Citation
Abstract
A generalized modulation scheme, which includes minimum shift keying (MSK) and staggered quadriphase shift keying (SQPSK) as special cases, is analyzed. The general modulator can be realized as a one-input, two-output sequence transducer whose outputs select the carrier signal for each baud. This form of the modulator has the practical advantage of not requiring any RF filtering since there is no actual mixing of the carriers with the modulating signals. It is shown that the optimum demodulator (whether hard-decision or soft-decision) always can make its decisions from the received waveform over two bauds when the interference is additive white Gaussian noise, thus generalizing a well-known result for hard-decision demodulation of MSK and SQPSK signals. The power spectra of MSK and SQPSK signals are derived to isolate the role played by coherency between the modulating signals and the carriers.
Details
- Volume
- 42-52
- Published
- August 15, 1979
- Pages
- 26–40
- File Size
- 1.2 MB