Comparative Analysis of HEMT LNA Performance Based On Microstrip Based Design Methodology

Transcription

1 International Conference on Trends in Electrical, Electronics and Power Engineering (ICTEEP'212) July 15-1, 212 Singapore Comparative Analysis of HEMT LNA Performance Based On Microstrip Based Design Methodology V.J.K.Kishor Sonti and V.Kannan Abstract In this paper, Comparative analysis of HEMT LNA performance was done with two different approaches that are designed using Micro strip based design methodology. Noise analysis has also been done and the design is carried out at a centre frequency of 5.8GHz and the noise bandwidth considered is GHz. Return loss, mismatch loss were obtained in the frequency range of 1GHz to 1GHz.Variation of VSWR w.r.t frequency is also obtained. In this paper the work is carried out using ADS simulation software.. From the results the best design of HEMT LNA was obtained by comparison with the other design models. Results obtained are in greater coherence with the theoretical observations. Keywords HEMT, Microstrip line, Noise, Scattering Parameters, VSWR. H I. INTRODUCTION EMT refers to High electron Mobility Transistor. This is very useful in designing Microwave Monolithic Circuits and also useful for designing circuits at higher frequency range of operation.. Optimization in performance can be obtained by considering various performance issues. Limitations in performance certainly do exist at these frequency ranges, where the influence of shot noise is one major area of concern. This noise influence is certain due to the fact that device parameters like gate resistance are significant in the noise performance of the device at GHz ranges of operation. Novel techniques are needed to lead towards the optimization and microstrip based design methodology is one among many that technology has seen in the recent past. These HEMT S are good because of the fact that they are high speed, radiation hard circuits with lower power consumption values. They are better in performance, when compared with MESFET and have cutting edge, when it comes to cryogenic applications. [1], [7]. An equivalent circuit that can be categorized into the extrinsic and intrinsic parts, that represents microwave HEMTs. The extrinsic part is related to device layout and modeled with linear elements. The intrinsic part is in general described in terms of state functions. These devices are fabricated using various substrates like Gallium Arsenide V.J.K.Kishor Sonti is the Research Scholar of Sathyabama University, Chennai, India ( ; jaykrishna_adc@yahoo.com). V.Kanna is the Principal of Jeppiaar Institute of Technology, Kunnam, Chennai, India (drvkannan123@gmail.com). (GaAS) and Gallium Nitride (GaN). Circuits with different topologies were developed for different applications, particularly at higher frequencies of operation. One such attempt is also made in this paper and this paper is organized as follows. Section I describes the introduction followed by Section II about the structure of the HEMT device, Section III about the design of low noise amplifier using HEMT device with different models. Section IV describes about the results and conclusion. II. HEMT STRUCTURE Typical AlGaN/GaN HEMT device structure is as shown in the Fig.1. The device structure consists of 1 μm thick GaN quantum well channel separated by 1nm of undoped Al.35Ga.5N spacer layer from 1nm thick n-type Al.35Ga.5N supply layer. The function of the un-doped spacer layer is to reduce impurity scattering. The structure of the device is shown with drain and source electrodes as ohmic contacts. The SiO2 layer is about 5-1 nm thick and can be grown by the liquid phase deposition (LPD) process that is a low temperature, low cost and reliable method [2]. Fig.1 Structure of AlGaN/GaN HEMT [2] High Electron Mobility Transistors or AlGaN/GaN MODFETs are high performance devices for their potential 92

2 International Conference on Trends in Electrical, Electronics and Power Engineering (ICTEEP'212) July 15-1, 212 Singapore use at higher frequencies because of the GaN as substrate, which offers thermal stability, and high electron velocity. Another typical model of Pseudomorphic HEMT (or PHEMTs) are rapidly replacing conventional MESFET technology in military and commercial applications requiring low noise figures and high gain, particularly at millimeterwave frequencies. The application of PHEMTs for highefficiency power amplification is gaining popularity. The structure of a basic HEMT is illustrated in Fig. 2. [3]. III. HEMT LNA DESIGN The Design of EE_HEMT LNA design is as shown in Fig.3. Fig.3. Design of EE_HEMT LNA Fig.2 AlGaAs/GaAs HEMT Device Structure [3] This PHEMT technology is used in the Avago MGA 5P8 model.the buffer layer, also typically GaAs, is epitaxially grown on the substrate. Many PHEMT structures contain a super lattice structure to further inhibit substrate conduction The most important point about the channel layer in the HEMT and PHEMT devices is the two dimensional electron gas (2DEG) that results from the band-gap difference between AlxGa1-xAs and GaAs. [3], [4].These substrates are properly chosen in accordance with the requirements or application. The device structure consists of parameters which are sources of noise. Parasitic contribution and channel noise is greater for HEMT structure. The influence of noise is predominant on this device performance at the range of frequencies. Due to higher gain, estimated device noise is greater for the MODFET than MESFET. Shorter channel lengths of MODFET s also contribute to higher noise current. Noise currents are inversely proportional to channel resistance which in turn to gate length. Therefore proper selection of device structure is very important for particular applications. The Design of PHEMT Low Noise Amplifier is as shown in Fig.4. Fig. 4 Design of PHEMT Low Noise Amplifier [] 93

