Coherence frequency determining system and associated radio apparatus
First Claim
1. An apparatus for determining frequency of a radio frequency signal comprising:
- a counter for counting zero amplitude transitions of a radio frequency signal in each of a plurality of time periods of identical duration;
a first register for storing counted zero amplitude transitions for a selected one of the time periods;
a second register for storing an accumulated count of zero amplitude transitions counted during a total counting time including the plurality of time periods; and
comparing means for comparing counted zero amplitude transitions for each time period other than the selected time period with the counted zero amplitude transitions for the selected time period, the second register discarding the accumulated count if the counted zero amplitude transitions for any of the time periods other than the selected time period are different from the counted zero amplitude transitions for the selected time period by more than a quantization error, wherein the frequency of the radio frequency signal is indicated by the accumulated count stored in the second register when the total counting time ends.
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Accused Products
Abstract
The invention provides an apparatus and a method for determining the frequency of a radio frequency signal. The coherency of a received signal is determined and only the frequency of a coherent signal is determined. Zero amplitude transitions of coherent signals are counted in respective time periods. If the counts in each time period agree within a quantization error, the accumulated counts for a fixed time period are employed to determine a frequency. The frequency determining apparatus and method are particularly useful with a frequency agile radio receiver for detecting the presence of radio frequency signals from nearby mobile and stationary transmitters. Upon determination of the frequency of the nearby transmitter, the channel of transmission can be determined from a memory within the receiver and the receiver can be tuned to monitor the transmission. Additional tests to verify the frequency determination may be applied using squelch and window detector circuits of the radio receiver.
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Citations
28 Claims
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1. An apparatus for determining frequency of a radio frequency signal comprising:
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a counter for counting zero amplitude transitions of a radio frequency signal in each of a plurality of time periods of identical duration; a first register for storing counted zero amplitude transitions for a selected one of the time periods; a second register for storing an accumulated count of zero amplitude transitions counted during a total counting time including the plurality of time periods; and comparing means for comparing counted zero amplitude transitions for each time period other than the selected time period with the counted zero amplitude transitions for the selected time period, the second register discarding the accumulated count if the counted zero amplitude transitions for any of the time periods other than the selected time period are different from the counted zero amplitude transitions for the selected time period by more than a quantization error, wherein the frequency of the radio frequency signal is indicated by the accumulated count stored in the second register when the total counting time ends. - View Dependent Claims (2, 3, 4)
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5. A method of determining frequency of a radio frequency signal comprising:
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counting zero amplitude transitions of a radio frequency signal in each of a plurality of time periods of identical duration; storing counted zero amplitude transitions for a selected one of the time periods; storing an accumulated count of zero amplitude transitions during a total counting time including the plurality of time periods; comparing counted zero amplitude transitions for each time period other than the selected time period with the counted zero amplitude transitions for the selected time period; discarding the accumulated count if the counted zero amplitude transitions for any of the time periods other than the selected time period are different from the counted zero amplitude transitions for the selected time period by more than a quantization error; accumulating counted zero amplitude transitions until the total counting time is reached; and determining the frequency of the radio frequency signal from the accumulated count stored when the total counting time is reached. - View Dependent Claims (6, 7, 8)
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9. A radio apparatus comprising:
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a radio receiver including an antenna for collecting electromagnetic energy, and receiver circuits for processing radio frequency signals received through the antenna and for producing an output, and a frequency determining apparatus including a counter for counting zero amplitude transitions of a radio frequency signal in each of a plurality of time periods of identical duration; a first register for storing counted zero amplitude transitions for a selected one of the time periods; a second register for storing an accumulated count of zero amplitude transitions counted during a total counting time including the plurality of time periods; and comparing means for comparing counted zero amplitude transitions for each time period other than the selected time period with the counted zero amplitude transitions for the selected time period, the second register discarding the accumulated count if the counted zero amplitude transitions for any of the time periods other than the selected time period are different from the counted zero amplitude transitions for the selected time period by more than a quantization error, wherein the frequency of the radio frequency signal is indicated by the accumulated count stored in the second register when the total counting time ends and the frequency determining apparatus supplies the frequency determined to the radio receiver for tuning the radio receiver. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16, 17)
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18. A method of tuning a radio receiver to a channel including a frequency of a received radio frequency signal comprising:
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counting zero amplitude transitions of a radio frequency signal in each of a plurality of time periods of identical duration; storing counted zero amplitude transitions for a selected one of the time periods; storing an accumulated count of zero amplitude transitions during a total counting time including the plurality of time periods; comparing counted zero amplitude transitions each time period other than the selected time period with the counted zero amplitude transitions for the selected time period; discarding the accumulated count if the counted zero amplitude transitions for any of the time periods other than the selected time period are different from the counted zero amplitude transitions for the selected time period by more than a quantization error accumulating counted zero amplitude transitions until the total counting time is reached; determining the frequency of the radio frequency signal from the accumulated count stored when the total counting time ends; and tuning the radio receiver to a channel including the frequency determined. - View Dependent Claims (19, 20, 21, 22)
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23. A method of determining frequency of a received radio frequency signal comprising:
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counting zero amplitude transitions of a radio frequency signal received through an antenna and storing an accumulated count of zero amplitude transitions counted; determining the frequency of the radio frequency signal received from the accumulated count of zero amplitude transitions accumulated during a total counting time; tuning a radio receiver having a pass band to a channel including the frequency determined; and after tuning, determining whether a signal is being received within the pass band of the radio receiver for confirming accuracy of the frequency determined.
