| 摘要 |
A step attenuator comprises two branchline couplers with two coupling transmission lines therebetween. Attenuation is accomplished through switchable resistors, in series with switching diodes, shunted across the transmission lines. These resistors reflect and absorb incident power. Switching signals are provided to the diodes through the branchline couplers and the coupling transmission lines. The reflected power is absorbed by a matched termination at the port of the input branchline coupler that is isolated from the port at which the signal to be attenuated is coupled. Phase shift and insertion loss are minimized by tuning the series inductance inherent in the diode resistor combination with tuning capacitors in series therewith. These capacitors are by passed by low-susceptance inductors which provide a dc path to ground for the diodes.
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