3 International Conference on Trends in Electrical, Electronics and Power Engineering (ICTEEP'212) July 15-1, 212 Singapore In the design shown in Fig.3.Micro strip line based methodology [5] is followed and a line of 4. dielectric constant value is considered with H=1.mm, W =3.mm and L =.79 mm and the centre frequency is considered to be 5.8GHz. EE_HEMT Model is considered. In Fig.4 Avago MGA 5P8 model is considered as it is based on PHEMT technology. []. Operating voltage is considered as 3v dc in both the cases. Impedance matching networks were designed using L and C components with terminations of 5 ohms at input and output. Avago MGA 5P8 model design is based on FR4 substrate. Sweep frequency is considered to be 1 GHz to 1GHz with a step value of 1GHz. The design shown in Fig.3 is also modified with regard to RT Duroid substrate, where the substrate parameters are H =.75mm, dielectric constant of 2.2 and Tan value of.15mm. IV. RESULTS AND CONCLUSION Performance evaluation of the above designs was done by comparison and the results obtained for the design shown in Fig.3 are as shown in Fig. 5,, 7 and Fig.8. Fig.5, Fig. and Fig.7 represents S11, S12 and S21 variation w.r.t frequency respectively. Fig.8 represents variation of NFmin w.r.t frequency, whereas Fig.9 represents variation of noise figure at port 1 and port 2 respectively. Fig.1 represents the variation of VSWR w.r.t frequency. NFmin db(s(2,1)) Fig.7 S21 variation w.r.t frequency db(s(1,1)) Fig. 8 Variation of NFmin w.r.t Frequency Fig.5 S11 variation w.r.t frequency db(s(1,2)) nf 2 1 Fig. S12 variation w.r.t frequency Fig.9 nf(1) and nf(2) w.r.t Frequency 94

4 International Conference on Trends in Electrical, Electronics and Power Engineering (ICTEEP'212) July 15-1, 212 Singapore 12 1 VSWR Fig.1 Variation of VSWR w.r.t Frequency Performance Summary of the designs shown in Fig.3, Fig.4 and also using RT Duroid substrate is shown in Table I. TABLE I PERFORMANCE COMPARISON OF DIFFERENT MODELS OF HEMT LNA HEMT LNA model AVAGO Model EE_HEMT FR4 Model EE_HEMT RT Duroid Model VSWR Return Loss in db Mismatch Loss in db Fig.12 Comparison of Return Loss and Mismatch Loss of different LNA designs From the results various conclusion can be drawn as the maximum gain value obtained for the PHEMT LNA design is 1dB with NFmin having a good range of values between 1GHz and 9.5GHz. VSWR variation w.r.t frequency also suggests that the design is good in the frequency range of 2 to 4 and 7 to 9.5GHz. Return loss obtained is about 4dB at the centre frequency. As the noise influence is more at higher frequencies the reason for this behavior is because of the shot noise, which is inherent within the device. Fig.11 and Fig.12 describes the performance comparison of different LNA models designed using HEMT devices. It can also be inferred that the influence of noise at higher frequencies is evident in all the three models and AVAGO MGA 5P8 model based HEMT LNA design is best when compared with the other models, whereas EE_HEMT RT duroid model based LNA design is better in performance, when compared with its counterpart designed using FR4 substrate. REFERENCES Fig.11 Comparison VSWR values of different LNA designs [1] Mark C. Lau, Virginia Polytechnic Institute and State University, Small Signal Equivalent Circuit Extraction From A Gallium Arsenide Mesfet Device, [2] Hasina F. Huq, Syed K. Islam,Self-Aligned AlGaN/GaN MODFET with Liquid Phase Deposited Oxide Gate formicrowave Power Applications, Department of Electrical and Computer Engineering, The University of Tennessee, IEEE@25. [3] L. Aucoin, HEMTs and PHEMTs, parts.jpl.nasa.gov/mmic/3-iv.pdf [4] B.VanZeghbroeck, Principles of semiconductor devices, ecee.colorado.edu/~bart/book/book/chapter3/pdf/ch3_.pdf. [5] ZHANG Hualiang, The Design of Low Noise Amplifier Using ADS, December 22, 24. [] V.J.K.Kishor Sonti, V.Kannan, Performance Analysis Of Modfet LNA, NCVSC, 212. [7] Peter J. Rudge, Robert E. Miles, Michael B. Steer, Fellow, IEEE, and Christopher M. Snowden, Fellow, IEEE, Investigation Into Intermodulation Distortion in HEMTs Using a Quasi-2-D Physical Model, IEEE transactions on microwave theory and techniques, Vol. 49, no. 12, December

5 International Conference on Trends in Electrical, Electronics and Power Engineering (ICTEEP'212) July 15-1, 212 Singapore This author was born in Bhimavaram, Andhra Pradesh, Inida in He received Master Degree in VLSI Design from Sathyabama University in the year 27. Currently he is doing Ph.D in Sathyabama University. He is working as Assistant Professor in Department of VLSI Design in Sathyabama University. He has 29 Research publications in National / International Journals / Conferences to his credit. His interested areas of research are VLSI Design, Solid State Electronics, and Mixed Signal circuits. He is a life member of Instrument Society of India and Indian Society for Non destructive testing. He was born in Ariyalore, Tamilnadu, India in 197. He received his Bachelor Degree in Electronics and Communication Engineering from Madurai Kamarajar University in the year1991, Masters Degree in Electronics and control from BITS, Pilani in the year 199 and Ph.D., from Sathyabama University, Chennai, in the year 2. His interested areas of research are Optoelectronic Devices,VLSI Design, Nano Electronics, Digital Signal Processing and Image Processing. He has 157 Research publications in National / International Journals / Conferences to his credit. He has 2 years of experience in teaching and presently he is working as Principal, Jeppiaar Institute of Technology, Chennai, India, He is a life member of ISTE. 9