A <i>W</i>-Band Waveguide Adjustable Attenuator Based on Quadrature Hybrid Couplers

In this work, a novel full <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">W</i>-band waveguide reflection-based adjustable attenuator (WRAA) based on quadrature hybrid couplers (QHCs) is presented. The attenuator consists of input and output couplers and two basic reflective elements. Attenuation is controlled by adjusting the height of the rectangular metallic posts on the broad wall of the waveguides. The attenuator’s return loss (RL) is improved due to using QHCs. Measured results from 75 to 110 GHz indicate that the attenuator has a flatness of better than ±1.89 dB (±3.86 dB) within the 0–15-dB (15–35 dB) attenuation range, with a typical RL of 20 dB and a minimum of 14 dB. In addition, the power capacity of attenuator is more than 3 W based on continuous-wave measurement. This design provides a simple and low-cost solution for waveguide adjustable attenuators.