Controlled absorbing attenuators on Schottky-gate FETs: T-circuit, T-shaped bridge circuit and transistor attenuator in the mode with controlled slope of voltage-current characteristic have been considered. Attenuator phase-frequency characteristics were modeled. The main difference of the circuits from the known ones consists in introduction of equalizers that conditions broadband feature and large attenuation range where minimum of the phase shift is achieved at regulation. As a result, the optimal parameters of adjusting circuits in attenuators are founded. It is shown that the least phase shift is provided in attenuators on transistor with controlled volt-ampere characteristic steepness. The comparative estimation of the considered base structures was given

Stukach, O. V.

Electronic archive of Tomsk Polytechnic University

REFERENCES1. Alekseev O.V., Groshev G.A., Chavka G.G. Multichannel frequencydividing devices and their application. – Moscow: Radio andcommunication, 1981. – 136 p.2. Fettweis A. Wave digital filters // TIIER. – 1986. – № 2. – P. 35–99.3. Neirynck J., Carlin C.H. Synthesis of the lossless reciprocal threeportbased on a canonic form of its scattering matrix // IEEE Transactionson Circuits and Systems. – 1981. – V. CAS28. – № 7. – P. 736–744.4. Youla D. Several key representations of circuit theory being a principle of filters calculation by the classical method of attenuation characteristic // TIIER. – 1971. – № 5. – P. 45–87.5. Belevitch V. On filter pairs with Butterworth characteristics // International Journal of circuit Theory and Applications. – 1987. – V. 15.– P. 51–60.6. Zhu Y.S, Chen W.K. On the design of a diplexer having Butterworth characteristics // IEEE Transactions on Circuits and Systems. – 1988. – V. CAS35. – № 11. – P. 1455–1457.7. Youla D. C., Pillai U., Winter F. Theory and design of maximally flatlowpass highpass reactanceladder diplexers // IEEE Transactionson Circuits and Systems. – 1992. – V. CAS39. – № 5. –P. 337–349.8. Neirynck J., Carlin C.H. Synthesis of the lossless reciprocal threeport based on a canonic form of its scattering matrix // IEEE Transactions on Circuits and Systems. – 1981. – V. CAS28. – № 7. –P. 736–744.9. Bondarenko A.V., Dovgun V.P. Synthesis of analog wave filters //Electricity. – 2005. – № 5. – P. 52–56.10. Dovgun V.P., Barybin P.A., Novikov V.V. The analog wave filters:main properties and procedure implementation // The Bulletin ofassociation of KSTU graduates. Krasnoyarsk. – 2005. – Issue 12. –P. 156–164.Received on14.05.2007Bulletin of the Томsк Pоlytеchnic University. 2007. V. 311. № 490The requirement of phase shift constancy at transferconstant adjustment is made to modules of active phaselattices, systems of automatic phasing in transmitters,precise wideband amplifiers, attenuators with smoothvariation of attenuation and other devices with adjustable characteristics of signal transmission. Change ofphase shift or group delay is conditioned by the influence of parasitic reactivity of elements with controlled resistance. There is a certain process limit in decreasingparasitic parameters. Therefore, one of the most important tasks is a balance of parasitic reactivities of the controlled elements by circuit solutions.1. The problem of phase shift invariance Electrically controlled attenuators (ECA) are intended for smooth change of signal level in a circuit. For anumber of practical tasks, for example, CDMA of communication systems, phased arrays, surface radars etc.,the excess requirement is made to attenuators; the requirement to phase shift stability of output signal relative tothe input one at adjustment of transfer constant [1]. Thisaim is complicated at system operation in a wide band,in general case from zero to several GHz. Phase variationis conditioned by the influence of parasitic reactivities ofthe controlled elements. They may be decreased technologically only to a certain limit, especially in superwideband. Therefore, the only method of supporting phaseshift invariance to attenuation is the balance of parasiticreactivities of controlled elements by a circuit way. Inparticular, the equalizers included specially into the basestructure find wide application in absorbing attenuators.The methods of phase correction are developed bestof all for ECA on pin diodes [1]. Schottkygate FETs(SFET) have a number of advantages although diodesgain in maximum power of controlled signal. In particular, the advantage is in switching time, decouplingbetween signal transmission circuit and control paths.Availability of using SFETs conditioned by low values ofparasitic