Evaluation of an Off-Centre Fed Dipole Antenna in Passive Harmonic Radar Tags

Harmonic tags are passive radio transponders that create a harmonic return when illuminated with an RF signal. They are used to reduce the effect of clutter for otherwise indistinguishable targets. A classic harmonic tag consists of a dipole antenna, a Schottky diode and an inductive loop. In this work, we evaluate the performance of an off-centre fed dipole in harmonic tags and show that along with improved power conversion efficiency it yields a directional radiation pattern which could be detrimental in certain applications.