InP-Based THz Beam Steering Leaky-Wave Antenna

For mobile THz applications, integrated beam steering THz transmitters are essential. Beam steering approaches using leaky-wave antennas (LWAs) are attractive in that regard since they do not require complex feeding control circuits and beam steering is simply accomplished by sweeping the operating frequency. To date, only a few THz LWAs have been reported. These LWAs are based on polymer or graphene substrates and thus, it is quite impossible to monolithically integrate these antennas with state-of-the-art indium phosphide (InP)-based photonic or electronic THz sources and receivers. Therefore, in this article, we report on an InP-based THz LWA for the first time. The developed and fabricated THz LWA consists of a periodic leaking microstrip line integrated with a grounded coplanar waveguide to microstrip line (GCPW-MSL) transition for future integration with InP-based photodiodes. For fabrication, a substrate-transfer process using silicon as carrier substrate for a 50-mu m thin InP THz antenna chip has been established. By changing the operating frequency from 230 to 330 GHz, the fabricated antenna allows to sweep the beam direction quasi-linearly from -46 degrees to 42 degrees, i.e., the total scanning angle is 88 degrees. The measured average realized gain and 3-dB beam width of a 1.5-mm wide InP LWA are similar to 11 dBi and 10 degrees. This article furthermore discusses the use of the fabricated LWA for THz interconnects.