Circularly polarised antenna with wide harmonics suppression by two angled C‐shaped structures

In this Letter, a circularly polarised (CP) antenna is proposed. The proposed antenna is realised by combining two angled C‐shaped structures. By setting different widths ( W L and W R ) for the left and right angled C‐shaped structures, respectively, an asymmetric structure is obtained. Therefore, the proposed antenna exhibits CP characteristics. From repeated simulation results, the authors find that the optimum ratio W L : W R to make the proposed structure operate as a CP antenna is 5: 8. Moreover, the measured reflection coefficient is lower than −2.4 dB within a stopband up to 12 GHz. This means that wide harmonics suppression (up to the fifth harmonic) is successfully achieved.