Since the optimum word-length is dependent on the desired fixedpoint
performance of a system, a performance measure has to be
included as a part of a system setup. SQNR is widely used as
the performance measure for many systems, such as linear timeinvariant
digital filters and waveform coders. Time-varying or nonlinear
systems may require different performance measures. For
example, the convergence time or the mean squared error power
after convergence would be a good measure for the implementation
of adaptive digital filters [8]. One can create a custom measurement
block. A performance measurement block must generate a positive
result when the quantization effects are acceptable. For example, the
SQNR block generates the difference of the measured SQNR and the
desired SQNR as the output. If the measured SQNR is 55.0 and the
desired SQNR is 50.0, it is reported as “FixedPerformance: 5.0.”