Phase-independent maximum modulation level extraction in IQ receivers

Interoperability is a central topic in enabling the global operation of mobile NFC payment systems within the existing infrastructure. However, this presents a challenge because not all devices in the infrastructure conform to standards, and the integration of suitable hardware into these devices happens slowly and is often not straightforward. On the other side, the receiver of mobile NFC systems must manage this extensive variety of devices to attain certification. Strictly speaking, the system is designed to use amplitude modulation (AM) principles, but under certain circumstances, parasitic phase modulation (PM) signals can be transmitted by these non-conforming NFC readers. In this paper, we introduce a novel signal processing algorithm that efficiently extracts the maximum BPSK modulation amplitude from AM or PM-modulated subcarrier signals. Through this algorithm, we demonstrate that the resulting signal amplitude is tripled compared to pure AM extraction. This significantly simplifies the subsequent demodulation process.