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A radar altimeter measures absolute altitude: the height "Above Ground Level" (AGL). As of 2010, all commercial radar altimeters use linear frequency-modulated continuous-wave (LFMCW or FMCW) and about 25,000 aircraft in the US have at least one radio altimeter. [3] [4]
Radar transmission frequency spectrum of a trapezoid pulse profile Recent advances in signal processing techniques have made the use of pulse profiling or shaping more common. By shaping the pulse envelope before it is applied to the transmitting device, say to a cosine law or a trapezoid, the bandwidth can be limited at source, with less ...
This technique can be used in continuous wave radar and is often found in aircraft radar altimeters. In these systems a "carrier" radar signal is frequency modulated in a predictable way, typically varying up and down with a sine wave or sawtooth pattern at audio frequencies.
Alternatively, Frequency Modulated Continuous-wave radar can be used. The greater the frequency shift the further the distance travelled. This method can achieve much better accuracy than the pulsed radar for the same outlay and radar altimeters that use frequency modulation are industry standard. The radar altimeter is used to measure height ...
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 engineering is the design of technical aspects pertaining to ... radar altimeter, air traffic ... The radar frequency is also chosen in order to ...
Marine radars are used by ships for collision avoidance and navigation purposes. The frequency band of radar used on most ships is X band (9 GHz/3 cm), but S band (3 GHz/10 cm) radar is also installed on most oceangoing ships to provide better detection of ships in rough sea and heavy rain condition.
RA (Radar Altimeter) is a single frequency nadir-pointing radar altimeter operating in the K u band. ATSR-1 (Along-Track Scanning Radiometer) is a 4 channel infrared radiometer and microwave sounder for measuring temperatures at the sea-surface and the top of clouds.