training course on weather radar systems - RTC, Regional Training ...

MODULE A- INTRODUCTION TO RADAR
c) Bandwidth (BW)
The difference between the upper and lower frequencies of a band of electromagnetic
radiation.
d) Wavelength ( λ )
The distance from wave crest to wave crest (or trough to trough) along an electromagnetic
wave’s direction of travel is called wavelength.
e) Pulse width (τ)
Time interval between the leading edge and trailing edge of a pulse at a point where the
amplitude is 50% of the peak value.
f) PRF&PRT
Pulse repetition frequency is the number of peak power pulses transmitted per second.
Pulse repetition time is the time interval between two peak pulses.
g) Duty Factor/Duty Cycle
Duty cycle is the amount of time a radar transmits compare to its listening or receiving time.
The ratio is sometimes expressed in per cent. It can be determined by multiplying PRF and
Pulse width or, by dividing the Pulse width with PRT.
h) Beamwidth (θ)
It is defined as the angle between the half-power (3 dB) points of the main lobe, when
referenced to the peak effective radiated power of the main lobe
Some Nomenclature
Name Symbol Units Typical values
transmitted frequency f t MHz, GHz 1000-12500 MHz
wavelength λ cm 3-10 cm
Pulse duration τ µsec 1 µsec
Pulse length h m 150-300 m (h=c τ)
Pulse repetition frequency PRF sec -1 1000 sec -1
interpulse period T millisec 1 millisec
peak transmitted power P t MW 1 MW
average power P avg kW 1 kW (Pavg = P t τ PRF)
received power P r mW 10 -6 mW
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TURKEY RADAR TRAINING 1.0 / ALANYA 2005