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24. A radio apparatus comprising:
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a radio receiver including an antenna for collecting electromagnetic energy, and receiver circuits for processing radio frequency signals received through the antenna and producing an output and including a tuner tuning only to allocated frequency channels, and a frequency determining apparatus for determining the frequency of a radio frequency signal received from the antenna, wherein the radio receiver includes a memory coupled to the tuner and to the frequency determining apparatus and storing frequency information for channels allocated to mobile transmitters and fixed frequency offsets between channels allocated to mobile transmitters and channels allocated to corresponding repeater transmitters repeating transmissions of respective mobile transmitters and, when the radio receiver determines that a channel for which a radio frequency signal has been received and that the frequency determined by the frequency determining apparatus is allocated to a mobile transmitter, the tuner of the radio receiver is tuned to a frequency offset from the channel including the radio frequency signal for which the frequency has been determined, by the fixed frequency offset stored in the memory for that channel, for detecting a radio frequency signal transmitted from a repeater transmitter. - View Dependent Claims (25)
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26. A method of tuning a radio receiver comprising:
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determining the frequency of a received radio frequency signal at a radio receiver including a tuner tuning only to allocated frequency channels and a memory coupled to the tuner and storing frequency information for channels allocated to mobile transmitters and fixed frequency offsets between the channels allocated to mobile transmitters and channels allocated to corresponding repeater transmitters repeating transmissions of respective mobile transmitters; and determining whether a channel including a frequency that has been determined from a received radio frequency signal is allocated to a mobile transmitter, and, if so, tuning the radio receiver to a frequency offset from the channel including the radio frequency signal for which the frequency has been determined, by the fixed frequency offset stored in the memory, for detecting a radio frequency signal transmitted from a repeater transmitter. - View Dependent Claims (27)
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28. A radio apparatus comprising:
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a frequency agile radio receiver including an antenna for collecting electromagnetic energy, a bandpass filter connected to the antenna and having a pass band passing radio frequencies within a first range of radio frequencies, and rejecting frequencies outside the first range of frequencies; receiver circuits for processing radio frequency signals received through the antenna and producing an output, a radio frequency preamplifier amplifying a radio frequency signal received from the antenna through the bandpass filter; and a microprocessor controlling tuning of the frequency agile radio receiver; and a frequency measuring apparatus for measuring the frequency of a radio frequency signal received from the antenna and through the bandpass filter and including a counter for counting zero amplitude transitions of the radio frequency signal received in each of a plurality of time periods of identical duration; a first register for storing counted zero amplitude transitions for a selected one of the time periods; a second register for storing an accumulated count of zero amplitude transitions counted during a total counting time including the plurality of time periods; and comparing means for comparing counted zero amplitude transitions for each time period other than the selected time period with the counted zero amplitude transitions for the selected time period, the second register discarding the accumulated count if the counted zero amplitude transitions for any of the time periods other than the selected time period are different from the counted zero amplitude transitions for the selected time period by more than a quantization error, wherein the frequency of the radio frequency signal is indicated by the accumulated count stored in the second register when the total counting time ends.
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Specification