Frequency-Tunable Slot-Loop Antenna Based on KNN Ferroelectric Interdigitated Varactors

A miniature frequency-tunable slot-loop antenna (0.128 lambda(0) x 0.077 lambda(0)) based on ferroelectric K0.5Na0.5NbO3 (KNN) interdigitated varactors is investigated at Ku-band. KNN material has been selected among the ferroelectric oxide family because of its competitive properties for microwave applications. Its high permittivity value (epsilon(r) approximate 360 at 10 GHz) and its wide frequency tunability under an external static electric field E-bias make it a promising candidate for frequency-agile antennas and circuits at microwaves. The antenna prototype has been designed and elaborated on MgO substrate (epsilon(r) = 9.8 and tan delta approximate 10(-4) at 10 GHz). Fabrication details including laser microetching process of the ferroelectric layer are also described. The center frequency of the slot-loop antenna can therefore be tuned monotonously from 15.22 to 15.97 GHz under E-bias = 88 kV/cm, leading to a frequency tunability rate equal to 4.6%. These results demonstrate for the first time the ability of the KNN material to be used for miniature tunable antennas, in comparison with BaxSr1-xTiO3, currently considered as the most relevant material for such applications.

Automated summary

This study investigates a miniature frequency-tunable slot-loop antenna based on KNN material, which has competitive microwave properties and is suitable for frequency-agile antennas. By fabricating the antenna prototype on an MgO substrate and using laser microetching technique, successful tuning of the antenna center frequency is achieved. The KNN material demonstrates for the first time the potential for application in miniature tunable antennas.