W-band Monopulse Antenna Array Manufactured by Diffusion Bonding

In this paper, a W-band monopulse array antenna has been designed and fabricated by diffusion bonding of thin copper sheets. The antenna consists of an array of 16 by 16 circularly polarized radiating cavities divided into four 8 by 8 sub-arrays, each fed by a corporate waveguide feeding network with a -20 dB Taylor distribution. An underlying beamforming network is implemented to provide monopulse capabilities in the two principal radiation planes. In the band from 90 to 98 GHz, the simulated axial ratio in broadside is under 2 dB, whereas the input matching is better than -15 dB in most of the band for the four input ports. The antenna has been fabricated and the experimental results show an impedance matching better than -10 dB in most of the band. Most notably, no frequency shift is observed in the results, corresponding to an improvement in the accuracy of the etching process compared to previous prototypes fabricated with diffusion bonding technology.