CN101593863B - Adjustable microwave band-pass filter - Google Patents
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- CN101593863B CN101593863B CN2009100878157A CN200910087815A CN101593863B CN 101593863 B CN101593863 B CN 101593863B CN 2009100878157 A CN2009100878157 A CN 2009100878157A CN 200910087815 A CN200910087815 A CN 200910087815A CN 101593863 B CN101593863 B CN 101593863B
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Abstract
The invention discloses an adjustable microwave band-pass filter. A microwave circuit substrate is provided with a double-resonance modal annular resonator and a corresponding input coupling unit, an output coupling unit and a disturbance unit, wherein an even number of micro mechanical bridge films are placed on the resonator in a mirror symmetry mode to adjust a center frequency; and one or more micro mechanical bridge films are placed on the disturbance unit to adjust the bandwidth. The filter uses a variable capacitance effect generated by a capacitance loading structure of the micro machined bridge films to load a dual-mode resonator and a disturbance structure thereof, so that the adjustment of filtering characteristics, such as the passband center frequency, the passband bandwidth and the like can be realized by fewer micro mechanical bridge films and less chip area occupation. Compared with the prior dual-mode filter and the micro mechanical adjustable band-pass filter, the adjustable microwave band-pass filter has the advantages of more flexible structure, lower technology complexity and better device overall performance, and is suitable for filtering devices based on planar transmission lines and on-chip waveguide at the same time.
Description
Technical field
The invention relates to radio frequency, microwave in the submillimeter wave field, the adjustable filtering device of filtering characteristics such as band connection frequency is specifically related to the micro mechanical adjustable microwave band-pass filter based on MEMS regulation and control device.
Background technology
In the RF front-end circuit of radio communication and radar system, filter is used to realize filtering, Noise Suppression, the frequency division multiplexing of image frequency interference; In high performance vibration, amplification, frequency multiplication, mixting circuit, filter then is used to realize have the selection of the signal of CF; In addition, can realize on the filter construction basis that effective broadband impedance is multiplexing, matching network and coupled structure.The enhancing of the microminiaturization of Wireless Telecom Equipment (comprising base station and terminal) and radar, electronic warfare equipment, broadband, mobility and frequency agility ability; And the evolution of high performance transceiver architecture; Impel the radio frequency components and parts that comprise filter constantly towards microminiaturized and monolithic integrated direction development; Also promoted simultaneously improving constantly of filter circuit configuration and performance level; And corresponding having expedited the emergence of can be according to the RF filter of its filtering characteristic of applied environment adjusting on every side, promptly adjustable (humorous) microwave filter.Action through various conditioning controller spares; Passband/stopband characteristic and work centre frequency that makes the RF filter etc. can be carried out rapid adjustment under computer control; This can improve the flexibility of radio frequency transceiver system and the adaptability in complex electromagnetic environment greatly; And be expected to promote to communicate by letter, the change of radar system, so tunable filter has obtained the great attention of countries in the world scientific research institution and transnational enterprise in recent years.
At present domestic and international employed tunable microwave filter mainly can be divided into four types according to the principle or the structure of the regulating and controlling mechanism of its filtering characteristic: 1) based on the adjusted and controlled filter of transmission line in the filter/waveguide electricity, magnetizing mediums parameter; 2) filter of regulating based on the conventional mechanical servo actuator; 3) filter of based semiconductor regulation and control device (as playing PIN pipe, the field-effect transistor of switch or capacitance adjustment effect); With 4) based on the filter of MEMS (hereinafter to be referred as MEMS) control element.First kind device is through the polarizing voltage that changes dielectric material, the methods such as exciting current of magnetic material; Change the equivalent transmission line parameter of filter, such device can bear high microwave power, and lossy microwave is lower; But ferroelectric, ferrite control device wherein commonly used are difficult to microminiaturization; And corresponding biasing circuit is complicated, needs to keep quiescent bias current, and it is very big therefore to control power consumption; Second type also can be born big microwave power, and lossy microwave is very little, but adjusting needs complicated servomechanism, and control power consumption and device volume are all bigger.Therefore, the application of the first kind and second type of filter be confined to device miniatureization require the supply of low, power supply stable, high power, non-moving microwave applications occasion.The 3rd type of filter can realize that monolithic is integrated; Compact conformation, but because wherein microwave need be through PN junction and semi-conducting material transmission, the lossy microwave of corresponding generation and non-linear its band-pass behavior of meeting appreciable impact; And required biasing circuit more complicated; Often need be made up of a plurality of transistors, the control power consumption is difficult to reduce, and does not therefore obtain at present promoting.The 4th type of filter is based on the filter of micro-machinery switch control element; But have significant advantage such as little, the multi-functional monolithic of lossy microwave is integrated; Be the novel microwave device that has occurred since the end of the nineties, be fit to be applied in the application of needs portability, mobility, high integration and low-power consumption such as mobile communication, satellite communication.
The MEMS technology that on the basis of microelectric technique, develops and come is the new and high technology platform of a multidisciplinary intersection.It extends from semiconductor, the integrated circuit technique of extensive use, but has surmounted itself and the sensing of many physical quantitys of outside and the limitation of regulation and control aspect existence.Corresponding M EMS device products has that volume is little, energy consumption and material consumption is low, easily manufactured, cost is low, function admirable, be convenient to and outstanding advantages such as microcosmos, particularly nanometer world interface.Whole technique just plays an increasingly important role at aspects such as the development of the national economy, national security and a plurality of ambit researchs, even might influence the development trend in some field.Utilize and make the used micromachining technology of MEMS, can produce the various passive components that are used for radio frequency (comprising microwave, millimeter wave) field, comprise electric capacity, inductance, switch control device, resonator/filter etc.These elements have insert that loss is little, isolation good, the Q value is high, non-linear and special advantages such as the intermodulation distortion degree is low, be easy to active circuit is integrated; Be expected to substitute a plurality of elements in the existing radio system; Reduce the power consumption of whole system, simplify its architecture.
