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Converting From A Normalized To Digital Highpass Filter
 Syntax `fn2dhp(`wc, dt, b_in, a_in, bz, az`)` Include: `include spt\fn2dhp.oms` See Also fn2dlp , fn2dbp , fn2dbs , fc2dig
```     wc: Real or Double scalar specifying desired radian cutoff frequency for the new digital highpass filter.     dt: Real or Double scalar, sampling interval, in [seconds]   b_in: Real or Double column vector, input numerator polynomial of the normalized continuous highpass          prototype filter.   a_in: Real or Double column vector, input denominator polynomial of the normalized continuous highpass          prototype filter.     bz: Real or Double column vector, output numerator   polynomial for the digital highpass filter.     az: Real or Double column vector, output denominator polynomial for the digital highpass filter. ```Description ``` ```This function converts an input continuous domain rational transfer function (H = b_in/a_in) to its corresponding z-domain digital transfer function. The function is intended to be used with normalized, s-domain, lowpass filter functions as can be obtained from functions such as: fnbut , fncheb1 , fncheb2 , fnbes . ``` ```The sampling interval for the new filter is "dt", making the system sampling rate fs = 1/dt. Generally, the new desired cutoff frequency is in [radians/sec], wc = 2*PI*fc, and should be strictly less than half of the sampling rate. ``` ```The complex gain for this resulting filter can be evaluated with the gainz function. ``` ```The output z-domain polynomial "bz" and "az" must be declared before calling the function, though their types do not matter. ``` ```Example ``` # Design BUTTERWORTH lowpass prototype filter, fc = 1 [radian/sec] Norder  = 5;                  # Filter Order b       = novalue;            # Declare numerator   polynomial a       = novalue;            # Declare denominator polynomial fnbes(Norder,b,a);            # Make analog prototype lowpass filter # Convert filter to a digital filter bz = novalue;                 # Declare output numerator   polynomial az = novalue;                 # Declare output denominator polynomial fs = 100e3;                   # Sampling Frequency [Samples/sec] = [Hz] dt = 1d0/fs;                  # Sampling interval [Sec] fc = 1d3;                     # New highpass cutoff frequency wc = 2d0*PI*fc;               # Equivalent radian frequency fn2dhp(wc, dt, b, a, bz, az); # Convert the filter # Evaluate this filter around its cutoff. fmin    =  1d1; # Plotting Limits fmax    =  fs; ymax    =  10d0; ymin    = -100d0; ny = round((ymax-ymin)/10d0); N       = 201; # Plotting information          n       = seq(N)'-1d0; f       = logspace(log10(fmin),log10(fs/2),N)'; H       = gainz(bz,az,f,fs); HdB     = db20(H); ``` ``` ```