Abstract: Extended binary phase shift keying (EBPSK) is a type of modulation which is flexible. By changing some modulation parameters, we could select among modulation method, spectrum efficiency, power efficiency, code rate and so on. Meanwhile, demodulator could self-adapt to these changes. We analyzed three simplest special cases of the EBPSK modulation under the same code rate, i.e. phase inversion modulation, missing cycle modulation, and narrow-pulse modulation, and simulated and compared their power spectrum, output of the impact filter, and demodulation performance without channel coding. Simulation result proclaims differences among the modulation signal, power spectrum, output of the impact filter and demodulation performance of the three modulation methods.