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Radar is an object detection that has a researchers going on focusing on every aspect. One of the most influential radar technicians of second half of the 20th Century was Peter Swerling. He was involved in many researchers on radar and his first Radio Array Neutrino Detector (RAND) report was "Probability of detection for fluctuating targets" in March 1954. Later in April 1960 he submitted another paper to IEEE on "Studies of target detection by pulsed radar". The term radar represents Radio, Detection and Ranging. Radar systems typically use wavelengths on the order of 10 cm, corresponding to frequencies of about 3 GHz. Radar is an electronic devise is used to detect the height, distance, velocity, direction and movement. This electronic devise is an active device used in both civilian and military applications. The aim of surveillance radar is to detect targets by illuminating an area of interest with electromagnetic radiation. In maritime environment, the term target usually refers to any radar backscatter that is not due to the scattering from an ocean surfaces. However, no matter what application it is used for, the basic principle of radar remains unchanged. Basic radar consist some operation unit such as transmitter, receiver, duplexe , antenna, signal processor, data processor and display unit for target detection. Radar operates by transmitting and receiving an electromagnetic wave via directive antenna to an open space to search for object. When the electromagnetic wave collides with an object, the object reflected a fraction of incident energy back towards the transmitter. Figure 2.1 show the basic operation that used in radar system.
Figure 2.1: Operation in radar system (Raju, 2008)
The reflected electromagnetic energy is called radar return or echoes. The echoes are processed by the radar receiver to obtain the information about the target (Raju, 2008). Radar transmits pulses of Radio Frequency (RF) energy for a duration known as pulse width (PW) at an interval known as pulse repetition frequency (PRF) represent Ï„ that show in figure 2.2. The return signal is simply a delayed attenuated version of the transmitted signal due to propagation loss and distortion due to the interaction of multiple reflections (Kay, 1998). Actually, radar consist of 2 types, pulse radar and continuous radar
Figure 2.2 : Example of radar pulses (a) Transmitted pulse (b) Received pulse (Raju, 2008)
2.1.1 Pulse Radar
Pulse Radar is waves that use amplitude modulation to receive and transmits a bundle of modulated pulse. It uses to detect the target, measuring, range and velocity, but it cannot measure speeds and ranges. It transmits electromagnetic wave in the form of burst or pulse. Pulse radar measure the time interval between transmitted and received pulse. It measure range of target by determine the time taken by transmitted to reflect back to receiver. It is important to determine direction and distance of the target by high power and frequency electromagnetic wave form of pulse. It designs a pulse to ensure the echoes are conveniently received before next pulse is transmitted. The antenna position and propagation time of the pulse signal can determined the altitude of the target.
2.1.2 Continuous Wave (Cw) Radar
Continuous wave (CW) radar systems emit electromagnetic radiation at all times. It detect object and measured velocity from Doppler shift. The Doppler shift is a change in the frequency of the electromagnetic wave caused by motion of the transmitter, target or both (classification of radar system, 2008) . For example, if the transmitter is moving, the wavelength is reduced by a fraction proportional to the speed it is moving in the direction of propagation. Since the speed of propagation is a constant, the frequency must increase as the wavelength shortens. The net result is an upwards shift in the transmitted frequency, called the Doppler shift. Conventional CW radar cannot measure range of target because there is no basis for the measurement of the time delay. A continuous wave radar can obtain the target speed by measuring the Doppler-Frequency (Chen, 2005) . The Doppler-frequency can be determined by equation:
Where the Doppler-Frequency, v is is speed of wave source in meter per second and is the wavelength in meter. The instantaneous rate-of-change can be measured by Continuous wave Radar in the target's range. The direct measurement can be obtained by Doppler shift of echo pulse of return signal.
