A compact broad-band helical antenna with two-wire helix

A new method of increasing the bandwidth of normal-mode helical antennas (NMHA) is proposed. The antenna has length of around 0.1 of the target wavelength, and consists of a helix constructed with two flat wire strips. The method exploits the two current modes of the two-wire design to obtain wideband response. Based on an analysis of the equivalent circuits of the two modes and subsequent optimization of design parameters, a final two-strip NMHA design is proposed that is demonstrated to have a bandwidth of 12% in the 760-MHz band at a voltage standing wave ratio of less than 2.