Cellnet Data Systems, Inc.

Schlumbergersema Inc.

Schlumberger Resource Management Systems, Inc.

Erik A Ramberg

Forrest F Fulton

Robert K Froelich

A digitally sampled spread spectrum signal is received, despread, and accumulated at a center frequency lower than the sampling rate and higher than zero.

Bandpass processing of a spread spectrum signal

A receiver for use in a spread spectrum communication system includes the following components: an acquisition system configured to detect a transmitted spread spectrum signal by simultaneously correlating multiple search phases of a reference spreading signal against an output from a receiver channel; a demodulation system configured to recover data embedded in the spread spectrum signal by simultaneously correlating the spread spectrum signal with multiple possible data phases of the reference spreading signal over consecutive data periods; and a bank of correlating devices configured for use both in the acquisition system and in the demodulation system.

Receiving a spread spectrum signal

A spread spectrum signal is processed after it is sampled at a selected sampling rate and tuned to a center frequency lower than the sampling rate and greater than zero. The signal is multiplied against a reference signal to produce a corresponding product output, and an accumulation output is formed by combining the product output with a phase-shifted version of the accumulation output.

Bandpass correlation of a spread spectrum signal

A spread spectrum signal is detected at an unknown spreading signal phase by sampling the signal at a selected sampling rate and performing a despreading function on the sampled signal using multiple reference signals, each of which represents one of multiple search phases of the spreading signal. Accumulation outputs then are produced by combining each despreading output with a phase-shifted version of the corresponding accumulation output.

Acquiring a spread spectrum signal

A spread spectrum signal sampled at a selected sampling rate is despread and accumulated in an accumulation element at a center frequency lower than the sampling rate and higher than zero. A frequency adjustment element may be used to adjust the accumulation element to have a resonant frequency approximately equal to the center frequency.

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Erik A Ramberg