188.8.131.52 Frequency-Modulated Continuous Radar
The continuous wave radar can only measure the Doppler frequency of the object but it cannot measure range of the object but the frequency-modulated can measure both Doppler frequency and range of the object by the change of the transmitted frequency as a function of time. The frequency difference between echo signal and radar transmission contain the range information. Without Doppler frequency, it only measures a range of object which given by equation:
Where B is the bandwidth of transmitted signal, T is the period of modulation wave, fr is the frequency difference between signal echo and transmitting signal and C is the light speed. If Doppler frequency is present there have a received frequency-time relationship as show in figure 2.3. Frequency-time relationship is mixer of reference and reflected wave to produce a temporal signal whose frequency is related to the propagation time of the signal wave and frequency modulation waveform. By measuring frequency of the beat signal, the distance of the target can be determined (Zheng, 2005).
Figure 2.3 : Received frequency-time relationship (Nezlin, 2007)
184.108.40.206 Doppler Shift
Doppler shift is an important phenomenon from astrophysics in the field of physic and cosmology to physic and laser's cold. Physicist of Russia, Christian Doppler (1803 - 1853) is a scientist who met it, Henceforth to introduce this Doppler phenomenon is that shift with reference to
frequency replacement or sound pick, where takes place in electromagnet's wave, that is produced by move cause or that is able to be monitored by move observer.
If i hear the vehicle sound to approach me, i will be able to hear sound change while the vehicle is approaching me and i can also hear the sound difference while the vehicle is distancing me.
I have noticed when an emergency vehicle with its siren blaring passes me that the tone that i hear changes in pitch. This is an example of what is called the Doppler shift, and it is an effect that is associated with any wave phenomena (such as sound waves). It is the same effect that Hubble used to measure the velocities of distant galaxies. (Raju, 2008)
The frequency change is stated as Doppler Shift. Here there are seven basic calculations that involves frequency and whip that is produced by sender and also acceptance from recipient is based by specific condition. The seven differences are:
1. The source is approaching a stationary observer.
2. The observer is approaching a stationary source.
3. The source and the observer are moving towards one another.
4. The source is moving away from a stationary observer.
5. The observer is moving away from a stationary source.
6. The source and the observer are both moving away from each other.
7. The source and the observer are moving in the same direction at different speeds.
I should also be able to easily convince myself that the shift will yield an increase in the perceived frequency whenever the source and the observer are approaching one another, and a decrease in the perceived frequency whenever the source and the observer are moving away from each other. This study will use Doppler's principle to study microwave.
2.2 Doppler effect principle
The Doppler effect, first investigated by Austrian physicist C.J. Doppler in 1842, is observed in any kind of wave motion such as sound, light or radio waves .The Doppler effect is the observed change in frequency of a waveform caused by a time rate of change due to the effective distance traveled by the wave between the transmitter and the point of observation. As the time rate of distance between transmitter and a source of constant vibration decreases, the received frequency is greater. As the time rate of distance increases, the frequency decreases.
A Doppler radar measures the velocity of a moving object by doing something useful with the detected shift in carrier frequency of the returned signal. The shift is proportionate to the speed of the object as it approaches or moves away. The Doppler effect is the basis of continuous wave radar.
The Doppler angular frequency Ï‰d,
If R is the distance from the radar to the target, the total number of the wavelengths ðœ† contained in the two way part between the radar and the target is 2R/ðœ†. The distance R and the wavelength ðœ† are assumed to be measure in the same units. Since the one wavelength corresponds to an angular excursion of 2Ï€ radians, the total angular excursion made by electromagnetic wave during it transit to and from the target is 4Ï€R/ðœ† radians. If the target is in motion, R and the phase are continually changing. A change in angular excursion with respect to time is equal to a frequency. (Skolnik, 1981)
2.3 Electromagnetic Field and Wave.
Electromagnetic wave consists of combination of oscillating electrical and magnetic field where its perpendicular to each other. Electromagnetic may be regarded as a study on interactive between electric charges at rest an in motion. Electromagnetic is a branch of physics or electrical engineering in which electric and magnetic phenomena are studied (Sadiku, 2007).
Electromagnetic find application in various field cost such as microwave, antennas, electric machine, satellite communication, radar meteorology, remote sensing and other. Electromagnetic devices consist of transformer, electric delay, electric motor, waveguides, optical fiber, radar, lasers and other. All design of these devices must have strong principle of electromagnetic. Although radio waves, microwave , X-ray and even visible light are part of the electromagnetic spectrum and each has different range of wavelength, it cause they waves to affect matter differently.
