A method for identifying simultaneously-transmitted signals from different transmit antennas in multi-antenna channel sounding experiments

A method is described for identifying simultaneous signals from different transmit antennas in multi-antenna sounders. Multiple orthogonal signals are produced from one pseudorandom code by using it to modulate RF carriers at pre-calculated offset frequencies. Although their frequency spectra are interleaved, the spectral lines from different transmitters are separable by Fourier transform at the receiver output. Since there is a one-to-one relationship between the length of the signal required for Fourier analysis and the number of orthogonal sounding signals, any arbitrary number of such signals can be generated, but Doppler spreads limit the number that can be employed with acceptable isolation among them.