TM-9-1290-365-24&P Technical and Parts Manual for Paladin Muzzle Velocity System M93 Upgraded Download
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ARMY TM 9-1290-365-24&P Figure D-40. Microwave Measurement Equipment Connection D.9.2.4 SENSITIVITY MEASUREMENTS THEORY OF OPERATION . The transceiver assembly trans- mits a low power X-band continuous wave signal. The transmitted signal strikes the outgoing projectile in flight and the reflected RF energy is received by the antenna. The reflected signal is different from the transmitted, due to the Doppler effect. The antenna unit detects the difference between the transmitted and received signals, which is directly relative to the projectile velocity. In order to achieve the simulation of the outgoing projectile, the transmitted signal is reflected and mod- ulated, so that the received frequency is within the velocity measuring range of the transceiver assembly. This is obtained by modulating a PIN switch in the microwave section at the appropriate frequency. The PIN switch is modulated by a square wave that causes it to switch from off to on and vice versa. When the PIN switch is off, the transmitted signal is reflected back to the antenna. When the PIN switch is on the signal is absorbed by the dummy load. Because of the square wave modulation, the reflected signal contains several spectral components. The first spectral component corresponds to the Doppler shifted frequency. The first spectral component power, in accordance with Fourier transform theory, is 1/II 2 (-9.94dB) of the transmitted power. Also, as a result of the on/off chopping of the signal and the absorption by the dummy load, only 1/2 (-3dB) of the transmitted power is reflected. D-115