CALIFORNIA STATE UNIVERSITY, NORTHRIDGE DESIGN OF NEGATIVE RESISTANCE OSCILLATOR A Graduate Project Submitted in Partial fulfillment of the Requirements For the degree of Master of Science in Electrical Engineering By, Thrilok Kodihalli Dayanand December 2016 The Graduate Project of Thrilok Kodihalli Dayanand is approved: ______________________________ __________________ Prof. Mallard, Benjamin F Date ______________________________ __________________ Dr. Valdovinos, John Date ______________________________ __________________ Dr. Matthew M. Radmanesh, Chair Date California State University, Northridge ii Dedication I take this opportunity to convey my regards towards Dr. Matthew Radmanesh, who has been an outstanding advisor for me. It’s because of his support and encouragement in this design project entitled “Design of negative resistance Oscillator”. This factor not only helped me to complete this oscillator design project on time but also increased my knowledge regarding the oscillator design. I would also like to show my appreciation to Professor Benjamin Mallard and Dr. John Valdovinos, who have given me the required support and inspiration to complete my project. My project would be incomplete without all the textbooks and research material that I used in order to complete my project paper. I would also like to thank my parents for their support and encouragement. iii Contents Signature page ii Dedication iii List of figures vi List of table’s viii Abstract ix Chapter 1: Introduction 1 1.1 Problem definition and goal 1 Chapter 2: Oscillator Design Theory 3 2.1 Literature Review 3 2.2 Transistor 4 2.3 Theory of Negative Resistance Oscillator condition 6 2.4 D.C Biasing of Common Source Transistor 8 Chapter 3: Oscillator Design procedure 11 3.1 Design steps for Oscillator 11 3.2 Stability Check 13 3.3 Stability Circle (output) 14 3.4 Selection of ΓT 15 3.5 Design of Negative Resistance Oscillator 16 3.6 Generator Tuning Network Design 17 3.7 Terminating matching network design 20 3.8 Microstrip calculation 25 iv Chapter 4: Simulation Results (Microwave office) 4.1 AWR subcircuit for transistor (FPD200P70) 33 Chapter 5: Summary of Analysis 41 5.1: Conclusions 42 References 43 Appendix A: Common source FPD200P70 transistor .s2p format 44 Appendix B: Matching circuit design using lumped elements 45 Appendix C: Microstrip gap capacitance formula sheet 54 Appendix D: Matlab program for the oscillator calculation 56 Appendix E: Roger corporation RT/duroid® 3035 65 Appendix F: Excel calculation for oscillator design. 69 Appendix G: Determination of impedance using Reflection co-efficient 72 Appendix H: Selection of DC bias circuit 73 Appendix I: Datasheet FPD200P70 transistor 74 v List of Figures Figure 1.1 Diagram for radio transmitter and receiver. 1 Figure 1.2 Diagram for radio transmitter. 2 Figure 1.3 Diagram for the transmitter and receiver 2 Figure 2.1 Steps to design negative resistance oscillator. 3 Figure 2.2 Block diagram for FET. 4 Figure 2.3 the cross section of an N-type GaAs MESFET. 5 Figure 2.4 Negative Resistance Oscillator diagram using two-port 7 Figure 2.5 common source DC Biasing of FET 9 Figure 3.1 Flow chart of the oscillator design. 12 Figure 3.2 Smith chart for output stability circle 14 Figure 3.3 Matching Network at generator tuning End using smith chart 17 Figure 3.4 Generator tuning network for distributed elements using smith tool 18 Figure 3.5 Transmission line length in degrees using smith tool 18 Figure 3.6 Circuit for Generator Tuning network 19 Figure 3.7 Matching Network at Terminating End using smith chart 20 Figure 3.8 Terminating matching for distributed elements using smith tool. 21 Figure 3.9 Length of the transmission line in degrees using smith tool 21 Figure 3.10 Circuit for Terminating Tuning network 22 Figure 3.11 Transmission line circuit for generator tuning and terminating network 23 Figure 3.12 Layout of generator tuning and terminating network. 24 Figure 3.13 3D Layout of generator tuning and terminating network. 24 Figure 3.14 Layout for the negative resistance oscillator design. 32 vi Figure 4.1 Transistor FPD200P70 33 Figure 4.2 |S21| and MSG vs frequency from AWR 34 Figure 4.3 |S21| and MSG vs frequency from datasheet. 34 Figure 4.4 N.F. min (dB) vs frequency from AWR. 35 Figure 4.5 N.F. min (dB) vs frequency from datasheet. 35 Figure 4.6 Block diagram of IV curve for transistor. 36 Figure 4.7 Id vs VDS curve for the transistor FPD200P70 from AWR. 36 Figure 4.8 Id vs VDS curve for the transistor FPD200P70 from datasheet. 37 Figure 4.9 Schematic of Low Noise Amplifier. 38 Figure 4.10 Gain and return loss vs frequency. 