reactivities simplifies considerably the problemof constructing wide band ECA in microwave range.The aim of the work is the investigation and simulationof circuit design characteristics for ECA on FETs, searchfor perspective circuit methods of phase shift correctionand comparison of the obtained results with known characteristics of base diode and transistor structures.UDC 621.372.852MODELING OF ATTENUATOR STRUCTURES ON FIELD EFFECT TRANSISTORS WITH MINIMAL PHASE SHIFT AT ATTENUATION REGULATIONO.V. StukachTomsk Polytechnic UniversityEmail: tomsk@ieee.orgControlled absorbing attenuators on Schottkygate FETs: Tcircuit, Tshaped bridge circuit and transistor attenuator in the mode withcontrolled slope of voltagecurrent characteristic have been considered. Attenuator phasefrequency characteristics were modeled. Themain difference of the circuits from the known ones consists in introduction of equalizers that conditions broadband feature and largeattenuation range where minimum of the phase shift is achieved at regulation. As a result, the optimal parameters of adjusting circuitsin attenuators are founded. It is shown that the least phase shift is provided in attenuators on transistor with controlled voltampere characteristic steepness. The comparative estimation of the considered base structures was given.2. Selection of transistor operating conditions in a circuit SFETs represent a semiconductor substrate with twoohmic contacts (drain and source) and rectifying junction metalconductor used as a gate [2]. UsuallySFETs are characterized by currentvoltage input, output and transfer dependences reflecting physical processes occurring in transistor at its different states. So,without bias voltages on the gate and drain the transistoris in thermodynamic equilibrium and all currents equalzero. This state of transistor is boundary for the transferprocesses occurring in SFET channel. Channel resistance at fixed voltage gatesource may be determinedby the Ohm law. But the channel effective section changes depending on the value of drainsource voltage at fixed gate voltage, as well as because of voltage drop intransistor subgate area at drain current flow. It is obvious that the channel resistance depends on thickness ofsubgate area depletion layer. Therefore, fieldeffecttransistor may be considered as a voltage controlled resistor. And such resistor is not sensitive to the effects ofminority carrier accumulation and has higher controlvelocity; application of reversedbiased junction withlow saturation current requires minor power consumption for controlling transistor.High operating speed of control devices as well aslow value of power consumption allows obtaining passive mode of transistor connection. SFET application inpassive mode allows controlling efficiently the decay inattenuators. SFET use is bounded by the absence ofcharacteristics and parameters required for design. Thisis the reason for additional and laborconsuming measurements. The adjusting characteristic is the main onefor estimation of control efficiency. It is determined byminimum and maximum transistor resistances as well asby the law of variation of SFET channel resistance fromvoltage on its gate. Therefore, the issue of selectingSFET consists in determining its channel resistancewithout voltage between the transistor source and drain.At transistor manufacturing there are process errorsresulting finally in deviation of the implemented characteristics from the expected ones. The range of theirdeviation is not known beforehand, as a rule; therefore,the comparison of the results of calculations by the fixedelectrophysical parameters of SFET with the results ofmeasuring single samples of transistors is illegal. At thesame time, use of transistors with different characteristics in control devices of microwave range results in nonidentity of their frequency characteristics. Therefore,definition of parameters of average transistor as well asthe value of their deviations from the most probablemagnitude for the applied type of SFET is one of themost important tasks of designing control devices.Let us examine some peculiarities of studying SFETin devices of controlling signal amplitude in the modewith the controlled slope of voltagecurrent characteristic which depends on voltage of gatesource or gatedrain shift. Transistors are usually connected by thecommonsource circuit, i.e. the attenuator represents ausual singlestage amplifier. The adjustable signal andcontrol voltage are supplied to transistor gate. Currentvoltage characteristic slope of transistor decreases atincrease of