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High PRF is limited to systems that require close-in performance, like proximity fuses and law enforcement radar. For example, if 30 samples are taken during the quiescent phase between transmit pulses using a 30 kHz PRF, then true range can be determined to a maximum of 150 km using 1 microsecond samples (30 x C / 30,000 km/s).
Ground targets further than this range cannot be detected, so the PRF can be quite high; a radar with a PRF of 7.5 kHz will return ambiguous echoes from targets at about 20 km, or over the horizon. If however, the PRF was doubled to 15 kHz, then the ambiguous range is reduced to 10 km and targets beyond this range would only appear on the ...
Pulse repetition frequency (PRF) is too low to sample Doppler frequency directly; PRF is too high to sample range directly; Pulse Doppler sonar uses similar principles to measure position and velocity involving liquids.
The difference between the sample numbers where reflection signal is found for these two PRF will be about the same as the number of the ambiguous range intervals between the radar and the reflector (i.e.: if the reflection falls in sample 3 for PRF 1 and in sample 5 for PRF 2, then the reflector is in ambiguous range interval 2=5-3).
The signal processing enhancement of pulse-Doppler allows small high-speed objects to be detected in close proximity to large slow moving reflectors. To achieve this, the transmitter must be coherent and should produce low phase noise during the detection interval, and the receiver must have large instantaneous dynamic range.
Below 3 MHz, the whole volume of the air acts as a waveguide to fill in the radar shadow and also reduces radar sensitivity above the duct zone. Ducting fills in the shadow zone, extends the distance of the clutter zone, and can create reflections for low PRF radar that are beyond the instrumented range.
Image source: Getty Images. 1. Lockheed Martin. After its stock price reached an all-time high earlier this year, Lockheed Martin and its defense contractor peers have sold off considerably over ...
The first advantage the ASR-11 offers is the use of a low peak-power, solid state transmitter with pulse compression technology, replacing the ASR-9's high peak-power, short pulse power system. This gives the radar the ability to provide the same amount of energy to a target at long range while making the radar less sensitive at shorter ranges.