Mobile radiotelephone station two-way ranging system
First Claim
1. In a system for communication of radio signals including a predetermined tone and other information signal frequencies and including means for comparing (41) the phases of transmitted and transponded versions of said predetermined tone and integrating (53) the output of the comparing means to indicate range between transmitting and transponding stations of the system, the phase comparing means being CHARACTERIZED IN THAT they comprisemeans for processing (46) said transmitted tone to produce a wave at a fraction of the frequency of said transmitted tone,means for processing (40) said transponded tone to produce a wave at a frequency which is a fraction of the frequency of said transponded tone, andmeans for providing (41) a binary indication in a first state when said fractional-frequency waves are of the same polarity and in a second state when they are of different polarities.
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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. The same received call signal is also separately processed 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.
51 Citations
14 Claims
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1. In a system for communication of radio signals including a predetermined tone and other information signal frequencies and including means for comparing (41) the phases of transmitted and transponded versions of said predetermined tone and integrating (53) the output of the comparing means to indicate range between transmitting and transponding stations of the system, the phase comparing means being CHARACTERIZED IN THAT they comprise
means for processing (46) said transmitted tone to produce a wave at a fraction of the frequency of said transmitted tone, means for processing (40) said transponded tone to produce a wave at a frequency which is a fraction of the frequency of said transponded tone, and means for providing (41) a binary indication in a first state when said fractional-frequency waves are of the same polarity and in a second state when they are of different polarities.
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2. In a system for communication of radio signals including at least a predetermined tone and including means (34) for indicating approximate range through which received radio signals have been propagated, the improvement comprising
means for detecting (24) the presence or absence of said predetermined tone in said received radio signals, and means, responsive to an output of said detecting means, for inhibiting (72, 58) operation of said indicating means during an interval of radio signal level reduction sufficient to cause said detecting means to indicate absence of said predetermined tone.
Specification