| 摘要 |
<p>AM receiver comprising a tuning oscillator (TO), a first phase detector (PD1) and a first loop filter (LP1) successively arranged in a first phase control loop, said tuning oscillator (TO) being synchronized with a reference oscillator (VCXO) coupled to the first phase detector (PD1) and applying a mixing frequency to a mixer stage (M) for conversion of a received AM signal into an IF-AM signal, said mixer stage - (M) being coupled to an AM demodulator (SD) for demodulation of the base-band modulation signal. To realise an AM receiver of this type at low cost, while maintaining an acceptable signal processing and particularly a sufficiently large dynamic range according to the invention, the reference oscillator (VCXO) is controllable and is disposed between a second loop filter (LP2) and a second phase detector (PD2) of a second phase control loop coupled to the mixer stage (M) for applying a local detection carrier synchronized with the IF-AM signal carrier to the AM demodulator (SD), said second loop filter (LP2) applying a control signal to the reference oscillator (VCXO) and being connected through a coupling circuit (C) to a control input of the tuning oscillator - (TO) for a negative feedback of the control signal of the reference oscillator (VCXO) to the tuning oscillator (TO).</p> |