People utilize the MEMS technological development to go out the miniature tunable filter based on micro mechanical structure at present.Their major control element is the fine motion capacity plate antenna mechanical structure that is positioned at (mainly being planar transmission lines such as microstrip line and co-planar waveguide) on the electromagnetic transmission structure; It is micro-machinery switch; Its shape can adopt and be similar to the fixing air bridge structure of both-end among the MMIC (monolithic integrated microwave circuit), and also can adopt can be up and down or the rectangular flat of horizontal movement.These structures constitute by metal materials such as the gold of sputter or the deposit of electroplating technology institute, aluminium.Under the electrostatic field that externally electric control signal (being generally voltage control signal) effect is produced; These capacitance bridge membrane structures can deform; Form the distinctive opening and closing movement of mechanical switch, its effect is equivalent to a variable capacitive impedance, thereby can realize the break-make control of element in the circuit or the adjusting of loading capacitance; Change the equivalent circuit parameter or the circuit structure of filter, and change the frequency response of filter.
In the result of study of present existing public reported, document (Brandon Pillans, Andrew Malczewski; RonAllison and Jim Brank. " 6-15 GHz RF MEMS Tunable Filters " .Raytheon-Space and AirbomeSystems, Dallas, TX; 75243, USA, 2005 IEEE MTT-S International Microwave SymposiumDigest; June 12～17; 2005) introduced a kind of method of variable band-pass filter, wherein band is logical utilizes low pass and high pass filter to make up to realize, and each low pass and high pass filter all are the ellipse tunable filters; Basic principle is the resonance frequency of regulating the elliptic filter series resonant tank, changes the cut-off frequency of this filter with this.This is to realize the simplest and direct method of variable band-pass filter, and circuit area takies greatly, needs use a plurality of switches, device total losses to be difficult to problems such as reduction but exist.Document (Abbas Abbaapour-Tamijani; Laurent Dussopt; GabrielM.Rebeiz. " A High Performance MEMS Miniature Tunable Bandpass Filter " .2003 IEEEMTT-S International Microwave Symposium Digest; Pp.1785-1788) utilize the micro-machinery switch loading capacitance to realize the change of transmission line slow wave structure performance in the 3 limit filter circuits, thereby realize the tuning of performance of filter; Document (B.Lakshminarayanan T.Weller. " Tunable Bandpass Filter Using Distributerd MEMSTranmission Lines " .2003 IEEE MTT-S Intemational Microwave Symposium Digest; Pp.1789-1792.) then through changing the characteristics such as band connection frequency that different loadings is regulated filter with the circuit characteristic of the micro-machinery switch on the DMTL (Distributed MEMS Transmission Line, distribution MEMS transmission line).The benefit of this method is that capacitive micro-machinery switch volume is little and is easy to control, and can regulate its capacitance easily, but need use a plurality of switches equally, and the circuit area occupied is big.Above-mentioned method all is based on traditional filter construction and control method is realized the adjustable microwave filter; Filter construction promptly follows conventional lines; And utilize MEMS to realize that the loading of some element perhaps changes the value of loading element, and for example micro-machinery switch itself can be an electric capacity, switch closure is equivalent to load an electric capacity; Realize the adjusting of filter with this, and the circuit structure of filter does not change almost before and after regulating.Document (Jae-HyoungPark, Sanghyo Lee, Jung-Mu Kim; Hong-Teuk Kim; Youngwoo Kwon, and Yong-Kweon Kim. " Reconfigurable Millimeter-Wave Filters Using CPW-Based Periodic Structures With NovelMultiple-Contact MEMS Switches " .Journal of microelectromechanical Systems, Vol.14; No.3; June 2005, utilize in pp.456-463) action of mems switch to change the change of filter circuit configuration, thereby realize the adjusting of filter center frequency; This method can change filter circuit construction easily, is that conventional filter can't realize.But shortcoming is in the time of will realizing than wide adjusting range, need to use a plurality of switches (quantity is higher than the twice of filter order), and the bandwidth of each circuit state and inconsistent.
In addition; Above-mentioned 8 pieces of achievements in research that representational document is reported; All adopted micro-machinery switch based on surface treatment; Its advantage is insertion loss little (no semiconductor loss), control power consumption consumption low (electrostatic control, almost nil), can on multiple substrate, makes, is easy to realize that with active circuit monolithic is integrated.The shortcoming of its existence is: 1) continued to use the transmission structure of existing non-adjustable, conventional filter basically, after adding adjustable device, device architecture is complicated, and takies more chip area; 2) often to use the regulation and control devices such as switch more than 3 could realize the switching of filter between two filter states; And realize regulating; And number of devices such as switch more for a long time; The loss of its device is difficult to reduce, and the inefficacy of single switch causes that the probability of device global failure is difficult to reduce; 3) because the bridge mould all uses the simple metal of electroplating perhaps sputter to constitute; And its break-make is to rely on the distortion of bridge film to realize; So phenomenons such as fatigue, creep appear in bridge film easily; This has influenced its reliability, 4) exist hot expansibility to differ greatly between the substrate of metal and high resistant, physical dimension and reliability all received very big influence when variations in temperature was big; 5) its bridge mode structure design is with the solid Zhi Weizhu of both-end; Drive threshold high (needing to adopt complicated booster circuits such as charge pump), size and traditional MIC (microwave integrated circuit) filter are approaching; Its processing technology step is many, the problem that is prone to adhesion in the structure release is arranged, and it is high to bear power; 6) user usually need make the electric isolation structure of isolating between high frequency/DC control Driver Circuit on the same device; Prevent the leakage of radiofrequency signal; These present devices are to make isolation resistance with the lead of the alloy formation of metal and silicon; Add reticle of the independent making of needs in man-hour, increased technology difficulty and cost.
