PhD graduate from SET group presents innovation project at global premier conference for IC design

PhD graduate Henry Kennedy has presented a further innovation in his wireless power technology project at the 2019 International Solid State Circuits Conference in San Francisco, the global premier conference for IC design. The leader of the research, Prof William Redman-White, was previously the chairman for the conference's analogue subcommittee. The project, led by Prof. William Redman-White, has addressed several fundamental issues in the operation of inductive link transmitters intended for such applications as wireless power, RFID and security systems, where both power and data need to be delivered simultaneously to some remote device. Because of the complexity restrictions placed on a device relying on inductively coupled power, such links are limited to quite simple data transmission schemes, such amplitude and phase shift modulation. To achieve good coupling range and power efficiency, the transmit inductor should operate at resonance with low losses, (or high Quality Factor). These requirements are in direct conflict with data transmission, as the bandwidth of a resonant circuit is inversely proportional to its Q-factor. The restriction of data bandwidth is a particular problem where security is critical, as in RFID or car security, as this restricts the amount of cryptographic information that can be transferred in a practical situation. Further, operation with a high Q-factor makes the transmitter very sensitive to environmental changes such as proximity to ferromagnetic objects, as well as to manufacturing tolerances.

Dr Kennedy, with support from Teerasak Lee and Dr Rares Bodnar, has developed fully integrated designs which can deal with the issues of environmental and tolerance effects on a high Q transmitter, by means of a novel adaptive switched fractional capacitance tuning technique that provides precise control without the need for off-line calibration or large numbers of external components. The work has continued, addressing the challenge of delivering fast data despite the theoretically restricted bandwidth. A second IC design has been developed that employs another new technique to achieve instantaneous adaptive/predictive tuning of the transmitter antenna coil, following the frequency and phase changes on a cycle-by-cycle basis, thereby allowing data modulation rates to exceed classical bandwidth/Q-factor limits.

Both designs have been demonstrated as fully integrated mixed analogue-digital IC implementations in a smart-power CMOS technology. As well as obtaining two patents for the techniques, this is the second time the team has presented a paper at the ISSCC conference, a very rare achievement for academic submissions from a single project. It also marks a particularly satisfying end to 35 years of analogue IC design research in Southampton, as Prof. Redman-White (also previously the chairman for the ISSCC conference's analogue subcommittee) is now retired as emeritus professor.

For more information on the project see the full ISSCC 2019 pape: 'A High-Q Resonant Inductive Link Transmit Modulator/Driver for Enhanced Power and FSK/PSK Data Transfer Using Adaptive-Predictive Phase-Continuous Switching Fractional-Capacitance Tuning' (https://ieeexplore.ieee.org/document/8662329).