| 摘要 |
<p>A transmitter for an independent sideband (lSB) AM stereo system is provided with a phase modulator which includes means for generating second order upper and lower sidebands which are proportional to the stereo difference signal. No second order upper and lower sidebands are generated when the L and R audio signals are equal. The phase modulator uses an ISB suppressed carrier signal generator and a quadrature demodulator which demodulates the quadrature component of the output of the ISB generator. This demodulated component is used in a balanced modulator to modulate the ISB signal and thereby generate a signal having a carrier and upper and lower first and second order sidebands. This signal is combined with a carrier signal of selected amplitude and the ISB suppressed carrier signal to provide an output signal which, after limiting, is a phase-modulated signal having first and second order upper and lower sidebands. When the Land R signals are equal, all of the sidebands of this signal vanish. The phase modulated signal is amplitude modulated using an audio signal corresponding to the summation of the L and R stereo signals.</p> |