38 Figure 4.11 Open loop response 39 Figure 4.12 Oscillator frequency spectrum 40 Figure B1 Smith chart for the Terminating matching network 46 Figure B2 Terminating network using smith tool 47 Figure B3 Terminating network value of lumped elements Using smith tool 47 Figure B4 Lumped Elements Circuit for Terminating Network 48 Figure B5 Smith chart for the generator tuning network 50 Figure B6 Generator tuning network using smith tool 51 Figure B7 Generator tuning network value of lumped elements Using smith tool 51 Figure B8 Lumped Elements Circuit for Generator Tuning network 52 Figure B9 Circuit for negative resistance oscillator design using lumped elements 53 vii List of Tables Table 3.4.1 Selection of ΓT 15 Table 3.7.1 Transmission line length values 23 Table 5.1.1 Summary table 41 Table B Table for lumped elements 53 viii ABSTRACT DESIGN OF NEGATIVE RESISTANCE MICROWAVE OSCILLATOR By Thrilok Kodihalli Dayanand Master of Science in Electrical Engineering The topic for this project is to design an Oscillator circuit, which has applications in microwave circuits such as satellite communication systems, etc. A MESFET is selected in the common source configuration such that it exhibits a negative resistance at the desired frequency. The thesis is divided into two segments, Linear Analysis and Harmonic Simulation. In this project, the design is built around a generator-tuning network with a negative resistance and a matching circuit for the terminating network. This design depends on the output stability circle, which can be derived from the S parameters of the transistor from the datasheet. The values obtained from the hand calculations have been compared and verified with the values obtained from MATLAB software. ix Chapter 1: Introduction The Oscillator produces an AC signal across the output terminal without needing an input RF signal. Oscillator is a device, which produces current, or voltage waveform using a dc power supply from the input port. The waveforms are classified into two groups: 1) Linear - sinusoidal waveform 2) Nonlinear - sawtooth waveform The shape of the waveform and amplitude are determined on the design of the negative resistance oscillator circuit design and its components. These types of oscillators are used in the frequency conversion in radio frequency transmitters or receiver. Similarly, it is used in modern day electronic devices such as television, watches, radio, modems, PLLs. 1.1 Problem definition and goal Oscillator is used based on the need for receiving and transmitter module of radio signals. Based on the frequency range 15 to 20 GHz. Figure 1.1: Diagram for Radio Reciever and Transmitter 1 Hence, the report is based on the designing of the high frequency negative resistance local oscillator. Design Goal: Oscillating Frequency: 18.5 ± 0.4 GHz Output Power: > 20 dBm 2 Chapter 2: Oscillator Design Theory 2.1 Literature review Oscillators can be designed based on the two different method: negative resistance method and positive feedback method. Since a transistor oscillates at certain frequency, this report is based on the negative resistance oscillator condition. The first step for designing the oscillator is to choose the transistor with s-parameter and verify the condition of the transistor. Next step is to choose the generating and terminating network for the transistor in order to create the negative resistance oscillator. The circuit can be built with the distributed elements for higher frequency and lumped elements for lower frequency. However, in this thesis selected distributed elements to design the circuit and added the lumped elements design in the Appendix B as an alternate method. There are three types of transistor configurations to design oscillators: common drain Common gate, and Common source. Common drain configuration is difficult to design for high frequency oscillator. So, common source or common gate configuration are used. The common source configuration has been chosen in this thesis. Generator Transistor Transitor tuning and Terminating Simulation Selection Simulation network Figure 2.1: Steps to design the Negative Resistance Oscillator 3 2.2 Transistor First, we have to choose the transistor, which have high frequency low noise figure. The brief summary of the transistor is explained below. Figure 2.2: Block diagram of FET There are three-transistor configuration that can be utilized to design 2-port oscillators: 1. Common source 2. Common drain 3. Common gate The common source configuration is selected in this thesis. The transistor FPD200P70 (pHEMT) is a depletion mode AlGaAs High Electron Mobility Transistor. It utilizes a (0.25 x 200) µm Schottky barrier gate field effect transistor. The primarily used device, which also happens to be one of the most crucial device in active circuits of the Microwave industry, is the GaAs based metal semiconductor in Field Effect Transistor’s. This importance can be justified with the fact that until the late 1980s, metallic GaAs MESFET’s was used in most of the integrated circuits in the Microwave industry. Even now with the advanced technology, better performing FET’s have been introduced in the market, metallic semiconductor FET’s still dominate the applications for Power Amplifiers and Microwave Spectrum Switching Circuits in active device category.