It is shown that the Direction-of-Arrival (DoA)information carried by an incident electromagnetic wave can beencoded into the evanescent near field of an electrically smallantenna array with a spatial rate higher than that of the incidentfield oscillation rate in free space. Phase conjugation of thereceived signal leads to the retrodirection of the near field in theantenna array environment which in turn generates aretrodirected far-field beam towards the original DoA. Thiselectromagnetic phenomenon enables electrically smallretrodirective antenna arrays with superdirective, angular superresolution,auto-pointing properties for an arbitrary DoA.Theoretical explanation of the phenomenon based on firstprinciple observations is given and full-wave simulationsdemonstrate a realisability route for the proposed retrodirectiveterminal that is comprised of resonance dipole antenna elements.Specifically it is shown that a 3-element disk-loadedretrodirective dipole array with 0.15λ spacings can achieve3.4dBi maximal gain, 3dBi front-to-back ratio and 13% returnloss fractional bandwidth (at 10dB level). Next it is demonstratedthat the radiation gain of a 3-element array can be improved toapproximately 6dBi at expense of the return loss fractionalbandwidth reduction (2%).
|Journal||IEEE Transactions on Antennas and Propagation|
|Publication status||Published (in print/issue) - 17 Apr 2016|
- Dipole antennas
- Antenna radiation patterns
- Directive antennas
- Phased arrays
- Receiving antennas