A Single Diode-Based Reflective Type Variable Analog Attenuator

This paper presents the design and implementation of an analog variable reflective type attenuator using only one voltage-dependent impedance network. This results in low DC power consumption, compact size, and a lower cost. It is based on the use of a single hybrid coupler and a T-junction power combiner that is used to connect the coupled and through ports to a single voltage-dependent impedance network. The analytical solution is provided based on an even and odd analysis of the proposed structure. For verification, the design is implemented from 1.1 GHz to 1.2 GHz. The attenuation range is 5 dB with a small insertion loss of 0.7 dB at zero bias. The attenuation levels are also controlled digitally through an FPGA so that the variable attenuator can be integrated easily into digital systems.