Radar Fundamentals

Radar Fundamentals
Prof. David Jenn Department of Electrical & Computer Engineering 833 Dyer Road, Room 437 Monterey, CA 93943 (831) 656-2254 jenn@nps.navy.mil, jenn@nps.edu http://www.nps.navy.mil/faculty/jenn

Overview
• • • • • • • • • Introduction Radar functions Antennas basics Radar range equation System parameters Electromagnetic waves Scattering mechanisms Radar cross section and stealth Sample radar systems
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Radio Detection and Ranging
Bistatic: the transmit and receive antennas are at different locations as viewed from the target (e.g., ground transmitter and airborne receiver). • Monostatic: the transmitter and receiver are colocated as viewed from the target (i.e., the same antenna is used to transmit and receive). • Quasi-monostatic: the transmit and receive antennas are slightly separated but still appear to SCATTERED WAVE FRONTS be at the same location as RECEIVER (RX) viewed from the target Rr (e.g., separate transmit θ TARGET and receive antennas on TRANSMITTER Rt the same aircraft). (TX)
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INCIDENT WAVE FRONTS
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Radar Functions
• Normal radar functions: 1. range (from pulse delay) 2. velocity (from Doppler frequency shift) 3. angular direction (from antenna pointing) • Signature analysis and inverse scattering: 4. target size (from magnitude of return) 5. target shape and components (return as a function of direction) 6. moving parts (modulation of the return) 7. material composition • The complexity (cost & size) of the radar increases with the extent of the functions that the radar performs.
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Electromagnetic Spectrum
Wavelength (λ, in a vacuum and approximately in air) Microns 10-2 10-1 Meters 10-1 UHF 10-3 1 10-5 10-4 10-3 10-2 1 101 VHF Radio Microwave Millimeter Ultraviolet Infrared Visible Optical 300 GHz 300 MHz HF 102 MF 103 LF 104 105

EHF

SHF

Typical radar frequencies

109

108

107

106

105

104 Giga

103

102

10

1

100 10 Mega

1

100

10 Kilo

1
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Frequency (f,...