Ch Frequency Response (MB-OFDM)

Menu Path: Trace > Data > Composite > Ch Frequency Response

Comp Ch Frequency Response shows the channel frequency response in which the equalizer is correcting. Ch Frequency Response is computed as the reciprocal of the equalizer frequency response. The Ch Frequency Response contains one complex value for each subcarrier plus an interpolated value for the middle unused subcarrier (a total of 123 values). The equalizer frequency response is normally estimated from the Channel Estimation Sequence portion of the MB-OFDM Orthogonal Frequency Division Multiplexing: OFDM employs multiple overlapping radio frequency carriers, each operating at a carefully chosen frequency that is Orthogonal to the others, to produce a transmission scheme that supports higher bit rates due to parallel channel operation. OFDM is an alternative tranmission scheme to DSSS and FHSS. preamble.

The composite result is computed only when performing FFI analysis (TFCs 5 - 7) or TFI/TFI2 analysis when Frequency Hopping Analysis is set to Force FFI. For hopped signals, there will be no results and the error message DATA? will display.

This is similar to, but not the same as, the Digital Demod Ch Frequency Response. The differences are:

Digital Demod computes this by comparing the IQ Meas Time and IQ Ref Time data, MB-OFDM demodulation computes it from the preamble/data of the burst.

Digital Demod typically uses a running average to average multiple scans when computing the equalizer frequency response. MB-OFDM demodulation does not average, but computes a new equalizer response for each burst.

The equalization filter is inherent to MB-OFDM Demodulation, it cannot be enabled/disabled like in Digital Demod.

See Also

Eq Impulse Response (Composite) (MB-OFDM)

Available Trace Data (MB-OFDM)