Chipless RFID Tag Based on Electrically Small Spiral Capacitively Loaded Dipole

This letter presents the novel 20 bit chipless radiofrequency identification transponder (tag) based on spiral capacitively loaded dipole scatterers of electrical size ka = 0.47, radar cross-section (RCS) σ = -29.3 dBsm, and bandwidth BW
_3dB
= 20.9 MHz. It outperforms U-folded dipole scatterer (ka = 0.79, σ = -34.3 dBsm, BW
_3dB
= 18.1 MHz) in the first two parameters in exchange for a slight increase in bandwidth. The total tag size (17 × 68 mm
²
) is roughly half the size of a credit card. The frequency and amplitude stability of its RCS response, when the zero bit information is coded via removal of individual scatterers, is improved by reordering scatterers in the array. The simulated results were verified by the monostatic measurement of tag RCS.