Frequency hopping system for intermittent transmission
First Claim
1. A radio transmission system comprising of a radio receiver and a plurality of radio transmitters using frequency hopping modulation to intermittently transmit messages indicative of a status of operation associated with the transmitters;
- wherein each said transmitter includes a control logic means to change the carrier frequency according to a predetermined pattern and a time interval generator means for activating said transmitter at predetermined time intervals, said intervals may be set at a predetermined nominal value or changed according to a predetermined pattern; and
wherein said receiver includes a frequency selective radio circuit that can be programmed to a desired frequency to receive and demodulate the transmitted carriers; and
wherein said receiver includes a plurality of digital counters or memory registers means to hold data indicative of (a) the time of the next transmission occurrence for each said transmitter and (b) the frequency of the next transmission occurrence for each said transmitter, and wherein said receiver includes a receiver control logic means to change the receiver frequency according to said data in said digital counters or memory registers and to change said data in said digital counters or memory registers in response to the received messages; and
wherein, said receiver control logic is operative to change the data in said digital counters or memory registers based on the time of arrival, the carrier frequency and the content of a message received from a transmitter for subsequent use for the determination of the time and frequency of the future transmissions for said transmitter, said determination is made individually for each transmitter of said plurality of transmitters, thus allowing the receiver to receive messages from many unsynchronized frequency hopping transmitters.
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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 preferably 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.
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Citations
45 Claims
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1. A radio transmission system comprising of a radio receiver and a plurality of radio transmitters using frequency hopping modulation to intermittently transmit messages indicative of a status of operation associated with the transmitters;
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wherein each said transmitter includes a control logic means to change the carrier frequency according to a predetermined pattern and a time interval generator means for activating said transmitter at predetermined time intervals, said intervals may be set at a predetermined nominal value or changed according to a predetermined pattern; and wherein said receiver includes a frequency selective radio circuit that can be programmed to a desired frequency to receive and demodulate the transmitted carriers; and wherein said receiver includes a plurality of digital counters or memory registers means to hold data indicative of (a) the time of the next transmission occurrence for each said transmitter and (b) the frequency of the next transmission occurrence for each said transmitter, and wherein said receiver includes a receiver control logic means to change the receiver frequency according to said data in said digital counters or memory registers and to change said data in said digital counters or memory registers in response to the received messages; and wherein, said receiver control logic is operative to change the data in said digital counters or memory registers based on the time of arrival, the carrier frequency and the content of a message received from a transmitter for subsequent use for the determination of the time and frequency of the future transmissions for said transmitter, said determination is made individually for each transmitter of said plurality of transmitters, thus allowing the receiver to receive messages from many unsynchronized frequency hopping transmitters. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28)
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29. An apparatus for receiving digital data from a plurality of frequency hopping transmitters comprising a receiver;
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said receiver including a frequency selective radio circuit that can be programmed to a desired frequency to receive and demodulate the transmitted carriers; and said receiver having a plurality of (a) time registers for holding data indicative of the next transmission occurrence separately for each said transmitter and (b) frequency registers for holding data indicative of the frequency of the next transmission occurrence separately for each said transmitter; and said receiver having a timer to measure the elapsing time; and said receiver using said receiver timer and said time and frequency registers to control said receiver frequency in the steps comprising; (1) said receiver determining which transmitter is the next transmitter to transmit a message on basis of the content of said time registers and changing said receiver frequency to the next frequency of said next transmitter at such time in advance before said message is transmitted as to allow for the reception of entire said message, wherein said frequency is determined on basis of the content of said frequency register associated with said next transmitter; and (2) said receiver, upon complete or partial reception of a message from a transmitter, changing the data in said frequency register associated with said transmitter to indicate the next frequency for said transmitter according to a predetermined algorithm, and changing current content of said time register associated with said transmitter, wherein said time register change is based on the time of the arrival of the received message and a number representative of the time interval between the current and the next transmission for said transmitter according to a predetermined algorithm; and
wherein(3) when said receiver fails to detect the transmitted signal at the due time due to signal fading or interference, said receiver changes the data in said frequency register associated with said transmitter to indicate the next frequency for said transmitter according to a predetermined algorithm, and said receiver changes the data in said time register associated with said transmitter, said time register change is based on the current status of said time register associated with said transmitter and the time interval between the presently due transmission and the next transmission determined according with a predetermined algorithm; and (4) said receiver using the available time between transmissions to sequentially scan other frequencies of a plurality of frequencies available for transmission in an attempt to receive signals from transmitters with which synchronization has been lost, and wherein when such a signal is detected, updating said time register for said transmitter according to step (2) and thus restoring synchronization; and (5) said receiver repeating steps 1 through 5. - View Dependent Claims (30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45)
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Specification