Permission to publish the above information is granted.
The program was developed using a TRS-80 Model 4 computer with the DOSPLUS IV operating system and Model 4 Basic, a version of Microsoft Basic which is very similar to the one used on the IBM PC. The program should run with very minor changes using any version of Microsoft Basic. The effects of any statements which are peculiar to Model 4 Basic, DOSPLUS, or the Gemini 10 printer are explained by remarks in the program at those lines.
The program requires 16K of memory and a monochrome display. The display formats in the program use 80 columns and 24 lines.
Abstract:
This program is used to design tuned amplifier coupling networks which consist of one to eight tuned circuits each. These filter networks may be of any conventional filter type, such as Butterworth, Chebyshev or Bessel. The program calculates capacitor, inductor and resistor values, and transformer turns ratios required to form a filter network with a specified shape, center frequency, and bandwidth which will provide the desired mismatch ratios for the transistors which are coupled by it. The program also calculates low-pass prototype element values for Butterworth and Chebyshev filters. For other types of filters these must be entered from the keyboard.
Variable Descriptions:
Am: Chebyshev filter passband ripple in dB. Am=0 for Butterworth filters.
Ap: Power gain in dB.
BS, BL: Imaginary parts of source and load admittances.
BW: Bandwidth in MHz.
Ck: Tuning capacitance of k'th tuned circuit in pF.
Ck,k+1: Coupling capacitance between tuned circuits k and k+1.
Ct: Total capacitance at each node in pF.
F0: Design center frequency in MHz.
Fc: Corrected center frequency used in calculations.
GS, GL: Real parts of source and load admittances.
K: Stern stability factor.
L: Tuned circuit inductance in nH.
Mia, Moa: Input and output mismatch ratios for transistor a.
Mib, Mob: Mismatch ratios for transistor b.
MS, ML: Source and load mismatch ratios.
N: Number of tuned circuits.
N1, N2: Turns ratios at filter input and output.
Q0: Reciprocal of filter fractional bandwidth. Q0=Fc/BW.
Q1, Q2: Q's of the first and last tuned circuits in the filter.
QL: Loaded Q of a single-tuned circuit.
Qu: Unloaded circuit Q; approximately equal to inductor Q.
r: Low-pass prototype filter termination resistance for N odd,
or conductance for N even.
R1, R2: Loading resistance values at filter input and output.
S: Alignment sensitivity.
Y11, Y21, Y12, Y22: Transistor short circuit admittance parameters.
Enter these values in data statements in that order,
real part of each Y parameter first.
Yi, Yo: Transistor input and output admittances.
Sample program run showing text which is displayed on the screen:
