Radar Data Acquisition System
In the RADAR data acquisition system, the data from the COTAL RADAR is processed by 8085 microprocessor and the processed data is first sent to the RADAR control room ,from there it is also transferred to main control room by means of a MODEM at a baud rate of 9600bps ,the coded data is decoded by INTEL's microcontroller 8051 .The microcontroller kit is equipped with a serial data transmission/receiver system . The RS 232 format is converted in to TTL format by RS232 converter IC's.
The data acquisition program resides on the EPROM of the trainer kit. The data regarding the RANGE, AZIMUTH, ELEVATION & QUALITY information are separated and fed to the DISPLAY system via peripheral I\O interface IC 8255 .The QUALITY information are taken from port 0 of 8051 directly and by using an interface circuit the mode of operation (auto/manual) and quality of received data are displayed.
Radar is an electro magnetic system for the detection and location of objects. It operates by transmitting a particular type of waveform, a pulse- modulated sine wave for example, and detects the nature of the echo signal.
Radar is used to extend the capability of ones senses for observing the environment, especially the sense of vision. In addition, radar has the advantage of being the able to measure the distance or range to the object. Radar is a contraction of the words "Radio Detection And Ranging". An elementary form of radar consists of a transmitting antenna emitting electro magnetic radiations generated by an oscillator of some sort, a receiving antenna and a energy detecting device or receiver. A portion of the transmitting signal is intercepted by a reflecting object (target) and is reradiated in all directions.
The receiving antenna collects the returned energy and delivers it to the receiver, where it is processed to detect the presence of the target and to extract its location and relative velocity. The distance to the target is determined by measuring the time taken for the radar signal to travel to the target and back.
The direction or angular position of the target may be determined from the direction of arrival of the reflected wavefront. The usual method of measuring the direction of arrival is with a narrow antenna beam. If relative motion exists between the target and the radar the shift in the carrier frequency of the reflected wave (Doppler effect) is a measure of the targets relative velocity and may be used to distinguish moving targets from stationary ones. In radars which continuously track the movement of a target a continuous indication of the rate of change of target position is also available.
The most common radar waveform is a train of narrow, rectangular shape pulses modulating a sine wave carrier. The distance or range to the target is determined by measuring the time TR taken by the pulse to travel to the target and return. Since electromagnetic energy propagates at the speed of light C=3 x 10 8 m/s the range R=CTR/2 .The factor 2 appears in the denominator because of the two way propagation of the radar, with the range in kilometers and TR nanoseconds R (km) =0.15TR (microseconds).
Once the transmitted pulse is emitted by the radar, a sufficient length of time must elapse to allow any echo signal to return and be detected, before the next pulse may be transmitted. Therefore the rate at which the pulses may be transmitted is determined by the longest range at which targets are expected. If the pulse repetition frequency is to high, echo signals from some targets might arrive after the transmission of the next pulse and ambiguities in measuring range might result.
Application Of Radar
1) Air traffic Control
2) Aircraft Navigation
3) Ship safety
5) Remote Sensing
6) Law Enforcement
The serial data received from the radar is converted into parallel format by 8051 microcontroller. This parallel data is then provided to the display device for display of AZIMUTH, ELEVATION, RANGE and AGC. Also from port zero the control signals are decoded and the radar status is displayed.