Improving Costas loop pull in range using pseudo BER detector

This paper describes a method for improving pull in range for the four-phase version of a Costas loop. The basic idea is that a pseudo bit error ratio (PBER) detector is used for fast detection of loop synchronization loss, and to trigger the frequency-sweeping circuitry. After synchronization is achieved the PBER detector detects the small BER and switches off the sweeping circuitry. Several types of PBER detector are considered and experimentally tested. One version is implemented in IMTEL's (Institute for Microwave Techniques and Electronics) digital radio relay systems (DRRS) RRU13A and RRU23A.