**5. Conclusions**

In this chapter, several 3DMA which provide a uniform phase response and stable phase center are presented for bend angles ranging from 15° to 30°, which are essential to achieve sub-centimeter accuracies in GPS receivers using carrier phase measurements. The excellent phase performance demonstrated for the moderately bent structures is of paramount importance if circumstances require bending the element but without a significant change in the radiation pattern of the FMA. It is interesting to note that this improvement is accompanied by a slight reduction in the bore sight gain and the polarization purity of the corresponding FMA. The same conclusion applies to the upward drooping, except for a sharp drop in gain observed for the 100 mm ground plane, 10 mm flat top, and the *ε*r = 2.2 substrate. The RMS phase error of the downward DMAs ranges from 0.42° to 4.3° for the three ground plane sizes, substrates, and flat portions considered for bend angles ranging from 0° to 90°. The corresponding RMS phase error for the upward DMAs ranges from 0.8° to 9.1°. For both the downward and upward DMAs, the RMS phase error decreases when the permittivity of the substrate increases and for increasing flat tops. In general, the downward DMA outperforms the upward DMA in terms of the RMS phase error performance.

On the other hand, higher bend angles allow improved GPS tracking performance for highly-dynamic marine navigation and space-borne applications. The length of the flat top, *L*f and the bend angle, *ϕ* are found to be instrumental in the control of the radiation pattern. The upward DMA demonstrated a wider range of beam coverage compared to the FMA and downward counterparts. The half-power-beamwidth can be increased by up to 40 and 80% for the downward and upward bends, respectively, with respect to the traditional flat microstrip patch using the 10 mm flat top portion.

Finally, it is significant to stress that the design process of the 3DMA involves inevitable tradeoffs between achieving wide beam coverage, uniform phase response, gain, and polarization purity. If broad beam coverage is of precedence, some level of compromise will obviously be needed in regard to gain and multipath rejection, which requires excessive gain roll-off at low-elevation angles. Nonetheless, it turns out that the polarization purity of the proposed antenna has not significantly deteriorated since a maximum reduction of only 3 dB has been observed at the horizon in contrast to the flat microstrip structure.

*Three-Dimensional Microstrip Antennas for Uniform Phase Response or Wide-Angular Coverage… DOI: http://dx.doi.org/10.5772/intechopen.108338*
