National Semiconductor Corporation

Comsys Communication & Signal Processing Ltd.

Ophir Shabtay

Ehud Reshef

Israel Greiss

Gideon Intrater

Yaniv Avital

Alexander Kleinerman

Ariel Zaltsman

Ohad Falik

Alon Eran

David Almagor

Tzvia Weisman

Gil Montag

Rami Drucker

Jacob Schelm

A method and apparatus for estimating channel tap delays of multipath components in a CDMA received signal. The search for the tap delays are split into two phases namely, a phaseand a phasesearch. The phasesearch is a coarse resolution quick search adapted to generate a rough estimate of the location of the tap delays. During this phase, the candidate codes are summed and the input signal correlated with the code sum creating an ambiguity in the code associated with the multipath. A finer resolution slower phasesearch resolves the code ambiguity present in the initial rough estimates of the phasesearch. Additional phasecorrelations may be performed to implement a code-tracking loop.

Multipath channel tap delay estimation in a CDMA spread spectrum receiver

A novel and useful whitening matched filter (WMF) for use in a communications receiver. The WMF is constructed by cascading a matched filter and a noise-whitening filter. The response of the matched filter is derived from the time reversed complex conjugate of the channel impulse response. The whitening filter is derived by extracting the minimum phase portion of the mixed phase channel impulse response using homomorphic deconvolution. The whitening filter is implemented using either an FIR or IIR filter adapted to process the data received before and after the training sequence using a minimum phase system in a direction in time opposite to that of the direction of corresponding data sample processing performed by the equalizer.

Whitening matched filter for use in a communications receiver

A multiprocessor system includes a plurality of processors. A debugger interface includes interface circuitry to interface the plurality of processors to a debugger. The debugger interface includes means for receiving a debugger command from the debugger. Debugger command directing means determines from the debugger command for which of at least one of the plurality of processors the debugger command is intended, directs the debugger command, via the interface circuitry to the at least one intended processor. A processor command is received from one of the plurality of processors, and processor command directing means directs the processor command, received from the one processor, via the interface circuitry to the debugger. The system is especially suited for debugging software that is executing on the plurality of processors of the multiprocessor system.

Multi-processor element provided with hardware for software debugging

Near-end echo-reduction is achieved by passing a transmit signal through a first filter bank and feeding a remote signal plus an echo of the transmit signal through a second filter bank, then subtracting a gain-coefficient-compensated (scaled) version of the filtered transmit signal from the filtered-composite-remote signal to obtain an echo-reduced receive signal. The echo-reduced receive signal is suitably employed by tone decoders, voice response mechanisms, and the like, in a telephone system, and avoids false alarms due to near-end echo. In one embodiment, the gain coefficients are fixed for each frequency of interest. In another embodiment, the gain coefficients are dynamically arrived at based on the filtered transmit signal and the echo-reduced receive signal. The two filter banks can be combined in one, multiplexed filter bank.

Band-energy near-end echo reducer for tonal signalling detectors

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Haifa, Israel

Ophir Shabtay