Existing dual-transfer mode line filter (hereinafter to be referred as dual mode filter) comprises following basic structure: be produced on the bimodulus resonance structure that planar transmission line on the microwave substrate, closed-loop shaped constitutes; Input coupling unit, output coupling unit, and asymmetric disturbance for realizing that the bandpass filtering response is added.Its basic thought proposed the nineties in 20th century.Wherein importing, export coupling unit is that the planar transmission line of the required value of system constitutes by characteristic impedance usually; Resonator element is made up of the transmission line of annular or sheet shape, and a resonator element has two identical resonance frequencys.Resonator with two identical resonance frequencys is because of being coupled as zero between its resonant mode; Can not produce corresponding filter effect; If but in dual-mode resonator, add disturbance; To make and division take place between two resonant modes and then produce the intermode coupling; This moment, this dual-mode resonator was equivalent to two single mode resonators that intercouple, so the filter of a bimodulus resonant element formation has the filter effect of second order single mode filter, and its area shared on the microwave substrate is far smaller than the Design of Filter of present routine.Document (Lung-HwaHsieh; Kai Chang. " Compact, Low Insertion-Loss, Sharp-Rejection; and Wide-Band MicrostripBandpass Filters "; IEEE Transactions on Microwave Theory and Techniques, Vol.51, No.4; Apr 2003, pp.1241-1246) and document (Ming-Fong Lei; Huei Wang. " An Analysis of MiniaturizedDual-Mode Bandpass Filter Structure Using Shunt-Capacitance Perturbation "; IEEETransactions on Microwave Theory and Techniques; Vol.53, No.3, March 2005; Pp.861-867) set forth the mechanism of bimodulus filtering from principle, proposed to do the dual mode filter method for designing of the disturbance of dual-mode resonator with the transmission line tip of a branch or lumped capacity.Document (X.D.Huang, C.H.Cheng, " A Novel MicrostripDual-Mode Bandpass Filter With Harmonic Suppression "; IEEE Microwave and WirelessComponents Letters; Vol.16, No.7, July 2006; Pp.404-406) proposed the method for compacting dual-mode resonator higher order resonances frequency, solved dual mode filter to a certain extent so the problem of the nearly parasitic passband that has.Dual mode filter does not belong to conventional filter classification (Butterworth on the principle; Chebyshev and ellipse etc.); But also can make it have the filter freguency response of Chebyshev or Elliptic form through appropriate reconstruction; Document (A.Gorur. " Realization of aDual-Mode Bandpass Filter Exhibiting Either a Chebyshev or an Elliptic Characteristic byChanging Perturbation ' s Size ", IEEE Microwave and Wireless Components Letters, Vol.14; No.3, pp.118-120) comparatively detailed introduction corresponding method.
Up to the present, existing dual-transfer mode line filter structure does not still possess the adjustable ability of filtering characteristic.
Summary of the invention
The object of the present invention is to provide a kind of micro mechanical adjustable microwave band-pass filter.The variable capacitance effect that this micromechanics tunable filter has utilized micromechanics bridge membrane capacitance loading structure to produce loads the adjusting that can take filtering characteristics such as realizing passband central frequency and pass band width with the micromechanics bridge film and the less chip area of lesser amt to dual-mode resonator and perturbations thereof.
Technical scheme of the present invention is:
A kind of micro mechanical adjustable microwave band-pass filter; On the microwave circuit substrate, being provided with one possesses the resonator structure of double resonance mode and imports coupling unit, output coupling unit and disturbance unit accordingly; Wherein said resonator is a toroidal cavity resonator; The planar graph that its axis constitutes has two-dimentional mirror symmetry, promptly has two orthogonal symmetry axis in this planar graph at least; Said input coupling unit is vertical each other with the axis of output coupling unit, and overlaps with two orthogonal symmetry axis of said planar graph respectively; Said disturbance unit one end links to each other with resonator, and other end open circuit, its axis are 45 ° with the angle of two orthogonal symmetry axis of said planar graph respectively; On said resonator, be placed with even number (minimum is 2) micromechanics bridge film; These bridge films are called centre frequency and regulate the bridge film; Their position is the mirror image symmetrical distribution with respect to the axis of disturbance unit, and any electrical length to the input coupling unit that is in the symmetrical pair of bridge film of mirror image equates with another electrical length to the output coupling unit; On said disturbance unit, place one or more micromechanics bridge films, be called bandwidth adjustment bridge film; All micromechanics bridge films are connected with the control circuit output of microwave circuit system respectively, change the driving DC voltage of micromechanics bridge film through the microwave circuit system, thereby realize the adjusting of filter passband centre frequency and pass band width.
The above-mentioned resonator (abbreviation dual-mode resonator) that possesses double resonance mode is a toroidal cavity resonator, can be made up of waveguide on planar transmission line or the sheet.The axis figure of waveguide on said planar transmission line or the sheet can be a planar graph circular, square or that have the fractal graph characteristic, and these planar graphs should have two-dimentional mirror symmetry.
Constitute said dual mode filter planar transmission line can for the microstrip line (being divided into ground plane) on substrate, made, band line at holding wire with the substrate lower surface of substrate top surface with methods such as deposit and etchings (comprise the two-layer parallel ground plane that lays respectively at the substrate upper and lower surfaces, and be distributed between two ground plane, the holding wire in the embedding substrate) or co-planar waveguide line (waveguide wire is divided into coplanar ground wire and the holding wire in substrate top surface) etc. have the planar transmission line of given shape.Wherein microstrip line and band line are applicable to the working frequency range of 500MHz～100GHz; The co-planar waveguide line is applicable to 20GHz～300GHz.
Constitute on the sheet of said dual mode filter waveguide can be on substrate with micro-machinings such as build etching make, parallel axes is in the rectangle of substrate surface or the tubular structure of circular cross-section; Its matrix is the microwave circuit backing material; High conductivity metal such as deposit Au, Ag, Cu on the wall of tubular structure, this waveguide can be transmitted the bigger signal of power of 20GHz～10THz wave band.
The structure of above-mentioned input coupling unit, output coupling unit is identical; Can constitute by the tight capacity coupled two sections planar transmission lines of mutual existence; Also can be waveguide transitions structure on planar transmission line-sheet, can also be waveguide transitions structure on coaxial cable-sheet.
Above-mentioned disturbance cellular construction can be made up of one section microwave short-term (being short transmission line), and the one of which end links to each other with toroidal cavity resonator, other end open circuit.This microwave short-term continues to use that waveguide makes up on used transmission line of toroidal cavity resonator or the sheet, and its impedance and physical dimension can be confirmed according to the reflection loss of filter bandwidht and device.This microwave short-term should equate with the distance of input coupling unit and output coupling unit respectively with the intersection point of toroidal cavity resonator; The axis of this microwave short-term is a straight line, and its direction all becomes 45 ° of angles with the axis of above-mentioned input coupling unit and output coupling unit.
