Ch Frequency Response (Channel Quality)
is the frequency response of the channel that is due to reflections/multipath. Channel frequency response is calculated for each measurement channel. The channel frequency response is related to the Ch Impulse Response through the DFT discrete Fourier transform transform. Background annotation indicates any tones which are in a disabled state for the current measurement.
The channel frequency response spans the same bandwidth as the stimulus signal. Note this bandwidth can be different than the bandwidth shown in the Spectrum trace.
When RMS or RMS Exponential averaging is enabled, this trace will show the averaged channel frequency response. The channel response measurement supports coherently averaging the channel response across multiple time records without the need for fine triggering (triggering at the start of the waveform is required to avoid the 180 degree ambiguity in the unbalanced response). This means that the average preserves the phase.
The non-averaged channel frequency response is shown in the Inst Ch Frequency Response trace.
I and Q Channel Frequency Response Traces
There are also traces for I and Q that express the frequency response separately for the In Phase and Quadrature Phase components of the channel. These traces are computed from the Balanced and Unbalanced responses.
See Also
