A Sequential-Phase Feed Using a Circularly Polarized Shorted Loop Structure

This communication presents a new 4-port feeding structure with sequential phase (SP) of 0°, 90°, 180° and 270 using a circularly polarized (CP) shorted loop. A 2 × 2 single-fed circularly polarized cornertruncated patch array is connected to the loop´s four shorting strips, which serve as 4 feeding ports with stable phase difference. By using the proposed SP feed, the axial ratio (AR) bandwidth of the array is increased to more than 7%, wider than the previous design. A prototype of the proposed antenna is built to validate the design experimentally, and a global bandwidth of 4.86-5.12 GHz is achieved (S₁₁ ≤ -10 dB, <;3 dB, and gain variation within 3 dB).