Embeddable NbO₂-Based Modulator with Carrier Generation and Direct Digital Modulation for Wireless Internet of Things

Wireless Internet of Things (WIoT) has garnered significant research interest in signal modulation hardware for data transmission, driven by the growing demand for smart scenarios. However, traditional modulation schemes suffer from the inherent physical separation between digital processing units and analog transmission modules, posing challenges in terms of hardware cost and power consumption. Here, an embeddable NbO₂-based frequency shift keying (NFSK) modulator is developed, which integrates a low-voltage NbO₂ oscillator with a modulation unit composed of 28 nm MOSFETs. The NFSK modulator merges the functions of carrier generation and digital modulation, enabling the direct conversion of binary signals into distinguishable oscillation frequency bands. Furthermore, to improve the bit-rate efficiency during data transmission, NbO₂-based multi-FSK (NMFSK) is further implemented by paralleling MOSFETs with various W/L ratios and assigning them sequentially according to the bit weights of the digital inputs. Using this NMFSK modulator, 4FSK-based modulation of consecutive letters is performed. The oscillation sequences exhibit smooth frequency transition, demonstrating the potential of NMFSK for applications in continuous tasks. This work provides a promising hardware deployment scheme for the embeddable modulation unit, promoting the further development of wireless transmission for IoT applications.