Theory and measurement of backscattering from RFID tags

Reference modulation for calibrated measurements of tag backscatter

“…The current ISO/IEC 18047-6 method introduces further systemic error by directly subtracting power quantities, neglecting phase effects, though existing works show how phase can be considered correctly [7][8] [9]. Adding and removing the entire thin rod calibration standard introduces systemic error via structuralmode modulation, which interacts with multipath in the test environment differently [2] than tags' antenna-mode modulation [7] [8].…”

“…[7] [13]) or "modulated" ( [14]) radar cross section (RCS). These terms are also sometimes used interchangeably with the terms "delta RCS" or "∆RCS" used in ISO 18047-6, though this term may cause confusion over the role of phase in tag scattering.…”

“…The modulated RCS model is formulated with power waves [7][13] [14][15], which should not be confused with the Sparameter traveling waves used in this paper. The power wave parameters are convenient for chip-to-antenna matching in tag design.…”

Remote Characterization of Microwave Networks - Principles and Applications

“…2(a) and (b), the scattering antenna should scatter back the same power irrespective of the type of lossless termination (including open and short), as they all produce a reflection coefficient of unity and therefore the radar cross-section (RCS) should be ideally constant. However, a counter-example in the form of 'minimum-scatter antennas' (Kahn 1965, Nikitin 2006 (6)) appears to be a more suitable metric. 4.…”

“…the antenna scatters so as to cancel some of the incident fields (Kahn 1965). Ideally we would prefer no 'structural scattering' (Nikitin 2006, Hansen 1989) from a scattering antenna, i.e. no scattering when the said antenna is terminated by a matched load.…”