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A plane flying past a radar station: the plane's velocity vector (red) is the sum of the radial velocity (green) and the tangential velocity (blue). The radial velocity or line-of-sight velocity of a target with respect to an observer is the rate of change of the vector displacement between the two points.
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. R a d i a l V e l o c i t y > 0.5 ( P R F × C T r a n s m i t F r e q u e n c y ) {\displaystyle Radial\ Velocity>0.5\left({\frac {PRF\times C}{Transmit\ Frequency}}\right)}
This is an issue only with a particular type of system; the pulse-Doppler radar, which uses the Doppler effect to resolve velocity from the apparent change in frequency caused by targets that have net radial velocities compared to the radar device. Examination of the spectrum generated by a pulsed transmitter, shown above, reveals that each of ...
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 30 kHz. Each transmit pulse is separated by between 5 km and 50 km of distance.
Radar is a system that uses radio waves to determine the distance , direction (azimuth and elevation angles), and radial velocity of objects relative to the site. It is a radiodetermination method [ 1 ] used to detect and track aircraft , ships , spacecraft , guided missiles , motor vehicles , map weather formations , and terrain .
The radar envelope describes the region where a specific level of performance is required. Radar system specifications require a specific level of performance within a specific radar envelope. This performance includes the following characteristics. Cross section; Blind range; Radial velocity; Instrumented range; Scan time; Altitude; Elevation ...
To capture most of this traffic, even when it is moving almost tangentially through the radar (i.e., perpendicular to the radar-target line), a system must have the ability to detect very slow radial velocities. As the radial component of a target's velocity approaches zero, the target will fall into the clutter or blind zone.
Radar scalloping for MTI radar begins to become a concern when the radial velocity is greater than the following value. V e l o c i t y > 0.5 × ( C 2 × P e r i o d B e t w e e n P u l s e s × T r a n s m i t F r e q u e n c y ) {\displaystyle Velocity>0.5\times \left({\frac {C}{2\times PeriodBetweenPulses\times TransmitFrequency}}\right)}