negative blanking voltage at the gate that results in signal attenuation.3. Circuit designs of transistor attenuators Circuit of Tshaped attenuator is given in Fig. 1. Theattenuator consists of two transistors in series arm andone transistor in parallel arm connected in the mode ofcontrolled resistance. Two voltages Uупр, entering thetransistor gates are required for attenuator control. Ifnegative blanking voltage is supplied to the gates VT1and VT2 then the resistance of drainsource channelsincreases and therefore, the decay introduced by attenuator raises. If the blanking voltage is supplied to the gate VT3 then attenuation decreases. Gate voltages enterthrough the filters consisting of elements C2, L3, R3 andC3, L1, L2, R4.Fig. 1. Circuit of Tshaped controlled attenuatorAttenuator characteristics were modeled by application package WorkBench 5.12 and transistor PhilipsBSJ110 from the builtin library of the elements. In order to decrease the phase shift at attenuation adjustmentthe correcting RCcircuit R2, R5, C4 was applied. Thecorrecting element rates should be selected so that thecircuit impacts the shape of AFC and PFC only on upper frequencies.Dependences of phase shift change on frequencyand attenuation obtained by simulation and constructedin program Statistica 6.0 are given in Fig. 2 and 3.In compensated attenuator the phase shift changedoes not exceed 10° in attenuation range 2,5...8,2 dBand in frequency band 0,05...4,0 GHz while it equals26° in attenuator without correction.Similar results were obtained in Tshaped compensated bridge attenuator consisting of two transistorsconnected in the mode with controlled resistance(Fig. 4). In comparison with usual Tshaped connectionit supports lower range of input signal adjustment,however, its advantage is minor initial attenuation. Thecorrecting circuit consists of resistors R2R4C3. Its principle of operation is like the operation of correcting circuit of the Tshaped attenuator. The difference consistsin the fact that transistor VT2 controls the influence ofcorrecting elements on the attenuator characteristics.Power engineering91Fig. 2. Change of phase shift depending on frequency and attenuation for uncompensated attenuatorFig. 3. Change of phase shift depending on frequency and attenuation for compensated attenuatorLet us compare the obtained results with the attenuator characteristics from the work [3]. The attenuatorrepresents a bridge of resistive sections switched by thefieldeffect transistors in passive mode. The initial lossof attenuator amount to 2,5 dB, peak attenuation is17 dB, phase shift change at adjustment equals 30° infrequency range 0...4 GHz. Thus, the simplified modelused in this article is rather adequate to the experimental results from [3].The results of simulation show that in Pshaped circuit of attenuator a minor change of phase shift couldnot be achieved at attenuation adjustment than inTshaped circuit just the same as in diode attenuators.SFET attenuator with controlled slope of currentvoltage characteristic represents a usual singlestageamplifier where transistor is connected by a commonsource circuit. Adjustable signal is supplied to the gate;control is fulfilled by the gate or by the gate and drain simultaneously. Increasing negative voltage on the gatethe currentvoltage slope decreases, so, signal amplitude at the output decreases as well. The disadvantage ofthe examined circuit is the absence of isolation betweenthe adjustable signal and control signal. The attenuatorcircuit is given in Fig. 5.Fig. 4. Circuit of Tshaped bridge attenuatorFig. 5. Attenuator on transistor with adjustable slopeIf voltage is adjusted simultaneously on the gate anddrain so that the gatedrain voltage remains constantthen only a gatesource capacity decreases. This causesminor changes of PFC then at adjustment only by thegate (Fig. 6). PFC change does not exceed 5° in thewhole range of frequencies and attenuations.Fig. 6. Attenuator PFC (Fig. 5) with adjustment by the gate anddrain4. ConclusionModel phasefrequency characteristics of attenuators controlled by voltage, carried out on Schottky fieldeffect transistors: Tshaped, Tshaped bridge circuitsand attenuator on transistor in the mode with controlledslope of currentvoltage characteristic were examined.Bulletin of the Томsк Pоlytеchnic University. 