Abstract: A transceiver uses feedback control to monitor a transmitted continuous phase modulation (CPM) waveform, such as a spread spectrum CPM waveform, and adjust the modulation index in response thereto. Codewords are selected from a table according to a data signal and applied to a pulse shaping network. The pulse shaping network outputs a CPM waveform to a prefilter. The prefilter is connected to an FM modulator, such as a voltage controlled oscillator. In one embodiment, a correlator in the transceiver monitors the transmitted waveform during times when the transceiver is not receiving signals, and provides a correlation signal to a feedback control circuit. The feedback control circuit dynamically adjusts the gain of the prefilter, and may comprise, e.g., a second order tracking loop filter. The feedback control signal thereby tracks the amplitude of the transmitted waveform and adjusts the output gain of the prefilter so as to maintain a constant signal envelope.

Abstract: A system for efficient time division duplex communication between a base station and a plurality of user stations over a single frequency band whereby guard time overhead is reduced through use of an interleaved frame structure and active adjustment of reverse link transmission timing as a function of round trip propagation time. A time frame is divided into a plurality of time slots. The base station transmits a forward link message to a first user station in a first time slot. The user station responds with a reverse link message in the following time slot. In the meantime, the base station receives a reverse link message from a second user station in the first time slot, and sends out another forward link message to a third base station in the first portion of the first time slot. The delay between transmitting the forward and reverse link messages to a particular user station allows for round trip propagation of the forward and reverse link messages.

Abstract: A technique is provided using a SAW device for correlating to a plurality of different chip code sequences, such as M different chip code sequences, using fewer than M individual SAW correlators. A received signal is provided to a SAW correlator capable of recognizing a plurality of different chip code sequences. The SAW correlator is pre-programmed so as to recognize each different chip code sequence at a different frequency. The received signal is given a programmably selected frequency offset from the center frequency of the received signal (or a downconverted version thereof) and applied to the SAW correlator. The SAW correlator correlates for the particular chip code sequence at the offset frequency. The output of the SAW correlator is given an opposite frequency offset and filtered with a bandpass filter to generate a correlator output at the designated center frequency.

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 system for time division multiplexed communication over a single frequency band in which guard time overhead is reduced by active adjustment of reverse link transmission timing as a function of round trip propagation time. In one embodiment, during a first portion of a time frame, a base station issues a single burst segmented into time slots comprising data directed to each user station. After a single collective guard time, the user stations respond, one by one, in allocated time slots on the same frequency as the base station, with only minimal guard times between each reception. In order to prevent interference among the user transmissions, the base station measures the round trip propagation time for each user station and commands the user stations to advance or retard their transmission timing as necessary.

Abstract: A receiver system for antenna diversity employing a single backhaul cable. A single backhaul cable couples a receiver to a plurality of antennas. The signals from the antennas are combined onto the single backhaul cable using frequency offsets, spread spectrum code division, time division, or a combination thereof. At the receiver, the signals from the antennas are decoupled. In the case of frequency offsets, the antenna signals are decoupled by splitting the backhaul signal into a plurality of duplicate signals, frequency shifting selected ones of the duplicate signals, and correlating said frequency shifted signals. In the case of spread spectrum code division, the antenna signals are decoupled by splitting the backhaul signal into a plurality of duplicate signals and demultiplexing each of the duplicate signals with a different spread spectrum code. One or more antennas may be selected for communication in response decoupling the antenna signals.

Abstract: A system for efficient time division duplex communication between a base station and a plurality of user stations over multiple frequency bands whereby guard time overhead is reduced through use of an interleaved frame structure and active adjustment of reverse link transmission timing as a function of round trip propagation time. A time frame is divided into a plurality of time slots. A user station transmits a preamble over a user frequency band. The base station receives the preamble and transmits, in a given time slot, a forward link message over a base frequency band to a user station. The user station responds with a reverse link message over the user frequency band in a subsequent time slot. While the base station is transmitting to a first user station over the base frequency band, it receives messages from another user station over the user frequency band, using the time slot differential between forward and reverse link messages for round trip propagation.

Abstract: A simple and flexible over-air protocol for use with a mobile telephone system, having hand-held telephones in a microcell or other type of cellular communication system. A method in which user stations communicate with one or more base stations to place and receive telephone calls, in which the user stations are provided a secure voice or data link and have the ability to handoff calls between base stations while such calls are in progress. Each base station has a set of "air channels" to which it transmits in sequence. The air channels supported by each base station are called that base station's "polling loop". A user station receives general polling information on an unoccupied air channel, transmits responsive information to the base station, and awaits acknowledgment from the base station. Each base station may therefore simultaneously maintain communication with as many user stations as there are air channels in its polling loop.

Abstract: A simple and flexible over-air protocol for use with a mobile telephone system, having hand-held telephones in a microcell or other type of cellular communication system. A method in which user stations communicate with one or more base stations to place and receive telephone calls, in which the user stations are provided a secure voice or data link and have the ability to handoff calls between base stations while such calls are in progress. Each base station has a set of "air channels" to which it transmits in sequence. The air channels supported by each base station are called that base station's "polling loop". A user station receives general polling information on an unoccupied air channel, transmits responsive information to the base station, and awaits acknowledgment from the base station. Each base station may therefore simultaneously maintain communication with as many user stations as there are air channels in its polling loop.

Abstract: A GPS single-receiver pointing/attitude system derives pointing/attitude measurements by correlating a selected GPS code (either P or C/A), recovered from GPS navigation signals using a single GPS receiver with multiple GPS antennas (a reference antenna and at least two slave antennas for pointing or three for attitude). For a two antenna pointing application, the GPS receiver (FIG. 4) includes, for each receiver channel, the incoming GPS signals are applied to three code correlators (72-75) assigned to the reference antenna, and three code correlators (76-77) assigned to the slave antenna, which provide corresponding reference and slave I and Q correlation outputs.