Wideband multibeam mushroom antenna array with low‐temperature cofired ceramic‐integrated pillbox transition for millimetre‐wave applications

Abstract This article presents a millimetre‐wave (MMW) wideband multibeam antenna array with a pillbox transition using multilayer low‐temperature cofired ceramic (LTCC) technology. The mushroom structure with dual resonant modes offers wideband performance for radiating array, while an integrated pillbox reflector achieves multibeam scheme. To reduce the design complexity of electrically large pillbox system, two popular pillbox transitions are investigated with a unit model method. The proposed unit model can be used to predict the transmission performance of pillbox reflector in any incident angle. Moreover, the mushroom antenna array and power divider fed by quasi‐TEM wave are also designed using unit model, greatly simplifying the design of electrically large pillbox antenna array. In the final design, the long‐slot pillbox transition, rather than multi‐slot transition, is selected due to its ultrawideband performance and simple structure. The proposed LTCC prototype is analysed and fabricated, obtaining a good agreement between simulation and measurement. The measured results show a −10 dB impedance bandwidth of 17.6% from 31 to 37 GHz, and five beams with ±45° scanning range is achieved with sidelobe level lower than −10 dB.