Channel sounder testing for tactical communications

The characterization of wideband radio channels requires knowledge of such parameters as the average delay, the delay spread, and their coherence bandwidth. These are also descriptors that provide relevant information to system design engineers. Channel sounding is a technique for developing this information for a specific communication's path and frequency range. The GTE Laboratories sounder is a computer-controlled, mobile, channel probe that uses a sliding correlator architecture to measure transmission loss and delay spread. The transmitter sends out a pseudorandom waveform with a predetermined chip interval and code word length. It is these two parameters that determine the minimum time resolution and maximum delay spread that is measurable. At the receiver, a replica of the transmitted pseudorandom waveform is correlated with the in-phase and quadrature-phase components of the received signal. The output of the correlator is integrated and sampled. This process is conducted for each chip in the pseudorandom code period in order to obtain a valid measurement of the entire delay-spread function. It is this delay spread that is one of the key parameters used to characterize channel performance, as it has the most significant effect on the channel error rate.<>