| 摘要 |
A velocity sensor system comprising a receiver capable of processing the narrow pulse speckle pattern return from a transmitting source in order to determine the velocity of the vehicle in which the velocity sensor is mounted. Three channels, each one connected to a receiving horn, receive the speckle pattern return signal equal in power but separated in space due to the spatial arrangement of the horns. A first local oscillator is connected to each channel and is controlled as part of an Automatic Frequency Control (AFC) loop. A carrier frequency from the first local oscillator along with the received signal is applied to the first mixer stage to produce a first IF signal which is applied to a wide band IF amplifier. The wideband IF amplifier is designed to blank the receiver during the transmitter pulse in order to prevent overloading of the receiver or overpowering of the echo. The output from the wide band IF amplifier in each channel is combined with the carrier frequency from a second oscillator and is applied to a second mixer. The output from the second mixer is applied to a narrow band IF amplifier which has the funnction of stretching returns in time so as to insure overlap of the total return energy. The signal from the narrow band IF amplifier is applied to the detector where the intelligence signal is removed from the carrier. From the detectors the signals are applied to frequency trackers which ultimately compute the ground speed and drift angle data of the vehicle by measuring the time it takes the speckle pattern to traverse the distance between receiving antennas.
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