| 摘要 |
The disclosed system comprises a testing system which measures the stability of a moving target indicator radar transmitter. It automatically measures the imperfections of its internal in-phase (I)/quadrature (Q) demodulator, and it consists of a control computer, a synchronizer, a frequency synthesizer, an IQ demodulator, a low noise amplifier and a waveform recorder. A unit under test is inserted across the test set for measurement and calibration. The system set has the following features: (a) An automatic calibration routine that requires a tunable RF source. This source provides the RF drive to the UUT. (b) A discontinuous analog to digital (A/D) sample clock that has a precise controllable relationship with the RF pulse. The A/D sample clock samples only during the presence of the RF. (c) A method for computing stability using a table of amplitude and phase weighting coefficients and pulse positions. This table is generated by the user and any desired combination of values is possible. The discontinuous sample clock is used in the acquisition of the raw stability data. During data collection, the computer commands the synchronizer to output a pulse train. The pulse train contains pulses with various pulse widths and pulse repetition frequencies. The synchronizer output turns on the UUT causing it to provide an RF output signal. The synchronizer also sends out bursts of pulses that make the waveform recorder digitize and I and Q video signal from the low noise amplifier. Under the control of the computer, the synthesizer generates two RF signals. One RF signal is applied to the UUT and the other RF is applied directly to the IQ demodulator where the two signals are compared. The IQ demodulator provides the I and Q signal inputs to the low noise amplifier.
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