A radio frequency identification device comprises an integrated circuit including a receiver, a transmitter, and a microprocessor. The receiver and transmitter together define an active transponder. The integrated circuit is preferably a monolithic single die integrated circuit including the receiver, the transmitter, and the microprocessor. Because the device includes an active transponder, instead of a transponder which relies on magnetic coupling for power, the device has a much greater range.

Radio frequency data communications device

A technique for spread-spectrum communication which uses more than one mode and more than one frequency band. Selectable modes include narrowband mode and spread-spectrum mode, or cellular mode and microcellular mode. Selectable frequency bands include both licensed and unlicensed frequency bands, particularly frequency bands including the 902-928 MHz, 1850-1990 MHz, and 2.4-2.4835 GHz frequency bands. Spread-spectrum communication channels are 10 MHz or less in width. The frequency band onto which spread-spectrum signals are encoded may be changed upon a change in environment or other control trigger, such as establishment or de-establishment of communication with a private access network. A multi-band transmitter comprises a single frequency synthesizer and a frequency source (e.g., a local oscillator), coupled to a selectable band pass filter. A multi-band receiver capable of monitoring one or more frequency bands comprises bank of bandpass filters and a demodulator comprising a single frequency synthesizer and a frequency source.

Multi-band, multi-mode spread-spectrum communication system

A subscriber unit for use in a multiple access spread-spectrum communication system includes a spread spectrum radio interface, responsive to a rate function signal from a base station, and first and second despreaders. The base station assigns the rate function spread-spectrum message channels and the first despreader recovers and modifies an information signal one of the spread spectrum message channels. The information channel mode is then modified for processing by the second despreader, with the second despreader supporting a different information signal rate. The subscriber unit has a capability of communicating with a dynamically changing a transmission rate of an information signal which includes multiple spread spectrum message channels. The system includes a closed loop power control system for maintaining a minimum system transmit power level for a radio carrier station and the subscriber units, and system capacity management for maintaining a maximum number of active subscriber units for improved system performance.

Code division multiple access (CDMA) communication system

A method and apparatus for carrying out synchronous co-division multiple access (SCDMA) communication of multiple channels of digital data over a shared transmission media such as a cable television system coaxial cable, a fiber optic or copper conductor telephone link, terrestial microwave, satellite link, local or wide area network, wireless including cellur network or some combination of these media using suitable interface circuitry. The system includes modems at remote units and a central unit to receive time division multiplexed digital data arranged into timeslots or channels and uses orthogonal codes to encode each channel of multiple data and spread the energy of each channel data over a frame of data transmitted in the code domain. Spreading the data this way makes the system less susceptible to impulse noise. Frames are synchronized as between remote and central units using a ranging scheme which is also useful in any other system transmitting data by frames in a distributed system where synchronizing the frames as between all units regardless of differences in propagation delays is necessary. Each frame in the SCDMA modulation scheme includes a gap or guardband containing no other data. The ranging process involves training each remote unit to impose enough delay prior to re-transmission of a barker code received from the CU such that a barker code sent by the RU arrives at the CU during the gap. The process of setting the delay in each RU is a trial and error process, and each RU starts the ranging process asynchronously. Contention resolution protocols such that only one RU is aligning to the gap at any particular time are taught.

Apparatus and method for digital data transmission using orthogonal codes

A system for bidirectional communication of digital data between a central unit and a remote unit wherein the need for tracking loops in the central unit has been eliminated. The central unit transmitter generates a master carrier and a master clock signal which are used to transmit downstream data to the remote units. The remote units recover the master carrier and master clock and synchronize local oscillators in each remote unit to these master carrier and master clock signals to generate reference carrier and clock signals for use by the remote unit receiver. These reference carrier and clock signals are also used by the remote unit transmitters to transmit upstream data to the central unit. The central unit receiver detects the phase difference between the reference carrier and clock signals from the remote units periodically and adjusts the phase of the master carrier and master clock signals for use by the central unit receiver to receive the upstream data.

Apparatus and method for trellis encoding data for transmission in digital data transmission systems

A spread spectrum receiver with filters matched to transmitter chip codes are implemented in digital circuits along with a digital circuit for acquisition and tracking of the arrival times of the chip codes. The digital circuit implementations are used for the noncoherent demodulation of pulse position spread spectrum modulation signals where the pulse is a carrier modulator by a chip code and for the noncoherent demodulation of multiple chip code modulation signals where each information symbol is represented by one of several chip codes modulating a carrier.

Method and apparatus for the modulation of spread spectrum radio signals

Method and apparatus for the reception and demodulation of spread spectrum radio signals

A spread spectrum receiver correlator for a with filters matched to transmitter chip codes are implemented in digital circuits along with a digital circuit for acquisition and tracking of the arrival times of the chip codes The digital circuit implementations are used for the noncoherent demodulation of pulse position spread spectrum modulation signals where the pulse is a carrier modulator by a chip code and for the noncoherent demodulation of multiple chip code modulation signals where each information symbol is represented by one of several chip codes modulating a carrier

Method and apparatus for the correlation of sample bits of spread spectrum radio signals

PURPOSE: To obtain non-coherent modulation with an inexpensive and simple circuit by generating a Manchester bit sequence from the respective bits of a data bit sequence. CONSTITUTION: A Manchester generator 12 encodes the data bit sequence by a Manchester encoding bit and generates a Manchester encoded bit sequence. A chip code device 113 responds to the respective bit pairs of the Manchester sequence, replaces a second bit with a normal chip code when a first bit and the second bit match, replaces the second bit with a shortened bit code when the first bit is '1' and the second bit is '0', and replaces the second bit with an enlarged chip code when the first bit is '0' and the second bit is '2'. An inversion device 114 inverts a connection code sequence generated in the chip code device 113 pseudo-randomly, and an RF modulator 115 modulates carrier signals at pseudo random.

Jimmy K. Omura

Papers

Method and apparatus for the modulation of spread spectrum radio signals

Method and apparatus for the reception and demodulation of spread spectrum radio signals

Method and apparatus for the correlation of sample bits of spread spectrum radio signals

Method of modulation/demodulation, spectrum diffusion modulator and spectrum diffusion receiver