Program Designs Tee Attenuator To Minimize Stress

Symmetrical Tee attenuators are designed on an image-impedance basis with R_O ohms as the matching resistance. The figure(a) shows the attenuator for R_A = R_B, power input P_J-1, and power output P_J in watts, where J is a counter variable. Definitions of the terms are:

RA = RB = RO(1 - √PJ/PJ - 1)
RC = (RO2 - RA2)/2RA
PA = PJ - 1(RA/RO)
PB = PJ(RB/RO)
PC = PDSP - (PA + PB)

where P_DSP is the power dissipation.

Note that single-attenuator designs have the most power-dissipation stress. Cascaded attenuators evenly distribute the necessary dissipation \\[P_DSP = (P_IN - P_OUT)/N\\] to reduce stress (Fig. b). Those terms are defined as:

PDSP = (PIN  - POUT)/N
PJ = PIN  - JPDSP
AJ = 10 log(PJ - 1/PJ) dB

The program will design one to 10 attenuators in cascade. It prompts for the number of attenuators needed, image impedance R_O, power input P_IN, and power output P_OUT. Then for each attenuator, it displays the computed resistor values (R_A, R_B, R_C), resistor dissipations (P_A, P_B, P_C), and attenuation A in decibels.

Consider a single-attenuator design for R_O = 100 Ω, P_IN = 10 W, and P_OUT = 1 W. Using the program produces the following results:

RA = RB = 68.377 Ω, RC = 38.935 Ω
PA = 6.838 W, PB = 0.684 W
PC = 1.479 W

But a three-network attenuator design with the same requirements ends in:

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