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Pulse-Doppler signal processing is a radar performance enhancement strategy that allows small high-speed objects to be detected in close proximity to large slow moving objects. Detection improvements on the order of 1,000,000:1 are common. Small fast moving objects can be identified close to terrain, near the sea surface, and inside storms. This signal processing strategy is unique for pulse-Doppler radar and multi-mode radar, which can be pointed into regions containing a large number of slow-moving reflectors without overwhelming computer software and operators. Other signal processing strategies, like moving target indication, are more appropriate for benign clear blue sky environments. ==Environment== Pulse-Doppler begins with coherent pulses transmitted through an antenna or transducer. There is no modulation on the transmit pulse. Each pulse is a perfectly clean slice of a perfect coherent tone. The coherent tone is produced by the local oscillator. There can be dozens of transmit pulses between the antenna and the reflector. In a hostile environment, there can be millions of other reflections from slow moving or stationary objects. Transmit pulses are sent at the pulse repetition frequency. Energy from the transmit pulses propagate through space until they are disrupted by reflectors. This disruption causes some of the transmit energy to be reflected back to the radar antenna or transducer, along with phase modulation caused by motion. The same tone that is used to generate the transmit pulses is also used to down-convert the received signals to baseband. The reflected energy that has been down-converted to baseband is sampled. Sampling begins after each transmit pulse is extinguished. This is the quiescent phase of the transmitter. The quiescent phase is divided into equally spaced sample intervals. Samples are collected until the radar begins to fire another transmit pulse. The pulse width of each sample matches the pulse width of the transmit pulse. Enough samples must be taken to act as the input to the pulse-Doppler filter. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Pulse-Doppler signal processing」の詳細全文を読む スポンサード リンク
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