Directly mixing synchronous receiver.

摘要

Directly mixing synchronous receiver having an RF input (1) and a first signal path (S1) which is coupled thereto and which incorporates a first synchronous demodulator (3) and a first low-pass filter (4), and having a carrier regeneration circuit comprising a first phase-locked loop (Q) incorporating in a loop configuration a first phase detector (5) which is coupled to the RF input (1), a first loop filter (6) and a first voltage-controlled tuning oscillator (8) an output of which is coupled to the first phase detector (5) on the one hand and to the first synchronous demodulator (3) via a phase shift circuit on the other hand for a direct demodulation of an RF reception signal to the frequency baseband. The local mixing carrier required for the direct synthonous demodulation should be accurately in phase or in antiphase with the carrier of a desired RF reception signal to be demodulated. To this end the phase shift circuit comprises a second phase-locked loop (P) incorporating in a loop configuration a second phase detector (8) which is coupled to said output of the first voltage-controlled oscillator (7), a second loop filter (9) and a second voltage-controlled tuning oscillator (10) an output of which is coupled to the second phase detector (8) on the one hand and to the first synchronous demodulator (3) on the other hand, the tuning of the first voltage controlled tuning oscillator (7) being coupled with that of the second voltage-controlled tuning oscillator (10).