Low Phase-Noise Self-Oscillating Cross-Coupled Active Antenna

A low phase-noise 7.1 GHz active oscillating antenna fabricated on a 10 mil Rogers 5880 is reported. Two low-cost bipolar transistors are employed to implement a cross-coupled oscillator. The proposed configuration consists of two planar antennas driven by the cross-coupled two-transistor oscillator. The differential symmetry of the proposed active antenna maximizes the radiated power along the antenna boresight at the fundamental oscillation frequency with reduced radiated power at the second harmonic. Due to the cross-coupled configuration, the radiated signal shows low phase-noise characteristic. Measurements on the fabricated active antenna indicate that it consumes 42 mW dc power and has a phase noise of -101.7 dBc/Hz at 100 kHz frequency offset. The proposed cross-coupled active antenna exhibits an estimated effective isotropic radiated power of 12.5 dBm.