Far-Field Testing Method of Spurious Emission Produced by HF RFID

We present measurements of spurious emission produced by high-frequency radio frequency identification (HF RFID) using carrier frequency of 13.56 MHz. HF RFID tags produce unwanted emission due to rectification and more generally due to nonlinearity of analog front end. Depending on the conducting material of an HF RFID coil and surrounding dielectric material, the coil behaves as more or less good antenna on some harmonic frequencies. Exact characterization and analysis of unwanted emission is important from the security perspective as well as from the perspective of interference with other systems. Consequently we measured the harmonics produced in the integrated circuitry and characterized radiation properties of the antenna. Finally we present the measurements of the spurious emission performed in a Gigahertz Transverse Electromagnetic (GTEM) cell

Optimal card design for non-linear HF RFID integrated circuits with guaranteed standard-compliance

The state-of-the-art design criteria for High Frequency (HF) Radio Frequency IDentification (RFID) cards at 13.56 MHz depend on the choice of a resonance frequency and a quality factor of the card. Our investigations show that these values are a result of the Integrated Circuit (IC)'s non-linearity and its dynamic range. We describe our accurate method for calculating the IC's circuit model during loaded and unloaded states. The dynamic range is identified where the IC is capable of achieving load modulation for all basic bit rates (106-848 kbit/s). The calculated IC's circuit model is simulated and compared to measurements showing good agreement. We formulate a constrained minimization problem based on the IC's circuit model, its dynamic range, including the entire card's parasitics, as well as loading effects from the reader side. The problem's solution is the optimum inductance for the card's coil that renders a standard-compliant HF RFID card. A prototype card is manufactured based on the optimum inductance and we show that it passes the standardized tests and operates for all basic bit rates within the field intensity range from 1.5 to 7.5 A/m, as specified.NXP semiconductors Austria GmbH47843478561