Millimeterwave and Terahertz Waveguide-Fed Circularly Polarized Antipodal Curvedly Tapered Slot Antennas

Antipodal curvedly tapered slot antennas (ACTSAs) with different slot profiles are investigated to achieve the optimum circular polarization performance. The profiles of the tapered slots can be determined by different curves, such as linear, exponential, and logarithmic curves. Therefore, the corresponding waveguide-fed circularly polarized (CP) antipodal linear, exponential, exponential-logarithmic tapered slot antennas (AL-, E-, EL-TSA) are designed, fabricated, and measured at Ka-band for a comprehensive study. The optimized AELTSA provides good impedance matching, gain above 10.3 dBi, sidelobe lower than -15 dB, low cross-polarization, and left-hand circularly polarized (LHCP) axial ratio (AR) lower than 3 dB, from 28 to 40 GHz. Moreover, a waveguide-fed LHCP antipodal exponential-exponential tapered slot antenna (AEETSA) is designed at 500 GHz and fabricated by silicon micromachining. The radiation characteristics are examined by measurement results of symmetric beams and ARs lower than 1.5 dB, from 490 to 510 GHz.