Filter Design Toolbox

noverflows

Return the number of overflows from the most recent FFT or IFFT operation

Syntax

• noverflows(F)
  noverflows(Hq)
  noverflows(Hq,'sum')
  noverflows (Q)
  

Description

noverflows(F) returns the number of overflows resulting from the most recent fft or ifft operation that used quantized fft (F).

noverflows(Hq) returns the number of overflows resulting from the most recent filter operation that used quantized filter (Hq).

noverflows(Hq,'sum') returns the number of overflows that resulted from the most recent qfilt operation. When the quantized filter has one section, this returns a scalar. When the filter uses two or more sections, noverflows returns a vector containing one element for each filter section.

noverflows(Q) returns the number of overflows resulting from the most recent quantize operation that used quantizer (Q).

Examples

Create a quantized fft f and apply it to a data set. Check the number of overflows that result when you use f. Then apply f to a second data set and check the overflows again.

• warning on
  n=128;
  t = (1:n)/n;
  x = sin(2*pi*10*t)/10;
  f = qfft('length',n);
  plot(t,abs([fft(f,x);fft(x)]))
  noverflows(f)
  

returns 24 for the number of overflows and a warning of 24 overflows.

Now, apply f to another data set.

• x = sin(2*pi*10*t)/5;
  plot(t,abs([fft(f,x);fft(x)]))
  noverflows(f)
  

Now you see 58 overflows.

See Also
get, max, range, reset

normalize

num2bin