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AssigneeInfineon Technologies AG
InventorMichael Lewis
Life of this patent
Estimating the term…
Abstract
In an apparatus and method for detecting a preamble in a message a shorter initial average is used to estimate the peak position peak symbol duration, and then the number of subsequent delay stages is reduced to 1 per symbol where the chosen peak position is stored along with the corresponding intermediate detection value. At the output, a weighting function is applied to eliminate detection values inconsistent with a symbol-spaced signal output.
Claims18
An apparatus for detecting a preamble in a message, wherein said preamble comprises symbols having a first transmission rate, fs, each of said symbols is overlaid with a known binary sequence having a second transmission rate, fc, and having low autocorrelation for lags other than zero, said apparatus comprises:
- a first correlator arranged to correlate a received signal with said known binary sequence producing a sequence of first correlation values, wherein each of said correlation values indicates that correlation between said received signal and said known binary sequence,
- a second correlator provided to receive said first correlation values from said first correlator and correlate said first correlation values with said symbols producing a corresponding sequence of second correlator values indicating the correlation between said first correlation values and said symbols,
- a peak selector provided to receive said first and second correlation values and to select a correlation value form a received set of first correlation values having the largest corresponding second correlation value producing a sequence of selected correlation values and a sequence of position values indicating the position of said selected correlation value in said set of first correlation values, and
- a third correlator provided to receive said selected correlation values and said position values and correlate said received selected correlation values with symbols in said preamble by weighting each selected correlation value depending on the relation between the position of said selected correlation value and the position of other selected correlation values, and combining said weighted selected correlation values to produce a result indicative of the detection of said preamble.
A method for detecting a preamble in a message wherein said preamble comprises symbols having a first transmission rate, f8, each of said symbols is overlaid with a known binary sequence having a second transmission rate, fc and having low autocorrelation for lags other than zero, comprising the steps of:
- correlating a received signal with said known binary sequence to produce a sequence of first correlation values wherein each of said correlation value indicates the amount of correlation between said received signal and said known binary sequence,
- correlating said first correlation values with a fraction of the symbols in said preamble to produce a corresponding sequence of second correlation values indicating the correlation between said first correlation values and said symbols,
- forming a sequence of arrays wherein each of said array comprises a number of said first correlation values, and wherein said number of said first correlation values is equal to the number of first correlation values received during a symbol time Ts,
- selecting the first correlation value from each of said of arrays having the largest corresponding second correlation value,
- forming a sequence of selected correlation values from said selected first correlation values,
- forming a sequence of position values wherein each of said position value is the position for a corresponding selected correlation value in said array of first correlation values, and
- for each selected correlation value and corresponding position value in said sequence of selected correlation values and sequence of position values performing:
- a) forming a set S of N subsequent selected correlation values and N position values,
- b) calculating a centre position value from said N position values,
- c) calculating a weight value for each position value in said set S wherein said weight value is inversely related to the minimum distance between said position value and said centre position value and where said distance is calculated in a circular manner so that the maximum position value is regarded to be next to the minimum position value, to form N weight values,
- d) multiplying each of said selected correlation values with a corresponding weight value,
- e) combining said N weighted selected correlation values to form a value indicating the correlation between said received signal and said preamble.
Dependencies are inferred from the claim text.