Electro-Mechanical Phase Shifters Based on MEMS Structure

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Journal ofMechanics Engineering and Automation 3(2013)421-423Electro．MechanicaI Phase Shifters Based on MEMSStructureAntonenko Anton Sergeevishl
，
Geraimchuk Michael Dem’yanivich2 and Dubrovka Fedir Fedorovich1．National Technical University ofUkraine Kiev Polytechnic Institute ．Kiev 03035．Ukraine2．Instrument—Making Department(High-Precision Mechanics)，NTUU“KPI”，Kiev 03056,Ukraine3．Theoretical Bases ofRadio Engineering Department,NTUU“KPI ．Kiev 03056,UkraineReceived：April 18，2013／Accepted：M rdy 17，2013／Published：July 25，2013lN 塔Abstract：The aim of the study of phase shifter on MEMS(micro-electro-mechanical systems)structures was to minimize thedimensions of the design achievement．Also，the main task was to achieve the reliability and durability of the device．The calculationwas based on the optimization technique(step by step)and the modeling of individual pans of the device，namely MEMS-keys thatperform the main function- switching．The urgency of this problem is the development and study of one device as a universal，that is，automaticaly switches from two signals simultaneously．Designs are original and devises are the intelectual property of the authors.

The program for modeling phase shifters Computer Simulation Technology Microwave Studio and its results are presented in thePaper.

Key words：MEM S，phase shifter，dielectric layer1．IntroductionRecently，the interest is a new class of microwaveswitching elements，which are based on M EM S(micro—electro—mechanical systems)． They areminiature mechanical switches，voltage controlled．Theability to create these elements is based on theprecision technology of monolithic microwaveintegrated circuits．All elements of the MEM S areperformed for two basic technologies：surface and bulk.

Surface technology involves the creation of the surfaceof the substrate metal and dielectric layers and theirsubsequent selective etching to form a cavity，whosesize varies depending on the control voltage．The paperis organized as follows：Section 2 discusses the designfeatures of phase shifers；Section 3 is fine~equencyestimation；Section 4 gives conclusions.

2．Design Features of Phase ShiftersCorresponding author： Antonenko Anton Sergeevish，post-graduate student，research fields：microwave systems anddevices，MEMS technology．E—mail：ehnaton7###rambler．ru.

There are two possible configurations of themicrowave switches based on MEM S．Onc of them isused as an upper electrode console．Voltage control，which operates two electrodes atracts them to eachother by electrostatic forces．In this capacity，the keychanges．Thus，the two states correspond to the two keyvalues of capacitance．In another configuration，themovable electrode is performed as a bridge，both endsare fixed．It works wel，as in the console version.

SQF(switching quality factor)for MEMS-key canbe set to order 10。 or more
， as the change incapacitance Cmax／Cmin estimated values 80—1 00，andlosses in the dielectric corresponds tgfi 0．00 1.

According to this parameter M EM S switches surpassall known types of microwave keys，it allows us tohope for a high—quality (PS)phase shifters，built onthe keys of this type．Another advantage is negligiblepower consumption for the control circuits． Theextremely small size allows these key perform ance upto frequencies 1 00 GHz．Of course，these devices，are422 Electro．MechanicaI Phase Shifters Based on MEMS Structurenot without drawbacks，the main of which—a relativelylow speed．The best is the response time of 1 0 ms.

Another drawback is the limited number ofmechanical switching，so the lifetime is much smallerthan the life of electronic keys．Nevertheless，the highquality of M EM S-key in terms of their electricalcharacteristics of PS atracts developers，and work toimprove the instruments of this type is carried outvery intensively.

As an example， Fig． 1 shows the design ofmicrowave switch console and the transmission losscharacteristics and locking in the frequency band【1].

Using these two keys in two-channel switch ensuresno loss ofmore than 0．2 dB in the open arm and theisolation of at least 30 dB in the second shoulder inthe frequency range 0—1 5 GHz．Building a digitalphase shifters on MEM S—keys is possible in principlefor any of the above schemes of discrete ejection.

