Intellon Corporation

Timothy J Vander Mey

James E Vander Mey

A transversal adaptive finite impulse response (FIR) filter is modified for automatically filtering modulated signal components from a received signal based on frequency modulation rate. Coefficients of the filter are adapted to provide for filtering of signals having undesired modulation rates. The adapting operation includes selectively updating the coefficients using an error signal and iteratively decaying all the coefficients towards zero. The adaptation of the filter coefficients ensures symmetrical coefficient growth and introduces a constant group delay to the received signal to provide for filtering of complex signal components from a received signal according to frequency modulation rate without the use of a reference source.

Automatic adaptive filtering according to frequency modulation rate

Spread spectrum chirps (i.e., wideband frequency packets) are propagated on a local area network in a hostile communications environment, such as a powerline or a crowded radio frequency band. Chirps are self-synchronizing, data bit (or subdata bit) in length and detectable by all network nodes, to allow the contention resolution and collision detection needed to support carrier-sense based network protocols. A matched filter of the same time length and encoding sequence as the transmitted chirp provides the self-synchronized chirp reception at each receiver.

Spread spectrum communications system for network

Spread spectrum communication using direct sequences that approximate a swept frequency waveform in which successive square waves are formed by the chips making up the sequence, and in which the durations of the square waves extend over a plurality of chips, and in which the frequency of the square waves varies across at least a portion of the sequence. Information is encoded by varying the direction of the direct sequence, so that the sequence is transmitted as either a forward or a reverse frequency-swept sequence. The spectrum of the direct sequences is in a passband. The direct sequence biphase modulates a carrier (e.g., RF) to produce a spread-spectrum signal with two passbands centered about the frequency of the modulated carrier. Received signals are fed to a correlator having forward and reverse sequence outputs, the outputs of the correlator are independently tracked, and generally different sampling times are used for taking samples of the forward and reverse correlator outputs for purposes of making decoding decisions. The receiver uses a local oscillator for demodulation that is not synchronized with the local oscillator used for modulation in the transmitter. The overall phase of successive direct sequences is pseudorandomly varied to produce a more uniform spreading of energy across the frequency band. Dual level coding is used, in which a quality and value outputs from the lower level decoding are used to provide, in effect, a correlator for the higher level decoding. Both 0 and 90 degree matched filter sections are provided to make the correlator insensitive to phase shifts.

Spread spectrum communication system particularly-suited for RF network

A method of transmitting and receiving data packets across a noisy communication medium, e.g., an AC power line. The data packets are transmitted using spread-spectrum chirps. A first sequence of the chirps forms a contention-resolution preamble used by transmitters to resolve conflicting contentions for access to the communication medium. The preamble is followed by a second sequence of chirps that form a start-of-packet symbol used by receivers to delineate the start of data within the packet. To simplify detection at the receiver, identical chirps are used in the preamble and the start-of-packet symbol. To enable the receiver to avoid erroneously interpreting preamble chirps as start-of-packet chirps, and thereby erroneously begin to accept packet data, chirps in the preamble are transmitted at a different pitch (i.e., different time period between inception of successive chirps) from chirps in the start-of-packet symbol.

Timing for spread-spectrum communication across noisy media

Spread spectrum chirps (i.e., wideband frequency packets) are propagated on a local area network in a hostile communications environment, such as a powerline or a crowded radio frequency band. Chirps are self-synchronizing, data bit (or subdata bit) in length and detectable by all network nodes, to allow the contention resolution and collision detection needed to support carrier-sense based network protcols. A matched filter of the same time length and encoding sequence as the transmitted chirp provides the self-synchronized chirp reception at each receiver.

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Ocala, FL, United States of America

Timothy J Vander Mey