The above-mentioned even number micromechanics bridge film that is placed on the toroidal cavity resonator is used to realize that variable capacitance loads; For centre frequency is regulated the bridge film; They are mirror image with respect to the axis of disturbance unit and are symmetrically distributed, and any bridge film is equal to the electrical length of output (or input) coupling unit with another bridge film that is the mirror image symmetry with it to the electrical length of input (or output) coupling unit.The micromechanics bridge film that is placed on the disturbance unit is called bandwidth adjustment bridge film.All micromechanics bridge films are connected with the corresponding control signal output of the control circuit of microwave circuit system respectively, and the control signal of output is generally d. c. voltage signal.Under the driving of the direct voltage (this voltage is also claimed the driving voltage of micromechanics bridge film) of the adjustable amplitude value of control circuit output; Air gap height between micromechanics bridge film and substrate and will change to the parameters such as equivalent loading capacitance of transmission structure; So the microwave circuit system at filter place can control the equivalent loading capacitance of bimodulus toroidal cavity resonator through the driving DC voltage that changes micromechanics bridge film; And control the power of perturbations, thereby accomplish the adjusting of filtering characteristics such as passband central frequency and pass band width respectively to the perturbation action of the double resonance mode of toroidal cavity resonator.
Said micromechanics bridge film production is above the used microwave circuit substrate of dual mode filter.When said toroidal cavity resonator made up with planar transmission line, these planar transmission lines were to be produced on upper and lower lip-deep metallic film of microwave circuit substrate or thick film, and the bridge film is fixed on the top of transmission line ad-hoc location through anchor point.One or more pairs of drive electrodes (being called drive electrode on the bridge film, being called on its below substrate be the attraction electrode down) are set on said bridge film and said substrate, and said electrode is connected with the control circuit of microwave circuit system; The driving DC voltage of control circuit output makes between the drive electrode of bridge film and substrate and produces electrostatic attraction; Spacing (this spacing is air gap height) between the planar transmission line holding wire of change bridge film and below; The variable quantity of spacing can be controlled by the driving voltage that provides; Can change the loading capacitance of bridge film thus, and change the characteristics such as centre frequency of filter planar transmission line.When said toroidal cavity resonator with sheet on waveguide when making up, waveguide can utilize build etching processing technology in this substrate, to form on the sheet, its matrix generally is the microwave circuit backing material; Waveguide sidewalls applies high conductivity metal such as Au, Ag, Cu; This moment, the bridge film was fixed on the top of waveguide cavity ad-hoc location through anchor point, and bridge film below is manufactured with the salient point that metal or dielectric constitute; The upper wall surface of waveguide is only covered to realize sealing by the layer of metal film on the sheet.On said bridge film and said substrate, one or more pairs of drive electrodes are set, said electrode is connected with the control circuit of microwave circuit system; The driving DC voltage of control circuit output produces electrostatic attraction between the drive electrode of bridge film and substrate; Spacing between the waveguide cavity of change bridge film and below; The metallic film of waveguide upper wall surface contacts and makes the downward deformation of metallic film generation on the salient point that makes bridge film below and the sheet; The deformation of metallic film has changed the inner electromagnetic field distribution of waveguide on the sheet, and its deformation quantity is decided by the size that attracts voltage, thus waveguide on the sheet has been realized variable capacitive load.
Said bridge film is a layer structure.When bridge film below was planar transmission line, the bridge film was specially monocrystalline silicon layer (or polysilicon layer), insulating barrier, metal level, dielectric layer from top to bottom; When bridge film below is on the sheet during waveguide, be specially monocrystalline silicon (or polysilicon layer) and insulating barrier from top to bottom.The both sides of said bridge film can be provided with the spring beam of several low rigidity respectively, and an end of said spring beam connects said bridge film, and the other end is connected with fixed anchor point on being produced on substrate.Said spring beam can be stretched out by the monocrystalline silicon layer (or polysilicon layer) of bridge film and form.Said bridge film can be the butterfly silicon structure of mirror image symmetry; Comprise bridge film stage casing and two flanks; When control circuit applies driving DC voltage; The monocrystalline silicon of bridge film flank or polysilicon layer are last drive electrode, produce electrostatic attraction jointly with following attraction electrode on the substrate of below, change the height of the air-gap between bridge film below and substrate.
The gross thickness of said silicon bridge film (refer to the thickness that the bridge film is total, comprise the gross thickness of crystal silicon layer and each layer of below thereof) is 10～40 μ m.
The insulating barrier of said bridge film can adopt dielectric constant less than 5 electrical insulating material; It is 5～30 electrical insulating material that dielectric layer can adopt dielectric constant, and concrete dielectric constant and thickness can be worn performance requirement according to the adjustable range of loading capacitance and resistance and confirm.
Compared with prior art, the invention has the beneficial effects as follows:
1) compare with existing dual mode filter, filter proposed by the invention has the ability of regulating filtering characteristic; Toroidal cavity resonator wherein is easy to load bypass elements; Compare with the micromechanics variable band-pass filter with existing dual mode filter, structure is more flexible, has reduced complexity on the technology; And the resonator element that makes filter has higher Q value, helps reducing pass-band loss.
2) compare with existing adjustable microwave filter; The filter that the present invention proposes just can be realized the adjusting of passband central frequency and bandwidth respectively with less bridge film (the most only needing 3); The area of the microwave circuit substrate that it takies significantly reduces, and helps reducing cost, reduction of device size and raising microwave circuit level of integrated system.In addition; Compare with existing micromechanics variable band-pass filter; The micro-machinery switch of filter of the present invention required use under the identical situation of order or the quantity of bridge film are still less; This helps reducing the lossy microwave of switch and the introducing of bridge film, the rate of finished products of raising device fabrication, the probability of the filter inefficacy that brings because of the single switch inefficacy when reducing long term device work.
3) analysis shows, the present invention compares with the micromechanics tunable filter design of existing domestic and international public reported owing to adopted the bimodulus principle, and it is more precipitous that the changeover portion between its passband and the stopband becomes, and helps improving the overall performance of filter.
