A Compact Wideband Circularly Polarized Tapered Slot Antenna With Bent Directors Based on Double-Ridge GWG

In this letter, a wideband circular polarized (CP) antenna based on a double ridge gap waveguide (GWG) with endfire radiation is proposed. The symmetric tapered slots are etched for CP condition. The periodic ridge structures are introduced between the transition ridge and periodic pins to increase the current path. By this means, the appropriate phase differences of orthogonal electric fields are achieved within a compact radiation aperture. The bent dipoles are added at the end of the tapered slot to improve the amplitude and phase condition at lower frequency. Additionally, the gradient transitions from the ridge to the radiation aperture are adjusted for wide impedance matching performance. To validate the proposed antenna, a 1 × 4 CP array fed from the double ridge GWG power divider was fabricated and measured. A measured bandwidth of 32.6% [(28.2 to 39.2) GHz] for both <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub><−10 dB and AR < 3 dB is achieved. Taking advantage of the double ridge GWG, the radiation performances of this antenna are measured with symmetric patterns and a peak gain of 15 dBi. Besides, the efficiency of this antenna is more than 74.5% over the frequency band.