Spectral compact method of UNB using orthogonal ABPSK

In the recent years, a kind of small angle modulation is booming, that is UNB, first named by Dr. H.R. Walker, a high bandwidth efficiency is attained using the power as BPSK, which is from 15bps/Hz to 100 bps/Hz and even high than that. But For the most existing modulation method called UNB, besides the strong ultra narrow carrier-like spectrum, there is a wide continuous spectrum spread, which is not expected. The article presents Orthogonal ABPSK modulation; spectral characteristics and the demodulation performance using digital match filter method are analyzed; the spectral characteristics shows that the Orthogonal ABPSK has a better spectral characteristics, besides the continuous spectrum, there is only carrier line spectrum existing. And the main lobe of the continuous spectrum is also compressed, which only equals 2 times of the data rates, so the continuous spectral is compressed greatly compared to other ABPSK modulation method. Besides, the demodulation performance is only 3dB lower than that of BPSK and much better than that of other ABPSK formats.