Novel method detects lock in Costas loops

摘要

In the well-established lock-detection scheme for conventional PLLs, the VCO or VCXO local oscillator splits the output into 0 and 90° signals (Figure 1). The incoming IF signal mixes with the 0 and 90° signals to perform phase locking and lock detection, respectively. This method gives unambiguous results even under noisy conditions.