LTPSK: simple, bandwidth efficient modulation for multi-rate satellite channels

A constant envelope modulation called linear-transition phase shift keying (LTPSK) is examined as a candidate for use as a bandwidth and power efficient modulation on nonlinear satellite channels. This modulation is similar to differential phase shift keying (DPSK), but with phase transitions realized as a linear phase ramp between symbols to decrease spectral occupancy without introducing amplitude variation. The ratio of phase-transition time to symbol duration is referred to as the LTPSK mode. Spectral occupancy and BER performance with differential detection vary between that of DPSK and differential minimum shift keying (MSK), depending on the mode selected. By making the LTPSK mode proportional to the data rate, a simple LTPSK modulator and differential demodulator can support multiple data rates without the need for a bank of filters. The highest rate supported has the lowest ratio of spectral occupancy to data rate, and spectral occupancy is approximately constant for all rates, allowing efficient spectrum allocation with fixed frequency assignments.<>