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CALIFORNIA STATE UNIVERSITY, NORTHRIDGE Frequency CALIFORNIA STATE UNIVERSITY, NORTHRIDGE Frequency Modulated Continuous Wave Radar Design and Simulation A graduate project submitted in partial fulfillment of the requirements For the degree of Master of Science in Electrical Engineering By Mark Christopher Fessia December 2018 The graduate project of Mark Christopher Fessia is approved: _____________________________________ __________________ Dr. Ali Amini Date _____________________________________ __________________ Mr. James A. Flynn Date _____________________________________ __________________ Dr. Deborah K. Van Alphen, Chair Date California State University, Northridge ii Table of Contents Signature Page ii List of Tables iv List of Figures v Abstract vi Section 1: Objective 1 Section 2: Introduction 3 Section 3: Literature Review 11 Section 4: Analysis and Design 13 Section 5: Implementation 31 Section 6: Testing and Results 57 Conclusion 65 References 67 Appendix A: MATLAB Source Code 69 iii List of Tables Table Number Caption Page 4.1 Modulator Simulation Parameters 15 4.2 Voltage Controlled Oscillator Simulation Parameters 17 4.4 Low Noise Amplifier Simulation Parameters 20 4.6 Antenna Simulation Parameters 23 4.9.1 Simulation Parameters for Radar Equation 27 4.9.2 Simulation Parameters for Maximum Range Calculation 29 5.2.1 phased.FMCWWaveform Parameters 33 5.2.2 comm.PhaseNoise Parameters 34 5.4 phased.ReceiverPreamp Parameters 37 5.6.1 phased.CustomAntennaElement Parameters 40 5.6.2 phased.Transmitter Parameters 41 5.6.3 phased.Radiator Parameters 42 5.6.4 phased.Collector Parameters 43 5.8.1 Low Pass Filter Specifications 45 5.9.1 phased.FreeSpace Parameters 49 5.9.2 phased.RadarTarget Parameters 50 6.1 Theoretical vs. Measured Signal Power 57 6.2 Target Range Calculation Parameters 59 6.3 Moving Target, Velocity and Range Calculation Parameters 62 7.1 Range and Velocity Measurement Errors 65 iv List of Figures Figure Number Description Page 2.1 Architecture of CW radar. 6 2.2 Architecture of FM-CW radar. 8 4.1 Modulator output voltage (one period). 16 4.2.1 VCO output signal. 18 4.2.2 Power spectral density of VCO FM signal. 18 4.6.1 The coffee can antenna design diagram. 21 4.6.2 The coffee can antenna gain pattern measurements. 22 4.6.3 Antenna gain pattern polar plots and 3D approximation. 23 4.9.1 Received power vs. target range using radar equation. 28 5.1 Modulator output voltage, triangle wave output. 32 5.2.1 Power spectral density of baseband VCO FM signal. 34 5.6.1 Modeled antenna gain pattern. 40 5.8 Magnitude response of the 5th LPF (video signal). 45 5.9.1 Satellite image of simulated radar test location. 47 5.9.2 Test location, showing 100 m distance and discretes. 48 5.9.3 Ground clutter triangle mesh superimposed on satellite image. 52 5.9.4 Modeled test location showing mesh, discretes, and target. 53 5.9.5 Exaggerated elevation plot of triangle mesh. 53 5.9.6 Subdivided triangle clutter mesh. 55 6.1 Resulting tone from stationary target at 100 m. 59 6.2 Resulting tone from stationary target at 60 m. 60 6.3 Resulting tones from target at 72 m, with velocity of 25 m/s. 61 6.4 Resulting tones from target at 43 m, with velocity of -25 m/s. 63 v Abstract Frequency Modulated Continuous Wave Radar Design and Simulation By Mark Christopher Fessia Master of Science in Electrical Engineering The intent of this project was to design and simulate a frequency modulated continuous wave (FM-CW) radar system capable of making target range and velocity measurements. MATLAB was used to model each component of the FM-CW radar system and simulate transmit and receive signal behavior, channel effects, and target radar cross section (RCS) characteristics. A top-down approach to the design of the FM-CW radar system was presented beginning with an overview of theory and architecture followed by a detailed explanation of each component in the signal path. Key interactions between components were discussed as well as potential differences between real world components and their simulated counterparts. An overview of the signal processing techniques and software architecture required to make target range and velocity measurements was also presented and implemented. An overall FM-CW radar system simulation was implemented in MATLAB including simulated channel effects and targets. The simulation was run so that resultant target range and velocity measurements were obtained and radar system performance and simulation fidelity were evaluated and presented. vi Section 1: Objective While the applications of radar systems are numerous, the main objective of this project was to design, model, and simulate an FM-CW radar system capable of making target range and velocity measurements inside of one kilometer for targets having an RCS approximately equal to that of a car. To achieve this, MATLAB objects were used to model the radar system components, radio frequency (RF) environment, target RCS characteristics, and behavior of