Design and Simulation of High Power Amplifier Used in Satellite Uplink Model Saw Kay Thwe Moe, Hla Myo Tun, Kyaw Soe Lwin Department of Electronic Engineering, Mandalay Technological University, Myanmar estherr1311@gmail.com, hmyotun@myanmar.com.mm, kyawsoelwin007@gmail.com Zaw Min Naing Technological University (Maubin), Myanmar zawminnaing@gmail.com Abstract- This paper describes design and simulation of high power amplifier used in satellite uplink model. In this paper, design procedure of high power amplifier is provided. The complete design process involves device selection, modeling and simulation. The targeted frequency range covers 4.9GHz to 5.1GHz or bandwidth of 200MHz with a center frequency of 5GHz. Design requirements for the small signal gain of high power amplifier is greater than 10.0dB across the band with an output power is greater than 24dBm at the center frequency. The desired requirements are achieved using two stages amplifiers with BSIM (Berkeley Short Channel IGFET Model) transistor model. The transistor selection is done from V-I characteristic curve of BSIM3v3 model which is simulated with Anasoft platform and MATLAB. According to the stability curve, high power amplifier is unconditionally stable all frequencies except from 1GHz to 3GHz. The matching networks are used for providing the maximum possible transfer of power between a source and its load. The simulation model for high power amplifier is constructed and simulation is conducted by using MATLAB. Simulation results show that C band high power amplifier in this paper is able to provide the desired specifications. Keywords- BSIM, C Band Satellite, High Power Amplifier, MATLAB, Uplink Model I. INTRODUCTION The power amplifier (PA) is a key element in transmitter systems, whose main task is to increase the power level of signals at its input up to a predefined level. Power amplifier s requirements are mainly related to the absolute achievable output power levels. Many applications for power amplifier design are used in broadcast digital television, satellite and military system [1]. In most RF and microwave power amplifiers, the largest power dissipation is in the power transistor. Since the main power supply consumer is power amplifier, the low power feature is directly translated to power amplifier specifications. Moreover, due to the widespread diffusion of communication applications, the power amplifier designer has usually to trade-off among the contrasting goals of high transmitted power, low power consumption and highly linear operation. The resulting challenge has however heavily influenced, in the last decade, industrial, technical and research directions in the power amplifier field. From the power amplifier designer point of view, both the selection of the active devices composing the power amplifier and especially the exploration of their non-linear operation regions, to fully exploit the output power capabilities become critical [2]. Dedicated and non linear design methodologies to attain the highest available performance become therefore crucial for successful results [3]. 19.1
Saw Kay Thwe Moe, Zaw Min Naing, Hla Myo Tun, and Kyaw Soe Lwin Power amplifier design strongly depends on operating frequency and applications, as well as on the available device technology. For high frequency applications however, two broad power amplifier design methodologies classes are available. They are switching mode (SM) amplifier [4] and transconductance-based amplifier [5]. The organization of the paper is constructed as follows: Section 2 involves design consideration of high power amplifier. Section 3 provides the simulation model and result for high power amplifier. Conclusion is presented in section 4. preamplifier stage. To accomplish two stages amplifier design, two transistors are used in the model. Each transistor has a width of 100μm and a length of 0.35μm. All of these design procedure of high power amplifier are implemented by using MATLAB. The flowcharts of the high power amplifier design procedure are illustrated in Fig. 3(a) and Fig. 3(b). Fig. 1 Block diagram of satellite ground station (transmitter) uplink model II. DESIGN CONSIDERATION Design consideration of high power amplifier includes transistor selection, amplifier design, checking stability, matching network design and building simulation model. A. Transistor Selection Transistor selection is chosen as following specifications: Frequency range: Model: Transistor: V gs : Simulation: 4GHz to 6GHz BSIM3v3 model MOS transistor 1V Anasoft, MATLAB The transistor selection is done from V-I characteristic curve of BSIM3v3 model which is simulated with anasoft platform and MATLAB. The simulation result is shown in Fig. 2. It was found that the operating point for this transistor is I D =11.91mA for V GS = 1V. B. Amplifier Design Procedure This research work aims to develop C band high power amplifier that has an output power of 33dBm and a gain of at least 10dB. To realise the required output power, class E power amplifier are cascaded with Fig. 2 Transfer characteristics curve of BSIM3v3 model In the design procedure, y parameters must be taken from the BSIM3v3 model transistor. Then, y parameters must be converted to the s parameters by using equations. The s parameters data file for high power amplifier is constructed as shown in Fig 4 and Fig 5. An object is created to represent the amplifier described by the frequency-dependent s parameter data file and then these data are extracted from this amplifier as the object type. Fig. 3(a) Flowchart of the high power amplifier design procedure Special Issue of the International Journal of the Computer, the Internet and Management, Vol. 19 No. SP1, June, 2011 19.2
