International Conference on Electrical, Electronics and Communication Engineering (ICEEC'2012) September 8-9, 2012 Bangkok (Thailand)

Broadband Traveling Wave Distributed (TWDA) with Variable Gain By Control the Source Bulk Voltage

Saeed.Zakeri, Dr. Ebrahim.Abiri, Hefzollah.Mohammadian

Abstract— This paper begins with a review of elements of the II. AND ITS APPLICATIONS distributed amplifier and with goal of to design an amplifier with a distributed structure with appropriate parameters has ended .In this TABLE I paper to build the amplifier also helps Structure designed to help and DIVIDES THE BAND more advanced technology has been used. Now that the parameters at high frequencies with good scattering and other quality attributes surveyed in a microwave amplifier, including power, input and output VSWR values and noise and etc give us. In the design of this amplifier is used two transmission lines that one of them, connected to the gate of several and the other one is connected to the drain of the same transistors. This transmission lines acts like a filter Which Gate – source capacitors and the inductors (that we have designed) create the Gate Filter. Also drain – source capacitors and the inductors (that we have designed it) create the drain transmission line TABLE II Filter .Finally we will arrive the desired result with Study and DIVISION BAND MICROWAVE FREQUENCIES analysis of whole network and using simulation results with calculate the parameters of .

Keywords— Scattering Parameters, Vswr, Available Power, Distributed Structure.

I. INTRODUCTION IGH frequency circuits and techniques used in Hcommunication systems have grown dramatically in recent years. One of the circuits used in high frequency circuits are microwave amplifiers. This type of construction Applications are very large range of microwave signals, has a variety of amplifiers are high. And manufacture of some of which include: advanced components and technologies are developed. Amplifiers with wide bandwidth in the field of A. Radars (with a very large family and a wide range can be made by integrated or hybrid technology will be of demand) implemented. General infrastructure systems such as the fields B. Point to point multi-channel of microwave, optical communications, Instrumentation and communications (microwave radio) electronic warfare are amplifiers. One of the broadband C. Radio communication systems (fixed and mobile) amplifiers are distributed amplifiers and These amplifiers have D. Microwave image distribution systems / mm a relatively wide bandwidth and low noise characteristics and (MVDS) their output is satisfactory. E. Transmitter - receiver for fiber-optic microwave F. Microwave Instrumentation G. Local area networks (wireless)

Saeed Zakeri was with Technical Junior College of Minab, Iran (Szakrey @yahoo.com). differential method disadvantages to some extent. Dr. Ebrahim Abiri was with Shiraz University of technology (SUTECH), Shiraz, Iran, ([email protected] ). Hefzollah Mohammadian was with Azad University of Bushehr. He is now with the Department of Instrument, South Pars Gas Complex, Iran. ([email protected]).

15 International Conference on Electrical, Electronics and Communication Engineering (ICEEC'2012) September 8-9, 2012 Bangkok (Thailand)

III. TRAVELING WAVE DISTRIBUTED AMPLIFIER includes a capacitor Cgdp the property and gate and drain and (TWDA) source terminals of the capacitor and the capacitance between the capacitive property Cdsp that the property Cgsp A. characteristics of a as an active part in capacitance between gate and source terminals are. The value distributed amplifiers of this capacitor is small and depends on the type of Hj-Fet a unilateral equivalent circuit in Figure.1 is shown as transistors are packed. The small signal equivalent circuit a simple transistor. Gate and drain terminals of respectively elements, for example, Hj-Fet transistor NE32584C numbers parasitic capacitors are a Cgs and Cds. Cgs feedback capacitor in Table.I NEC factory has been shown [1,8]. as shown in point is China and usually small due to the transistor model, it is ignored. The transfer conductance of TABLE III transistor (gm), a voltage-controlled current source is that THE EQUIVALENT CIRCUIT PARAMETERS OF TRANSISTORS HJ-FET (NE32584C) Current proportional to the voltage Vgs (Voltage across the capacitor Cgs) at this terminal provides.

B. Available power gain in Traveling Wave Distributed Amplifier (TWDA) Figure.3 shows the circuit of a conventional distributed Fig.1 A simplified model for small signal transistors Hj-FET amplifier (TWDA), which are composed of four identical active elements and are parallel. Each stage of the amplifier The equivalent circuit for small signal Fet is much more can be considered as a T network, the networks of T are complex. For example, Small signal equivalent circuit of Hj- parallel with each other. [1] Fet show in Figure.2 Elements that are enclosed with the Chinese point lines, the intrinsic transistor elements and the remaining parts or external elements are parasitic. [1]

Fig.3 Structure of a TWDA consists of four pieces

Figure.4 is a simplified model shows TWDA with n stage. No

Fig.2 complete model of a small signal Hj-FET transistor losses have been considered as transistors. [1]

