| 摘要 |
A modulator circuit comprises an input for receiving an audio frequency (AF) signal, an oscillator circuit for providing a carrier wave signal, a mixer circuit for mixing the AF input signal with the carrier wave signal to provide an AM modulated signal, a switch having a first position in which the AM modulated signal is provided to an output and the switch having a second position in which the AM modulated signal is provided to a vector adding circuit where the AM modulated signal is vector added to the carrier wave signal, and the circuit including phase shift circuitry for shifting the phase of the AM modulated signal prior to vector adding with the carrier wave signal whereby to provide an FM modulated version of the AF input signal on the oscillator carrier wave.
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