Dual-band shared-aperture variable inclination continuous transverse stub antenna

This paper presents a dual-band shared-aperture variable inclination continuous transverse stub (VICTS) antenna with large beam coverage for both frequency bands. A novel hybrid radiating structure is introduced to enable approximately consistent initial beam direction at the boresight for both bands and therefore large beam coverage, by exciting different sets of the radiation elements at each of the two bands. The hybrid structure is formed of interlaced conventional CTS elements and those backed by double-ridge waveguide-slots. The latter suppresses the lower band while allowing the high band to radiate. This configuration allows maximum aperture reuse. A parallel-plate waveguide (PPW) diplexer combines the generated plane waves from the two bands to enable one-side excitation. Combined with the non-uniform slow-wave structure (SWS), optimized amplitude distribution is achieved across the two frequency bands, thereby improving the antenna efficiency. A prototype is designed, fabricated and measured for 12.25-12.75 GHz (Ku-band) and 19.6-21.2 GHz (K-band). The measured reflection coefficients are kept less than -11.5 dB during the beam steering. At the center frequencies of 12.5 and 20.4 GHz, the measured beam coverage of over ±49° and ±59° in elevation plane is demonstrated from a relative rotation angle of 40°. During the beam steering, the measured peak gain varies in the range of 26.1-21.1 dBi / 30.4-25.2 dBi at these two frequencies.