High-gain low-cross-polarization 60-GHz LTCC patch antenna array with differential-fed and soft-surface structures

A 2×2 60-GHz differential-fed patch antenna array was developed using low-temperature co-fired ceramic (LTCC) multilayer technology with high gain and low cross-polarization level. The antenna elements were constructed by radiation patches and folded L-shaped feeds. A novel soft-surface structure was designed to suppress the surface wave and enhance antenna gain. Substrate-integrated waveguide (SIW) and differential-fed structures were applied to reduce the loss of feeding network and the cross polarization level. The proposed antenna array achieves flat gain curve over the range of 55-65 GHz with a peak gain of 13.6 dBi at 62.1 GHz. The simulated cross polarization level was lower than -35 dB in both E-plane and H-plane.