Apparatus and method for efficient wireless communications in the presence of frequency error
First Claim
1. A receiving means for efficient wireless communications in the presence of frequency error in a radio frequency received signal, comprising:
- a) a receiver channel having a variable bandwidth and an approximately fixed receiver mid-channel frequency;
b) a wide band frequency acquisition mode comprising a wide channel filter which initially defines said bandwidth to be greater than said frequency error in said received signal and wherein said frequency error is determined by comparing said received signal frequency to said receiver mid-channel frequency;
c) automatic frequency control means comprising at least one frequency adjustable local oscillator and which adjusts it, based upon said frequency error so determined, such that the frequency difference between said receiver mid-channel frequency and said received signal is made negligible, thereby approximately centering said received signal within said bandwidth in said wide band frequency acquisition mode;
d) a narrow band demodulation mode comprising a narrower channel filter which narrows said bandwidth of said receiver channel with respect to said wide band frequency acquisition mode and maintains approximately the same said receiver mid-channel frequency; and
e) a demodulator which demodulates said received signal in said narrow band demodulation mode.
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Accused Products
Abstract
A receiver for efficient wireless communications in the presence of frequency errors in a radio frequency received signal is disclosed. The receiver comprising a receiver channel, a wide band frequency acquisition mode, automatic frequency control, a narrow band demodulation mode and a demodulator. The receiver channel has a variable bandwidth and an approximately fixed receiver mid-channel frequency. The wide band frequency acquisition mode comprises a wide channel filter which initially defines the bandwidth to be greater than the frequency error in the received signal and wherein the frequency error is determined by comparing the received signal frequency to the receiver mid-channel frequency. The automatic frequency control comprises at least one frequency adjustable local oscillator which it adjusts based upon the frequency error such that the frequency difference between the receiver mid-channel frequency and the received signal is made negligible, thereby approximately centering the received signal within the bandwidth in the wide band frequency acquisition mode. The narrow band demodulation mode comprises a narrower channel filter which narrows the bandwidth of the receiver channel with respect to the wide band frequency acquisition mode and maintains approximately the same receiver mid-channel frequency. The demodulator demodulates the received signal in the narrow band demodulation mode. Automatic frequency control and bandwidth selection using-adaptive digital signal processing based filters is also disclosed. In this case instead of the local oscillator being adjusted to tune in the desired signal, the filter center frequency is adapted.
217 Citations
25 Claims
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1. A receiving means for efficient wireless communications in the presence of frequency error in a radio frequency received signal, comprising:
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a) a receiver channel having a variable bandwidth and an approximately fixed receiver mid-channel frequency; b) a wide band frequency acquisition mode comprising a wide channel filter which initially defines said bandwidth to be greater than said frequency error in said received signal and wherein said frequency error is determined by comparing said received signal frequency to said receiver mid-channel frequency; c) automatic frequency control means comprising at least one frequency adjustable local oscillator and which adjusts it, based upon said frequency error so determined, such that the frequency difference between said receiver mid-channel frequency and said received signal is made negligible, thereby approximately centering said received signal within said bandwidth in said wide band frequency acquisition mode; d) a narrow band demodulation mode comprising a narrower channel filter which narrows said bandwidth of said receiver channel with respect to said wide band frequency acquisition mode and maintains approximately the same said receiver mid-channel frequency; and e) a demodulator which demodulates said received signal in said narrow band demodulation mode. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A method for achieving efficient wireless communications in the presence of frequency errors in a radio frequency received signal, comprising the steps of:
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a) providing a receiving means which receives said received signal and which has at least one frequency adjustable local oscillator; b) selecting a receiver channel for said receiving means with a wide band frequency acquisition mode bandwidth greater than any frequency error in said received signal and having a receiver mid-channel frequency; c) determining said frequency error between said received signal and said receiver mid-channel frequency; d) applying automatic frequency control which responds to said frequency error and which adjusts the frequency of said at least one frequency adjustable local oscillator such that the frequency difference between said receiver mid-channel frequency and said received signal is made negligible, thereby approximately centering said received signal within said wide band frequency acquisition mode bandwidth; and e) switching from said wide band frequency acquisition mode bandwidth to a narrow band demodulation mode bandwidth while maintaining approximately fixed receiver mid-channel frequency; and f) demodulating said received signal. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22, 23)
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24. A method for achieving efficient wireless communications in the presence of frequency errors in a radio frequency received signal, comprising the steps of:
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a) providing a receiving means which receives said received signal and which has at least one frequency adjustable local oscillator; b) selecting a receiver channel for said receiving means with a bandwidth greater than any frequency error in said received signal and having a receiver mid-channel frequency; c) adjusting automatically the frequency of said at least one frequency adjustable local oscillator based upon said frequency error such that the frequency difference between said receiver mid-channel frequency and said received signal is made negligible, thereby centering said received signal within said bandwidth; d) narrowing said bandwidth; and e) demodulating said received signal.
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25. A method for achieving efficient wireless communications in the presence of frequency errors in a radio frequency received signal, comprising the steps of:
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a) providing a receiving means which receives said received signal and which has at least one adaptive digital signal processing based filter with a center frequency; b) selecting a receiver channel for said receiving means with a bandwidth greater than any frequency error in said received signal and having a receiver mid-channel frequency; c) determining the frequency error between said received signal and said receiver mid-channel frequency; d) adjusting automatically said center frequency of said at least one adaptive digital signal processing based filter based upon said frequency error such that the frequency difference between said center frequency and said received signal is made negligible, thereby centering said received signal within said bandwidth; e) narrowing said bandwidth; and f) demodulating said received signal.
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Specification