Electrically Small Antennas with Miniaturized Impedance Matching Circuits for Semiconductor Amplifiers

In order to reduce the size of a wireless system, we propose a design theory for the broadband impedance matching circuit which connects an electrically small antenna (ESA) to a semiconductor amplifier. We confirmed its validity for the case of connection between a small slot loop antenna with a small radiation resistance of Ra = 0.776Ω and a semiconductor amplifier with high input impedance of ZL = 321 − j871Ω with the aid of the simulations by the electrical circuits using transmission lines as well as the electromagnetic field (EM field) simulator. We also made experiments on this antenna with matching circuits using high temperature superconductor YBCO thin films on MgO substrates. key words: RF front-end, miniaturized matching circuit, electrically small antenna, semiconductor amplifier, coplanar waveguide