A Waveguide-based Variable Attenuator for Terahertz Applications

This article presents a novel waveguide-based terahertz (THz) variable attenuator, integrated with a piezo-electric motor, to achieve precise and fine step values of signal attenuation. A low-resistivity silicon slab, coated with a thin layer of Titanium metal, is inserted inside a waveguide that absorbs some of the electromagnetic waves traveling through the guide. Impedance matching is achieved by gradually perforating the silicon slab and thus, creating variable impedance needed for matching. The amount of signal absorbed by the slab is determined by the sheet resistance value of the metal coating and the position of the slab in the waveguide. A miniature nanometer-scale precision piezo electric motor is used for precise control of the signal attenuation. In this work, we present the attenuator design for a frequency band of 500-750 GHz where up to 40 dB of signal attenuation was achieved, using a 1.75 mm long silicon slab with a 25 nm Titanium metal coating. The presented variable attenuator design offers compactness, scalability, and easy integration with THz sources and receivers. Furthermore, the compact size and low power consumption open up possibilities for implementation on CubeSat/Smallsat/Drone-based platforms, further expanding its potential space applications.