Compact circularly polarized asymmetric‐slotted microstrip patch antennas

A technique is demonstrated to generate circularly polarized (CP) radiation of the compact diagonally asymmetric‐slotted microstrip patch antennas. Design rules for the single‐feed, compact, circularly polarized microstrip antennas (CPMA) with any arbitrary‐shaped slots along the diagonal directions are first summarized. Four, compact, CPMA with circular‐, square‐, cross‐, and square‐ring‐shaped slots along the diagonal directions are proposed and compared based on a fixed overall antenna size. A compact, CP, cross‐shaped slotted, microstrip antenna is fabricated and measured to verify the proposed technique experimentally. The measured 3‐dB axial‐ratio bandwidth of about 6.0 MHz is achieved with 10‐dB return loss bandwidth of 19.0 MHz while measured gain of the antenna is 4.0 dBic at 930 MHz.