Compensation Tab (Flex Frame - Basic Mode)

The Measurement Control tab configures the Flex Frame measurement characteristics.

Frequency Error Compensation determines whether the frequency error is estimated and compensated. Having an incorrect carrier frequency estimate can lead to significant errors during the demodulation process. The carrier frequency estimate is indicated in the Measurement Control tab, where each component carrier has an absolute center and offset from that center frequency.

Off - Frequency error estimation and compensation is disabled.
Normal - The frequency error is estimated and compensated during the measurement interval. Normal frequency estimation mode should work for most cases.

Normal signal processing follows the steps below:
1. Estimate the symbol timing and compensate it
2. Detect the frame boundary
3. Estimate the frequency error using the known signal and compensate it
4. Estimate the channel response and compensate it
5. Second round of frequency/phase estimation and compensation
If the preamble, pilot or any known part of the signal is too short, the frequency estimation based on them may not be reliable. Likewise, if the signal is very noisy or seriously distorted by the channel, the frequency estimation (and the resulting measurement) will not be accurate. In this case, After EQ mode may the best choice for frequency estimation.
After EQ - The frequency estimation before channel estimation and equalization is skipped, and after the second round of frequency estimation compensation, another round of channel estimation/compensation is added. This works well when the channel unflatness seriously affects the initial frequency offset estimation, and the frequency offset has little impact on the channel estimation.

Default: Normal

Choices: Off, Normal, After EQ

Symbol Clock Error Compensation enables or disables compensation for measured symbol clock error.

Selected - Compensation for measured symbol clock error is applied to the signal.
Cleared - No symbol clock error compensation is applied to the signal.

Default: Cleared

Range: Selected, Cleared

IQ Offset Compensation enables or disables compensation for measured IQ offset.

Selected - Compensation for measured IQ offset is applied to the signal.
Cleared - No IQ offset compensation is applied to the signal.

Default: Selected

Range: Selected, Cleared

IQ Imbalance Compensation enables or disables compensation for measured IQ imbalance.

Selected - Compensation for measured IQ imbalance is applied to the signal.
Cleared - No IQ imbalance compensation is applied to the signal.

Default: Cleared

Range: Selected, Cleared

Equalization Reset will reset the eq channel response back to flat (no flatness correction). This setting is also available on the Demod tab.

Off- equalization is not performed. There is no tracking for equalization impulse response, so the equalization impulse response is re-calculated for each run.
Track- equalization is performed. Equalization impulse response is updated run by run (based on data).
Hold- equalization is performed. Equalization impulse response is held to the most recent equalization impulse response estimate.

Choices: Off, Track, Hold

Default: Off

Convergence (only useful when Equalization is on) controls the rate of convergence of the adaptive equalizer of the digital demodulation measurement. This setting is also available on the Demod tab.

Convergence determines how quickly the equalization filter coefficients converge to the estimated values for each measurement. Larger values converge faster but might not be as consistent, based on noise in the data. Smaller values converge more slowly but provide a more consistent equalization filter for a given channel. This provides a trade-off in the number of measurements required for convergence of the equalization filter taps, and the stability of those taps. For more information, see Convergence (Digital Demod).

Default: 1E-06

Eq Filter Taps This is the total number of taps in the equalization filter, just like DigDemod or Custom IQ (to relate to Normalized Delay Spread, Eq Filter Taps = 2* normalized delay spread + 1). This setting is also available on the Demod tab.

Default: 3 symbols