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Radar pulsing causes a phenomenon called aliasing, which occurs when the Doppler frequency created by reflector motion exceeds the pulse repetition frequency (PRF). [1] This concept is related to range ambiguity resolution. Doppler frequency shift is introduced onto reflected signals used by radar.
This happens with all radar systems. [1] Radar aliasing happens when: 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.
Range ambiguity resolution is a technique used with medium pulse-repetition frequency (PRF) radar to obtain range information for distances that exceed the distance between transmit pulses. This signal processing technique is required with pulse-Doppler radar .
Continuous-wave radar (CW radar) is a type of radar system where a known stable frequency continuous wave radio energy is transmitted and then received from any reflecting objects. [1] Individual objects can be detected using the Doppler effect , which causes the received signal to have a different frequency from the transmitted signal ...
Pulse-Doppler radar sensors are therefore more suited for long-range detection, while FMCW radar sensors are more suited for short-range detection. Monopulse : A monopulse feed network, as shown in Fig. 2, increases the angular accuracy to a fraction of the beamwidth by comparing echoes, which originate from a single radiated pulse and which ...
Medium PRF is used with Pulse-Doppler radar, which is required for look-down/shoot-down capability in military systems. Doppler radar return is generally not ambiguous until velocity exceeds the speed of sound. A technique called ambiguity resolution is required to identify true range and speed. Doppler signals fall between 1.5 kHz, and 15 kHz ...
In 1951, Carl A. Wiley invented synthetic-aperture radar, which, though distinct from mainstream Doppler radar, was based on Doppler principles, and originally patented as "Pulsed Doppler Radar Methods and Means," #3,196,436. Modern Doppler systems are light enough for mobile ground surveillance associated with infantry and surface ships.
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 ...