Millimeter-Wave Wideband, Low-Profile Stub-Loaded Dipole Array Fed by SICL

A wideband, low-profile stub-loaded dipole array fed by substrate-integrated coaxial line (SICL) is proposed for millimeter-wave (mmW) applications. The antenna element consists of a stub-loaded dipole with opposite arm orientations, which suppresses the undesirable cross-polarized radiation. Particularly, two grounded stubs are loaded on the two sides of the dipole radiator, not just for suppressing mutual couplings. “Quasi-loop” currents can be produced along the dipole arms and the grounded stubs, which can be equivalent to a quasi-magnetic dipole source. Compared with an element without the grounded stubs loaded, the introduced stubs not only expand the impedance bandwidth at lower frequencies and realize a higher isolation level between the adjacent elements, but also suppress both the back lobes of the presented element and cross-polarized waves in the H-plane at lower frequencies. For demonstration, a 1 × 8-element array is fabricated and measured, exhibiting a wide impedance bandwidth of 77.7% [(21 to 47.7) GHz] and a peak gain of 15.4 dBi. Owing to its advantages of wideband, low profile (0.699 mm ∼ 0.08λ₀), low cross-polarization, high front-to-back ratio level (>25 dB), compact size, and ease of integration, the proposed array represents a promising candidate for mmW wireless systems.