Constructive interference may be obtained by spacing elements at multiples of λ/4. Placement on a λ/2 square grid is

shown in figure 7. The resulting enhanced gain is shown in the lower part of figure 8.

Figure 8. Antenna gain for single helix in upper figure (2 dBi maximum). Gain for 16x16 helix array in lower figure

with (26 dBi maximum).

The 2 dBi gain for the single helix may be improved with additional windings. The 26 dBi gain achieved by the 16x16

array demonstrates the additive effect produced by the array layout. Both the single helix and 16x16 array were

simulated with a flat ground plane; the side lobes seen in the patterns may be reduced through modifications to the

ground plane.

The effects of constructive interference on the magnitude of the electric field for an 8x8 helical array are

pictured in figure 9. In 9(a) the field surrounding the antenna is guided from a diverging wavefront to a near-planar

wavefront. In figure 9(b) it is apparent that the individual fields add in a constructive manner to yield a field strength

approaching 0 dB. Field addition is optimized by the unison phasing of the individual sources and the λ/2 grid spacing.

To obtain a scaling rule for the performance as a function of antenna elements, simulations were run for various

array configurations as given in table 3. The figures of merit in the table are the gain and the half-power beam width.

The HPBW measures the angular spread between -3 dB points in the antenna gain pattern. As the HPBW decreases with

the addition of more antenna elements, the beam is more directive and the gain is increased. The HPBW performance is

plotted in figure 10 and antenna array gain in figure 11.