A Broadband Low Reflection Electronically Variable PIN Diode-based Attenuator

In this paper, variable π-type PIN diode-based attenuators are analyzed and the condition for the bias currents of the PIN diodes is extracted to achieve exact matching over the full range of attenuation. Then, a simple bias circuit is proposed based on the obtained condition to improve the input and output VSWR. The concept was demonstrated experimentally from 0.2GHz to 2GHz that shows a maximum input and output return loss of -15dB at the worst conditions over the complete range of frequency and attenuation.