Partially open corrugated waveguide frequency scanning antennas with linear and circular polarizations

A fully metallic partially open corrugated waveguide (CW) is employed to construct the Ka-band linearly polarized (LP) and circularly polarized (CP) frequency-scanning (FS) periodic leaky-wave antennas (PLWAs) with the spatial coverages from backward ( \theta < 0 ) to forward ( \theta > 0 ). The waveguide structure is obtained by cutting a conventional CW in half along its longitudinal symmetry plane. The n =-1 space harmonic is generated effectively by the half-wavelength radiating slots on the corrugations. The broadside frequency is about 31.5 GHz. The LP and CP radiations are realized by rotating the radiating slots to different angles. The measured scanning ranges of the LP and CP PLWAs are from -42.7° to 16.5° in the band of 26.5-33.5 GHz and from -48° to 22.7° in the band of 26.5-34 GHz, respectively. The measured axial ratio of the CP PLWA is below 3 dB in the mainlobe directions varied with frequency. The prototypes and experimental results make contributions to the polarization control, scanning rate improvement, and profile reduction in the frequency-controlled millimeter-wave imaging and radar systems.