Receiver Synchronization of Ultra-Wideband Phase Modulated Signals with a Fully Analog QPSK Costas Loop

A fully analog QPSK Costas loop is verified by measurements and shows long term stability and locking for ultra-wideband signals with bit rates up to 2 Gbit/s of BPSK and QPSK modulated signals. The loop is used for receiver synchronization and tested with carrier frequencies up to 7.5 GHz. The effects of time delay on the locking behavior of the loop are briefly addressed in a theoretical manner and generally confirmed by measurements. To the best of the author's knowledge, this is the first successful QPSK measurement of a long-term stable locked, fully analog QPSK Costas loop.