On-Chip Automatic LC Tuner for RFID Tags Based on Negative Resistances

It is possible to automatically tune LC networks using a Q-enhanced technique as the core of the analog tuning system. In this regard, we describe herein the design of an LC tuner based on negative resistances suitable for radio frequency identification (RFID) applications. In this brief, we review the LC tuning technique and show how the equivalent quality factor of the LC network is controlled over different voltage levels. We integrated the tuner prototype in a standard 130-nm CMOS process using an active area of 150 μm × 150 μm. Its performance was validated using off-the-shelf components that emulate the resonating circuits of an RFID system.