Abstract
Batteryless compact radios are highly needed to realize many Internet-of-Things (IoT) applications, such as miniaturized radio-frequency identification (RFID), wear- able/implantable devices, and counter-counterfeit electronics. To miniaturize the radios, it is necessary to integrate an antenna on chip to transfer both power and data, eliminating the I/O pads and crystal. In addition, the ultra-small die area precludes the use of any on-chip energy storage (such as large capacitors or induc- tors); therefore, sufficient power must be supplied wirelessly. As a result, two challenges must be overcome for uplink communi- cation. First, the wireless power tone acts as a large blocker for the uplink communication signal, resulting in a poor uplink signal-to-noise ratio (SNR). Second, without a crystal, the on- chip oscillator will be noisy and subject to further degrading the uplink SNR. In this article, we have demonstrated an RFID system used to detect counterfeit electronics that addresses the design challenges by the proposed two-tone technique. With an overall dimension of 116 µm × 116 µm, the “dielet” radio chip is fabricated by a 65-nm CMOS technology, which is batteryless, padless, and crystalless. This is the smallest functional radio chip to date, and the measurement results show that both the uplink signal-to-blocker ratio (SBR) and SNR can be improved by the new two-tone technique.