Convergence (Custom IQ)

Nominal value: 1e-07
Step size (using arrow keys or mouse wheel): 1-2-5 sequence

Convergence determines the rate at which the equalization filter converges.

The nominal value for Convergence presented in PSA and X-Series VSAs is normalized. To convert the Convergence value in the VSA to the normalized value, divide the 89600 VSA Convergence value by 1e-07.

Convergence determines how quickly the equalization filter coefficients converge to the estimated values for each measurement. Larger values converge faster. Values that are too large can cause the adaptation algorithm to become unstable or may cause the algorithm to fluctuate from stable to unstable limiting the minimum EVM Error vector magnitude (EVM): A quality metric in digital communication systems. See the EVM metric in the Error Summary Table topic in each demodulator for more information on how EVM is calculated for that modulation format. or SNR Signal-to-Noise Ratio.

Adjust the Convergence while the adaptation algorithm is running. For example, the Convergence may be increased to obtain faster convergence and then decreased to obtain better results.

At the start of your measurement, set the convergence high to quickly shape the filter. Then decrease the convergence to fine-tune the filter to the optimum shape.

The best value for Convergence is affected by the following parameters:

Normally, Convergence values between 1e-7 and 1e-6 yield good results.

If the adaptation algorithm becomes unstable, reduce the Convergence value and then reset the equalization filter. Use the up/down arrow keys or mouse wheel to change the Convergence in a 1-2-5 sequence.