Ch Frequency Response (Channel Sounding)
is the frequency response of the channel calculated from Channel N. The channel frequency response is calculated by taking the DFT discrete Fourier transform of the channel impulse response.
The channel impulse response spans the same bandwidth as the Sounding Time signal if you were to take the DFT of . Note that this bandwidth can be different than the bandwidth shown in the Spectrum trace due to resampling (to correct symbol clock error for example).
When or averaging is enabled, this trace will show the averaged channel frequency response. The channel sounding software supports coherently averaging the channel response across multiple time records without the need for triggering. This means that the average preserves the phase.
The non-averaged channel impulse response is shown in the Sounding Inst Ch Frequency Response trace.
The impulse response is windowed with a 25% Tukey window (raised cosine taper applied to the beginning and ending 12.5% of signal, flat elsewhere) before the frequency response is calculated. This is to reduce the effect of the discontinuity between the beginning and end of the impulse response.
See Also
