A Near-Perfect Transmissive Metamaterial Heater for Radar Applications

Microwaves are used in a variety of industries including mobile communication, satellite broadcasting, aviation altitude meter, and radar sensor, depending on the bandwidth of interest. Specifically, W-band microwaves (a frequency band of 76 to 81 GHz) are used for accurate real-time obstacle detection in radar sensors of smart mobility such as autonomous vehicles and drones. A typical radar module is equipped with a protective cover and an electrical heater, which enables an automobile to navigate even in harsh environments (i.e., icy and frost conditions). However, conventional grid-shaped heaters have a trade-off relationship between microwave attenuation and temperature uniformity because these two features heavily rely on the inherent metallic characteristics of electrodes. To address this issue, we propose a metamaterial-based transparent heater as an effective route to simultaneously achieve both high microwave transmittance and temperature uniformity/electrical conductivity.<br/>We experimentally demonstrated an electrically and thermally interconnected metamaterial-based electrical heater. A properly designed heating electrode induced artificial electromagnetic resonances and it behaves as a low-permittivity dielectric material at W-band frequencies. This enables remarkably high microwave transmission while preserving the electrical conductivity of bulk metal. We also conducted electromagnetic simulations to predict the properties of developed metamaterials and compared their simulated and measured transmission spectra in the f = 50–110 GHz range. The measured spectra were well-matched with the simulated ones; the maximum transmittance was over 90 % near 80 GHz despite the metal filling ratio exceeding 70 %, which was readily tuned by changes in structural variables. Developed metamaterial-based heaters were fabricated based on the standard semiconductor manufacturing process but can be manufactured by other scable techniques such as three-dimensional printing.