ENHANCED PLL CARRIER RECOVERY CIRCUIT
Original Publication Date: 1997-Sep-01
Included in the Prior Art Database: 2002-May-30
Phase locked loops can be used for RF carrier recovery. The flip-flop phase detectors and lowpass filters in such loops tend to idle midway between the supply voltage rails when no RF signal is present. The signal acquisition range, time, and sensitivity are influenced by how far from the idle voltage the VCO input voltage needs to be. This is dependent on ~VCO part variations, temperahue, and the desired RF signal frequency. The higher RF signal frequencies used in many of today's systems can put greater burdens on these systems, due to frequency tolerance requirements. The initial signal acquisition, fade recovery time, and over-tempera- ture performance could all be improved if the ideal PLL idle frequency could be measured and controlled.