Compact Reconfigurable Matching Network for Antenna Detuning Mitigation in Smart Surfaces

To address the specific design challenges posed by the Internet of Things (IoT), a compact reconfigurable matching network (RMN) is designed to mitigate detuning of smart-surface-integrated antennas. The RMN is based on a third-order Chebyshev topology, composed of quarter-wavelength stubs, having a well-decoupled varactor at the end of the three shunt stubs. The circuit is designed to mitigate the impedance mismatch between a power amplifier and an antenna being detuned by objects in its reactive near field. The low-loss transmission of the circuit is tuned by controlling the varactor voltages, thereby ideally guaranteeing a low reflection coefficient at all times. Moreover, a systematic investigation of the different loss contributions is performed by means of full-wave simulations that are verified by TRL-calibrated two-port measurements. The RMN is fabricated on a 0.25-mm-thick I-TERA substrate, exploiting printed circuit board (PCB) technology, occupying 20mm×10 mm. Measurement results show that the RMN has a minimum insertion loss of 1.83 dB over the [5.15–5.85] GHz band. Finally, the proposed RMN is validated by correcting a detuned antenna in eleven different representative IoT scenarios, herein optimizing the transducer gain while keeping the input matched at all times.