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Most recent fixed-point filtering operation report


rlog = qreport(h)


rlog = qreport(h) returns the logging report stored in the filter object h in the object rlog. The ability to log features of the filtering operation is integrated in the fixed-point filter object and the filter method.

Each time you filter a signal with h, new log data overwrites the results in the filter from the previous filtering operation. To save the log from a filtering simulation, change the name of the output argument for the operation before subsequent filtering runs.

    Note   qreport requires Fixed-Point Designer™ software and that filter h is a fixed-point filter. Data logging for fi operations is a preference you set for each MATLAB session. To learn more about logging, LoggingMode, and fi object preferences, refer to fipref in the Fixed-Point Designer documentation.

    Also, you cannot use qreport to log the filtering operations from a fixed-point Farrow filter.

Enable logging during filtering by setting LoggingMode to on for fi objects for your MATLAB session. Trigger logging by setting the Arithmetic property for h to fixed, making h a fixed-point filter and filtering an input signal.

Using Fixed-Point Filtering Logging

Filter operation logging with qreport requires some preparation in MATLAB. Complete these steps before you use qreport.

  1. Set the fixed-point object preference for LoggingMode to on for your MATLAB session. This setting enables data logging.

  2. Create your fixed-point filter.

  3. Filter a signal with the filter.

  4. Use qreport to return the filtering information stored in the filter object.

qreport provides a way to instrument your fixed-point filters and the resulting data log offers insight into how the filter responds to a particular input data signal.

Report object rlog contains a filter-structure-specific list of internal signals for the filter. Each signal contains

  • Minimum and maximum values that were recorded during the last simulation. Minimum and maximum values correspond to values before quantization.

  • Representable numerical range of the word length and fraction length format

  • Number of overflows during filtering for that signal.


qreport depends on the LoggingMode preference for fixed-point objects. This example demonstrates the process for enabling and using qreport to log the results of filtering with a fixed-point filter. hd is a fixed-point direct-form FIR filter.

f = fipref('loggingmode','on');
hd = design(fdesign.lowpass,'equiripple');
hd.arithmetic = 'fixed';
fs = 1000;          % Input sampling frequency.
t = 0:1/fs:1.5;     % Signal length = 1501 samples.
x = sin(2*pi*10*t); % Amplitude = 1 sinusoid.
y = filter(hd,x); 
rlog = qreport(hd)

View the logging report of a direct-form II, second-order sections IIR filter the same way. While this example sets loggingmode to on, you do that only once for a MATLAB session, unless you reset the mode to off during the session.

hd = design(fdesign.lowpass,'ellip');
hd.arithmetic = 'fixed';
y = filter(hd,rand(100,1));
rlog = qreport(hd)

See Also

Introduced in R2011a

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