A Balanced, Switching Audio Modulator with High Carrier Rejection,
NAVAL UNDERSEA WARFARE CENTER SAN DIEGO CA
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In the conversion and analysis of active sonar data, it is often desirable to up or down shift the frequency spectrum of analog data to a more easily handled band. One method of doing this is to use an analog multiplier to heterodyne the signal. However, this method has the disadvantages of non-linearity, sensitivity to thermal changes and high cost. The above difficulties may be overcome by using a switching modulator. This device multiplies the input data signal by a square wave of any chosen frequency. The output of the modulator can then be passed through a bandpass filter to select the upper or lower sideband of the heterodyned signal. The filter output will be an up or down shifted version of the input signal.
- Electrical and Electronic Equipment
- Acoustic Detection and Detectors