High rate, time division multiplexed, multi-MPSK MODEM with imbedded high signal-to-noise ratio tracking channel

A novel MODEM and method of operating a MODEM usable in spread spectrum communication utilizing multiple waveforms in orthogonal spread signals imbeds a tracking signal in one of the spread signals for efficient tracking by a receiver so that both spread signals can have wideband characteristics. Therefore, one spread signal contains a tracking channel and a wideband channel, allowing for higher order modulation in the wideband channel for transmitting information, while still providing good tracking features. The second spread signal is an orthogonal wideband channel serving as the main high data rate conduit. In the preferred embodiment, the first portion of the waveform (in the first spread signal) is modulated using Bi-Bi-Phase Shift Keying (Bi-BPSK), while the second portion of the waveform (in the second spread signal) is modulated using Multiple Phase Shift Keying (MPSK). The two waveform portions are Time Division Multiplexed (TDM) at the chipping rate. A higher overall data bandwidth can be achieved for the Bi-BPSK modulation technique using the same channel bandwidth.