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CALIFORNIA STATE UNIVERSITY, NORTHRIDGE Negative Resistance Oscillator Design at 16 GHz A Graduate Project Submitted in the Partial fulfilment of the Requirements For the degree of Master of Science in Electrical Engineering By, Ashwini Anil Latne May 2017 The Graduate Project of Ashwini Anil Latne is approved: _______________________________ ________________________ Prof. Benjamin F. Mallard Date _______________________________ ________________________ Dr. John Valdovinos Date _______________________________ ________________________ Dr. Matthew M. Radmanesh, chair Date California State University, Northridge ii Acknowledgement It gives great pleasure to acknowledge the sense of gratitude to all those who helped me in making “Negative resistance oscillator design” project a success. It has been immense pleasure to work under supervision of Prof. Matthew Radmanesh to complete this project. I am deeply obliged to Prof. Matthew Radmanesh for his invaluable guidance, encouragement and support that I received throughout my project. I would like to thank Prof. Matthew Radmanesh for being my graduate advisor and helping me in completing my graduate project. His courses like Active Microwave Circuit Design and Advanced Microwave Circuit Design has helped me to understand many concepts of design which were useful for my project. The basic concepts of design from his book named “RF and Microwave Design Essentials” helped me in completing my project. I want to thank my committee members Prof. Benjamin Mallard and Dr. John Valdovinos for their advice and valuable time. iii Table of Contents Signature page ii Acknowledgement iii List of the Figures vi List of Tables vii Abstract viii Chapter 1: Introduction 1 1.1: Design Specifications 1 1.2: Organization of report 2 Chapter 2: Oscillator Design Theory 3 5 2.3: Negative Resistance Oscillator Design Theory 7 2.4: DC Biasing of NPN Transistor 10 Chapter 3: Negative Resistance Oscillator Design 13 13 3.2: Oscillation Conditions 15 3.3: Stability Check 17 3.4: Output Stability Circle 18 21 3.6: Design of Negative Resistance Oscillator 22 3.7: Generator Tuning Network Design 24 3.8: Terminating Tuning Network Design 26 3.9: Microstrip Line Design 29 Chapter 4: AWR Microwave Office 35 iv Chapter 5: Summary 36 5.1: Conclusion 36 References 38 Appendix A: Circuit design using lumped elements 39 Appendix B: CD ROM calculations 44 Appendix C: MATLAB program for oscillator design 48 Appendix D: MATLAB program for microstrip line design 50 Appendix E: Roger’s corporation RO3035 52 Appendix F: Datasheet of NE661M04 Transistor 54 v List of Figures Figure 1.1: Block diagram of Negative Resistance Oscillator 1 Figure 2.1: Two-port oscillator block diagram 3 Figure 2.2: NPN Transistor 5 Figure 2.3: Voltage and current in negative resistance device 7 7 Figure 2.5: Circuit diagram of DC biasing of BJT 10 Figure 3.1: Negative resistance oscillator circuit 14 Figure 3.2: Two-port oscillator design conditions 16 Figure 3.3: Plot of stability circle on smith chart 20 Figure 3.4: Generator tuning network design on smith chart 24 Figure 3.5: Terminating tuning network design on smith chart 26 Figure 3.6: Circuit diagram 28 29 Figure 3.8: Electric and magnetic field lines 29 Figure 3.9: Layout of the circuit 34 Figure 4.1: Circuit layout 35 Figure 4.2: |S21| graph 35 Figure A1: Generator tuning network (lumped elements) 40 Figure A2: Terminating tuning network (lumped elements) 42 Figure A3: Circuit layout (lumped elements) 43 vi Table 3.5.1: Selection of the ΓT 21 Table 3.6.1: Value of Zin 22 Table 3.9.1: Microstrip line results 33 Table 5.1: Summary of results 37 vii Abstract NEGATIVE RESISTANCE OSCILLATOR DESIGN AT 16 GHz By, Ashwini Anil Latne Master of Science in Electrical Engineering This project explores the design process of Negative Resistance Oscillator operating at 16GHz which has many microwave applications. An NE661M04 BJT is selected to achieve requirements of the transistor used for negative resistance oscillator design. The transistor satisfies the oscillation conditions. Then the output stability circle is plotted using S-Parameters from the datasheet of transistor. Using an output stability circle, the generating tuning network and matching tuning network is plotted on the smith chart. The value of negative resistance is then determined from the smith chart. The calculations for the design process are also calculated theoretically. Smith chart values and theoretical values are verified using MATLAB software. viii Chapter 1: Introduction An oscillator is an important part of any microwave communication system, since it can convert DC power to microwave power. An oscillator is designed to convert a DC signal to RF signal, thus it forms an important device of the microwave system. To design one port negative resistance oscillator, a two-terminal device is used. Oscillators are mainly used in microwave applications like satellite receivers, radar speed gun, radar transmitters and microwave ovens. Oscillators can also be used in circuits of feedback oscillators