2007. V. 311. № 492It is shown that use of correcting circuits allowsachieving phase shift uniformity at adjustment of powerattenuation. It is assigned that in modified Tshaped attenuator the phase shift change does not exceed 10° inattenuation range 2,5...8,2 dB in frequency band0,05...4,0 GHz; it is almost in 2,6 times lower than inattenuator without correction. In comparison with diode attenuators, the Tshaped bridge circuit does not give considerable advantages from the point of view ofphase shift minimum.In attenuator in the mode with adjusted slope of currentvoltage characteristic a minor change of phase shift– to 5° in the same range of frequencies and attenuations may be achieved. The obtained results are close tothe experimentally observed values.Power engineering93REFERENCES1. Stukach O.V. Condition of minimal dependence of phase shift onamplitude frequency characteristic in devices with variable conditions // Bulletin of the Tomsk Polytechnic University. – 2005. – № 4.– V. 308. – P. 157–160.2. Fieldeffect transistors on gallium arsenide. Principles of operationand manufacturing technique / Ed. by D.V. Di Lorentzo, D.D. Kadeluola. – Moscow: Radio and Communication, 1988. – 496 p.3. Tolstolutskiy S.I., Li A.I., Kazachkov V.V., Popov M.A., Tolstolutskaya A.V., Komor V.P. Solidstate fourbit microwave attenuator ongallium arsenide for the range 0–4 GHz / Microwave engineeringand telecommunication technologies (CriMiCo’2007): Writings ofthe 17th International conference in the Crimea. – September10–14, 2007, Sevastopol. – Sevastopol, 2007. – P. 85–86.Received on 07.12.2006Introduction In order to provide competitiveness with independent feed systems on the basis of well known sources ofelectric energy, the systems on the basis of fuel cells(FC) should operate with comparable efficiency [1].Such systems behavior in transients is one of the key issues at the stage of their design [2]. Simulator of FCcharacteristics is the device having at loading terminalsthe same characteristics of output power as the real system. In order to develop the simulator of FC characteristics the mathematical model of electrochemical generator directed to the analysis of the system bytechniques of automatic control theory and electricalengineering should be designed.Currently, the investigations in this field, introducedin domestic and foreign sources, may be conditionallydivided into two directions: the first one (given in themajority of works) is the investigation in the field ofelectrochemistry the aim of which is the development ofthe FC components (electrolytes, gasdiffusion electrodes etc.) and selection of optimal work areas on currentvoltage, parametric and other curves. Such models arebased on laws of electrochemistry of porous structures,thermodynamics and mechanics of gaseous and liquidmedia [3, 4]. They are not suitable for analysis of transients in FC system by the techniques of automatic control theory and electrical engineering.Another direction is the investigation in the field ofelectronics and microprocessor engineering allowingmodeling FC characteristics [5]. However, insufficientcoverage of these questions in scientific literature resulted in necessity of developing mathematical model ofclosedloop control of FC, designing physical modelcomputer control simulator of FC characteristics for experimental investigations of its characteristics; as well asdeveloping the control system allowing providing thespecified characteristics of the transients.The authors proposed a new device on the basis ofcomputer controlled pulse converter of direct currenton the basis of FC electrochemical model (software)included in it. The simulator on the basis of the mentioned converter has on its loading terminals the samedependence of output continuous stress on load currentas the real FC [6, 7].UDC 621.3SIMULATOR OF FUEL CELLS CHARACTERISTICS ON THE BASIS OF THE SEMICONDUCTOR CONVERTERV.G. Titov, S.V. AbramovState technical university, Nizhny NovgorodEmail: s.abramov@mail.ruThe results of development and research of the simulator of fuel cells characteristics based on the operated pulse converter with directcurrent and digital alarm processor have been considered. The electrochemical model of fuel cell considering its static and dynamic characteristics is incorporated in the algorithm of the processor work. The specified simulator has on loading terminals the same characteristics of output capacity as a real system. It allows abandoning the use of both the elements and expensive accompanying systems atstages of research, design and realization of independent systems of power supply on the basis of fuel cells.

Modeling of attenuator structures on field effect transistors with minimal phase shift at attenuation regulation

Abstract

Similar works

Full text

Available Versions

Electronic archive of Tomsk Polytechnic University