Gigahertz Large-Area-Electronics RF Switch and its Application to Reconfigurable Antennas

Future IoT and 5G networks place significant new demands on antennas, where unguided EM waves are generated to access densely distributed sensor nodes. Reconfigurable antennas, capable of changing key parameters (directionality, frequency response, polarization), are starting to play a critical role, but are limited by the assembly of discrete RF components across the large antenna apertures typically desired. This work presents the design, and use in a reconfigurable antenna, of RF switches for 2.4 GHz-band wireless applications, based on large-area-electronics (LAE) zinc-oxide (ZnO) thin-film transistors (TFTs). ZnO TFTs can be fabricated monolithically on meter-scale and flexible substrates, as done in flat panel displays, but where their frequencies have been limited to 10's of MHz. RF switch performance is enabled for ZnO TFTs (fabricated at flex-compatible temp. <; 200°C) via self-aligned processing, thick-composite gate electrodes, breakdown-safe biasing, and resonant operation, leveraging high-Q LAE inductors. Reconfigurable antenna radiation patterns are demonstrated.

I. Introduction and RF Switch Application

IoT/5G networks envision wireless sensing from a large number of densely distributed nodes, to control on-demand delivery of high-bandwidth content. Accessing sensors, typically in the 2.4 GHz band, raises critical requirements (such as direction finding/steering, spectrum allocation, etc.), motivating reconfigurable antennas that are capable of changing key parameters (directionality, frequency response, polarization), to meet simultaneous constraints¹.