Abstract: A wave two port circuit arrangement for simulating a resistive elementary port two device for use in a wave digital filter. First and second ports are each arranged for receiving input and output signals. A summing device is connected to the first and second ports and produces a sum signal which represents the sum of the input signals present at the first and second ports. A multiplier is connected to the summing device and to one of the first and second ports for producing a negatively scaled sum signal and feeding it to the one port as part of the output signal present at that port.

Abstract: A method for interchanging the frequency positions of n partial bands, each having a bandwidth b, of a signal frequency band, by the steps of: sampling signals in the frequency band at an input sampling rate; separating the sampled signals associated with each partial band into separate channels in stages in each of which sample signals are separated into high frequency and low frequency groups and the sampling rate is reduced; altering the positions of the channels in a scrambling matrix controlled by a random sequence generator; and spectrally recombining the signals in the separate channels into a signal extending across the signal frequency band.

Abstract: A system for the digital conversion of a time division multiplex signal into a frequency division multiplex signal wherein the signals of the individual time multiplex channels are filtered by means of bandpass filters, their sampling rates are increased by the factor N to fA and the output signals of these bandpass filters are combined, by means of a summing member, into the frequency multiplex signal, and/or a system for the digital conversion of a frequency multiplex signal into a time division multiplex signal, wherein the digitalized frequency multiplex signal is divided by means of respective bandpass filters into the signals of the individual frequency multiplex channels and their sampling rate fA is reduced by the factor N. The individual bandpass filters (BP) are designed as recursive filters having the transfer functionH(z)=U2(z)/U1(z)=P(z)/Q(z.sup.N)where U1(z) and U2(z) represent the filter input and filter output spectra respectively, z=e.sup.j2.pi.f/fA, and f is the signal frequency.