Guest Editorial Low-Cost Wide-Angle Beam-Scanning Antennas

One of the key antenna requirements in many modern wireless systems for communications and sensing is wide-angle beam-scanning [1] . The traditional method to achieve wide-angle beam-scanning is to employ mechanically controlled reflectors or lenses, which are bulky, heavy, and suffer from slow beam scanning speed. Other important limitations of mechanical scanning antennas include the lack of multi-beam scanning capability and the ability to conform with non-planar structures (conformal geometries), which are essential in a number of emerging systems requiring very low-profile antennas. An alternative technique is to employ electronically beam-scanning antennas using passive or active phased arrays [1] . Main disadvantages of phased arrays are high complexity, high power consumption, and high cost due to a large number of radio frequency (RF) or microwave phase shifters and T/R modules required. The problems worsen for phased arrays at millimeter-wave, sub-THz, and THz frequencies, due to significant losses in phase shifters and feed networks at higher frequencies combined with lower efficiency of power amplifiers [2] . The digital beamforming approach is even more costly and energy hungry due to the employment of large number of RF modules and digital devices [1] , [3] , [4] .11Nsciescopu