2.3.1 Electromagnetic Spectrum
Figure 2.4 show a spectrum which various types of energy in the electromagnetic spectrum occur. The range of wavelengths for electromagnetic waves is called the Electromagnetic Spectrum:
Figure 2.4: Electromagnetic spectrum
Frequency usable for radio communication occurs near the lower and of the electromagnetic spectrum. As frequency increase, the manifestation of electromagnetic energy becomes dangerous to human being (Sadiku, 2007) . The practical difficulties of using electromagnetic energy for communication purpose also increase as frequency increase, until finally it can no longer use. Each of electromagnetic spectrum has their function.
Radio and TV waves are the longest usable waves, having a wavelength of 1 mile (1.5 kilometer) or more.
Microwaves are used in telecommunication as well as for cooking food.
Infrared waves are barely visible. They are the deep red rays you get from a heat lamp.
Visible light waves are the radiation you can see with your eyes. Their wavelengths are in the range of 1/1000 centimeter.
Ultraviolet rays are what give sunburn and are used in "black lights" that make object glow.
X-rays go through the body and are used for medical purposes.
Gamma rays are dangerous rays coming from nuclear reactors and atomic bombs. They have the shortest wavelength in the electromagnetic spectrum of about 1/10,000,000 centimeter.
Microwave is one of the waves that are often used in daily life of a person. This use of wave is used much, radar in the defense system, the utensil cooks towards one phenomenon, study and many more other used. Microwave is a wave that uses frequency that is very high. Each use of microwave want to be ensured in condition that doesn't dangerous the person or the life at vicinity. Microwave is a form of electromagnetic wave. The most familiar kind of electromagnetic wave is light. Here are some things that light and microwave have in common.
Light is a form of energy. It takes energy to produce light, whether it comes from a kerosene lamp or a fluorescent tube. It also takes energy to produce microwaves. A typical microwave oven consumes several hundred watts of energy to make microwave that are powerful enough to heat food. But simply the warmth of your own body provides enough energy to produce very weak microwave that can be detected by sensitive instrument. According to Oxford American Dictionary (1980) microwave is electromagnetic radiation of frequency between 1.0GHz to 300GHz (wavelengths of 1.0m to 1.0mm). The microwave frequency band starts at the highest end of the radio frequency spectrum VHF and ends where the optical frequency starts.
The behavior of microwave in space is very familiar to the VHF band. The microwave frequency band can be divided into three decades called ultra high frequency (UHF), supra high frequency (SHF) and extra high frequency (EHF). Figure 2.5 show the several microwave frequency band with it wavelength and their frequency.
Figure 2.5 : Microwave frequency band
This band can be divided into narrower bands as shown in the table 2.1
Table 2.1: Narrow bands of microwave
Therefore, the three decades can also be called decimeter waves (UHF), centimeter waves (SHF) and millimeter waves (EHF). Microwave is high frequency waves and this causes their wavelengths to be short. There are many other uses of microwaves, but they all fit into one or more of these categories. The categories are wireless, medical, telecommunication, space communication, and scientific applications. Type of microwave with their usage show in table 2.2 .
TYPE OF WAVE
Ultra High Frequency
Very High Frequency
This wave is used for long distance communication among satellite, telephone and television. This wave can penetrate and bounce without absorbed to sky.
( SW )
It is used for long distance shine by ionosphere's layer because this wave can be bounce. The rebound is that communication crosses that the continent can be made to weather condition but it is influenced.
( MW )
It is used for local communication and between ship and land.
( LW )
It is also used for local communication. This wave can cross surface condition that is mountain and hilly.
