The invention relates to a phase comparison circuit for determining the phase deviation between an input signal and a reference signal. The input signal is integrated during two consecutive defined integration intervals which are derived from the reference signal. The integral values assigned to the integration intervals are weighted and the difference is formed. The output signal of the phase comparison circuit is derived from the result of forming this difference.

The present invention comes within the field of synchronous digital transmission. It relates to the recovering the carrier (which may be suppressed carrier) of an amplitude modulated synchronous digital signal. It provides a circuit which includes an oscillator (41) of adjustable frequency and phase to generate a local carrier, a demodulation circuit whose input(s) receives the local carrier (possibly phase shifted by .+-..PSI. (42,44,46,47) and the amplitude modulated synchronous digital signal e(t) and control means (48,49) which control the phase and the frequency of the oscillator from the signals delivered by the demodulation circuit and which comprise at least one sign coincidence autocorrelator. It advantageously applies to demodulating amplitude modulated single side band bipolar coded synchronous digital signals.

An improved phase detector apparatus which includes a charge pump. The charge pump includes a first integrating node and a second integrating node. The first and second integrating nodes generate node voltages which ramp downward and upward during a given period of a reference signal. When a signal is received to which a reference signal is to be locked on, the integrating sequence of the first and second nodes is altered so that the differential voltage across the nodes indicates a difference in phase between the reference signal and the second signal. A filter is connected between the output signal and the first integrating node, while the second integrating node is referenced to a DC bias level and returns to that level at the beginning and end of each cycle. The charge pump apparatus is driven by variable current sources which give the apparatus a variable frequency response. The frequency response is variable over a very wide range by the inclusion of multiple banks of variable current sources which can be switched in and out for driving the charge pump apparatus as desired.

A self-calibrating threshold detector for use with receivers adapted to receive an incoming transmitted signal carrying a prescribed code. The detector comprises a single demodulating channel which includes a mixer having one input receiving the incoming signal and another input receiving a local replica code. During a short time interval, an incorrect local code is applied to the mixer to incorrectly demodulate said incoming signal and to provide a reference level that calibrates the noise propagating through the channel. A sample-and-hold circuit is coupled to the channel for storing a sample of the reference level. During a relatively long time interval, the correct replica code provides an output level which ranges between the reference level and a maximum level that represents incoming signal presence and synchronism with the replica code. A summer subtracts the stored sample reference from said output level to provide a resultant difference signal indicative of the acquisition of the expected signal.

The present invention relates to devices for correlating two phase-modulated signals, in order to determine the delay between said two signals. The signals are applied to phase detectors which receive one and the same local wave. One of the signals is delayed by a variable delay time. The phase values obtained are subtracted from one another. The result is then integrated in the complex plane for a given period of time. The variation of the variable delay permits to determine the correlation function and in particular, the position and the amplitude of the correlation peak.