Scrambling and error correction by means of linear time-varying filters

In numerous communication applications, it is desirable to scramble the contents of the information. In addition, we seek to design a scrambling system which has maximum immunity to additive noise. This paper presents a method of analogue signal scrambling/unscrambling by means of linear periodic time-varying filters for any frequency selective noise. It is well known that linear periodic time-varying filters transform a stationary process into a cyclostationary signal. This thus spreads the spectral representation of the input process. The original part of the paper consists of using this property to reconstruct an initial band-limited process without error for any frequency selective noise.