An Energy-Efficient and High-Data-Rate IR-UWB Transmitter for Intracortical Neural

Abstract

This article presents an implantable impulse-radio ultra-wideband (IR-UWB) wireless telemetry system for intracor- tical neural sensing interfaces. A 3-D hybrid impulse modulation that comprises phase shift keying (PSK), pulse position modula- tion (PPM), and pulse amplitude modulation (PAM) is proposed to increase modulation order without significantly increasing the demodulation requirement, thus leading to a high data rate of 1.66 Gbps and an increased air-transmission range. Operating in a 6–9-GHz UWB band, the presented transmitter (TX) s upports the proposed hybrid modulation with a high energy efficiency of 5.8 pJ/bit and modulation quality [error vector magnitude (EVM) <−21 dB]. A low-noise injection-locked ring oscillator (ILRO) supports 8-PSK with a phase error of 2.6 ◦. A calibration-free delay generator realizes a 4-PPM with only 115 µW and avoids potential cross-modulation between PPM and PSK. A switch-cap power amplifier (PA) with asynchronous pulse-shaping performs 4-PAM with high energy efficiency and linearity. The TX is implemented in 28-nm CMOS technology, occupying a 0.155 mm 2 core area. The wireless module including a printed monopole antenna has a module area of only 1.05 cm 2. The TX consumes in total 9.7 mW when transmitting −41.3-dBm/MHz output power. The wireless telemetry module has been validated ex-vivo with a 15-mm multi-layer porcine tissue, and achieves a communication (air) distance up to 15 cm, leading to at least 16 × improvement in distance-mo