ABSTRACT
This thesis presents the analysis and computer simulation of continuous wave radar detection system for moving targets. In the past, radio detection has been used as an integral part of complicated applications like reconnaissance mission, navigation, weather, air-traffic management, missile targeting and defense. Analysis of measuring systems for such applications needs the representation of radar operation and performance within the context of the system. The impact of measuring these systems needs to be evaluated and quantified. Signal processing in radar systems was carried out using MATLAB with linear frequency modulated continuous waveform(LFMCW) to obtain the target distance and relative speed for moving targets. A model for detection of continuous wave radar was developed to generate different frequencies at different distances. The results obtained were able to detect normal frequency whenever a change in radar distance occurred within the moving targets environment. The analysis of delay time and modulation frequency reviewed the degree to which delay time contributes to the detection of targets. For fast moving targets, a higher delay time was needed while for slow moving targets, a lower delay time was needed. The analysis of radar distance and modulation frequency confirmed the need to increase our modulation frequency to detect fast moving targets while there is need to reduce the modulation frequency to detect slow moving targets. Analysis of blind speed and range affirmed that, moving targets in an irregular pattern can be detected by the developed model. Hence, the developed model was not limited to targets moving in a straight line but for targets moving in any direction.
TABLE OF CONTENTS
Title page i
Declaration ii
Certificate iii
Dedication iv
Acknowledgement v
Table of contents vi
List of Tables x
List of Figures xi
List of Appendices xii
List of Abbreviations xiii
Abstract xv
CHAPTER 1: INTRODUCTION
1.1 Background of the study 1
1.2 Problem statement 4
1.3 Aim and objectives of the study 5
1.4 Scope of the study 5
1.5 Significance of the study 6
1.6 Outline of thesis 7
CHAPTER 2: LITERATURE REVIEW
2.1 History of RADAR system 8
2.2 RADAR technologies 9
2.2.1 Moving target indicator RADAR 10
2.2.2 Bistatic RADAR 10
2.2.3 Continuous wave RADAR 10
2.2.4 Doppler RADAR 11
2.2.5 Monopulse RADAR 11
2.2.6 Passive RADAR 11
2.2.7 Instrumentation RADAR 12
2.2.8 Weather RADAR 12
2.2.9 Mapping RADAR 12
2.2.10 Navigation RADAR 12
2.3 RADAR range equations 13
2.4 Theoretical minimum detection range and signal to noise ratio equation 14
2.5 Low pulse repetition frequency (PRF) RADAR equation 17
2.6 High pulse repetition frequency (PRF) RADAR equation 18
2.7 Types of continuous wave RADAR 19
2.7.1 Unmodulated continuous wave 19
2.7.2 Modulated continuous wave 20
2.7.3 Sawtooth frequency modulation 21
2.7.4 Sinusoidal frequency modulation 21
2.8 Antenna configuration 23
2.8.1 Monostatic RADAR antenna 23
2.8.2 Bistatic RADAR antenna 23
2.8.3 Monopulse antenna 25
2.8.4 Leakage 25
2.8.4.1 Null 26
2.8.4.2 Filter 26
2.8.4.3 Interruption 26
2.9 Limitations of continuous wave RADAR 27
2.10 Applications of continuous wave RADAR system 28
2.10.1 Military 28
2.10.2 Air traffic control 29
2.10.3 Ground traffic control 29
2.10.4 Remote sensing 29
2.10.5 Space 29
2.11 Doppler frequency and target velocity 30
2.12 Related works 31
2.13 Identified knowledge gaps 40
CHAPTER 3: MATERIALS AND METHODS
3.1 Materials 51
3.2 Methods 54
3.3 Developed model for the detection of continuous wave radar system 55
3.4 RADAR key performance indicators 58
3.4.1 Delay time 59
3.4.2 Beat frequency of RADAR 59
3.4.3 Maximum range 60
3.4.4 Radar cross section (RCS) 60
3.4.5 RADAR blind speed 61
CHAPTER 4: COMPUTER SIMULATIONS, RESULTS AND DISCUSION
4.1 Results 62
4.2 Discussion of results 65
