Time-Modulated Antenna Array With Beam-Steering for Low-Power Wide-Area Network Receivers

The Internet of Things (IoT) denotes a concept of connected devices that communicate seamlessly over the Internet. The wireless connectivity between IoT nodes and the Internet gateways can be realized in unlicensed frequency bands upon the low-power wide-area network (LPWAN). It is foreseen that due to a massive introduction of IoT devices the unlicensed bands will experience an increased interference level which will negatively affect the communication performance. Therefore, adaptive solutions should be considered to obtain robustness. This letter presents a time-modulated antenna array (TMAA) for LPWAN receivers and demonstrates its interoperability with a commercial of-the-shelf LoRa device. According to the conducted experimental investigation, whereby the beam-steering is obtained over the sidebands inherently generated by the TMAA, both the received signal strength and the signal-to-noise ratio (SNR) are improved by means of the progressive delay applied to the time modulation functions.