Showing posts from November, 2018

CW ( continuous wave ) Doppler radar advantages and disadvantages/ limitations

CW Doppler Radar  Advantages and disadvantages/ limitations are as following: 1. It can give accurate measurement of relative velocity, using low transmitting powers, simple circuitry,low power consumption and equipment whose size is much smaller than that of comparable pulsed equipment. 2. It can measure a large of target speed quickly and accurately. 3. It is unaffected by the presence of stationary targets. Disadvantages/ limitations 1. It is limited in the maximum power it transmits . 2. It cannot indicate the range of target ; it can only show its velocity , because the transmitter signal is unmodulated.

What is the radar system ? with block diagram.

INTRODUCTION radar is a short form of radio detection and ranging. It was developed more or less simultaneously in USA, Great Britain and France a few years before world war 2nd.
RADAR is an electronic device for the detection and location of objects.It operates by transmitting back particular type of wave- form, a pulse modulated sine wave for example, and detects the nature of the returned echo signal.It is used to extend the capability of man's sense for observing his environment.Especially the sense of vision.
Basic principles
A typical radar system consists of a transmitter and a receiver , each connected to a directional antenna through a duplexer.
The transmitter sends a large UHF or microwave power through the antenna.The receiver receivers, analyses and displays the information in the reflected energy picked up by the antenna. Normally the same antenna is used for transmission and reception. This is accomplished with the help of a switch called duplexer.     Fi…

Satellite communications objective type questions

1.GEO-stationary satellite are placed in equatorial orbits at a height of approximately?
ANS- 36000 km

2. Before transmitting to the satellite the wide band satellite signal is amplified by
ANS- effective isotropically radiated            power

3.the number of satellite needed for global communication is-
ANS - 3

4.The telephone channel is a communication satellite are assembled in -

5. The noise temperature of sky is the about-
ANS- 30 k

6. ....... IS India's first three - axis stabilised GEO stationary communication satellite.
ANS - Apple

7. From which of the following places india's first domestic geo stationary satellite INSAT-1A was launched ( on 10.4.1982)?
ANS- kourou in French Guyana

8. Long distance communication system via satellites use frequency in the range
ANS- 3- 6 GHz

9.The center of gravity of the earth is called
ANS- geo- center

10.The typical bandwidth of a satellite band is


Communication Satellite

The real beginning in the field of satellite communication was made in 1957, as a first man made satellite went into the ordit.the process of sending information around the world has been revolutionized by the advent of satellites.C COMMUNICATIONSATELLITES

A communication satellite is basically a microwave link repeater. it receives the energy beamed up from an earth station, amplifiers and returns it to the earth at a frequency of a couple of GHz away to prevent interference between the uplink and downlink.A satellite 35800 km from the earth will complete a revolution in 24 hours.Early bird was the first satellite which was launched by USA in august , 1965.If the direction of the satellite's revolution is the same as the earth rotation then the orbit is said to a posigrade orbit.when the satellite is in an elliptical orbit , the highest point from the earth of that orbit is called the Apogee.In an elliptical orbit, the lowest point of that orbi…