4) adopted micromechanics bridge film to come the characteristic of control filters; That this micromechanics bridge film basic structure can be utilized is that build silicon-base micro-mechanical processing technology is made, be the multilayer complex films of skeleton with the monocrystalline silicon layer; Its monocrystalline skeleton thickness can reach 10～40 μ m; Higher restoring force can be provided; Therefore therefore the bigger adhesive electrostatic force that occurs in the time of can preventing to bear the HIGH-POWERED MICROWAVES signal and cause the mistuning joint (also claiming misoperation) of filter is compared with the tunable filter of existing based semiconductor switch and micro-machinery switch, and micromechanics adjustable microwave filter of the present invention can bear high-power.The lossy microwave of this bridge film is little, therefore compares with the tunable filter that has adopted semiconductor switch, helps reducing the pass-band loss of filter.Bridge film of the present invention can move continuously, thereby can realize the accurate adjusting of filter center frequency.
5) the present invention is applicable to the filtering device based on waveguide on planar transmission line and the sheet simultaneously.
Description of drawings
The vertical view of basic structure when Fig. 1 adjustable microwave band-pass filter of the present invention adopts circular rings.
A kind of vertical view of implementing structure when Fig. 2 adjustable microwave band-pass filter of the present invention adopts Q-RING.
A kind of vertical view of implementing structure when Fig. 3 adjustable microwave band-pass filter of the present invention adopts the bridge film of circular rings, a plurality of switch motions.
Based on a kind of sketch map of implementing structure of the micromechanics bridge film of microstrip transmission line, wherein (a) is stereogram, (b) is longitudinal sectional view in Fig. 4 adjustable microwave band-pass filter of the present invention.
The structure chart of waveguide on Fig. 5 sheet, wherein (a) is STRUCTURE DECOMPOSITION figure, (b) longitudinal sectional view behind each textural association.
Fig. 6 adjustable microwave band-pass filter of the present invention adopts a kind of sketch map of implementing structure of the loading capacitance of waveguide on the micromechanics bridge membrane change sheet, and wherein (a) is stereogram, (b) is longitudinal sectional drawing.
Embodiment
Below in conjunction with accompanying drawing and embodiment the present invention is described in further detail:
Micromechanics adjustable microwave bimodule band-pass filter of the present invention has adopted the adjustable bimodulus loop filter structure of resonance characteristic.Be that example is explained its structure and operation principle below with the microstrip transmission line.
The basic circuit structure of said dual mode filter is as shown in Figure 1; Comprise that (axis of microstrip line is an annular to the bimodulus toroidal cavity resonator of being located on the substrate 61 that has disturbance among Fig. 1; But also can or have a closed loop pattern of fractal characteristic for Q-RING) and capacitively coupled input coupling unit 2a, output coupling unit 2b, disturbance unit 3, play micromechanics bridge film 4a, the 4b of centre frequency regulating action and play the micromechanics bridge film 5 of pass band width regulating action.The microwave signal of treating filtering is exported from output coupling unit 2b through the microwave signal of filtering from input coupling unit 2a input.Under the control of the driving DC voltage that the control circuit of microwave circuit system is exported; The bridge film of centre frequency adjusting bridge film 4a and 4b can change to the air-gap height h of substrate, and promptly the bridge film can move up and down, and it is to the equivalent loading capacitance of resonator; Be on the bridge film position microstrip line holding wire to the equivalent capacity between ground plane; Also respective change, thus two resonance frequencys of toroidal cavity resonator can be changed, and corresponding change its band connection frequency and centre frequency up and down; Bandwidth adjustment bridge film 5 also can move up and down under the driving DC voltage effect that the control circuit of microwave circuit system is exported; Respective change also takes place in its equivalent loading capacitance to the disturbance unit; According to the principle of dual mode filter, this variation can bring the variation of filter passband bandwidth.The girth of toroidal cavity resonator can be less than or equal to the guide wavelength λ at microwave input signal centre frequency place
g, the characteristic impedance of the disturbance unit 3 that constitutes by open circuit microwave short-term and length according to this filter the bandwidth range that will reach confirm.General used transmission line impedance 50～80 Ω of toroidal cavity resonator, the disturbance unit should be made up of the high resistant transmission line, and its characteristic impedance is greater than 80 Ω.Transmission line shown in Fig. 1 is a microstrip line, by the holding wire (being each above-mentioned construction unit) in front and the ground plane formation that covers the substrate 6 whole back sides.Dual mode filter is a stage structure in this example, can realize stop band attenuation preferably but compare with common band pass filter.And the design is also applicable to the higher filter of exponent number.
When the present invention implemented, the axis shape of toroidal cavity resonator was not limited to circle, also can be to be other planar graphs with two-dimensional symmetric property, and like Q-RING etc., as shown in Figure 2; Or even figure with fractals characteristic.Specifically select which kind of figure for use, can choose according to the equivalent electric length of toroidal cavity resonator under the particular job frequency, generally how much girths of its axis are not more than and the corresponding guide wavelength of microwave signal centre frequency.
In this example, the height of bridge film can be regulated continuously, makes loading capacitance also can regulate continuously, thus control filters passband central frequency and bandwidth accurately; But consider adhesive effect (pull-in), what it was regulated continuously is limited in scope, and analysis shows that the deviation range of the centre frequency of this moment is merely about 5%.So the bridge film also can be operated on off state (promptly under non-adhesive and adhesive two states, switching), this moment, its switch front and back changes in capacitance ratio can reach 1: 20, and the deviation range of the centre frequency of filter has reached 15%.If guarantee to have less adjusting stepping when will improve the adjustable range of centre frequency; Then can on described toroidal cavity resonator, place >=4 even number and be used to the micromechanics bridge film of realizing that variable capacitance loads; Wherein the position of half bridge film and other half bridge film is the mirror image symmetry with respect to the symmetry axis such as diagonal on the resonator axis line graph (usually select to let this and the dead in line of disturbance unit 3), becomes in the pair of bridge film of mirror image symmetric relation any equal with another electrical length to the output coupling unit to electrical length of input coupling unit.As shown in Figure 3.The capacity ratio of these bridge films before and after the switch be less than 1: 10, can reach required adjusting stepping through letting bridge membrane switch or let its unit switch successively.
Minimum of this filter needs to adopt two micro-machinery switchs can realize the adjustable of filter characteristic, compared with prior art significantly reduces the probability that this can reduce the loss, processing technology difficulty of whole filter and occur losing efficacy because of switch failure.
