A 5.8GHz power-harvesting 116μmx116μm “dielet” near-field radio with on-chip coil antenna

The proliferation of the Internet of Things (IoT) and low-power sensors would benefit greatly from batteryless compact radios that require no external components. Such a radio could be used for future RFID, wearable/implantable devices, and counter-counterfeit electronics. Previous demonstrations have focused primarily on miniaturizing the radio size [1,2], but relying on off-chip antennas. Two challenges must be overcome to enable sufficiently small radios with on-chip antennas [3]: 1) In most state-of-the-art radios [3-6], the device antenna is connected to both the downlink signal path and the power management unit. Relying on separate signal and power paths incurs an area penalty and degrades antenna matching. In addition, it would be difficult to get a high downlink data-rate since the weak power transfer cannot be disturbed by communication data with a high-index modulation. 2) The ultra-small die area precludes the use of any on-chip energy storage (such as large capacitors or inductors) or a large antenna, so sufficient power must be supplied wirelessly. The wireless power tone acts as a large blocker for the uplink communication signal, resulting in a poor uplink signal-to-noise ratio (SNR) and signal-to-blocker ratio (SBR). In [4], the radio dimension was reduced to 500μm×250μm, but the achieved uplink SNR was only 10dB. To circumvent the blocker issue in the uplink, dual antennas were adopted in [5] and [6] to split the wireless powering tone and uplink tone into two frequencies, resulting in a die area larger than 4.4mm
²
.