Loss of SNR in Low Pass Filtered FM/MSK

Abstract

In a direct sequence pseudonoise (DSPN) spread spectrum link the minimum shift keying (MSK) modulation method is used to achieve good spectral containment with constant carrier envelope. Here the spectral containment is improved by direct FM modulation with a low pass filtered chip stream. The resulting loss of signal-to-noise ratio (SNR) from intersymbol interference is traded against improved spectral characteristics.