U-blox Ag

Daniel Kaegi

Andreas Thiel

Heinz Mathis

A sychronization circuit comprising an analog feedback shift register for generating an internal sequence which is synchronized with an external sequence containing repetitions of a fundamental sequence has a feedback circuit which, for the formation of a new value of a fundamental sequence, combines at least two values (x,x) stored in the shift register according to a feedback function (f(x,x)), which is then scaled with a factor k, 0.9&#x3c;k&#x3c;0.99. The synchronization behaviour is improved, especially in the case of signals with strong background noise, by using a feedback function which is substantially linear in the sectors defined by the signs of the arguments and whose sign corresponds to that of the negative of the product of the negative arguments and whose magnitude is 1 if the magnitudes of the arguments are each 1. A function which meets these requirements and has proved useful is f(x, . . . , x)=&#x2212;sig((&#x2212;x)&#xb7; . . . &#xb7;(&#x2212;x))&#xb7;(|x|+ . . . +|x|)/m. For improving the signal/noise ratio, there is a buffer in front of the analog feedback shift register, where, for the generation of the external sequence, segments of an input sequence which contain several, e.g. twenty, successive instances of the fundamental sequence are added and then read out repeatedly.

Synchronization circuit

A method for generating an internal sequence of analog values having a specific period includes producing an intermediate value by a logical combination of an actual value of the external sequence with an actual value of a second generating sequence, producing an input value to an analog feedback shift register by superposition of the intermediate value with an analog feedback value derived according to a feedback function from analog values in the analog feedback shift register, and feeding the input value to an input of the analog feedback shift register. A position of an actual value of the second generating sequence corresponds to a position of a segment in the first generating sequence, the segment including a determinative set of n binary values derived from the analog values in the analog feedback shift register.

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Rueti, Switzerland

Daniel Kaegi