4.2.1 RADAR distance and normal frequency 65
4.2.2 Radar distance and delay time 66
4.2.3 RADAR Distance and Beat frequency 66 4.2.4 Normal frequency and maximum Range 67
4.2.5 RADAR distance and RADAR cross section 68
4.2.6 RADAR distance and blind speed 69
CHAPTER 5: CONCLUSION AND RECOMMENDATION
5.1 Conclusion 71
5.2 Recommendation 71
5.3 Contribution to Knowledge 72
Reference 73
Appendices 79
LIST OF TABLES
3.1 Parameters for continuous wave RADAR system 54
4.1 RADAR distance, error frequency, detected error and normal frequency from developed model. 63
4.2 Summary of evaluated KPI data 64
LIST OF FIGURES
3.1 Components of RADAR system 53
3.2 Block diagram of the simulated model 55
3.3 Developed model for detection of continuous wave RADAR system 58
4.1 Normal frequency against RADAR distance 65
4.2 Delay time against distance 66
4.3 Beat frequency against RADAR distance 67
4.4 Normal frequency against maximum range 68
4.5 RADAR cross section against distance 69
4.6 RADAR blind speed against RADAR distance 70
LIST OF APPENDICES
1 Matlab code for the graph of RADAR distance against normal frequency 79
2 Matlab code for the graph of RADAR distance against delay time 79
3 Matlab code for the graph of RADAR distance against normal and beat frequencies 79
4 Matlab code for the graph of normal frequency and RADAR maximum Range 80
5 Matlab code for the graph of radar distance against radar cross section 81
6 Matlab code for the graph of RADAR distance against blind speed 81
7 Matlab code for the key performance indicator 81
8 Screenshot of the KPI simulation result code 82
9 Source code block parameter of pulse generator 83
10 The transmitter sub-system 83
11 The function block parameters for Bandpass Filter 84
12 The function block parameters for Lowpass Filter 84
13 The source block parameter constant 85
14 The function block parameters: AWGN Channel 85
15 The function block parameters: AWGN Channel 2 86
16 The function block parameters: Product 86
17 The RADAR modulator sub-system 87
18 The RADAR demodulator sub-system 87
LIST OF ABBREVIATIONS
ACC Adaptive Cruise Control
CF carrier frequency
CFAR Constant False Alarm Rate
CS Conducted Susceptibility
CW: Continuous wave
CWAT Continuous-Wave Angle Tracking
dsPIC digital signal peripheral interface controller
ECCM Electronic Counter countermeasures
EMC electromagnetic compatibility
EMI electromagnetic interference
EnONLP enhanced optimized nonlinear phase
FFT fast Fourier transform
FIR finite impulse response
FM frequency modulation
FMCW Frequency modulated continuous wave
GHz: Giga hertz
HUD head up display
IF intermediate frequency
IFFT Inverse fast Fourier Transform
IOPs input/output operations per seconds
JORN Jindalee operational radar network
KPI key performance indicator
LCD liquid crystal display
LFM Linear Frequency Modulation
MATLAB matrix laboratory
MICs microwave integrated circuits
MLEs maximum likelihood estimations
MMICs microwave monolithic integrated circuits
MORSE Microwave Ocean Remote Sensor
MTI Moving Target Indicator Radar
NASCAR National Association of stock Car Auto Racing
OMP orthogonal matching pursuit
ONLP open network Linux platform
OTAD over the air deramping
OTHR over the horizon radars
PRF Pulse Repetition Frequency
PRT Pulse Repetition Time
RADAR: Radio detection and ranging
RF radio frequency
SAR specific absorption rate
SFCW Stepped-Frequency Continuous Wave
SIU system international of units
SNR signal-to-noise ratio
STFT Short Time Fourier Transform
CHAPTER 1
INTRODUCTION
1.1 BACKGROUND OF THE STUDY
Radio detection and ranging (RADAR) is a well-known active remote sensor application which is mostly used by researchers and engineers these days. Basically, RADAR technology transmits microwave signal into space until it hits target and some portion of radiation return from a reflected target is collected by receiver antenna.
