Design and implementation of a novel digital Interplex modulator for future navigation satellite system

Coherent adaptive subcarrier modulation (CASM) and Interplex can be seen as particular cases of the QPSK modulation or as an evolution of the conventional constant-envelope subcarrier modulation. Interplex uses exclusively additive methods to multiplex the signals, while CASM employs a combination of angle modulation and additive methods. Binary offset carrier (BOC) and Binary phase shift keying (BPSK) are the suitable candidate navigation purpose. In this paper we are proposing a novel method for combining these two modulation scheme in order to get constant modulation envelope i.e., the total transmitted power does not vary over time, so that the transmitted information is not contained in the signal amplitude and the transmitted signal amplitude becomes less critical.