Compensation circuit for multi-path propagation distortion in binary frequency modulated signals

Claim 1

A system for the reception of digital communication signals which are impressed on a carrier in the form of a binary frequency modulation, through a propagation medium that may have multi-path wave propagation and in particular for reception by mobile stations, long-distance traffic and scattered-ray systems in which information losses occurring as a result of phase and amplitude distortions are automatically detected in two mutually supplementary arrangements, one of which has a frequency discriminator, behind which a device for recognizing interference peaks caused by reflection distortions is connected, a circuit which compensates for these interference peaks, and the other arrangement contains an amplitude demodulator, which is connected in parallel with the frequency demodulator in another branch, wherein the outputs of both demodulators are supplied to a switch which is controlled by an amplitude modulation evaluation device and which with a detectable amplitude modulation of sufficient magnitude connects the amplitude demodulator, and which with detectable frequency modulation, connects the frequency discriminator, together with the interference-peck-recognizer, to a common output, and wherein the output of the AM demodulator includes a polarization inverter connected after it which is controlled by a polarity integrator, that reverses the AM demodulation product as a function of the height of the FM demodulation product characterized in that said AM demodulator contains at its output an alternating voltage separating circuit which includes a first and second sampling circuit (16, 17) with the second sampling circuit connected in parallel with the first sampling circuit, the first of said sampling circuits (16) controlled directly and the second sampling circuit (17) indirectly controlled with a switch (22), by a pulse (T) derived at the receiver from the incoming signal, said alternating voltage separating circuit contains at its output side, a subtractor (18) which receives inputs from said first and second sampling circuits, and said switch for the pulse feed to said second sampling circuit is actuated as a function of the changes in amplitude characteristic of the output signal of said first sampling circuit.

Claim 2

A system for the reception of digital communication signals which are impressed on a carrier in the form of a binary frequency modulation, through a propagation medium that may have multi-path wave propagation and in particular for reception by mobile stations, long-distance traffic and scattered-ray systems in which information losses occurring as a result of phase and amplitude distortions are automatically detected in two mutually supplementary arrangements, one of which has a frequency discriminator, behind which a device for recognizing interference peaks caused by reflection distortions is connected, a circuit which compensates for these interference peaks, and the other arrangement contains an amplitude demodulator, which is connected in parallel with the frequency demodulator in another branch, wherein the outputs of both demodulators are supplied to a switch which is controlled by an amplitude modulation evaluation device and which with a detectable amplitude modulation of sufficient magnitude connects the amplitude demodulator, and which with detectable frequency modulation, connects the frequency discriminator, together with the interference-peck-recognizer, to a common output, and wherein the output of the AM demodulator includes a polarization inverter connected after it which is controlled by a polarity integrator, that reverses the AM demodulation product as a function of the height of the FM demodulation product characterized in that said AM demodulator contains at its output an alternating voltage separating circuit which includes a first and second sampling circuit (16, 17) with the second sampling circuit connected in parallel with the first sampling circuit, the first of said sampling circuits (16) controlled directly and the second sampling circuit (17) indirectly controlled with a switch (22), by a pulse (T) derived at the receiver from the incoming signal, said alternating voltage separating circuit contains at its output side, a subtractor (18) which receives inputs from said first and second sampling circuits, and said switch for the pulse feed to said second sampling circuit is actuated as a function of the changes in amplitude characteristic of the output signal of said first sampling circuit.