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The pulse-repetition frequency (PRF) is the number of pulses of a repeating signal in a specific time unit. The term is used within a number of technical disciplines, notably radar . In radar, a radio signal of a particular carrier frequency is turned on and off; the term "frequency" refers to the carrier, while the PRF refers to the number of ...
Radar designers try to use the highest PRF possible commensurate with the other factors that constrain it, as described below. There are two other facets related to PRF that the designer must weigh very carefully; the beamwidth characteristics of the antenna, and the required periodicity with which the radar must sweep the field of view.
Radial velocity aliasing occurs when reflections arrive from reflectors moving fast enough for the Doppler frequency to exceed the pulse repetition frequency (PRF). Frequency ambiguity resolution is required to obtain the true radial velocity when the measurements is made using a system where the following inequality is true.
Areas outside the blue zones are blind ranges and blind velocities, which are filled in using multiple PRF and frequency agility. The unambiguous zone is in the lower left corner. All of the other blocks have ambiguous range or ambiguous radial velocity. Pulse Doppler radar relies on medium pulse repetition frequency (PRF) from about 3 kHz to ...
The PVI is recalculated when the trading volume increases from the previous period, and the NVI is recalculated when the trading volume decrease from the previous period. [8] These two metrics, when put together, show how volume is affecting the price of a security. A change in PVI indicates that prices are driven by high volumes.
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 swath width constrains the pulse repetition interval (PRI) or equivalently pulse repetition frequency (PRF), which equals to 1/PRI in the following way. If the SAR sensor flying with speed v {\displaystyle v} , and there are two targets P and Q on the ground, the azimuth angle is calculated as Δ ϕ = ϕ P − ϕ Q {\displaystyle \Delta ...
Pulse-Doppler typically uses medium pulse repetition frequency (PRF) from about 3 kHz to 30 kHz. The range between transmit pulses is 5 km to 50 km. Range and velocity cannot be measured directly using medium PRF, and ambiguity resolution is required to identify true range and speed.