Acquiring a spread spectrum signal
First Claim
Patent Images
1. An apparatus for use in detecting a spread spectrum signal at an unknown spreading signal phase, the apparatus comprising:
- accumulation devices that receive a signal sampled from the spread spectrum signal at a selected sampling rate and centered at a center frequency lower than the sampling rate and higher than zero, each accumulation device including;
a despreading element configured to perform a despreading function on the sampled signal using a reference signal representing one of multiple search phases of the spreading signal;
an accumulation element configured to receive a despreading output centered at the center frequency from the despreading element and produce an accumulation output by combining the despreading output with a phase-shifted version of the accumulation output; and
wherein the accumulation element in each accumulation device is configured to clear the accumulation output periodically.
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Abstract
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.
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Citations
21 Claims
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1. An apparatus for use in detecting a spread spectrum signal at an unknown spreading signal phase, the apparatus comprising:
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accumulation devices that receive a signal sampled from the spread spectrum signal at a selected sampling rate and centered at a center frequency lower than the sampling rate and higher than zero, each accumulation device including;
a despreading element configured to perform a despreading function on the sampled signal using a reference signal representing one of multiple search phases of the spreading signal;
an accumulation element configured to receive a despreading output centered at the center frequency from the despreading element and produce an accumulation output by combining the despreading output with a phase-shifted version of the accumulation output; and
wherein the accumulation element in each accumulation device is configured to clear the accumulation output periodically. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. An apparatus for use in detecting a spread spectrum signal at an unknown phase of a spreading signal that cycles through a known number of discrete steps, the apparatus comprising:
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correlation devices, at least one more than the number of discrete steps in one cycle of the spreading signal, each correlation device including;
a despreading element configured to produce an output signal centered at a center frequency lower than the sampling rate and higher than zero by applying a despreading function to the spread spectrum signal using a reference signal representing one of multiple search phases of the spreading signal;
an accumulation element configured to accumulate the output signal from the despreading element; and
wherein the correlation devices simultaneously search for the spread spectrum signal at a selected carrier frequency which is updated periodically; and
a processing element configured to receive the accumulated output signal from each correlation device and to determine whether any accumulated output signal signifies detection of a spread spectrum signal. - View Dependent Claims (12)
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13. A method for use in detecting a spread spectrum signal at an unknown spreading signal phase, the method comprising:
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producing despreading outputs centered at a center frequency lower than the sampling rate and higher than zero by performing a despread function on a signal sampled from the spread spectrum signal at a selected sampling rate using multiple reference signals, each representing one of multiple search phases of the spreading signal;
producing accumulation outputs by combining each despreading output with a phase-shifted version of the corresponding accumulation output; and
clearing each accumulation output periodically. - View Dependent Claims (14, 15, 16, 17, 18, 19)
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20. A receiver for use in processing a spread spectrum signal comprising:
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an acquisition system configured to detect the spread spectrum signal at an unknown spreading signal phase and including accumulation devices that receive a signal sampled from the spread spectrum signal at a selected sampling rate and centered at a center frequency lower than the sampling rate and higher than zero, each accumulation device including;
a despreading element configured to perform a despreading function on the sampled signal using a reference signal representing one of multiple search phases of the spreading signal;
an accumulation element configured to receive a despreading output centered at a center frequency lower than the sampling rate and higher than zero from the despreading element and produce an accumulation output by combining the despreading output with a phase-shifted version of the accumulation output and a frequency adjustment element to periodically adjust the center frequency to a different frequency.
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21. A receiver for use in processing a spread spectrum signal comprising:
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an acquisition system configured to detect the spread spectrum signal at an unknown phase of a spreading signal that cycles through a known number of discrete steps and including correlation devices, at least one more than the number of discrete steps in one cycle of the spreading signal, each correlation device including;
a despreading element configured to produce an output centered at a center frequency lower than the sampling rate and higher than zero by applying a despreading function to the spread spectrum signal using a reference signal representing one of multiple search phases of the spreading signal;
an accumulation element configured to accumulate the output signal from the despreading element;
wherein the correlation devices simultaneously search for the spread spectrum signal at a selected carrier frequency, with the carrier frequency being updated periodically; and
a processing element configured to receive the accumulated output signal from each correlation device and to determine whether any accumulated output signal signifies detection of a spread spectrum signal.
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Specification