A signal processing technique was implemented to measure and analyze the collected raw data of the feedback signal to give information of the required object. Over the past century conventional RADAR was only used for detecting and allocating a target. However, modern RADARs were produced by extending the capacity of the RADARs, such as accurate targeting, targets identification, classification, navigation, guidance and imaging (Guochao et al., 2014).
RADAR system operated at microwave frequency range of 300MHz to 300GHz. It generated and emitted a short wavelength of electromagnetic signals which made its operation to be unaffected by all types of weather and light conditions such as darkness, rain, snow, fog, smoke and dust during transmission of signal into space. In addition, RADAR was best used for long range applications as the radiation travels with a very high speed in space. RADAR system was an efficient tool for scientific measurement (Nor, 2017).
The principle of RADAR operated like the reflection of sound waves. For a sound wave incident on the target to be reflected and heard, the returned signal was called an echo. If the speed of sound was known, the distance was estimated and the direction of the object were obtained.
The RADAR was composed of a transmitter which radiated the electromagnetic signal of a specific waveform and the receiver which detected the returned signal from the target. Only a fraction of the transmitted energy was radiated back to the RADAR (Sulaiman et al., 2013).
The process in which the presence of the target was detected in form of competing signs arising from the background echoes, atmospheric noise, or noise generated in the RADAR receiver was called RADAR detection. Noise power present at the output of the RADAR receiver was reduced using filters, the frequency response function maximized output peak-signal-to-noise power called matched filter (Ghani et al., 2014).
Within aircraft, for the guidance of missiles for air intercept sparrow 7, continuous wave and frequency modulated continuous wave RADAR had been very useful. It was also useful in semi active RADAR homing devices and altimeter for RADAR with accuracy close to one centimeter. Recently, frequency modulated continuous wave RADAR had made progress due to the improved power of computer processors. Many industries had incorporated RADAR usage for Adaptive cruise control, enhanced synthetic RADAR and distronic RADAR which used a head-up display (Akash et al., 2015).
Frequency modulated continuous wave (FMCW) RADAR provided range and range-rate information. It had difficulty in the detection of targets moving in a circular motion with respect to the RADAR location. In that case the target had zero relative velocity with respect to the RADAR position hence, produced zero Doppler shift within the received signal. It was in such case that the target was incorrectly defined by the RADAR as a target at a point. The ability of the FMCW RADAR to provide range and range-rate information for moving targets was a non-zero determination which exposed the RADAR to designating ghost targets (Michael, 2017).
Continuous wave systems of RADAR were useful at both sides of range spectrum which ranged from radio altimeters, sport accessories and proximity sensors which operated from one meter to several kilometers to costly early-warning continuous wave angle track RADAR operated beyond 100Km. The advantage of continuous wave RADAR was in its simplicity to manufacture and its operation as energy was not pulsed. Continuous wave RADAR system do not have minimum or maximum range. Continuous wave RADAR system maximized the entire power on the target as the transmitter broadcasts continuously (Schellenberger, 2018).
Semi active RADAR homing, the standard missile family and air-to-air missiles were guided by the military using continuous wave RADAR system. The launched aircrafts enlightened the target with a continuous wave signal and the weapon homes on the reflected radio waves. Since the weapon was moving at high velocities relative to the aircraft, there was a strong doppler shift. Most modern air combat RADARs including pulse doppler sets, had a continuous wave function for weapon guidance purposes (Jing, 2010).
This thesis focused on the performance evaluation of a continuous wave RADAR system for moving targets. A model for detection of moving targets by a continuous wave RADAR system in varying traffic densities and complexities using MATLAB simulator was created. The simulation implemented the algorithms and tested the efficiency of the final triangular wave frequency modulated continuous wave RADAR system within the simulation area.
