A 13.56MHz Wireless Power and Data Transfer Receiver Achieving 75.4% Effective-Power-Conversion Efficiency with 0.1% ASK Modulation Depth and 9.2mW Output Power

Implantable and wearable devices require both wireless power transfer (WPT) and wireless data transmission (WDT) in biomedical systems [1-3], e.g., neural recording applications [4]. Very often, amplitude modulation (AM) is preferred in these applications due to its lower power consumption and less circuit complexity in (de)modulation. To achieve the required bit-error rate (BER) lower than 10^-3, a large modulation depth (MD), typically in the range of 8% to 100%, is needed. Unfortunately, as shown in Fig. 8.4.1, the available power on the coil is reduced quadratically with respect to 1-MD during the low-amplitude time interval (t2). Large MD leads to low effective power-conversion efficiency (EPCE), defined as the combined efficiency of modulation and rectification of the WPT receiver. One solution to this problem is to separate the power and data link using two different frequencies [2-4]. This requires an extra coil or antenna, and the corresponding (de)modulator consumes higher power, not suitable for compact ultra-low power design. The challenge, which has not been addressed previously, is how to use the same coil (frequency) to transfer the maximal power (thus high WPT EPCE) while achieving the required BER.