Mobile radiotelephone station two-way ranging system
First Claim
1. In a system for communication of radio signals including a predetermined tone, a plurality of tones, including said predetermined tone, being used in said system, circuitry (24) for detecting the presence of said predetermined tone in received signals for a predetermined signal channel and being CHARACTERIZED IN THAT there are providedmeans, responsive to said received signals, for producing (31, 32) a further tone corresponding to the presence in said received signals of only a predetermined one of said plurality of tones and that is much closer in frequency to a spectral spacing frequency between adjacent ones of said plurality of tones than it is to the frequency of any of said plurality of tones, andmeans having a responsive frequency bandwidth less than said spectral frequency for detecting (36) said producing means further tone.
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Accused Products
Abstract
Some cellular mobile radiotelephone systems use tones for certain call connection supervisory functions on radio links. The presence of the correct tone in a received radio channel call signal is determined by using the received signal for producing (32) a lower frequency tone that is readily selectable (36) from similar tones produced in response to incorrect supervisory tones. Circuits are also shown for separately processing received call signals to produce (41, 53) supervisory tone phase information that is indicative of range between communicating stations. Several circuits (72; 40 and 46; 59-62) are shown for enhancing the accuracy of the produced phase information of the correct tone.
53 Citations
8 Claims
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1. In a system for communication of radio signals including a predetermined tone, a plurality of tones, including said predetermined tone, being used in said system, circuitry (24) for detecting the presence of said predetermined tone in received signals for a predetermined signal channel and being CHARACTERIZED IN THAT there are provided
means, responsive to said received signals, for producing (31, 32) a further tone corresponding to the presence in said received signals of only a predetermined one of said plurality of tones and that is much closer in frequency to a spectral spacing frequency between adjacent ones of said plurality of tones than it is to the frequency of any of said plurality of tones, and means having a responsive frequency bandwidth less than said spectral frequency for detecting (36) said producing means further tone.
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4. In a system for communication of radio signals including a predetermined tone and other information signal frequencies, a plurality of tones, including said predetermined tone, being used for call status supervisory functions, a circuit (24) for detecting the presence of said predetermined tone in received call signals for a predetermined signal channel CHARACTERIZED IN THAT there are provided
means for producing (31) a tone at a frequency equal to the sum of said predetermined supervisory tone frequency and a predetermined frequency Δ - f which is much less than said supervisory tone but greater than a spectral spacing frequency between different ones of said supervisory tones employed in said system,
means for modulating (32) said producing means tone with said received signals, and means for detecting (36) said frequency Δ
f in an output of said modulating means, said detecting means having a responsive frequency bandwidth which is much less than said spectral spacing frequency between tones. - View Dependent Claims (5, 6)
- f which is much less than said supervisory tone but greater than a spectral spacing frequency between different ones of said supervisory tones employed in said system,
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7. In a system for communication of radio signals in a channel including information signal frequencies and one of a predetermined plurality of tones, the method for detecting the presence in received signals of said one tone to the exclusion of others of said plurality of tones, said method comprising the steps of
modulating signals received in said channel with a local tone at a frequency differing from said one tone by a frequency Δ - f which is much less than the frequency of said one tone, but greater than a spectral spacing frequency between the highest and lowest frequency ones of said plurality of tones, and
detecting in an output of said modulating step the presence of said frequency Δ
f to indicate reception of said one tone, this detecting step being performed in a detection bandwidth that rejects difference frequencies between said local tone and tones of said plurality of tones other than said one tone. - View Dependent Claims (8)
- f which is much less than the frequency of said one tone, but greater than a spectral spacing frequency between the highest and lowest frequency ones of said plurality of tones, and
Specification