Digital implementation of a demodulator for HF RFID reader device

Tilen Svete


This paper presents a demodulator for high frequency radio frequency identification (HF RFID) signals based on the Costas loop [1]. A description is presented of how correlation between two signals can be simplified in terms of the operations involved and implemented using a digital Costas loop [2, 3]. The demodulator is used to demodulate a subcarrier signal, after carrier direct conversion and bandpass filtering. A brief description is given of the signal characteristics of HF RFID signals at a carrier frequency of fc = 13.56 MHz and the operation of the subcarrier demodulator. Packet error rate (PER) measurement results for protocols ISO/IEC 14443 type A and type B at a bitrate fc/128 (approximately 106 kbit/s), FeliCa at fc/64 (approximately 212 kbit/s), and ISO/IEC 15693 at fc/512 (approximately 26.48 kbit/s) are presented. A comparison is given between the measured PER results and the theoretical BPSK PER limit,  and with a HF RFID reader IC ST25R3911 [4], where an almost 11 dB improvement in PER performance for ISO/IEC 14443 type B fc/128 was achieved.


HF RFID reader; digital demodulator; correlation; Costas loop; packet error rate

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J. Costas, “Synchronous Communications,” Proceedings of the IEEE, vol. 44, p. 1713-1718, 1956.

B. Shamla, K. G. Gayathri Devi, “Design and Implementation of Costas loop for BPSK Demodulator,” India Conference (INDICON), 2012 Annual IEEE, Kochi, 2012.

P. Shachi, Rahul Mishra, Ravi Kumar Jatoth, “Coherent BPSK Demodulator using Costas Loop and Early-Late Gate Synchronizer,” 2013 Fourth International Conference on Computing, Communications and Networking Technologies (ICCCNT), 2013.

STMicroelectronics, “ST25R3911 NFC/HF Reader IC." Available:

Y.-H. Kim, M.-W. Seo, Y.-C. Choi, H.-J. Yoo, “A 13.56 MHz Receiver SoC for Multi-Standard RFID Reader,” Electron Devices and Solid-State Circuits, 2008.

H. Min, Y. Liu, C. Huang, “Digital Correlation Demodulator Design for RFID Reader Receiver,” Wireless Communications and Networking Conference, 2007.

C. Angerer, “A Digital Receiver Architecture for RFID Readers,” Symposium on Industrial Embedded Systems, 2008.

John G. Proakis, M. Salehi, Digital Communications, Fifth edition. McGraw-Hill, 2008.


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