Folded L-antennas

The concept of folded L-antennas is to increase the radiation by adding additional parasitic L-radiators. To enhance the performance, these parasitic L-radiators are shorted to the driving L-radiator about a quarter of a wavelength (/spl lambda//4) away from the feeding point. The circuit models for the inverted and folded L-antennas were established to investigate the unloaded antenna quality (Q) values, the intrinsic and commonly used 50-ohm bandwidths, and radiation and broadbanding capabilities. It is shown that folded L-antennas broaden the antenna bandwidth via the increase of the effective antenna thickness, impedance step-up, and proper susceptance compensation. The impedance increase of folded L-antennas depends not only on the wire thickness ratio but also on the relative positions of the driving and parasitic radiators.