Resonant-Tunneling Diode with Spiral Bias Connections for Circularly Polarized Radiation

Resonant-tunneling diodes (RTDs) are promising electronic sources for terahertz wireless communications. A recently proposed RTD with a series-fed patch array indicates that surface waves can propagate along the extended biasing structure. In this paper, we follow this concept and present a cavity-coupled RTD with a spiral bias configuration for circularly polarized (CP) radiation with high efficiency. Full-wave simulations suggest that the structure can radiate with an axial ratio generally lower than 2 dB and a radiation efficiency above -5 dB from 400-600 GHz. A broadside directivity of around 25 dBi can be achieved at 500 GHz when the spiral structure is used to feed a hyper-hemispherical silicon lens.