Itt Manufacturing Enterprises, Inc.

Exelis Inc.

Itt Manufacturing, Inc.

Michael Mayor

Ning H Lu

Dennis D McCrady

Eric A Whitehill

Donald John Rasmussen

Ning Hsing Lu

Charles A Simmons, Jr

Robert D Martin

John H Gass

Mhairi N McCune

David W Lagrow

Lester G Matheson

Enhanced reception in a communication system is achieved by synchronously combining transmissions from a cluster of transmitting communication devices at a group of distant receiving communication devices. The transmitting communication devices coordinate their transmissions such that each device transmits the same signal on the same communication channel at different transmission times. As a consequence of the spatial diversity of the transmitting and receiving communication devices and the temporal diversity of the transmission times, the transmitted signals arrive at the receiving communication devices at different times. The receiving communication devices each essentially treat the different transmitted signals as though they were different multipath signals from a single transmitting communication device. This permits detection at a greater range or with a lower bit error rate. In addition, the many-to-many configuration enables a communication protocol to be maintained without modification of the protocol or termination (or interruption) of a protocol message sequence.

Method and apparatus for cooperative communications between groups of communication units

A Direct Sequence Spread Spectrum receiver is described in which a complex spread spectrum signal is cross correlated by four digitally matched filters. The filters and subsequent multipliers correlate the in-phase and quadrature components as well as the current and previous symbols. The result is a more robust signal acquisition at very low signal to noise ratios.

Method and apparatus for robust acquisition of spread spectrum signals

Enhanced reception of transmitted signals in a communication system is achieved by synchronously combining transmissions from a cluster of transmitters at a distant receiver. The transmitters coordinate transmissions such that each substantially simultaneously transmits the same signal on the same communication channel. As a consequence of the spatial diversity of the transmitters, the transmitted signals arrive at the receiver at different times. The receiver essentially treats the different transmitted signals as though they were different multipath signals from a single transmitter. A multipath equalizer or combiner is used to determine timing offsets among the received signals, and the received signals are time aligned by phase rotating the signals in accordance with the estimated timing offsets. The time-aligned signals are then coherently combined and detected. The combined signal has a greater signal-to-noise ratio than the individual received signals, permitting detection at a greater range or with a lower bit error rate.

Methods and apparatus for synchronously combining signals from plural transmitters

A radio communication unit employs passive devices and a loop filter to receive a coded frequency modulated wakeup or synchronization signal that enables the receiving radio unit and initiates communications. The loop filter simultaneously tracks phase and frequency and provides smoothing to enable synchronization with weak signals (e.g., signals that typically do not enable a standard phase locked loop (PLL) to lock). In particular, when the communication unit is in a standby mode, the passive circuits of the present invention are receiving energy from a unit antenna and initially function as a phase locked loop (PLL) to lock onto an incoming signal. The wakeup or synchronization signal includes a series of tones at different frequencies, where the specific sequence is prearranged between the transmitting and receiving units. When each tone in the sequence has been detected by the receiving unit, the unit is enabled for communications.

Method and apparatus for securely enabling a radio communication unit from standby mode

Operational parameters for transmitting a signal over a communication channel of a network are selected by first determining RF conditions on the communication channel from a received signal transmitted over the communication channel. An initial set of parameter values is selected for transmitting the signal based on RF conditions determined from the received signal. The initial set of parameter values is used to identify other sets of parameter values as other potential candidates for transmitting the signal. The parameter values in the other sets of parameter values differ from parameter values in the initial set of parameter values by less than a predetermined amount. The expected performance of the candidate sets of parameter values is compared to determine which set of parameter values has the best expected performance among the candidate sets of parameter values. The signal is transmitted on the communication channel using the selected set of parameter values.

Methods and apparatus for organizing selection of operational parameters in a communication system

An EMI testing scheme involves analyzing an analog input signal in frequency band segments. The input signal is passband filtered and digitally sampled before being converted to a complex analytic signal via a Hilbert transform filter and then transformed into a frequency domain signal via a Discrete Fourier Transform (DFT). Pre-stored frequency window filters are then applied to the frequency domain signal. The set of discrete filter sample points which form the window filters are designed such that particular frequency sub-bands of a desired bandwidth within the frequency segment are selected for EMI analysis. By applying different frequency window filters to the frequency domain signal, different frequency sub-bands are sequentially selected for analysis. An inverse DFT transforms the filtered signal back to the time domain, and the peak voltage of the time domain signal is compared with a threshold to determine whether EMI levels within the selected sub-band are acceptable.

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Fort Wayne, IN, United States of America

Michael Mayor