Although microstrip antennas are very popular in the microwave frequency range because of their simplicity and compatibility with circuit board technology, their limited bandwidth often restricts their usefulness.
Various methods may be used to overcome this limitation, one of which uses gap- or direct-coupled parasitic patches. These are either placed along the non-radiating edges, along the radiating edges or along all four edges of the driven patch element.
The introduction of parasitic patches of slightly different lengths to the driven patch allows the staggering of resonant frequencies to yield a broader bandwidth. The impedance bandwidth of the NEGCOMA is approximately 3 times wider than that of a standard microstrip patch antenna....Typical total gain pattern at 0.975f0, f0 and 1.025f0 Typical reflection coefficient versus frequency of a standard pin-fed patch vs NEGCOMA