Dual‐loop antennas with an expanded axial ratio bandwidth

Abstract

The authors propose a novel dual‐wire antenna with a balanced feed to increase a 3‐dB axial ratio bandwidth. The antenna comprises loop elements with quasi two‐sources, and the effects of the element distance on the axial ratio bandwidth are revealed using the method of moments (MoM). It is found that the antenna has a maximum bandwidth of 41% at a distance of 0.15 wavelengths, three times as wide as that of an isolated loop element. Subsequently, the balanced feed is changed to a quasi‐balanced one using L‐figured parallel feedlines. It is found numerically and experimentally that the antenna shows an axial ratio bandwidth of 28%.

Series-fed Loop Antenna Arrays with an Expanded Bandwidth of Circular Polarization

“…For this, the parameters (P , h B ) and (P , ℓ) of the present and reference loop elements are optimized for CP radiation [9 and 7], respectively, with the loop distance d being for the normal beam formation. We also optimize the height h L of a straight feedline F -T for impedance matching [12]. Note that the reference antenna has a coplanar feedline F -T as a spiral element array [8], h L = H.…”

“…This paper contributes to the fact that mutual coupling effects of loops [12] are applied to a series-fed array antenna to realize an axial ratio bandwidth comparable to that of a non-resonant element array. In [12], the mutual coupling effects between two loops with quasi-two sources expand the axial ratio bandwidth of an isolated loop with quasi-two sources by a factor of 3. These significant effects are the working mechanism of the present loop element array.…”