Micro mechanical adjustable microwave band-pass filter of the present invention used, as shown in Figure 4 based on the structure of the micromechanics bridge film of microstrip transmission line; This micro-machinery switch is produced on the microwave circuit substrate 6; The metal film microstrip transmission line be set on substrate and be the compound bridge film of skeleton with silicon, substrate 6 can also be simultaneously as the substrate of filter; Make one deck shape metal film identical with the shape of substrate 6 on substrate 6 lower surfaces, promptly ground plane 7, and this ground plane is as the ground plane of microstrip transmission line; Substrate top surface is provided with the microstrip transmission line holding wire 8 that is made up of metal film; The upper surface of substrate also is manufactured with following attraction electrode 9a and the 9b that is made up of metal film simultaneously, is symmetrically distributed in holding wire 8 both sides.
Attract electrode 9a and 9b also to realize being electrically connected with the ground plane 7 of substrate back down through the via hole 10 of filling metal.The silicon bridge film is to be cascaded by monocrystalline silicon or polysilicon layer 11, insulating barrier 12, metal level 13, dielectric layer 14 etc.; The bridge membrane plane is shaped as the butterfly structure of mirror image symmetry, and this bridge film can be divided into three parts, i.e. bridge film stage casing 15, flank 16a and flank 16b; Bridge film stage casing 15 all comprises monocrystalline silicon or polysilicon layer 11, insulating barrier 12, metal level 13 and dielectric layer 14 with flank 16a and 16b; The suspended structure of bridge film adopts lower four spring beam 17a, 17b, 17c, the 17d of rigidity, and (suspended structure shown in Fig. 4 is 4 straight thin beams; But also can be the thin beam of the shape that crawls); Each two spring beam of the two ends of bridge film; One of each spring beam is terminated at the bridge film, and the other end is connected with fixed anchor point 18a or 18b on being bonded to substrate 6, and fixed anchor point 18a or 18b are monocrystalline silicon layer.In addition; The anchor point 18a of bridge film and anchor point 18b can carry out highly doped and on substrate, extend; Formation has the monocrystalline silicon or the polysilicon resistance line 19 of thin section and big equivalent length (can realize through making it to have the crawl flat shape of shape line), as the isolation structure between microwave signal and static DC driven.
The insulating barrier 12 of said bridge film can adopt earth silicon material, and metal level can be Au, Ag, Cu material, and dielectric layer can be silicon nitride.The rete 12 and 14 of bridge film also can adopt other to come the electrical insulating material of deposit with semiconductor integrated circuit technique (strengthening vapor deposition like plasma).
The control circuit of microwave circuit system can change the size of bridge film to the equivalent loading capacitance of microstrip line 8 through the driving voltage that changes the bridge film, thereby realizes the regulation and control to the filtering characteristics such as centre frequency of filter.In this example, the equivalent parallel plate capacitor C of the air-gap between the holding wire 8 of microstrip line, bridge film and substrate, bridge film medium layer 14, bridge film metal level 13 formations
1, bridge film metal level 13, dielectric layer 14, air-gap, attract electrode 9a or 9b to constitute another equivalent parallel plate capacitor C down
2C
1And C
2Value directly related with air-gap height h, reducing and increase with h.Consider the symmetry of the flat shape of bridge film, and attract electrode to link to each other with the ground plane at substrate 7 back sides through via hole 10, so according to the electromagnetism principle, the equivalent loading capacitance C of filter
Load, promptly consider holding wire when the bridge film exists 8 to the equivalent capacity between the ground plane 7, in fact should for
The driving voltage V of bridge film can be the direct voltage of control circuit output; Its method of attachment is: the high potential lead-out terminal of control circuit links to each other with resistive conductor 19; Its electronegative potential lead-out terminal can be connected with the ground plane 7 of microstrip line, perhaps directly with down attracts electrode 9a, 9b to be connected.
The driving DC voltage of the control system output of microwave circuit system can be controlled the air gap height h on micromechanics bridge film and microstrip line surface, and corresponding control is to the equivalent loading capacitance C of microstrip line
LoadWhen the driving voltage of micromechanics bridge film was 0V, the bridge film was in free vacant state, very weak (the promptly equivalent loading capacitance C of the holding wire of microstrip line and the loading effect between ground plane
LoadVery little).When needing to change loading effect; Can let external control circuit apply a direct current high potential V to the bridge film through resistive conductor 19; This moment, monocrystalline silicon or the polysilicon layer of bridge film flank 16a and bridge film flank 16b also had identical current potential V, attracted to form between electrode 9a and the 9b electrostatic field and electrostatic attraction respectively and down.This gravitation has changed the height h of bridge film to holding wire, thereby can change the equivalent loading capacitance C of microstrip line
Load, when electrostatic potential V increased continuously gradually, the loading capacitance of equivalence also increased continuously gradually.When increasing to, corresponding electrostatic force surpasses certain threshold value V
Th(corresponding to h=2/3h
Max) after, bridge film generation adhesive phenomenon contacts with substrate, and this moment, the bridge film was in switch working state, when driving voltage is 0V and the equivalent loading capacitance C during adhesive
LoadThe ratio of value can reach 1: 20 even be higher.
Numerical computations and finite element simulation show; Because the bridge film adopts large-area flank structure; When applying bias voltage, can produce bigger electrostatic attraction; Therefore; If the width at spring beam 17a, spring beam 17b, spring beam 17c, spring beam 17d is under the situation of 2～20 μ m, if level is selected 500～1000 μ m (can adopt the foldable structure that crawls to realize) to effective length, then these spring beams 17a, spring beam 17b, spring beam 17c and spring beam 17d can guarantee the driving voltage threshold value V of structure
Th＜10V (belonging to low threshold drive), this threshold value has the bias voltage of source control circuit and active signal treatment circuit close with microwave commonly used, is micromechanics microwave tunable filter of the present invention and the integrated condition of having created of active circuit realization monolithic.