1.2 PROBLEM STATEMENT
Frequency modulated continuous wave (FMCW) RADAR system had the difficulty of detecting the velocity of beaming targets as the target lacked relative velocity with respect to the RADAR position which caused zero Doppler shift within the received signal. In such case, targets were incorrectly defined by the RADAR as a target at a point (Michael, 2005).
The issue of signal loss in the receiver antenna of the RADAR system had made it difficult for FMCW RADAR to accurately track slow moving targets and fast moving targets. The slow moving targets were observed incorrectly as stationary targets. These effect was a product of insufficient filtration sub-systems needed to eliminate greater percentage of the noise signals emanating from the transmission network (Schellenberger, 2018).
Based on the above, RADAR system with performance evaluation of RADAR parameters should be suggested. Therefore, this thesis is aimed at evaluating the performance of a continuous wave RADAR detection system for moving targets using MATLAB.
1.3 AIM AND OBJECTIVES OF THE STUDY
This thesis is aimed at the performance evaluation of a continuous wave RADAR detection system for moving targets. The specific objectives are:
I. To develop a simulink model for frequency modulation with improved filtration structure.
II. To simulate the developed model using Matlab to generate normal frequencies, error frequencies and detected errors at different RADAR distances.
III. To evaluate analytically the KPI which include: delay time, beat frequency, maximum range, RADAR cross section and RADAR blind speed.
IV. To simulate the results evaluated using Matlab, so as to observe the relationships between the key performance indicators (KPI) and the moving target’s distance.
1.4 SCOPE OF THE STUDY
This thesis is limited to the performance evaluation of a continuous wave RADAR detection system for moving targets. A model for detection of continuous wave RADAR system was created and simulation performed on the model using MATLAB. Normal frequencies, error frequencies and detected errors were obtained from the simulated model as the RADAR distance was changing. Analytically, the key performance indicators of RADAR system for moving targets were evaluated. This thesis covered continuous wave RADAR and the elements which affects the RADAR sensitivity to improved performance. In addition, this research utilized specific techniques of digital signal processing for clutter rejection and moving target indication.
1.5 SIGNIFICANCE OF THE STUDY
Based on the simplicity of continuous wave RADAR system, it was less expensive to manufacture, it was cheap to maintain, fully automated and free from failure. Accurate detections exceeding 98km distance with provision of illumination for missiles was reliably achieved by sophisticated continuous wave RADAR systems.
By increasing the filtration structure, the noise signal was reduced and a better detection achieved. The frequency of modulation was essential in the detection of moving targets, hence, the model was able to produce excellent modulation frequencies with the help of the finite impulse filter and the additive white Gaussian noise channel.
The simulation result of the KPI reviewed the relationship between the target’s distance with modulation frequency, delay time, beat frequency and the RADAR cross section.
Fourier integration was used instead of azimuth integration to provide superior signal to noise gain for doppler measurement. Processing of doppler frequency was allowed for signal integration between consecutive receiver samples. To extend the detection range without increasing the transmitter power, the number of samples was be increased.
By measuring the doppler shift of the returned signal, the continuous wave RADAR measured the rate of change of range. Electromagnetic radiation was emitted instead of pulses in a continuous wave RADAR which was basically used for speed measurements. The study of improved sensitivity of continuous wave RADAR system helped improve results in application.
1.6 OUTLINE OF THESIS
A brief description of the contents of each chapter in this thesis is as follows:
Chapter 1 shows the background of study, problem statement, aim and objectives, scope of the thesis, significance of study and outline of thesis.
Chapter 2 gives historical background of radio detection and ranging, RADAR technologies, RADAR range equations, theoretical minimum detection range and signal to noise ratio, pulse repetition frequency (PRF), types of continuous wave RADAR, antenna configuration, limitations of continuous wave RADAR, applications of continuous wave RADAR system, and a detailed literature review of related works from previous researchers.
Chapter 3 talks about the materials and method of analysis.
Chapter 4 shows a well detailed results and discussion.
Chapter 5 gives the conclusion and recommendations.
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