Frequency hopping system for intermittent transmission with receiver using individual tracking, FFT, and authentication
First Claim
1. A telemetry system comprising:
- a plurality of transmitters, each of which intermittently transmits a carrier at time intervals and at a plurality of frequencies that are independent of the time intervals and frequencies at which the other transmitters transmit and that are independent of a receiver of said carrier; and
said receiver comprising means for simultaneously detecting a plurality of carriers transmitted by said plurality of transmitters;
wherein said means for simultaneously detecting a plurality of carriers comprises sampling and time-domain-to-frequency-domain transform, and is capable of producing an indicium of the signal strength of each of said plurality of carriers.
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Accused Products
Abstract
A radio transmission system including many radio transmitters using frequency hopping carriers to intermittently transmit very short messages indicative of status of sensors associated with the transmitters. In operation, a time interval generator included in a transmitter generates pulses activating the transmitter at time intervals according to a predetermined algorithm. When activated, the transmitter transmits a message at one or several different frequencies. The frequencies are changed according to a predetermined algorithm and differ for each subsequent transmission. Alternatively, when an abnormal sensor status is detected, the transmitter transmits repeated messages at a plurality of predetermined alarm frequencies for a predetermined time regardless of the time interval generator. The system also includes one or more receivers containing a plurality of memory registers to hold digital data indicative of (a) the time and (b) the frequency of the next transmission occurrence independently for each transmitter. The registers are programmed separately for each transmitter based on the time, frequency, and the content of the received messages. In addition, the receiver includes an improved RSSI circuit based on FFT to detect transmitted carrier power at several different frequencies in order to improve synchronization and acquisition. The receiver also includes one or more frequency selective circuits that are tuned in response to the outputs from FFT and the status of the time and frequency registers. In addition, there is provided a method for authentication of the received messages.
114 Citations
34 Claims
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1. A telemetry system comprising:
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a plurality of transmitters, each of which intermittently transmits a carrier at time intervals and at a plurality of frequencies that are independent of the time intervals and frequencies at which the other transmitters transmit and that are independent of a receiver of said carrier; and
said receiver comprising means for simultaneously detecting a plurality of carriers transmitted by said plurality of transmitters;
wherein said means for simultaneously detecting a plurality of carriers comprises sampling and time-domain-to-frequency-domain transform, and is capable of producing an indicium of the signal strength of each of said plurality of carriers. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
wherein said receiver tunes at least one of said frequency selective circuits to one of said plurality of carriers based on said indicium, said time of at least one future transmission, and said frequency of at least one future transmission.
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11. A method of operating a telemetry system comprising:
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intermittently transmitting a carrier from each of a plurality of transmitters at time intervals and at a plurality of frequencies that are independent of the time intervals and frequencies at which the other transmitters transmit and that are independent of a receiver of said carrier;
simultaneously detecting said plurality of carriers with a receiver by sampling and time-domain-to-frequency-domain transforming said plurality of carriers; and
producing an indicium of the signal strength of each of said plurality of carriers. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20)
wherein said receiver tunes at least one of said frequency selective circuits to one of said plurality of carriers based on said indicium based on said indicium, said time of at least one future transmission, and said frequency of at least one future transmission.
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21. A telemetry receiver comprising:
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means for simultaneously detecting a plurality of carriers transmitted by a plurality of transmitters, and said means for simultaneously detecting a plurality of carriers comprises sampling and time-domain-to-frequency-domain transform, and is capable of producing an indicium of the signal strength of each of said plurality of carriers, and wherein said carriers are transmitted intermittently by each of said plurality of transmitters at time intervals and at a plurality of frequencies that are independent of the time intervals and frequencies at which the other transmitters transmit and that are independent of a receiver of said carriers. - View Dependent Claims (22, 23, 24, 25, 26, 27)
wherein said receiver tunes at least one of said frequency selective circuits to one of said plurality of carriers based on said indicium, said time of at least one future transmission, and said frequency of at least one future transmission.
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25. The telemetry receiver of claim 21 wherein said time-domain-to-frequency-domain transform is discrete fourier transform.
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26. The telemetry receiver of claim 21 wherein said indicium for a first carrier is produced at a rate that is slower than the data rate of said first carrier.
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27. The telemetry receiver of claim 21 wherein said receiver holds data indicative of:
- (1) the time of at least one future transmission from each of said plurality of said transmitters, and (2) the frequency of at least one future transmissions from each of said plurality of said transmitters.
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28. A method of operating a telemetry receiver, said method comprising:
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simultaneously detecting a plurality of carriers transmitted by a plurality of transmitters by sampling and time-domain-to-frequency-domain transform, and producing an indicium of the signal strength of each of said plurality of carriers, and wherein said carriers are transmitted intermittently by each of said plurality of transmitters at time intervals and at a plurality of frequencies that are independent of the time intervals and frequencies at which the other transmitters transmit and that are independent of a receiver of said carriers. - View Dependent Claims (29, 30, 31, 32, 33, 34)
wherein said receiver tunes at least one of said frequency selective circuits to one of said plurality of carriers based on said indicium, said time of at least one future transmission, and said frequency of at least one future transmission.
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Specification