140 GHz Differential Antennas in Embedded Wafer Level Ball Grid Array Technology

Three differential antenna designs, realized with the standard embedded wafer level ball grid array (eWLB) technology, for a 140 GHz hand gesture recognition radar, are presented in this paper. The antenna gain, reflection coefficient and radiation patterns were measured in the D-band (110–170 GHz) with a probe-based measurement setup, and are compared with electromagnetic simulations results. The rhombic, dipole and bow-tie antennas all have relative bandwidths of greater than 25% and peak gain values of 8.1 dBi, 7.1 dBi and 6.3 dBi, respectively. The probe-based measurement setup used in this work requires a ground-signal-ground pad for the probe-and-antenna contact, thus a balanced-to-unbalanced (i.e. balun) transition is necessary to measure the antennas. Therefore, a Chebyshev quarter-wave stepped balun transformer, operating over the entire D-band frequency range, is also presented and characterized here.