Table 2.2 : Type of microwave
2.4 Radar Antennas
Radar antennas is functionally to receiving and transmitting a signal. An antenna has identical direction pattern for receiving and transmit modes of operation. Radar antennas are designed for the following function:
Target angular position measurement
Angular resolution position of targets
Rejection of unwanted signal (noise) while directions of arrival differ from that of the useful signal
Maximization of useful received signal power
Radar antennas has same fundamental characteristics. The antenna gain G(Î±)can be defined for the transmitting antenna as G(Î±) =
Where PD1 (Î±) is the power flux density produced by the antenna and PD2 is the power flux density created at point M by a uniform-gain (isotropic) radiator co-located. The antenna pattern (AP) is a given plane is define as the relation AP(Î±) =
The function of AP(Î±) , as well G(Î±) is a power characteristic of the antenna. Main types of antennas used in radar. Types of antenna commonly used in modern are the mirror antenna and the phased array lens antennas and end. Fire array has limited application in radar. (Nezlin, 2007)
Mirror (reflector) antennas are represented by three varieties:
2.4.1 Parabolic antennas
Parabolic antenna is a type of radar engineering that consist of one circular parabolic reflector and a point source called primary feed where situated in the focal point of this reflector as show in figure 2.6. The parabolic reflector is constructed of metal, usually a frame covered by metal mesh at the inner side. This type of reflector all reflected rays will be parallel to the axis of paraboloid that gives a ideally one single reflected ray parallel to the main axis with no sidelobes .The radiation pattern for the parabolic antenna consist major lobe, that is directed along the axis of propagation, and several small minor lobes.
Figure 2.6 : Parabolic antenna
2.4.2 Cassegrain antenna
Cassegrain antenna is an antenna where the feed radiator is placed at or near the surface of a concave main reflector and it aimed at a convex subreflector as show in figure 2.7. This antenna also have a common focal point where energy from the feed unit illuminates the secondary reflector, which reflects it back to the main reflector.Cassegrain antenna have advantage and disadvantage in usage. Advantage of Cassegrain antenna are the feed radiator is more easy supported, geometrically compact and provides minimum losses as the receiver can be mounted directly near the horn. The disadvantage is the subreflector of a Cassegrain type antenna are fixed by bars. The bars and secondary reflector constitute an obstruction for the rays coming from the primary reflector in the most effective direction.
Figure 2.7. : A Cassegray antenna used in a fire-control radar
2.4.3 Parabolic-cylinder antenna
The parabolic cylinder antenna can be fed by a point-source feed horn. The horn illumination function is defined by energy that falls off with the square of distance. The reflected waveform will be a cylinder with elements perpendicular to the element of parabolic cylinder. In one plane the point source is focused, and the other plane the cylinder reproduces the pattern of the feed horn. The figure 2.8 below show the parabolic-cylinder antenna that used in high-power radar observation (Volakis, 2007)
Figure 2.8 : Parabolic-cylinder antenna used in high-power radar observation
2.5 Radar Gun Overview
The Radar Gun is a development technology to detect speed of object. The Radar Gun operates according to the Doppler radar principle. Doppler radar is named after the Doppler effect principle, which explains the frequency shift associated with energy waves reflected by or emanated from a moving body. A familiar example of Doppler shifts the change in pitch in sound of passing train. If sound change is higher, the train is approaches and lower as it leaves. It transmits a lower power microwave and receives energy reflected by object. If the movement of the objects is detected by microwave motion sensor, the reflected microwave frequency is shifted away from the transmit frequency. The
shifted microwave is mixed with the transmit microwave and results a low frequency voltage at the output of the sensor. The output frequency is approximately proportional to the transmission frequency and the absolute of target velocity.
The operation of the Radar Gun is show in the figure 2.9 below:
Radar speed Gun transmit frequency
Reflect back to Antenna Receiver Part 1
Detect with Doppler radar speed sensor
Microcontroller (frequency counter and analog to digital converter)
Port of microcontroller to LCD Part 2
Figure 2.9 : Flow Chart of Radar gun's operation.
This project will discuss about development of Radar gun. The basic operation of Radar gun must be elaborate to identify and analysis the operation of Radar Gun before making it. Base on the figure 2.9, this project divided into two parts. In part 1 is transmitter and receiver part. This equipment used to find that's Doppler frequency those functions as that part to be needed. The second part will process received data of Doppler Frequency to get the speed on display. Microcontroller is important part to analyze the data receive compare with reference frequency to get Doppler shift. After that, the analog signal will convert to digital to be displayed in LCD. However, Radar Gun has a lot of method based on the Doppler principle to build it. Basic understanding about Doppler radar and Doppler principle can be use to build my own Radar Gun.
