Non-Foster Matching of a Resistively Loaded Vee Dipole Antenna Using Operational Amplifiers

A non-Foster matching network using negative impedance converters (NICs) is proposed for a resistively loaded vee dipole antenna (RVD). The RVD suffers from considerable reflection at the feeding transmission line at low frequencies because of its large negative input reactance. To reduce the reflection, a non-Foster matching network, which is composed of NICs based on operational amplifiers (op-amps), is proposed. For the practical design, the effects of input parasitic capacitances of the op-amp and the finite open-loop gain are considered. The stability analysis is performed according to the Barkhausen stability criterion. The non-Foster matching network is implemented with the RVD as a load. The measured impedance demonstrates that the matching network significantly reduces the input reactance of the RVD. In the time-domain analysis, the matched RVD is shown to reflect significantly less incident pulse. A target was imaged through a series of radar echo experiments. The images show that the non-Foster matching network enhances the performance of the RVD as an antenna for the ground-penetrating radar.