Resistors Rg, Rd and Rs, are respectively, indicating the resistance of wires connected to the terminal gate, drain and source and Inductors Lg, Ld, and Ls, are respectively, indicating the property of the inductor wires connected to the gate terminal, drain and source. Cgd capacitance of the feedback gain from output to input or the so-called reverse or isolated output - input (S12) is. This amount represents the capacitance of the transistor is unilateral or bilateral. If the capacitor Cgd is small so that the transistor acts as a one-way Fig.4 is a simplified model shows TWDA with n stage and if its value is large, the transistor will work bilaterally. Format and packaged transistor parasitic capacitors is also. Each transistor includes Cgs, Cds and In this flow is Capacitance between the drain terminals of the capacitor considered. This simplifies the analysis of other circuit

16 International Conference on Electrical, Electronics and Communication Engineering (ICEEC'2012) September 8-9, 2012 Bangkok (Thailand) elements is ignored. Similarly, artificial transmission lines are assumed to be no losses (The inductors of the transmission lines and Lg and Ld are made at this transmission line).Gate and drain line characteristic impedances Zg and Zd, respectively, have been terminated. External signal source and load impedance can be assumed that Zg and Zd be a pure real part (Usually 50 ohms). Relations with the simplification available power obtained as follows:

The above statement can simply assume that βg → βd and x → 0 and the function Sin x we mail to x.So the power of Fig.5 traveling wave distributed amplifier gain as a function of the distributed amplifiers can be stating as follows: number of active stage

IV. SIMULATION OF A TRAVELING WAVE DISTRIBUTED AMPLIFIER SIMULATION OF A TRAVELING WAVE The above equation is of the order value that distributed DISTRIBUTED AMPLIFIER amplifiers gains (up to cutoff frequency transmission lines) Figure.6 Structure of a traveling wave MESFET distributed are independent of frequency. It seems that the above equation amplifier to boost the number NE33284a is used to show .In can be with increasing n (number of active components) designing this amplifier Micro strip transmission lines (for distributed amplifier direct gain for a fixed bandwidth is connection between amplifier and inductor needed to increased. But this is true only for no losses of transmission implement the distributed amplifier) is used. To improve lines. Actually due the loss gate and drain lines ,distributed impedance matching amplifier input and output of a filter is amplifiers Direct gain with increasing n as will not be large used. uniformly. The exact expression for the direct gain of distributed amplifier (gate and drain transmission lines with consideration of the loss) is as follows:[10,11]

In the above expression and Ad and Ag are, respectively, indicating the losses of gate and drain lines. Optimum number of active components (Nop) that can be best achieved in a specified bandwidth is as follows. [12]

Effect of stage number on gain and bandwidth on the distributed amplifier is shown in the figure below. [1]

This analysis shows that gain in traveling wave distributed Fig. 6 S-Parameter simulation results of conventional distributed amplifiers (TWDA) by increasing the number of active stage amplifier will improve but increasing the number n greater than 5 increasing active stage not much effect in the distributed amplifier gain. In general, increasing the number of stage amplifiers, bandwidth uniform response will be corrupted. Actually, by optimizing the transmission line terminals Can little improved uniformity of distributed amplifier bandwidth.

Fig.7 Simulation results of output noise characteristic and least characteristic of conventional distributed amplifier noise

17 International Conference on Electrical, Electronics and Communication Engineering (ICEEC'2012) September 8-9, 2012 Bangkok (Thailand)

Fig.11 Structure and the Physics of small signal MOSFET model

Fig.8 Simulation results of conventional distributed amplifier input and output VSWR

Fig.12 Gain small signal amplifier with a 3-storey conventional boost at best (VSB = 0.3v)

Fig.9 Simulation result of conventional distributed amplifier stability

V. SIMULATION OF A DISTRIBUTED AMPLIFIER WITH VARIABLE GAIN Figure.10 shows the structure of a MOSFET and Figure.11 Small signal model of the structure and physics of the MOSFET and considering the body of the show. With control VSB voltage can be control a mutual conductance of a MOSFET. Using this technique can be a conventional distributed amplifier with variable gain achieved. Figure.12 conventional distributed amplifier structure with variable interest shows. Fig.13 Gain small-signal amplifier to boost common with 3 floors per VSB different voltages

Fig.10 Structure of a MOSFET

Fig.14 Common characteristics of the amplifier noise with 3 floors per VSB different voltages

18 International Conference on Electrical, Electronics and Communication Engineering (ICEEC'2012) September 8-9, 2012 Bangkok (Thailand)

[14] Bahl, I. J., et al., ‘‘Low Loss Multilayer Microstrip Line for Monolithic Microwave Integrated Circuits Applications,’’ Int. J. RF and Microwave VI. CONCLUSION Computer-Aided Engineering,Vol. 8, November 1998, pp. 441–454. By comparing the type of amplifier (conventional [15] Zakrei,saeed, “Analisis ‚ design and simulation of broud band amplifier amplifiers and variable gain amplifier) observed that: with distributed structure”,MS,Azad University,Bushehr-Iran,2007- 2008,133,2008

