Exelis Inc.

Itt Manufacturing Enterprises, Inc.

Harris Global Communications, Inc.

Terrance Wayne Charbonneau

William Ellis Rodgers

Bruce Edward Reidenbach

Gregory Thomas Barnett

John P Johnston

Gregory T Barnett

A technique for equalizing a distributed pilot OFDM signal with decision feedback involves correlating a received OFDM signal against a pilot reference to obtain a coarse channel estimate, where the received OFDM signal includes a distributed pilot signal and an OFDM data signal. The received OFDM signal is equalized based on the coarse channel estimate and the distributed pilot signal is removed to generate a coarse data signal estimate. The coarse data signal estimate is removed from the received OFDM signal using the coarse channel estimate to generate a residual pilot signal. The residual pilot signal can then be correlated against the pilot reference to obtain a fine channel estimate. The received OFDM signal is equalized based on the fine channel estimate, and the distributed pilot signal is removed to produce a fine data signal estimate from which data is recoverable.

Equalization of a distributed pilot OFDM signal

A technique for removing a band-limited distributed pilot signal from an orthogonal frequency division multiplexed (OFDM) signal involves converting a received OFDM signal, which includes a distributed pilot signal and an OFDM data signal, into a frequency domain signal having populated frequency bins containing respective subcarrier signals, each including a constituent data signal of the OFDM data signal and component pilot signal of the distributed pilot signal. An average magnitude of the populated frequency bins is determined based on the absolute values of the complex components of the populated frequency bins of the frequency domain signal, and the average magnitude of the populated frequency bins is used to estimate a pilot signal magnitude. The distributed pilot signal is removed from the frequency domain signal using a stored replica of the pilot signal scaled in conjunction with the pilot signal magnitude to yield the OFDM data signal.

Removal of a band-limited distributed pilot from an OFDM signal

A technique for applying crest factor reduction to a signal involves identifying peaks of an oversampled digital signal that exceed a threshold and generating a correction waveform corresponding to a sequence of correction pulses for respective peaks. The correction waveform is applied to the oversampled digital signal via a delta-sigma modulator to generate an oversampled digital output signal with reduced peaks. The delta-sigma modulator causes most of the energy of the correction waveform in the oversampled digital output signal to fall outside a frequency band of the oversampled digital signal. The oversampled digital output signal is low pass filtered to remove energy outside the frequency band of the oversampled digital signal such that noise introduced into the oversampled digital output signal by the correction waveform is reduced. The oversampled digital output signal is down sampled to produce a digital output signal with a lower sampling rate.

Application of crest factor reduction to a signal

The invention includes a method of communicating in a network of multiple nodes transmitting and receiving messages to and from each other. The method includes (a) scanning in synchronism a receive directional beam of an antenna of a first node and a receive directional beam of an antenna of a second node; (b) steering, in azimuth, a transmit directional beam of an antenna of the first node to a relative bearing of the second node; and (c) transmitting a message from the first node to the second node, when the transmit directional beam of the first node and the receive directional of the second node are substantially aligned in relative bearing to each other.

Method of steering smart antennas

A technique for down converting signals from an Intermediate Frequency (IF) input signal to Inphase (I) and Quadrature (Q) signal samples at baseband replaces power-consuming A/D converters and AGC circuits with a low-cost zero-crossing comparator. The comparator converts the IF signal to a hard-limited signal having one value when the IF signal is positive and another value when the IF signal is negative. I and Q samples are generated by performing the equivalent of multiplication of the hard-limited signal by cos(2&#x3c0;fo*t) and sin(2&#x3c0;fo*t). By sampling the hard-limited signal at a rate that is an integer multiple of the intermediate frequency and an even number greater than or equal to four, multiplication by cos(2&#x3c0;f*t) and sin(2&#x3c0;f*t) required to generate I and Q baseband signal components is greatly reduced. The I and Q samples are summed (or integrated) by binary up/down counters over one bit duration and then dumped. The dumped counter outputs are estimates of the lowpass filtered I and Q signal components.

Growing community of inventors

Fort Wayne, IN, United States of America

Terrance Wayne Charbonneau