along with two port devices like transistor and tubes. Oscillators are also used in electronic devices like TV, radio, cell phone, modems and computers. Figure 1: Block diagram of Negative Resistance Oscillator 1.1 Design specifications: Transistor: Operating frequency: 16 GHz. Output power: <5dBm 1 1.2 Organization of Report: Chapter 1: Introduction Chapter 2: Oscillator design theory Chapter 3: Negative Resistance Oscillator Design Chapter 4: Simulation Results Chapter 5: Conclusion 2 Chapter 2: Oscillator Design Theory 2.1 Review of Literature RF and microwave oscillators has many applications in wireless communications, remote sensing systems and radar, since it provides high signal sources to convert frequency and carrier signal generation. At high frequencies, using diodes and transistors with cavity can produce fundamental frequency oscillations up to 100GHz. Using transistors in the oscillators is more compatible than diode, since it is easy to integrate transistors with amplifiers and mixers in the circuits. Transistors allow more control on frequency oscillation, output noise and temperature stability. They are also useful to frequency tuning, phase and injection locking. An RF/microwave oscillator is a non-linear circuit that converts DC power to microwave power. In this project, a three-terminal device is used which provides two-port oscillators and is operated in an unstable region. Figure 2.1: Two-port oscillator block diagram 3 The design steps for oscillator are like that of the microwave amplifier. The main difference between the two is that design of the amplifier requires microwave signal as an input, but oscillator design does not require any input. To design oscillator, first we select the transistor, whose S-parameters satisfies the condition for oscillation. Since power is generated in an oscillator, the reflections are greater than unity. Thus, we require compressed smith chart for the oscillator design process. Then, the generator tuning network and terminating tuning network are designed using smith chart. The generator tuning network in design gives the oscillation frequency, whereas the terminating network gives the proper loading function. Since, it is a non-linear device, the complete analysis of oscillator operation is complicated. The circuit is built using distributed elements for high frequency. The hand calculations result and smith chart values are verified on MATLAB. 4 2.2 Transistor selection A transistor, in general, is a nonlinear three terminal devices in which the flow of current between terminals is controlled by the third terminal. It is used mainly in amplifiers, oscillators, switches and detectors. There are two classes of transistors, In this project, we have used BJT NE661M04. It is an NPN silicon high frequency transistor. Figure 2.2: NPN Transistor Bipolar Junction Transistors consist of three layers of semiconductors and two junctions. The semiconductor layers can be of N-type or P-type. Thus, BJT can be NPN or PNP. The three terminals of the transistor are called emitter, base and collector and two junctions are called emitter base junction (EBJ), and the collector base junction (CBJ). To use the transistor, we must do DC biasing of the transistor. That is, we must find DC bias values of the transistor. Based on the biasing conditions on each of the two junctions there can be four modes of operation of the transistor. It can be a forward biased or reverse biased. NEC’s NE 661M04 are fabricated on wafer using NEC’s UHS0 25 GHz fT wafer process. Thus, NE661M04 provides better low voltage and low current performance. NEC’s today is used in many wireless applications. An NE661M04 is a preferred choice for design of LNA and Oscillator and has many requirements in mobile communications. 5 The transistor is selected such a that its S-parameters should satisfy the oscillation conditions. There are three conditions required to be satisfied at “steady state” for an oscillation to occur. The conditions are, Condition 1: It should be an unstable device. K<1. Condition 2: Oscillating input port. ΓinΓg=1. Condition 3: Oscillating output port. ΓoutΓt=1. Where, condition 1 indicates that the negative resistance device itself is in the oscillation mode. Since, these conditions are satisfied, NE661M04 transistor is used in the design process. 6 2.3 Negative Resistance Oscillator Design Theory To design a Negative Resistance Oscillator, we need to understand negative resistance device. The concept of the negative resistance device is directly related to the concept of the power generation which is important for oscillator to work. In negative resistance, the voltage and current are 180 degrees out of phase. Thus, an increase in voltage in negative resistance device leads to decrease in current and product of voltage and current becomes negative. This corresponds to the concept of power generation. Figure 2.3: Voltage and current in the negative resistance device Negative resistance oscillator design uses transistor that can operate in an unstable region.
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