all-pass coupling line |
| CN116454574A (en) * | 2023-06-20 | 2023-07-18 | 无锡频岢微电子有限公司 | Reconfigurable band-stop filter |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN110148817A (en) * | 2019-06-11 | 2019-08-20 | 上海海事大学 | The four transmission zero Double-frequency band elimination filters based on all-pass coupling line |
| CN116454574A (en) * | 2023-06-20 | 2023-07-18 | 无锡频岢微电子有限公司 | Reconfigurable band-stop filter |
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Application publication date: 20160720 |