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What type of antenna used in the mobile?

Answer is Omni directional antenna used in the mobile. There are various types of antenna used in mobile like, PIFA (Polar Inverted F Antenna) FICA etc

Radar Equation

The power Pr returning to the receiving antenna is given by the radar equation:

P_r = {{P_t G_t  A_r \sigma  F^4}\over{{(4\pi)}^2 R_t^2R_r^2}}

where

  • Pt = transmitter power
  • Gt = gain of the transmitting antenna
  • Ar = effective aperture (area) of the receiving antenna
  • σ = radar cross section, or scattering coefficient, of the target
  • F = pattern propagation factor
  • Rt = distance from the transmitter to the target
  • Rr = distance from the target to the receiver.

In the common case where the transmitter and the receiver are at the same location, Rt = Rr and the term Rt² Rr² can be replaced by R4, where R is the range. This yields:

P_r = {{P_t G_t  A_r \sigma  F^4}\over{{(4\pi)}^2 R^4}}.

This shows that the received power declines as the fourth power of the range, which means that the reflected power from distant targets is very, very small.

The equation above with F = 1 is a simplification for vacuum without interference. The propagation factor accounts for the effects of multipath and shadowing and depends on the details of the environment. In a real-world situation, pathloss effects should also be considered.

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Sunday, July 19, 2009

Radar Systems Question Papers

UNIT I
1. Draw the block diagram of a Pulsed radar and explain its operation
2. Write the relative factors between the radar’s cross section of the target and its true cross sections
3. Derive basic radar’s equation
4. Explain about the frequencies used for radar
5. Discuss in detail the choice of various parameters that are affecting the radar range
6. Derive the range equation and discuss about its limitations
7. what do you understand by false alarm
8. A pulsed radar operating at 10GHz has an antenna with a gain of 28dB and a transmitter power of 2KW . If it is defined to detect a target with a cross section of 12sq.m and the minimum detectable signal is Pmin= -90dBm. What is the maximum range of the radar
UNIT II
1. What is meant by minimum detectable signal in radar. Discuss the effects of integration of radar pulses
2. What are the desirable pulse characteristics and the factors that govern them in a radar system
3. Discuss about detection of signals in noise
4. Describe the different noise components present in radar systems
5. Explain about PRF and range ambiguities
6. Explain about radar cross section of targets
UNIT III
1. Explain about Doppler effect
2. Explain the operation of CW radar with neat block diagram
3. derive the expression for the velocity of the target when the target is moving away from the radar in the case FM-CW radar
4. an 8GHZ Police radar measures a Doppler frequency of 1788HZ from a car approaching the stationary police vehicle in an 80 km/h speed limit zone .what should the police officer do?
5. Differentiate the operation of pulse radar from simple CW radar
6. Draw the block diagram of non coherent MTI radar and explain the function of each block in detail
7. Explain the advantages of non coherent MTI Radar
8. Explain the applications of CW radar.
9. Explain the principle of Doppler effect and its application CW radar.
10. Derive an expression for unambiguous range of a two frequency CW radar.
UNIT IV
1) Explain the principle of operation FM –CW altimeter with suitable diagrams.
2) Determine the beat frequency due to range and the quantization error if range=100m, and the frequency excursion is 75Hz and modulating frequency is 1Khz.
3) Explain the operation of sideband superhetreodyne CW Doppler radar with block diagram.
4) Explain how the noise signals are limiting the performance of FM-altimeter .
5) What are advantages and disadvantages of FM-CW radar over multiple frequency CW radar.
UNIT V
1) A simple MTI delay line canceller is an example of time domain filter .Why? Explain.
2) Enumerate the advantage of the time delay line canceller as compared to the convention frequency domain filter.
3) Draw the bloc diagram of four pulse canceller and find the weight for the same.
4) Differentiate three- pulse canceller from four pulse canceller.
5) Description of Range gate Doppler filters.
6) Differentiate blind phases from blind speeds.
7) Explain the effect of Doppler frequency ‘fd’ for the stationary objects and moving targets.
8)Explain the butterfly effect that is produced by MTI.
9) Draw and explain frequency response characteristics of a MTI using range gates and filters.
10) How does MTI radar differ from CW radar?
11) How does MTI radar differ from pulse Doppler radar?
12. What is the distinctive feature that makes the MTI radar and Pulse Doppler to differ ?
UNIT VI
1) Explain Tracking Principles
2) Explain the block diagram of amplitude comparison monopulse radar for single angular coordinate and explain its operation
3).Explain phase comparison monopulse tracking radar technique
4).Explain the block diagram of AGC portion of tracking radar receiver
5).Explain about sequential Lobing
6).What are the advantages of monopulse radar over conical scan radar?
7).Distinguish between search radar and tracking radar?
8).Compare the tracking techniques
9).How is radar target acquired in a typical radar?
UNIT VII
1).Explain the characteristics of a matched filter receiver with necessary equations
2).Explain about matched and non –matched filters
3).Explain the characteristics of a cross –correlation receiver with a block diagram
4)Derive and explain the efficiency of non-matched filters
5).Explain about matched filter with non –white noise
UNIT VIII
1).Define the following terms
a)noise figure b)noise temperature c)system noise
2).Explain various types of radar displays
3).Three networks units ,each of 6db noise figure and 10db, 6db and 3db gains respectively are cascaded.Determine the Overall noise figure of the system.
4).Explain different types of Duplexers
5).Explain about Phased Array Antennas.

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