| 摘要 |
<p>14 A polar loop transmitter in which a negative feedback bias adjusting system (76,78,80) is provided to control the bias voltage applied to a differential amplifier (30) which supplies the input envelope information to an amplitude modulator (36), so that the R.F. modulated output goes to zero for a zero in the input envelope information. The negative feedback bias adjusting system (76,78,80) comprises a threshold circuit (76) for deriving a threshold voltage from the D.C. component in the output of the differential amplifier (30). This enables negative going spikes to be separated from the output waveform and their amplitude used to control the D.C. correction component which is applied to an input of the differential amplifier.</p> |
