From Modern Antenna Design by Milligan , "An Alford loop feeds two dipoles curved into a loop that radiates an omnidirectional pattern with horizontal polarization when located horizontally over a ground plane." An Alford loop has a 1 wavelength circumference, but has a similar radiation pattern as that of an electrically small loop.
When the elements of the folded dipole and the Alford loop are combined, the desired impedance match can be achieved using the properties of a folded dipole, and the desired radiation pattern can be reached from the Alford loop shape.
There is no imaginary component of the input impedance because the Alford loop is a resonant loop antenna.
Form the two elements from step 1 into an Alford loop.
In this paper, a triband omnidirectional CP cylindrical dielectric resonator antenna (DRA) with a top-loaded modified Alford loop which satisfies 1.9 GHz GSM, 2.4 GHz WLAN, and 3.5 GHz WiMAX applications is proposed.
As shown in Figure 1(a), the circular patch of the modified Alford loop that locates on the top of the DRA has a diameter of [d.sub.1].
In this paper, a triband omnidirectional CP DRA with a top-loaded modified Alford loop is proposed.
Adopting the left-hand loading loop  and the Alford loop
structure  can obtain good impedance match, but which have a disadvantage of complicated configuration.
The most famous HP omnidirectional wire-structure antenna is the Alford loop .
R., "Omni-directional horizontally polarized Alford loop strip antenna," US Patent 5767809, Jun.