the transmitted and received signals. Additional signal processing to derive range and velocity measurements was also demonstrated using MATLAB. Real-world FM-CW radar designs for educational purposes such as the MIT "coffee can" radar by Charvat, Williams, Fenn, Kogan and Herd (2011, [3]) provided the inspiration for this project. It was intended that the project data and simulation results presented in this report will be useful to those who wish to explore the field of radar design and will provide deeper insight to those who are interested in completing real-world do-it-yourself radar projects or radar kits like those offered by Pasternack or Quonset Microwave. As such, the radar system for this project was modeled using a frequency of 2.45 GHz and low transmit power of 13 dBm since under these conditions, a number of cost effective real-world radar designs could be constructed and tested utilizing the industrial, scientific, and medical (ISM) band which would not require a license to operate.[5] In order to achieve the main objective of this project there were five sub-objectives that drove key decisions during design, modeling, and simulation: 1. Design, model, and simulate a FM-CW radar system using MATLAB. 1 2. Accurately model the environmental RF channel effects that the radar signal will experience as it propagates to and from the target. 3. Accurately model physical properties of the target such as range, velocity and RCS in order to simulate a return signal. 4. Process radar return data in order to demonstrate target range measurements. 5. Process radar return data in order to demonstrate target velocity measurements. The main objective and all sub-objectives were completed successfully for this project. 2 Section 2: Introduction Continuous wave (CW) radar has widespread applications. Every time one steps through the automatic doors at a grocery market they enjoy the benefits provided by a CW radar system which detected their movement and cued the door to open. Alternately, if one has ever gotten a speeding ticket, it is very likely that the officer issuing the citation used a speed detection radar based on a CW radar design. Indeed, this is a case where the cited individual perhaps did not enjoy the use of such radar. While the applications for CW radar are numerous, this project focused on how a CW radar system may be designed, modeled, and simulated using MATLAB. In this section the basic theory of a CW radar system will be introduced followed by a discussion on how the system may be used to obtain target velocity measurements and lastly how the system can be adapted using frequency modulation (FM) to obtain both target range and velocity measurements. The fundamental theory behind CW radar operation has been known since 1928 where it was initially conceptualized for the use of altitude determination and later practically implemented for such purposes by the Western Electric Company in 1938.[14] The architecture of CW radar is generally less complex when compared to that of pulsed radar systems which makes it particularly accessible to those looking to complete a do-it- yourself radar project or explore the ways in which useful information can be obtained from the echo of a CW radar system. It is expected that the reader is comfortable with basic electromagnetic (EM) wave theory, communication principles such as the time and frequency domain relationship, fundamental linear algebra concepts, and physical phenomena such as the Doppler effect. 3 Radar systems are devices that transmit controlled, oscillatory, EM energy towards an object of interest. When the EM energy reaches the surface of the object it is scattered in many directions; some of the energy is scattered back towards the direction of the radar. The radar system receives this energy, often referred to as the return or echo, and analyzes it to determine useful information about the object. Information can include the direction of the object relative to the radar, distance of the object relative to the radar, referred to as the range, and the direction and speed of the object relative to the radar, referred to as relative (or radial) velocity. This is the very basic notion of a radar and it is for this reason that the acronym RaDAR (which has been turned into a word) stands for radio detection and ranging. Pulsed radar systems transmit EM energy in the form of short bursts; however CW radar systems are aptly named since they transmit a continuous sinusoidal pulse (or wave) with a 100% duty cycle at a particular frequency. Because of the continuous nature of the transmission, a CW radar must usually be bistatic, having separate transmit and receive antennas. Additionally, the coupling of transmitter energy into the receiver becomes a serious concern when the antennas are close together or do not have adequate isolation.[15] The basic premise of a CW radar is to transmit a continuous pulse in the direction of a target and receive the resultant echo.
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