Synchronization systems
First Claim
1. A radio transmitting and receiving system, comprisinga radio transmitter,transmitter control means operative to control the transmitter so that it transmits successively at each one in a predetermined sequence of different transmitting frequencies each of which is held for a respective predetermined transmitting period,a radio receiver,receiver control means operative to control the receiver so that it receives successively at each of the frequencies in the said sequence, andsynchronisation means operative to synchronise the transmitter control means and the receiver control means by means of the provision of timing information which tends to make the receiver frequency at any time the same as the transmitter frequency,the synchronisation means comprising formatting means at the transmitter for producing, and transmitting to the receiver during some, only, of the said predetermined transmitting periods, a synchronisation signal whose value represents part of the timing information and whose time of occurrence represents another part of the timing information, and sync receiving means at the receiver for extracting the value of the synchronisation signal and its time of occurrence.
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Accused Products
Abstract
A syncrhonization arrangement is disclosed for synchronizing a receiver with a transmitter whose frequency is hopping through a sequence of predetermined frequencies arranged pseudo-randomly. The transmitter includes a time base circuit in the form of a string of dividers operated from a stable oscillator. One divider produces (in this example) a 28 bit synchronization signal which changes state once every sixty four hop frequencies. The 28 bits control a keystream generator which produces a pseudo-random output sequence controlling the transmitting frequencies. This 28 bit signal is formatted by repeating it several times successively, with its bits partially re-circulated to a predetermined extent each time, masking bits are added, and the result transmitted to the receiver on one of the hop frequencies. At the receiver, a correlator subtracts the mask, partially re-circulates the bits to offset the partial recirculation at the transmitter, and recognizes receipt of the 28 bits when successive groups of the resultant bits are identical (or do not differ by more than predetermined total error). The 28 bits are used to pre-set a divider at the receiver which then in turn resets the receiver'"'"'s keystream generator, thereby synchronizing the receiver.
34 Citations
16 Claims
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1. A radio transmitting and receiving system, comprising
a radio transmitter, transmitter control means operative to control the transmitter so that it transmits successively at each one in a predetermined sequence of different transmitting frequencies each of which is held for a respective predetermined transmitting period, a radio receiver, receiver control means operative to control the receiver so that it receives successively at each of the frequencies in the said sequence, and synchronisation means operative to synchronise the transmitter control means and the receiver control means by means of the provision of timing information which tends to make the receiver frequency at any time the same as the transmitter frequency, the synchronisation means comprising formatting means at the transmitter for producing, and transmitting to the receiver during some, only, of the said predetermined transmitting periods, a synchronisation signal whose value represents part of the timing information and whose time of occurrence represents another part of the timing information, and sync receiving means at the receiver for extracting the value of the synchronisation signal and its time of occurrence.
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14. A radio transmitting and receiving network arranged to hop at a predetermined rate through frequency channels in a predetermined range of frequency channels remaining on each channel for a predetermined length of time, comprising
a plurality of radio transmitting/receiving means, each comprising frequency control means operative to control the transmitting/receiving frequency, pseudo-random sequence generating means operative to control the frequency control means to set the frequency to each one in a pseudo-random sequence of frequencies, a timing arrangement operative to control the timing of the pseudo-random sequence generating means, and synchronisating means for synchronising the timing arrangement in accordance with synchronisation data received from the other radio transmitting/receiving means; -
each timing arrangement comprising a stable frequency source and a cascaded chain of frequency counting means; each synchronising means comprising sync transmitting means responsive to the count value of the final counting means in the chain and operative when activated by the respective pseudo-random sequence generating means to cause the digits of the count value to be transmitted by the transmitting/receiving means on some, only, of the channels in the predetermined range, each transmission being at a predetermined digital rate of transmission determined by another one of the counting means and starting and finishing at times at times determined by a further one of the counting means, and sync receiving means operative to receive the digits of the transmitted count value and to preset the final counting means in dependence on the received count value and to pre-set the other and further counting means respectively in dependence on the rate of receipt of the digits and on the time of receipt of the count value. - View Dependent Claims (15, 16)
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Specification