CPW-fed oscillating microstrip antennas

The use of active microwave solid state devices providing localized power drive for planar antenna elements has simulated interest over the past few years particularly for low cost phased array radar, spatial power combiner and automatic vehicle tolling applications. This article describes two oscillators that use a CPW-fed microstrip antenna not only as the radiating element, but also as the output resonating load which determines the oscillation frequency. The antenna is excited by an inductively coupled slot for the first oscillator and a slot-loop for the second oscillator. As CPW lines make connection of active components easier, they have been chosen for the feeding of the excitation slots. Since it facilitates the DC bias isolation, a microstrip antenna excited by a slot-loop is proposed as a compact and easy-to-fabricate oscillating antenna with a small number of soldering points and no via holes, unlike oscillating antennas fed by microstrip lines.