Bit synchronization arrangement for a data modem or data receiver
AssigneeTelecommunications Radioelectriques et Telephoniques T.R.T.
InventorRobert Boudault
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Abstract
In an asynchronous transmission mode, the bit synchronization arrangement receives data signals in the form of binary pulse trains (at A). It includes an oscillator (3) whose output signal (at C) has a frequency F.sub.OS approximately equal to twice the binary rate of the pulse trains and a transition detector (1, 22) which supplies a calibrated voltage pulse (at B.sub.2) at each data signal transition. The oscillator supplies a triangular internal signal (at D) at the frequency F.sub.OS and a phase correction circuit (2) is provided to reduce the algebraic value of the slope of this signal during each calibrated pulse so as to produce a predetermined constant advancing or delaying phase shift according as the calibrated pulse occurs during a negative or a positive ramp of this signal.
Claims12
A bit synchronization apparatus for furnishing an output signal synchronized to asynchronously received data signals constituted by binary pulse trains having a base frequency and detectable transitions between binary states, comprising,
- transition detector means for receiving said data signals and generating a correction pulse having a predetermined duration in response to each transition of said data signals;
- oscillator means for generating a sequence of triangular signals each having a first and second side respectively having a finite first and second slope, said sequence of triangular signals having a frequency corresponding to said base frequency whereby an instantaneous phase shift exists between said received data signals and said triangular signals;
- phase correction means interconnected between said transition detector means and said oscillator means for changing said first or said second slope in a direction decreasing said phase shift during occurrence of each of said correction pulses when said correction pulse occurs during said first or second side, respectively;
- and
- means for generating said output signals in synchronism with said triangular signals.
Dependencies are inferred from the claim text.