Compact 2 x 2 Coupled Double Loop GPS Antenna Array Loaded With Broadside Coupled Split Ring Resonators

The design and nulling capability of a compact 2 x 2 dual-band coupled double loop (CDL) GPS antenna array loaded with broadside coupled split ring resonators (BC-SRR) are presented. The high level of L-2 band mutual coupling is reduced by utilizing mu-negative (MNG) BC-SRR metamaterial within the array volume. This metamaterial loading is possible due to the small L-2 band electrical size (lambda(0)/8.5 x lambda(0)/8.5) of the CDL antenna elements. Different than the existing work on coupling reduction of linearly polarized antenna arrays, mutual coupling mechanism within the circularly polarized GPS array is considered and MNG metamaterials are shown to reduce the mutual coupling if they are placed between the antennas in a particular alignment. Specifically, a 2 x 2 array with lambda(0)/3.7 inter-element spacing is designed to be loaded with BC-SRRs and experimentally verified to exhibit a 10 dB L-2 band mutual coupling reduction. Through simulations and experiments, it is also demonstrated that the reduction in L-2 band mutual coupling improves the L-2 band array nulling capability in terms of accuracy and null depth without affecting the already well-behaved L-1 band performance. The presented array has an overall footprint size of 4.3 '' x 4.3 '' and can be potentially miniaturized further for different inter-element spacing.