
                       SUBPROGRAM PZ

This program helps define the individual second order stages that are
cascaded for specific filter functions. In the case of odd order filters
one first order stage will also be included. Data is entered in response
to questions such as:

         Filter shape ( lowpass, highpass etc. )
         Polynomial ( Butterworth, Chebyshev, elliptic )
         Maximum allowable passband ripple
         Minimum attenuation in the stopband

Once this information is entered, the program calculates the required order
and the poles and Q for each section. In the case of bandpass filters the
program also calculates the numerical factor ( Gain Adjustment Factor )
needed for computing the proper gain at the system center frequency. This is
required when stages with differing individual center frequencies are cascaded.

At the option of the user, the frequency response of the filter is also
calculated, providing information on amplitude, phase and group delay. Several
different response checks can be made, focusing on different frequency ranges
if desired.
***
                          GRAPHICS

During subprogram PZ the user has the option of examining the frequency
response using the FV graphics option. If the output files are to be used for
graphics then it is advisable to use sufficient sample points to make a smooth
curve. The minimum should be 50 and the graphics can handle at the most 200.
If the output files are to be used as printed files then any number of points
may be used. If the user expects to plot with a log frequency axis then best
results will be obtained using the log option for the plotting intervals.
The graphics option may be used later so long as the output files remain in the
directory.
***
                           PROGRAM OUTPUT FROM PZ

A brief report appears on the screen and a more detailed report is sent
automatically to disk files named PZ1.R, PZ2.R etc. and directly to a
printer on request.

Frequency response data relating to the designs will be in files:

        PZ1A, PZ1B, PZ1C, etc. for design PZ1.R
        PZ2A, PZ2B, PZ2C, etc. for dedign PZ2.R

After leaving the program and returning to DOS the output files may be
accessed by commands such as the following:

A:\> type b:pz1.r       Output appears on screen. Start and stop scrolling
                        with CONTROL-s

A:\> print b:pz1.r      If a suitable printer is connected

A:\> copy b:pz1.r prn    If a suitable printer is connected
***

