Inv Ch Frequency Response (Channel Quality)
is the balanced part of the inverse channel frequency response. Inverse channel frequency response is calculated for each measurement channel. The inverse channel frequency response is related to the Inv 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 inverse 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 triggering. This means that the average preserves the phase.
The non-averaged inverse channel frequency response is shown in the Inst Inv Ch Frequency Response trace.
A signal can be predistorted according to the following equation:
X_predistorted(f) = HB_inv(f)X(f) + HU_inv(f)X(-f)
Where X(f) is the frequency domain version of the signal to be predistorted, HB_inv(f) is the balanced part of the inverse channel frequency response and HU_inv(f) is the unbalanced part of the channel frequency response.
I and Q Inv Channel Frequency Response Traces
There are also traces for I and Q that express the inverse 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
