A Novel High-Dynamic-Range PLL System for Synchronous Detection in AM Receivers

This paper presents a novel nested phase-lock loop system for synchronous detection in AM radio receivers with frequency-synthesizer tuning. The VCXO of the phase-lock loop simultaneously acts as the reference frequency for the synthesizer. A unique compensation technique that ties the poles of the PLL transfer function down in fixed positions effectuates an extremely high dynamic range, thereby alleviating the i. f. filter requirements drastically. With a loop bandwidth of 3.5Hz, an interfering carrier with a 50dB higher level and at a distance of 9kHz from the desired carrier is adequately rejected.