Design and Simulation of High Power Amplifier Used in Satellite Uplink Model Before making this design, the data at which the amplifier is unconditionally stable are determined. Equation (1) is used to calculate the stability factor at each frequency and this factor is plotted as shown in Fig. 6 to check the stability condition at all frequencies. In the stability curve, the proposed high power amplifier is unconditionally stable at all frequencies except from 1GHz to 3GHz. Fig. 3 (b) Flowchart of the high power amplifier design procedure Fig. 6 Checking stability for high power amplifier Input and output matching networks are designed by transforming the reflection coefficients for simultaneous conjugate match at the amplifier interfaces into the appropriate source and load admittance. The complex source and load reflection coefficients are firstly calculated and plotted for simultaneous conjugate match at all calculated frequency data points that are unconditionally stable. These reflection coefficients are calculated at the amplifier interfaces. Fig. 4 S parameters data file for high power amplifier (1GHz to 5.5GHz) Fig.5 S parameters data file for high power amplifier (4.5GHz to 9GHz) Fig. 7 Reflection coefficient plot (source and load) In Fig. 7, the smith chart shows the values of the source reflection coefficients 19.3
Saw Kay Thwe Moe, Zaw Min Naing, Hla Myo Tun, and Kyaw Soe Lwin and the load reflection coefficients that have between 1GHz and 9 GHz. After cascading the circuit elements and analysing the amplifier with and without the matching networks over the frequency range of 4.9GHz to 5.1GHz, the simultaneous conjugate match at the input and output of the amplifier can be verified for both the matched and unmatched circuits. When plotting the transducer gain (G t ) and the maximum available gain (G max ) in db for the matched circuit, the transducer gain and the maximum available gain are very close to each other at 5GHz. Fig. 8 Calculating the input and output matching networks Fig. 11 Gain plot for the high power amplifier Fig. 9 Comparing original amplifier with the input matched amplifier After determining source and load reflection coefficient for the input and output matching networks at the design frequency 5.0GHz, the input and output matching networks are designed as these design process. III. MODELLING AND SIMULATION RESULTS The simulation model for high power amplifier is illustrated in Fig. 12. In this model, the high power amplifier is simulated with MATLAB. The s parameters between 4GHz to 6GHz for high power amplifier are extracted from aaa.s2p file in MATLAB. This aaa.s2p file is converted to aaa.dat file to mention the function of the amplifier to simulate with MATLAB. When this data file is put into the amplifier block set by giving the 4GHz to 6GHz of input signal into the high power amplifier, the output spectrum that is amplified by high power amplifier based on the input signal can be seen in FFT block. Fig. 10 Comparing the original amplifier with output matched amplifier Special Issue of the International Journal of the Computer, the Internet and Management, Vol. 19 No. SP1, June, 2011 19.4
Design and Simulation of High Power Amplifier Used in Satellite Uplink Model Fig. 12 Simulation model of high power amplifier Fig. 14 shows the output spectrum of high power amplifier. This output spectrum operates between frequency 4.9GHz and 5.1GHz. The maximum output power spectrum density is achieved at the operating frequency 5GHz. The amplitude of power spectrum is nearly 30dBm as the output power of high power amplifier s specifications. IV. CONCLUSION High power amplifier for C band satellite has been discussed in this paper. High power amplifier was designed and simulated using MATLAB. In designing the high power amplifier, the main goal is to be unconditionally stable for the complete range of frequencies where the device has a substantial gain. The power amplifier delivers maximum output power and small signal gain has greater than 10dB at 4GHz to 6GHz within C band. C band high power amplifier produces the output power of nearly 30dBm, small signal gain of 10dB and 200MHz bandwidth at the centre frequency 5GHz. Simulation result show that high power amplifier designed in this paper is able to fulfil the desired specifications. ACKNOWLEDGEMENT I would wish to acknowledge the many colleagues at Mandalay Technological University who have contributed to the development of this paper. The author is greatly indebted to her parents and all of her teachers who have taught her during the whole life. Fig. 13 Input signal of high power amplifier Fig. 14 Output spectrum of the high power amplifier REFERENCES [1] A. Mihai, RF power amplifier, Nobel printing corporation, 2001. [2] B. Chris, RF circuit design, 1 st ed., John Wiley & Son, 2000. [3] N. O. Sokal and A. D. Sokal, High efficiency tuned switching power amplifier, US patent 3 919 656, Nov 11, 1995 [4] Data sheet of BSIM3v3. [Online]. Available: http://www.silvaco.com [5] R. M.Porter and M. L. Mueller, High Power Amplifier Method, US patent 5 187 580, Feb 16, 1993 [6] M. K. Kazimierczuk and K. Puczko, Analysis of Class E tuned power amplifier at any Q and switch duty cycle, IEEE Transition on Circuit and System, Vol CAS-34, No. 2, pp 149-159, Feb 1997 19.5