Finite truncated cosine series design of full response signaling offset quadrature binary modulation systems

Abstract

Classical cosine series functions have been applied to the synthesis of finite impulse response filters because of their closed analytic form and low sidelobe levels. It is proposed that cosine series functions be applied to the synthesis of pulse shapes for full response signaling quadrature binary modulation systems in the interest of controlling the spectral characteristics of the resulting modulated signals. Synthesis criteria which govern the selection of cosine series coefficients include provisions for controlling modulated signal envelope nonuniformity and provisions for selecting spectral nulls in the modulated signal. The respective modulation systems are analyzed and compared to conventional modulation techniques QPSK, MSK, SFSK and DSFSK on the basis of modulated signal envelope uniformity and spectral confinement. It is shown that the freedom to select spectral zeroes in the closed form design of the pulse shape introduces a vehicle for suppressing narrowband interference without introducing intersymbol interference into the system. Design examples are provided and modulation system implementations are proposed and discussed. >