However， such keys are bad for its technologyembedded in the monolithic microwave integratedcircuits and are not suitable for hybrid technology.

Therefore，all known to date with the EF—key MEM Sare analog switched line pe PS．One of the mainadvantages of MEMS technology， high—quality，combined with a high degree of miniaturization.

Ref．【2]shows the results ofthe development oftwo—and four-digest ejection at 1 8 GHz frequency．ThesePS perform ed on the loaded transmission line，as theload used serial connection M EM S．variants andmicrostrip stubs．Two-digit PS has insertion loss ofless than．2．8 dB and maximum phase delay 262。.

曲Fig．1 (a)The designconsole；(b)the keyfrequency range.

珏F．1ineOp∞Direct lg dB OutcOn~ de量
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b)0f M EMS-key with a picture of thecharacteristics Of MEM S in theFour—digit PS has lost less than 3 dB and maximumphase delay 333。.

3．Fine Frequency EstimationPrincipal design of piezo-driven phase shifter basedon the microstrip line is shown in Fig．1．Experimentsand calculations show that their phase shift is stronglydependent on design architecture.

Only one of designs(shown in Fig．2a)waspublished previously[3].

However，it is obvious that other designs shown inFigs．2b一2d show higher effect because dielectricdiscontinuity is created in the plane perpendicular toelectrical field of the microstrip line．The effectivenesswas verified and proved experimentally．The bestresults is obtained with the new idea of“detached”upper electrode，Figs．2c and 2d that is electrodediscOnnected from substrate and attached to themoveable dielectric plate．Close to these cases phaseshift would be obtained if the bottom electrode wouldbe disconnected．Simulation in Fig．3 confirms thatstronger perturbation of electromagnetic fielddistribution results in higher differential phase shift.

This effect also could be explained in terms ofeffective permittivity change．As one can see in Fig．4，designs with detachable electrode exhibit larger changein effective dielectric constant．which in turns iSobserved as larger phase shift.

In other words，propagation constant at a givenfrequencyfcan be estimated as y= whereP~ezomovcr(《Fig．2 Mechanicaly tuned microstrip phase shiflers.

Electro．Mechanical Phase Shifters Based 0n MEMS StructureAirgap 舞Fig．3 Comparison of(a)known and(b，C，d)new proposeddevices．Phase shift(standardized)is shown as function oftunable air gap.

Airgap 鞔Fig．4 Comparison of effective dielectric permittivity Eef in(a)known and(b，C，d)new proposed devices.

C is the light velocity．So the main task of deviceanalysis is to determine effective perm ittivity forprescribed geometrical configuration．This problem issolved numerically using finite element method.

4．Conclusions423Creation of microwave switching elements based onMEMS has opened a new chapter in the design ofswitching microwave devices，including possible tolaunch a new type of discrete ejection．Method MEMSswitch switches outperform all known types ofswitching keys.

M ain mechanisms of piezoelectric control by the~'efof some devices based on dielectric layers arediscussed．It is supposed that the most effective way isto use a composition“microwave dielectric-air gap”，controled by the fast actuator．At that，a minimal lossis inserted in tunable component.

Using high quality microwave dielectrics， it ispossible to realize low loss filters and phase shifiers asin the microwaves SO as in the millimeter waves.

Proposed structures are studied as in the rectangularwaveguide，SO in some microstrip designs.

References【1】 0．F．BertaHK，M．且．HapHec，AHTeHHbl C 3JICKTpI4qCCKHMCKaHHpOBaHHCM．200 1．PP．1 80-l 82.

J．S．Hayden，A．Malczewski，J．Kleber，C．L．Goldsmith，2and 4．bit DC．1 8 GHz microstrip MEMS distributedphase shifters． in：200l IEEE MTT-S InternationalMicrowave Symposium Digest．Phoenix AZ USA，200 1.

T．Y．Yun．K．Chang．Analysis and optimization of aphase shifter controlled by a piezoelectric tran sducer，IEEE Transactions on Microwave Theory andTechniques 50(2002)105．1 1 1.

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