| 摘要 |
<p>A first variable attenuator is coupled between the FDM baseband source and the FM modulator. The output signal of the first attenuator is RMS detected to provide a control signal for this attenuator to adjust the amplitude of the baseband signal applied to the FM modulator and, hence, the frequency deviation thereof. An increase in frequency deviation enables a reduction in the EIRP (effective isotropic radiated power) for the same S/N, or an increase in S/N for the same EIRP. A second variable attenuator controlled by the same control signal operates in an inverse fashion, as compared to the first variable attenuator, on the carrier amplitude to maintain a constant S/N ratio.</p> |
