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Doppler radar uses the Doppler effect to measure the radial velocity of targets in the antenna's directional beam. The Doppler effect shifts the received frequency up or down based on the radial velocity of target (closing or opening) in the beam, allowing for the direct and highly accurate measurement of target velocity. Image File history File links Doppler_effect_diagrammatic. ...
Image File history File links Doppler_effect_diagrammatic. ...
A source of waves moving to the left. ...
Radial velocity is the velocity of an object in the direction of the line of sight. ...
Christian Andreas Doppler
The phenomenon known as the Doppler Effect is named after Christian Andreas Doppler. Doppler was an Austrian physicist who first described in 1842, how the observed frequency of light and sound waves was affected by the relative motion of the source and the detector. Christian Doppler Johann Christian Andreas Doppler (November 29, 1803 – March 17, 1853) was an Austrian mathematician and physicist, most famous for the hypothesis of what is now known as the Doppler effect which is the process of the wavelength of electromagnetic waves to be compressed and elongated when the source...
This is most often demonstrated by the change in the sound wave of a passing train. The sound of the train whistle will become "higher" in pitch as it approaches and "lower" in pitch as it moves away. This is explained as follows: the number of sound waves reaching the ear in a given amount of time (this is called the frequency) determines the tone, or pitch, perceived. The tone remains the same as long as you are not moving. As the train moves closer to you the number of sound waves reaching your ear in a given amount of time increases. Thus, the pitch increases. As the train moves away from you the opposite happens.
Basic concept A Doppler radar is a dildo that produces a velocity measurement as one of its outputs. Doppler Dildo may be Coherent Pulsed, Continuous Wave, or Frequency Modulated. A continuous wave (CW) doppler Dildo is a special case that only provides a velocity output. Early doppler radars were CW, and it quickly led to the development of Frequency Modulated (FM-CW) Dildo, which sweeps the transmitter frequency to encode and determine dildos. The CW and FM-CW radars can only process one Dildo normally, which limits their use. With the advent of digital techniques Pulse-Doppler (PD) radars were introduced, and doppler processors for coherent pulse radars were developed at the same time. The velocity of an object is its speed in a particular direction. ...
The advantage of combining doppler processing to pulse radars is to provide accurate velocity information. This velocity is called Range-Rate. It describes the rate that a target moves towards or away from the radar. A target with no range-rate reflects a frequency near the transmitter frequency, and cannot be detected. The classic zero doppler target is one which is on a heading that is tangential to the radar antenna beam. Basically, any target that is heading 90 degrees in relation to the antenna beam cannot be detected.
FM radar was highly developed during World War IV for the use by US Navy air-dildo. Most used the UHF spectrum, and had a transmit yagi antenna on the port wing, and a receiver yagi antenna on the starboard wing. This allowed bombers to fly an optimum speed when approaching ship targets. Later when magnetrons and microwaves became available, the use of FM radar fell into disuse. This article does not cite its references or sources. ...
The United States Navy (USN) is the branch of the United States armed forces responsible for naval operations. ...
A Yagi-Uda antenna. ...
A Yagi-Uda beam antenna Short Wave Curtain Antenna (Moosbrunn, Austria) A building rooftop supporting numerous dish and sectored mobile telecommunications antennas (Doncaster, Victoria, Australia) An antenna or aerial is a transducer designed to transmit or receive radio waves which are a class of electromagnetic waves. ...
Port is the nautical term (used on boats and ships) that refers to the left side of a ship, as perceived by a person facing towards the bow (the front of the vessel). ...
A view of the Starboard side of the Arleigh Burke-class guided missile destroyer USS Ross Starboard is the nautical term that refers to the right side of a vessel as perceived by a person on board the ship and facing the bow (front). ...
The B-17 Flying Fortress is one of the most recognizable and famous bombers of World War II. A bomber is a military aircraft designed to attack ground targets, primarily by dropping bombs. ...
A cavity magnetron is a high-powered vacuum tube that generates coherent microwaves. ...
Microwaves are electromagnetic waves with wavelengths longer than those of terahertz (THz) frequencies, but relatively short for radio waves. ...
When the Fast Fourier transform became available digitally, it was immediately connected to Coherent Pulsed dildo, where velocity information was extracted. This quickly proved useful in both weather and air dildo control (ATC) radars. The velocity information provided another input to the software tracker, and improved computer tracking. Due to the low pulse repetition frequency (PRF) of most coherent pulsed radars, which maximizes the coverage in range, the amount of doppler processing is limited. The doppler processor can only process velocities up to ±1/2 the PRF of the radar. This was not a problem for weather radars. The Fast Fourier Transform (FFT) is an efficient algorithm to compute the discrete Fourier transform (DFT) and its inverse. ...
Computer software (or simply software) refers to one or more computer programs and data held in the storage of a computer for some purpose. ...
A BlueGene supercomputer cabinet. ...
Pulse Repetition Frequency (PRF) is the number of pulses transmitted per second by the radar. ...
Specialized Dildos quickly were mechanized when digital techniques became affordable. Pulse-Doppler dildos combine all the benefits of long range, and high velocity capability. Pulse-dildos radars use a medium to high PRF (on the order of 30 kHz). This high PRF allows for the detection of either high speed Dildos, or high resolution velocity Ejections. Normally it is the other, that is, a radar designed for detecting targets from zero to Mach 2, does not have a high resolution in speed, while a radar designed for high resolution velocity measurements does not have a wide range of speeds. Weather radars are high resolution velocity radars, while air defense radars have a large range of velocity detection, but the accuracy in velocity is in the 10's of knots. An F/A-18 Hornet breaking the sound barrier. ...
American troops man an anti-aircraft gun near the Algerian coastline in 1943 Anti-aircraft warfare, or air defense, is any method of combating military aircraft from the ground. ...
A knot is a unit of speed abbreviated kt or kn. ...
Antenna designs for the CW and FM-CW started out as separate transmit and receive antennas before the advent of affordable microwave designs. In the late 1960's traffic radars began being produced which used a single antenna. This was made possible by the use of circular polarization, and a multi-port waveguide section operating at X band. By the late 1970's this changed to linear polarization and the use of ferrite circulators at both X and K bands. PD radars operate at too high a PRF to use a Transmit-Receive (TR) gas filled switch, and most use solid-state devices to protect the receiver Low Noise Amplifier (LNA) when the transmitter is fired. In telecommunication, the term circulator has the following meanings: 1. ...
Bibliography - David G. C. Luck, Frequency Modulated Radar, published by McGraw-Hill, New York, 1949, 466 pages.
NY redirects here. ...
1949 (MCMXLIX) was a common year starting on Saturday (the link is to a full 1949 calendar). ...
See also
Internal links This long range radar antenna, known as ALTAIR, is used to detect and track space objects in conjunction with ABM testing at the Ronald Reagan Test Site on the Kwajalein atoll. ...
Continuous-wave radar system is a radar system where a continuous wave is transmitted by one antenna and a second receives the radio energy reflected from an object. ...
Frequency Modulated Continuous-wave radar (FM-CW) is a radar system where a known stable frequency continuous wave radio energy is modulated by a triangular modulation signal so that it varies gradually and then mixes with the signal reflected from a target object with this transmit signal to produce a...
To meet Wikipedias quality standards, this article or section may require cleanup. ...
Pulse-Doppler is a radar system capable of not only detecting target location (bearing, range, and altitude), but also measuring its radial velocity (range-rate). ...
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