Two Resonator based Approach to Extend the Tuning Range of Negative Resistance Oscillators in Active Integrated Antennas

A switched dual-band oscillator using two resonators is proposed in this paper for application in the design of active integrated antennas. In this oscillator, two independent resonators are placed in parallel which is connected to a single transistor. For the resonator to work one at a time, surface mounted (SMD) trimpots are used to emulate switches by varying the resistance from high to low. The transistor acts as a negative resistance device for two resonators independently by using two different positive feedback elements which are then switched using trimpots. Two bands of oscillation, one from 1.123 GHz to 1.505GHz and another from 1.493 GHz to 1.758 GHz are obtained by this design approach. A Wilkinson power divider is integrated with the single port oscillator circuit using an output matching network. This allows the integration of two antenna elements to form a two-element active antenna array.