QPSK Direct Regenerator with a Frequency Tripler and a Quadrupler

This paper describes a regenerator for quadriphase phase shift keying (QPSK) signals at the carrier frequency, which is called a "direct regenerator." The direct regenerator proposed here is realized using a tripler and a quadrupler. This regenerator is characterized by the symbols , and , which denote the intermediate combiner amplitude ratio, the final combiner amplitude ratio and the limiter dynamic range, respectively. Complete regeneration is obtained at and . Even if this condition is not satisfied, sufficient regenerative performance for practical use is preserved, when and dB. To verify the operation principle, an experiment was carried out for 1.7 GHz QPSK signals transmitted at 40 Mbits/s. It is shown that this regenerator has satisfactory decision and reshaping capability in dynamic operation. Using this direct regenerator, decision and reshaping of the QPSK signals can be made without detection. Thus, a repeater can be simplified, compared to a conventional repeater composed of a detector, a baseband regenerator and a modulator.