Abstract: A digital transmission system including synchronizing circuits for estimating and compensating for errors between a local oscillator signal and an input signal. The synchronizing circuits include a phase/frequency detector and correction circuit for correcting errors in an unlocked mode, and a phase detection and correction circuit for correcting errors in a locked mode. Requests for changing the synchronization circuits from the locked mode to the unlocked mode are implemented by state control circuits only after application of at least one decision condition. The state control circuits may also save and restore specific adjustments responsive to the decision condition.

Abstract: Digital transmission system (10) for digitally modulated signals, comprising a receiving device (14) which includes a demodulator (110), processing apparatus (120) and carrier synchronizing apparatus (16) for estimating and compensating for synchronization errors. The synchronizing apparatus includes a first loop (1) for phase/frequency correction and a second loop (2) for phase correction, the operation of these loops being controlled by a mode detector (130) depending on whether the receiving device is seeking to unlock or lock. The second loop (2) transforms a phase error signal into a phase correction signal which is mixed in mixer (246) with the signal coming from the demodulator. Preferably, the signals are modulated via a coded modulation.

Abstract: Automatic gain control circuit comprising amplifier means (10) which produce an output signal that has an amplitude controlled by a control signal (CT). Recursive filter apparatus (20) (22) measures the power of the output signal and yield a measure of power which is compared (24) with a window of permitted power values to generate the control signal (CT). Depending on the result of the comparison, an initialization signal (INI) is transmitted which enforces a reference power value on a recursive filter to accelerate the gain control. Utilization in apparatus that use signals that have fast and considerable amplitude variations, as in digital modulation signal receivers.