A nearly square patch with a single feed along the diagonal as shown in
Figure 8.12(a) is one of the simplest MSA configurations to generate CP.
The ratio of the two orthogonal dimensions L1 /L2 should be generally in
the range of 1.01–1.10 depending upon the substrate parameters as described above.
When the patch is fed along the diagonal, then the two resonance
modes corresponding to lengths L1 and L2 are spatially orthogonal.
The CP is obtained at a frequency, which lies between the resonance frequencies
of these two modes, where the two orthogonal modes have equal magnitude
and are in phase quadrature.