Single-Transistor Impedance Matching Circuit for Over-Hundred-Octave Active Antennas
Shuyu Wang, Yue Li
Abstract
In this article, a novel active impedance matching circuit with a single transistor is studied for antennas to cover over a hundred-octave bandwidth. In the proposed matching circuit, only one field effect transistor (FET) is utilized and biased in the ohmic region. The FET is integrated with a dipole antenna at the gate, and connected with a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$50~\Omega $ </tex-math></inline-formula> transmission line at the drain. With small dimensions, this active antenna performs as a receiver with a wide impedance bandwidth of 10 MHz–1.9 GHz, in which the reflection coefficient is lower than −10 dB, covering 190 octave bandwidth. An equivalent circuit model of the ohmic-biased FET is built to analyze this unusual wideband performance, which exhibits promising applications in ultrawideband (UWB) electromagnetic sensing systems with extremely restricted volume.