Self-Oscillating Semi-Ring Active Integrated Antenna With Frequency Reconfigurability and Voltage-Controllability

A compact frequency-agile self-oscillating semi-ring active integrated antenna is presented and investigated. Without changing the circuit footprint, the proposed active antenna achieves frequency reconfigurability and voltage-controllability simultaneously with a PIN diode, a varactor diode, and proper biasing network. The oscillation frequency can be controlled from 4.47-4.85 GHz in the OFF state and 5.03-5.33 GHz in the ON state. The VCO gains are 17.7 and 16.4 MHz/V in the two states. Benefitting from the feedback path, the proposed active antenna, with a miniature size of 0.046λ 0 2 , shows well-behaved phase noises of -106.2 and -98.7 dBc/Hz at a 1-MHz offset from the carriers.