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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)}
A positive radial velocity indicates the distance between the objects is or was increasing; a negative radial velocity indicates the distance between the source and observer is or was decreasing. William Huggins ventured in 1868 to estimate the radial velocity of Sirius with respect to the Sun, based on observed redshift of the star's light. [6]
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 .
Radar cross-section (RCS), denoted σ, also called radar signature, is a measure of how detectable an object is by radar. A larger RCS indicates that an object is more easily detected. [1] An object reflects a limited amount of radar energy back to the source. The factors that influence this include: [1] the material with which the target is made;
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 ...
Data is extracted and recorded from the radar system while aircraft, balloons, ships, drones, missiles or other objects are moved within the radar envelope. The recorded data is compared to distance, altitude, and speed of the objects to evaluate the pass-fail criteria. These are the typical shapes of the physical radar envelope. Flattened donut
and where f d is the Doppler frequency, B is the frequency sweep of the chirp, T is the duration of the chirp, f m is the mid (centre) frequency of the chirp, V r is the radial velocity of the target and c is the velocity of light (= 3×10 8 m/s). Consider as an example, a chirp centered on 10 GHz, with pulse duration of 10μs and a bandwidth ...