Abstract: A method and device for measuring the slope of the envelope delay characteristic in a transmission channel. The slope is determined from a received measurement signal having a frequency spectrum that includes three rays at frequencies f.sub.o, f.sub.1 and f.sub.2, which are approximately located in the center and at the edges of the useful passband of the channel. At the output of the channel, the three components at frequencies f.sub.o, f.sub.1 and f.sub.2 are extracted from the received measurement signal, and the instantaneous phases .psi.0, .psi.1 and .psi.2 of these three components are measured. The value of the slope S of the envelope delay characteristic is obtained from the relation ##EQU1## where .phi..sub.o ', .phi..sub.1 ' and .phi..sub.2 ' are the phases of the three rays at frequencies f.sub.o, f.sub.1 and f.sub.2 of the measurement signal sent over the channel.

Abstract: A method and device for measuring the slope of the envelope delay characteristic of a transmission channel and deriving the phase intercept value therefrom. A measurment signal having a frequency spectrum including three rays at frequencies f.sub.o, f.sub.1 and f.sub.2 is sent over the transmission channel. Frequency f.sub.o is the carrier frequency and frequencies f.sub.1 and f.sub.2 are defined as f.sub.1 =f.sub.o -1/2T and f.sub.2 =f.sub.o +1/2T, where 1/T is the signaling rate. At the output of the channel, the three components at frequencies f.sub.o, f.sub.1 and f.sub.2 are extracted from the received measurement signal, and the instantaneous phases .psi..sub.o, .psi..sub.1 and .psi..sub.2 of these three components are then measured. The value of the slope S of the envelope delay characteristic is obtained in accordance with the relation ##EQU1## where .phi..sub.o.sup.', .phi..sub.1' and .phi..sub.2' are the phases of the three rays at frequencies f.sub.o, f.sub.1 and f.sub.

Abstract: A new adaptive digital tuning filter for tracking a sinusoidal signal within a frequency band is described. The input signal representative of both said sinusoidal signal and noise is fed to a Hilbert transformer which provides the in-phase and quadrature components, x.sub.k and x.sub.k, respectively, of said sinusoidal signal. These components are applied to the input of a filter having a transfer function K where ##EQU1## WHERE .phi. = 2.pi.FT, f is the tuned frequency of the filter,T is the signal sampling period and a is a constant close to unity.The output signals y.sub.x and y.sub.x of the filter are applied to a computing means which provides a frequency control signal e.sub.k such thate.sub.k = x.sub.k y.sub.k - y.sub.k x.sub.kThe above value of .phi. is adjusted through a conventional gradient method where.phi..sub.k + 1 = .phi..sub.k + .mu.e.sub.kand controls are provided to adjust .phi. in a direction to change e.sub.k toward zero.

Abstract: The feature of the invention is an adaptive equalizer for modulated carrier transmission systems in which a received signal is subjected to a Hilbert transformation to obtain a second signal having a 90.degree. phase shift for all components. The two signals are then passed through a pair of filters each and the outputs are cross-combined to generate the cartesian coordinate signals of an equalized signal. The coordinate signals are combined in a polar converter and are then decoded to detect the amplitude and phase data components of the received signal.The equalizers are made adaptive by determining at each sampling time, the phase and amplitude errors in the signal and using these errors to modify the coefficients of the equalizing filters. The phase and amplitude errors are recoded into Cartesian coordinates and multiplied by the values of the samples at each tap of the filters to generate four error signals for each tap.