Phase difference based frequency correction channel detector for wireless communication system
AssigneeSpreadtrum Communications Corporation
InventorsJingdong Lin, Justine Zhuang, Tong Zhao
Life of this patent
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Abstract
A method of detecting a tone signal from complex input samples r(n) in a wireless communication system is disclosed. The method comprises calculating the phase difference of the samples r(n) as a signal x(n). Next, the signal x(n) is filtered with a notch filter to generate a notched output y(n). The power of both the signal x(n) and the notched output y(n) is estimated. The ratio of the powers of the notched output y(n) and signal x(n) is calculated. The tone signal is detected if the ratio is below a predetermined threshold for a predetermined duration of time.
Claims23
A method of detecting a tone signal from complex input samples r(n), said method comprising:
- (a) calculating the phase difference of the samples r(n) as a signal x(n);
- (b) filtering said signal x(n) with a notch filter to generate a notched output y(n);
- (c) estimating a power E(n) of said notched output y(n);
- (d) estimating a power P(n) of said signal x(n);
- (e) forming a ratio of said powers from said notched output y(n) and said signal x(n);
- (f) declaring said tone signal detected if said ratio satisfies a constraint.
A method of detecting a frequency correction tone signal from an input signal r(n) comprising:
- (a) determining a phase difference signal c(n) of the input signal r(n);
- (b) filtering said phase difference signal c(n) using a low pass filter to provide a filtered signal x(n);
- (c) notch filtering said filtered signal x(n) with a notch filter to generate a notched filtered signal y(n);
- (d) calculating a power estimate E(n) of said notched filtered signal y(n);
- (e) calculating a power estimate P(n) of said filtered signal x(n);
- (f) forming a ratio of said power estimates as E(n)/P(n);
- (g) comparing said ratio with a predetermined threshold, and if said ratio is continuously lower than a predetermined threshold for a predetermined duration in the case of said ratio being formed as E(n)/P(n), and if said ratio is continuously higher than said predetermined threshold for a predetermined duration in the case of said ratio being formed as P(n)/E(n), declaring that said frequency correction tone signal is detected.
A detector for detecting a tone signal from complex input samples r(n), said detector comprising:
- (a) a phase differentiator for calculating the phase difference of the samples r(n) as a signal x(n);
- (b) a notch filter that filters said signal x(n) to generate a notched output y(n);
- (c) a first power estimator for estimating a power of said notched output y(n);
- (d) a second power estimator for estimating a power of said signal x(n);
- (e) a ratio calculator for determining a ratio of said powers from said notched output y(n) and said signal x(n);
- (f) a processor for determining if said ratio satisfies a constraint and declaring said tone signal is detected if said constraint is satisfied.
Dependencies are inferred from the claim text.