Planar Broadband Higher-Order Mode Millimeter-Wave Microstrip Patch Antenna Array With Low Sidelobe Level

Abstract

In this letter, a planar broadband higher-order mode millimeter-wave (MMW) microstrip patch antenna array with low sidelobe level (SLL) is presented. For the antenna element, antiphase-TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">30</sub> mode is excited by unequally etching the radiating patch with two transverse slots. Meanwhile, an SIW-based pin-loaded slot coupling feeding structure is introduced to achieve merits of broadband, low cross polarization, and low backward radiation. Then, a one-eight power divider with in-phase unequally tapered amplitude distribution is adopted to excite an eight-element array with SLL. The GCPW–SIW transition structure is also selected to achieve broadband impedance matching. Finally, both element and array antenna are optimized and fabricated for verification. For the antenna array, the measured −10 dB impedance bandwidth is from 25.1 to 31.3 GHz (22%) with a maximum gain of 14.6 dBi at 29.5 GHz and a 3 dB gain bandwidth of 27.9%. The measured SLLs at 26, 28, and 30 GHz are all less than −20 dB.