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We present experimental measurements and analysis of RF interference between a passive RFID system and a generic frequency hopping communications system in the 902 MHz to 928 MHz ISM radio band. Interference in both directions is considered, RFID to communications and vice-versa, and interference mitigation strategies are assessed. Variables of interest include transmission power, antenna locations and polarization, and frequency hopping channel bandwidth and dwell time. Among the findings are the susceptibility of the RFID backscatter link to sources operating within regulatory limits, characterization of the performance asymmetry between the systems, and the constructive effect of interference to RFID at low powers.

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This paper examines the relative roles of the forward and reverse links in determining the operational range of passive UHF RFID systems. Simple free space examples in free space show when the forward or reverse link may be the main range constraint in practical systems, depending on reader and tag characteristics. Measurements of transmission and scattering off of a dipole in a real environment demonstrate showed different multipath effects; transmission power fading squared disagreed with backscattered fading in the test environment by up to 8 dB within a measurement range of 2 m.

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Abstract-This paper presents an approach for calibrating backscattering measurements from 860-960 MHz Ultra-High Frequency Radio Frequency Identification (UHF RFID) tags. An Sparameter model is formulated to relate diode switch and antenna input circuit parameters with the scattering performance of the calibration device. Measurements of modulated backscattered power agree with the model to within ±0.1 dB. Tag backscatter measurements can then be calibrated by comparing them to the reference signal. In an example testbed, the expanded uncertainty of these measurements is estimated to be ±0.4 dB, compared with uncertainties worse than -0.9 dB, +1.2 dB for methods that calibrate against radar cross section (RCS) standards in the same testbed.