Several constant and quasi-constant envelope modulation techniques are compared to a new modulation technique called SEQAM for the purpose of fulfilling the requirements of PCS cellular radio technology. Constant envelope modulations are desirable for portable digital radios due to the reduced power amplifier backoff needed and consequent increase in power efficiency and decrease in handset dc power requirements and physical size. SEQAM has been adopted by IS-661 for its reduced spectral occupancy, allowing it to efficiently meet FCC emissions requirements and system channel spacing requirements while simultaneously allowing non-linear operation of the power amplifier. It is shown that SEQAM is a flexible modulation allowing for the tradeoff between spectral occupancy and BER performance.
"Constant envelope modulation techniques for PCS data transmission", Proc. SPIE 2601, Wireless Data Transmission, (8 December 1995); doi: 10.1117/12.228130; https://doi.org/10.1117/12.228130