Frequency Tunable Millimeter-Wave Patch Antenna Integrating Ferroelectric Capacitors

We present the design, realization and performance of a millimeter-wave patch antenna with frequency reconfiguration capabilities generated by integrating ferroelectric interdigitated tunable capacitors (FIDC). The tunable capacitors are based on Ba ${}_{\mathbf {0.8}} {\mathbf { Sr}} _{\mathbf {0.2}} {\mathbf { TiO}} _{\mathbf {3}} {\mathbf {(BST)}}$ ferroelectric layers and exhibit very good and stable performances over the microwave and millimeter-wave bands, with a maximum tunability of 40% for a bias voltage of 100 V. The ferroelectric layers have been integrated in the slot-loop excitation circuit of the antenna and their Direct Current (DC) polarization allows a continuous frequency reconfiguration of the antenna around 30 GHz. An electrical model of the whole radiating device has been developed allowing extracting the range of capacitance values to be integrated into the excitation slot for an optimum frequency tuning. The fabricated antenna shows a variation of the operation frequency from 28.5 GHz to 34.95 GHz, corresponding to a frequency tuning of 22.6%. The antenna is very well matched all over the operating frequency band, with total efficiencies between 20% (0 V bias on FIDCs) and 65% (100 V bias).