A CIRCULARLY POLARIZED ANTENNA ARRAY WITH A CONVENIENT BANDWIDTH/SIZE RATIO BASED ON NON-IDENTICAL DISC ELEMENTS

This paper presents design and development of a Circularly Polarized microstrip antenna array for C-band application. The proposed antenna exhibits convenient trade-off between bandwidth and dimension. The array design is based on the Sequential Phase Arrangement (SPA) of 2×2 non-identical disc based patch elements, operating in modal degeneration. Exploiting the properties of the SPA, capable to force CP even operating on linear polarized elements, each disc is independently detuned to operate on non perfectly overlapped bandwidth. When properly fed by a Sequential Phase Network (SPN), the set of four discs seamlessly covers the wide cumulative bandwidth which is the combination of the four sub-channels. To verify the design, a single-layer via-less array is fabricated in a compact printed square board of side 40 mm, meaning a surface of 0.64λ20 at the center frequency of 6.0 GHz, assembling the elements with a compact space-filling SPN. The measurements show a wide 10 dB return loss bandwidth of 28.5%, a 3 dB Axial Ratio (AR) bandwidth exceeding 1 GHz, and a realized gain ranging from 4.1 dB to 7.25 dB inside the AR bandwidth. The global bandwidth of the proposed array, almost coincident with the AR bandwidth, is 17.0%.