Abstract: An apparatus and method for receiving spread spectrum signals, and, further, for decoding phase encoded information from such signals, requires correlation of input signals into real and imaginary components and determination of the phase angles of the received signal. A transmitter can divide an input signal into a plurality of data streams, independently modulate these streams, and then superpose the plurality of resultants for transmission. A receiver can receive the superposed signal and separate it into real and imaginary parts. In one embodiment, the receiver uses a plurality of spread spectrum codes to generate a plurality of real correlation signals and a plurality of imaginary correlation signals. A transmitter may also generate a differentially phase encoded signal. Phase encoding of a signal generally involves the imposition of known phase changes in the transmitted signal at selected intervals. Decoding of the phase changes at the receiver allows recognition of the phase encoded information.

Abstract: A technique for modulating and demodulating CPM spread spectrum signals and variations of CPM spread spectrum signals. A spread spectrum transmitter includes a chip sequence generator for generating a chip sequence from a data stream, a switch for dividing said chip sequence into an odd chip sequence and an even chip sequence, and a modulator for generating and transmitting a continuous phase modulated signal from said odd chip sequence and said even chip sequence. A spread spectrum receiver comprises a plurality of non-coherent serial CPM correlators, each generating a correlation signal. In a preferred embodiment, the chip sequence generator of the transmitter comprises a table of symbol codes, each symbol code comprising a series of chips corresponding to a unique series of bits in said data stream, and each non-coherent serial CPM correlator is configured to detect one of the symbol codes.

Abstract: A method and apparatus for phase encoding and decoding a CPM spread spectrum signal. A transmitter divides a data stream into a data symbol portion and an associated phase information portion. The data symbol portion is used to select one of a plurality of spread spectrum codes for transmission from a symbol table. The phase information portion is used to differentially phase encode the data symbol prior to transmission. The transmitter divides the phase encoded spread spectrum codes into a plurality of data streams (such as I and Q data streams), independently modulates the I and Q data streams using CPM or a related technique, and superposes the plurality of resultants for transmission. A receiver receives the superposed spread spectrum signal and simultaneously attempts to correlate for a plurality of chip sequences (such as I and Q chip sequences), and derives a real correlation signal and an imaginary correlation signal.

Abstract: A technique for demodulating CPM spread spectrum signals and variations thereof. A receiver receives a CPM spread spectrum signal, splits it into two signals, demodulates the signals (either coherently or non-coherently) and simultaneously attempts to correlate for a plurality of chip sequences (e.g., I and Q or even and odd), ultimately combining the results into a unified correlation signal. A plurality of A/D converters quantize the demodulated signals into multi-bit digital signals prior to correlation, and multi-bit correlators operate on the multi-bit digital signals to produce correlation signals that are combined to form a unified correlation signal for detection.