Demodulation process for binary data

Abstract

Two signals at different frequencies are optionally amplified or attenuated in an automatic gain control amplifier (1) after their reception, then separated from each other by means of band pass filters (2, 5) and amplitude-modulated by means of envelope curve detectors (3, 6), whereupon the envelope curve signals (z.sub.0 [t], z.sub.1 [t]) are sampled by means of sampling switches (4, 7) once per bit to produce sample values (z.sub.0 [kT.sub.b ], z.sub.1 [kT.sub.b ]) which are passed to a calculator unit (8) whose memory stores values of a decision table which are derived from a probability table. Each table area of the latter contains two probability values of which a first is the probability that the sample values (z.sub.0 [kT.sub.b ], z.sub.1 [kT.sub.b ]) lie in the respective table area if the first signal were sent and a second is the probability that the sample values (z.sub.0 [kT.sub.b ], z.sub.1 [kT.sub.b ]) lie in the respective table area if the second signal were sent. Set down in a table area of the decision table is a respective first logic value if the first probability value is greater than the second probability value and a respective second logic value if the first probability value is less than or equal to the second probability value. The process combines the advantages of the noncoherent demodulation process and the spread spectrum process.