Waveguide digital step attenuator using quarter-wave resonators and memristors

Abstract A novel design of a digital step attenuator in waveguide technology is presented. The attenuator design is based on a novel unit cell that consists of a quarter-wave resonator (QWR), modified with an RF memristor and an RF resistor. The resonators are printed on the same side of a thin dielectric substrate, which is inserted in the E-plane of a standard WR-90 waveguide. In order to control the attenuation level, memristive switches change their state (ON/OFF) and turn ON or OFF every unit cell. An equivalent circuit model that consists of a cascade connection of single unit cells is developed for rapid prototyping of the attenuator. This equivalent circuit enables fine-tuning of the design, thus reducing the number of time-consuming three-dimensional electromagnetic (3D EM) simulations and the usage of computer memory. The proposed design is verified through fabrication and measurement of a waveguide attenuator that consists of three proposed unit cells. For prototype fabrication, RF resistors of 100 Ω are used. However, RF memristors are not commercially available and their characteristics in ON and OFF state are emulated by a short and open circuit, respectively. The 3D EM simulations show that memristors can indeed be emulated in such manner.