A Balanced,Switching Audio Modulator with High Carrier Rejection,

摘要

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.