A. Distributed amplifier has a good boost in the broad Saeed Zakeri was born in Minab/Hormozgan/Iran in 1980, frequency bandwidth are and And their structure can 2007: M.S. in Electronic, IAUB (Islamic Azad University of be used in other applications. Bushehr), Iran, 2004: B.S in Electronic Engineering, IAUB (Islamic Azad University of Bushehr) , Iran. B. with control amount of Vbs can be achieved greater He is working in technical junior college of Minab, Iran . Gain One article:"Optimization Fire Protection Systems of Gas C. using variable Vbs can be achieved the variable Gain Condensate Reservoirs" in the 2th International Conference on Control, amplifier Instrumentation, and Automation (ICCIA), (27-29th Dec. 2011) D. Return loss S(1,1) increases with increasing frequency Mr. Zakeri is a member of Iranian automation & control engineers as appropriate committee (www.isice.ir)

E. Return loss s(2,2) to less than 40 Ghz frequency Ebrahim Abiri received the B.Sc. degree in Electronics increases and then there is a sharp decline Engineering from Iran University of Science and Technology F. Noise reduction process is to frequencies less than 45 (IUST) in 1992, MSc. Degree from shiraz university in 1996 Ghz (and then a rapid rise) and the Ph.D. degree in electronic in 2007. He has authored G. According to the results simulated VSWR values of more than 60 published technical papers in electronics and power electronics. He has been with the Department of VSWR at the input and output in the worst of cases Electrical Engineering, shiraz university of technology (SUTECH), since are good and also optimal conditions. 2007.His current research activities include analog circuit design and power H. According to the simulation result of stability at worst electronic. of cases the coefficient of stability conditions are stable and good condition. Hefzollah Mohammadian was born in Dashtestan/Bushehr/Iran in 1982, 2009: M.S. in Electronic, IAUB (Islamic Azad University of Bushehr), Iran, 2006: B.S in Electronic Engineering, IAUB (Islamic Azad University of REFERENCES Bushehr), Iran. [1] Ayasli, Y., et al., “2- to 20-GHz GaAs Traveling Wave Power He is working in south Pars Gas Complex Company for Amplifier,” IEEE Trans. On Microwave Theory and Techniques, Vol. more than 6 years as an ESD & Fire and Gas control systems engineer in 32, No. 3, 1984, pp. 290–295. instrument department. One article:"Optimization Fire Protection Systems of [2] Ayasli, Y., et al., “2- to 20-GHz GaAs Traveling Wave Amplifier,” IEEE Gas Condensate Reservoirs" in the 2th International Conference on Control, Gallium Arsenide Symp., November 1982. Instrumentation, and Automation (ICCIA), (27-29th Dec. 2011) [3] Archer, J. A., F. A. Petz, and H. P. Weidlich, “GaAs FET Distributed Mr.Mohammadian is a member of Iranian automation & control engineers Amplifier,” Electronics Letters, June 1981, pp. 433–434. committee (www.isice.ir) [4] Ayasli, Y., et al., “Monolithic Traveling-Wave Amplifier,” Electronics Letters, June 1981,pp. 413–414. [5] Aitchison, C. S., and Y. J Liang, “A Proposal for Broadband High Gain Block Using Cascaded Single Stage Distributed Amplifiers,” IEEE EDMOt, 1995, pp. 173–178. [6] Agarwal, B., et al., “112 GHz, 157 GHz, and 180 GHz InP HEMT Traveling-Wave Amplifiers,” IEEE Trans. On Microwave Theory and Techniques, Vol. 46, No. 12, December 1998, pp. 2553–2559. [7] Ayasli, Y., et al., “2 To 20 GHz GaAs Traveling Wave Power Amplifier,” IEEE Trans. On Microwave Theory and Techniques, Vol. 32, No. 3, 1984, pp. 290–295. [8] Aitchison, C. S., et al., “The Dual-Fed Distributed Amplifier,” IEEE MTT-S Digest, 1988,pp. 911–914. [9] Ayasli, Y., et al., “Capacitively Coupled Traveling Wave Power Amplifier,” IEEE Trans. On Microwave Theory and Techniques, Vol. 32, No. 12, 1984, pp. 1704–1709. [10] Ayasli, Y., et al., “Capacitively Coupled Traveling Wave Power Amplifier,” IEEE Trans. On Devices, Vol. ED-31, No. 12, December 1984, pp. 1937–1942. [11] Beyer, J. B., et al., “MESFET Distributed Amplifier Guidelines,” IEEE Trans. on Microwave Theory and Techniques, Vol. 32, No. 3, 1984, pp. 268–275. [12] Bahl, I. J., and D. K. Trivedi, ‘‘A Designer’s Guide to Microstrip Line,’’ Microwaves, Vol. 16, May 1977, pp. 174–182. [13] Beyer, J. B., et al., “MESFET Distributed Amplifier Guidelines,” IEEE Trans. on Microwave Theory and Techniques, Vol. 32, No. 3, 1984, pp. 268–275.

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