2.6 Doppler Radar
The uses of radar are to determine detecting the range of target that includes the speed. In fact, this application of the acronym radar which derives before. Before this, we know that the target's velocity also could be determined by using Doppler effect. It comes from an apparent frequency shift of a reflected wave resulting from the target velocity. However, this development had to wait for the development of oscillators that can be generating sufficient power at very high frequency with good frequency stability. The oscillator frequency stability is important because Doppler frequency shift is not large so that the Doppler effect would be obscured by a wandering oscillator frequency (Schetzen, 2006). A small amount of frequency energy can get from an oscillator by generate the microwave frequency to give the radar more power to transmit signal.
Microcontrollers are used in industrial world to control many type of equipment, ranging from consumer product to specialized device. They have replaced older types of controllers, including microprocessors. A microcontroller is a computer-on-a-chip. It is also called a programmable single chip integrated circuit (IC) that controls the operation of the system. A microcontroller consist of four main element that is central processing unit (CPU), internal memory, register, and I/O subsystem. These parts are connected internally by an internal bus. Microcontroller used and store information in the form of binary number. I often refer to the devise (the chip) as a microcontroller unit (MCU). The build in interface (I/O) capability is used for sensors, actuator, and communication. Figure 2.10 shows a microcontroller system block diagram. (Spasov, 2002)
Figure 2.10 : Block diagram of a typical microcontroller system
2.7.1 Microcontroller Unit.
Generally microcontroller unit(MCU) has three basic part that consist CPU, memory and register. Figure 2.11 shows a generic block diagram of MCU. They are connected by an internal bus. Externally, it has pins for power, I/O, and some special signal.(Spasov,2002)
Figure2.11 : Block diagram of a typical microcontroller shown in single chip mode (Thomson-csf, 1996)
220.127.116.11 Center Processing Unit (CPU)
The center processing unit (CPU) control the operation of the microcontroller. The CPU has its own registers. The program counter (PC) is a special register that tells the CPU where to get an instruction or data byte. The other register store specialized data or address information. The instruction decoder tell arithmetic and logic unit (ALU) what to do with the data. The control sequence manages the transfer of instruction and data byte along the external data bus. The address register sets the condition of the address bus. The external address bus selected a specified location memory. The data driver condition data signal to be sent to or from memory or I/O register. (Spasov,2002)
CPU has two 8 bit accumulators (A & B) that can be concatenated to provide a 16 bit double accumulator (D). two 16 bit index registers are present (X,Y) to provide indexing to anywhere in the memory map. A 16 bit stack pointer is also present, and instructions are provided for stack manipulation. CPU also has 16 bit program counter and condition code register (CCR).
Memory generally organizes its bit storage cells into group of eight. Thus each group of eight cell can store an information byte. Each byte has unique numerical address, consisting of four or more hex digits. Memory stores two kinds of information which that program instruction opcodes, and data. Memory can include RAM, ROM, or storage media, and holds program, data, or lookup table information.
18.104.22.168 Input/output Subsystem
The I/O subsystem allows the microprocessor (MPU) to exchange information with the outside world. I/O includes analog-digital converter, parallel communication devices, serial communication devices, and various timing mechanism. The I/O subsystem is grouped into units called I/O ports. Each I/O port has I/O lines (usually eight lines) to transfer information between the external devices and the ports. These lines can be input only, output only, or programmable to be either. Each port has its own I/O register. The register types are control, status, and data.
Registers are used to handle specialized information. Essentially registers are equivalent of workbench. It is a place where the CPU works on (modifies) a binary number. There are I/O register and CPU registers. These registers, together with the CPU and I/O ports are used in I/O operations. Each I/O register holds I/O data associated with the corresponding I/O port. An I/O port is a collection of I/O pins on the chip that represent a unit of data. Usually I/O ports have eight lines to transfer a byte of data.