Multibeam Antenna for Wide-Angle 96-Beam Coverage at Ka-Band Using a Multifocal Transmit-Array

Cost-effective multibeam millimeter wave antenna solutions are required to enable the deployment of 5G and beyond systems operating in the frequency range 2 (FR2). The tradeoff between system complexity and RF requirements (such as high gain, number of beams, beam forming/scanning capability, etc.) is a challenging problem fomenting the development of new antennas. Spatially fed transmit-arrays (TAs) where the aperture is illuminated by a planar array placed in a focal plane, is a canonical solution. However, the design is constrained by the focal distance to aperture diameter ratio (F/D). On the one hand, reducing the F/D allows designing more compact feeding array elements, on the other hand, it limits the maximum angle coverage due to scanning aberrations. In this work, we show that a TA optimized for operating simultaneously with low F/D and wide-angle coverage can improve the performance of this classical configuration. We design a Ka-band multibeam antenna with a TA fed by a 19x5 array of standard WR38 waveguide operating with F/D=0.34. It provides 25 dBi of gain with scan losses below 3 dB when scanning in a zenith plane up to -55 degrees, covering 80 degrees (−55 to 25 degrees) with cross-over levels around 3 dB.