Compact Self-Oscillating Active Integrated Loop Antenna With Concurrent Dual-Band Operation

In this letter, a compact concurrent dual-band self-oscillating active integrated loop antenna is proposed. In the design, an active switching circuit is integrated and multiplexed into two RF channels of a modified loop radiator to achieve concurrent dual-band self-oscillation and pulse radiation in a small system size. Two capacitors are embedded in the loop radiator to block the dc paths without cutting off the RF oscillation and radiation channels, thereby ensuring that the dc power supply could charge the antenna. In this way, dc energy can be stored in the antenna during the charging phase and be converted to dual-band pulses during the radiation phase. Experiments are carried out to validate the proposed design. The overall circuit size is only 0.03
$\lambda _{m}^{2}$
at the mean frequency of the two frequency bands.