The advantage of above-mentioned micromechanics bridge film is: 1) regulate the micro-machinery switch basic structure use that build silicon-base micro-mechanical processing technology is made for utilizing, with monocrystalline silicon layer or polysilicon layer multilayer complex films as skeleton; Its skeleton thickness can reach 10～40 μ m like a cork; If level is selected 500～1000 μ m to effective length; Higher restoring force can be provided; Therefore the bigger equivalent adhesive electrostatic force that occurs in the time of can preventing to bear the HIGH-POWERED MICROWAVES signal and cause the mistuning joint (also claiming misoperation) of filter bears powerful microwave filter thereby can produce like a cork; 2) when regulating filter characteristic; Multiple switching adhesive action will take place in micro-machinery switch bridge film; And the monocrystalline silicon or the polycrystalline silicon material that adopt good mechanical property (no creep, in-fighting is little, fatigue resistance good) can prevent because of hanging the component failure that fatigue failure causes as suspended structure; 3) the bridge film is fixing through monocrystalline silicon anchor point and microwave material; In general the thermal expansion coefficient difference that belongs between dielectric microwave substrate (like quartz, glass, LTCC etc.) of monocrystalline silicon or polycrystalline silicon material and the overwhelming majority is less; So cause structure crack because of variations in temperature in the time of can avoiding adopting metallic framework, thereby influence the problem of device reliability; 4) isolation structure between microwave-bias voltage also can adopt monocrystalline silicon or polysilicon resistance line; This structure can be accomplished processing synchronously in the processing step of processing bridge film; And pairing technology when needing deposit, the etching technics of extra increase and letting it pass through the transmission line signals line from the below when having avoided adopting conventional metal-silicon resistance alloy as isolation structure helps to reduce manufacturing cost; 5) planar structure of bridge film has adopted the butterfly structure of mirror image symmetry, has the large tracts of land flank, therefore can produce bigger electrostatic attraction, so compare with the conventional bridge membrane plane structure of present employing, can effectively reduce driving voltage.
The above embodiments of the present invention all are to be transmission structure with the planar transmission line; But the present invention is equally applicable to waveguide on the sheet; Waveguide is the metal waveguide structure of making in multi-lamellar microwave circuit substrate interior on the sheet; The microwave circuit substrate is by upper surface panel at this moment, and one or more layers Intermediate substrate and lower surface stack of plates constitute.The exploded view of a kind of possible structure of waveguide is as shown in Figure 5 on the sheet.Wherein 20a, 20b and 20c are respectively the upper surface panel of microwave circuit substrate, the Intermediate substrate that is etched with waveguide cavity and following table panel.The 21st, the waveguide cavity that in substrate 20b, processes, on the vertical substrate surface direction, run through substrate; After 20a, 20b and 20c pile up; The side up and down of waveguide cavity 21 is by upper surface panel 20a and following table panel 20c sealing; The duct-like waveguiding structure of final formation, its wall is coated with high conductivity metal such as Au, Ag, Cu.
Micromechanics bridge film loading structure also can be used for the loading of waveguide on the sheet.With reference to figure 6, waveguide can utilize build etching processing technology in filter substrate 6, to form on the sheet at this moment, and its matrix generally is microwave circuit backing materials such as LTCC; Waveguide sidewalls applies high conductivity metal such as Au, Ag, Cu on the sheet, and the upper wall surface of waveguide no longer is made up of upper surface panel on the sheet of bridge film below, covers and change by layer of metal film 22, to form the waveguiding structure of sealing.The bridge film is manufactured with the salient point 23 that metal or dielectric constitute through the top that anchor point 18a, 18b are fixed on the waveguide cavity ad-hoc location below the bridge film at this moment; On said bridge film and said substrate, be provided with two pairs of drive electrodes (be 16a and 22 with 16b and 22), said electrode is connected with the control circuit of microwave circuit system; The driving DC voltage of control circuit output produces electrostatic attraction (22 connect electronegative potential) between described bridge film flank 16a and metallic film 22 and bridge film flank 16b and metallic film 22; Change the spacing between the planar transmission line holding wire of itself and below; The salient point 23 of bridge film below is contacted with metallic film 22 and downward deformation takes place; The deformation of metallic film 22 has changed the inner electromagnetic field of waveguide and has distributed; Its deformation quantity is decided by the size of driving voltage, has changed the loading capacitance of the inner equivalence of waveguide on the sheet thus.
More than through specific embodiment micro mechanical adjustable microwave band-pass filter provided by the present invention has been described, it will be understood by those of skill in the art that in the scope that does not break away from essence of the present invention, can make certain deformation or modification to the present invention; Its preparation method also is not limited to disclosed content among the embodiment.
Claims (10)
1. a micro mechanical adjustable microwave band-pass filter comprises microwave circuit substrate and the resonator that possesses double resonance mode that is provided with on it, and imports coupling unit, output coupling unit and disturbance unit accordingly; Wherein said resonator is a toroidal cavity resonator, and the planar graph that its axis constitutes has two-dimentional mirror symmetry, promptly has two orthogonal symmetry axis in this planar graph at least; Said input coupling unit is vertical each other with the axis of output coupling unit, and overlaps with two orthogonal symmetry axis of said planar graph respectively; Said disturbance unit one end links to each other with resonator, other end open circuit, and the angle of two orthogonal symmetry axis of its axis and said planar graph is 45 °; On said resonator, be placed with >=2 even number micromechanics bridge film; Their position is the mirror image symmetrical distribution with respect to the axis of disturbance unit, and any electrical length to the input coupling unit that is in the symmetrical pair of bridge film of mirror image equates with another electrical length to the output coupling unit; On said disturbance unit, place one or more micromechanics bridge films; Said resonator and disturbance unit constitute by being made in the upper and lower lip-deep planar transmission line of microwave circuit substrate; Said bridge film is a layer structure, is monocrystalline silicon or polysilicon layer, insulating barrier, metal level and dielectric layer from top to bottom; Said micromechanics bridge film is fixed on the top of planar transmission line ad-hoc location through anchor point; On said micromechanics bridge film and said substrate, one or more pairs of drive electrodes are set; These electrodes are connected all micromechanics bridge films respectively with the control circuit output of microwave circuit system; The driving DC voltage of control circuit output makes between the drive electrode of bridge film and substrate and produces electrostatic attraction; Spacing between the planar transmission line holding wire of change bridge film and below; The variable quantity of spacing is controlled by driving DC voltage, changes the loading capacitance of bridge film to planar transmission line thus, thereby realizes the adjusting of filter passband centre frequency and pass band width.
2. filter as claimed in claim 1; It is characterized in that; Said input coupling unit is identical with the structure of output coupling unit; Constitute by the tight capacity coupled two sections planar transmission lines of mutual existence respectively, or waveguide transitions structure on planar transmission line-sheet, or waveguide transitions structure on coaxial cable-sheet.
