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Speech Scrambler, Descrambler, Balanced Modulator

A speech scrambler transforms low frequency to high frequency components and vice versa so that a baseband signal of bandwidth B is transformed to another baseband signal of the same bandwidth and a components at the frequency f is transformed into a component at the frequency B-f, where B is the bandwidth of the signal. An example is shown in the following figure...

a) Give the block diagram of a linear system to accomplish this scrambling.
b) Give a block diagram to descramble the signal.

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Speech Scrambler

A possible speech scrambler circuit is diagrammed in Figure 1(see attached file). The input signal is a voice signal from the output of a microphone preamplifier. A band-pass filter limits the bandwidth of the signal. The output of the filter is applied to a balanced modulator ...