3. filter as claimed in claim 1 is characterized in that, the figure that the axis of said resonator constitutes is planar graph circular, square or that have the fractal graph characteristic.
4. filter as claimed in claim 1 is characterized in that, the planar transmission line that constitutes said resonator is microstrip line, band line or co-planar waveguide line.
5. filter as claimed in claim 1 is characterized in that, said disturbance unit is made up of one section microwave short-term, and this microwave short-term is continued to use the used planar transmission line of resonator and made up, and its axis is a straight line.
6. a micro mechanical adjustable microwave band-pass filter comprises microwave circuit substrate and the resonator that possesses double resonance mode that is provided with on it, and imports coupling unit, output coupling unit and disturbance unit accordingly; Wherein said resonator is a toroidal cavity resonator, and the planar graph that its axis constitutes has two-dimentional mirror symmetry, promptly has two orthogonal symmetry axis in this planar graph at least; Said input coupling unit is vertical each other with the axis of output coupling unit, and overlaps with two orthogonal symmetry axis of said planar graph respectively; Said disturbance unit one end links to each other with resonator, other end open circuit, and the angle of two orthogonal symmetry axis of its axis and said planar graph is 45 °; On said resonator, be placed with >=2 even number micromechanics bridge film; Their position is the mirror image symmetrical distribution with respect to the axis of disturbance unit, and any electrical length to the input coupling unit that is in the symmetrical pair of bridge film of mirror image equates with another electrical length to the output coupling unit; On said disturbance unit, place one or more micromechanics bridge films; Said resonator and disturbance unit are made up of waveguide on the sheet that is formed in the microwave circuit substrate; Said bridge film is a layer structure, is monocrystalline silicon and insulating barrier from top to bottom, or polysilicon layer and insulating barrier; Said micromechanics bridge film is fixed on the top of waveguide cavity ad-hoc location through anchor point, and bridge film below is manufactured with the salient point that metal or dielectric constitute, and the upper wall surface of waveguide is only covered to realize sealing by the layer of metal film on the sheet; On said bridge film and said substrate, one or more pairs of drive electrodes are set, these electrodes are connected with the control circuit of microwave circuit system; The driving DC voltage of control circuit output makes between the drive electrode of bridge film and substrate and produces electrostatic attraction; Spacing between the waveguide cavity of change bridge film and below; The metallic film of waveguide upper wall surface contacts and makes the downward deformation of metallic film generation on the salient point that makes bridge film below and the sheet; The deformation of metallic film has changed the inner electromagnetic field distribution of waveguide on the sheet; Its deformation quantity has been realized variable capacitive load to waveguide on the sheet thus by the size decision of driving DC voltage, thereby realizes the adjusting of filter passband centre frequency and pass band width.
7. filter as claimed in claim 6; It is characterized in that; Said input coupling unit is identical with the structure of output coupling unit; Constitute by the tight capacity coupled two sections planar transmission lines of mutual existence respectively, or waveguide transitions structure on planar transmission line-sheet, or waveguide transitions structure on coaxial cable-sheet.
8. filter as claimed in claim 6 is characterized in that, the figure that the axis of said resonator constitutes is planar graph circular, square or that have the fractal graph characteristic.
9. filter as claimed in claim 6; It is characterized in that; Constituting on the sheet of said resonator waveguide and be with the microwave circuit substrate is matrix, and parallel axes is deposited with high conductivity metal in the rectangle of substrate surface or the tubular structure of circular cross-section on the wall of tubular structure.
10. filter as claimed in claim 6 is characterized in that, said disturbance unit is made up of one section microwave short-term, and this microwave short-term continues to use that waveguide makes up on the used sheet of resonator, and its axis is a straight line.
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| TWI472151B (en) * | 2011-08-30 | 2015-02-01 | Richwave Technology Corp | Filter system capable of automatically adjusting bandwidth and method of automatically adjusting bandwidth of a filter |
| CN102820503B (en) * | 2012-08-20 | 2015-06-17 | 上海交通大学 | Half-lumped miniaturized microwave filter and design method thereof |
| CN105161799B (en) * | 2015-08-25 | 2019-04-09 | 电子科技大学 | Microwave tunable filter |
| CN105281670B (en) * | 2015-11-11 | 2018-04-24 | 中国电子科技集团公司第四十一研究所 | 220GHz-325GHz applied bias efficient broadband varactor doublers |
| CN108183295B (en) * | 2017-12-26 | 2019-05-28 | 上海交通大学 | Double-passband filter based on commensurability transmission circuit network |
| CN108470988B (en) * | 2018-05-16 | 2023-09-26 | 广东圣大电子有限公司 | Broadband low-profile high-gain satellite antenna |
| CN109904631B (en) * | 2019-02-22 | 2020-06-09 | 厦门大学 | Microstrip patch antenna for radiating third-order vortex wave beam |
| CN111595318A (en) * | 2020-06-24 | 2020-08-28 | 北京信息科技大学 | T-shaped micro-mechanical double-shaft film gyroscope with single heat source |
| CN113708620A (en) * | 2021-08-25 | 2021-11-26 | 慧石（上海）测控科技有限公司 | Charge pump circuit structure and miniature charge pump |
| CN113946014B (en) * | 2021-12-20 | 2022-03-04 | 南京高华科技股份有限公司 | Dimmable resonator |
| CN114824707B (en) * | 2022-04-28 | 2023-09-26 | 西南科技大学 | 5G millimeter wave reconfigurable waveguide filter and passband adjusting method thereof |
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| CN1551275A (en) * | 2003-03-31 | 2004-12-01 | 韩国机械研究院 | Method for enlarging stoke of piezoelectric sensor and MENS switch using said method |
| CN101431172A (en) * | 2008-07-29 | 2009-05-13 | 华东师范大学 | Reconfigurable microwave low-pass filter containing MEMS switch and its manufacturing method |
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| CN1551275A (en) * | 2003-03-31 | 2004-12-01 | 韩国机械研究院 | Method for enlarging stoke of piezoelectric sensor and MENS switch using said method |
| CN101431172A (en) * | 2008-07-29 | 2009-05-13 | 华东师范大学 | Reconfigurable microwave low-pass filter containing MEMS switch and its manufacturing method |
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