Ultra-Wideband Endfire Long-Slot-Excited Phased Array for Millimeter-Wave Applications

An ultra-wideband phased array with endfire radiation is proposed for millimeter-wave (mm-wave) applications. This array consists of a linear long slot array (LSA) source and a transverse-electromagnetic (TEM) horn radiator. For each unit, a Gamma-shaped probe based on a substrate integrated coaxial line (SICL) is adopted to generate a primary slot source. Then, the slot flares in the E-plane with an exponential profile to form a horn unit. The antenna unit is studied with periodical boundaries (PBs) in simulation and operates from 15.4 to 46.4 GHz with active standing wave ratio (SWR) < 3 for a scan angle of up to 45 degrees in H-plane. To verify the design concept, two 1 x 16 finite arrays, Array-1 for 0 degrees scan and Array-2 for 45 degrees scan, are fabricated and tested. Over the operating band of 15.4-46.4 GHz, both arrays obtain good impedance matching in measurements with SWR < 2.3. The measured gain varies from 11.8 to 19.1 dBi for Array-1 and from 10 to 16.9 dBi for Array-2 within 16-40 GHz. Besides, Array-2 exhibits a scan angle of 48 degrees and an average scan loss of 2.4 dB. Moreover, both arrays achieve a radiation efficiency exceeding 73% because of employing the low-loss SICL feed network.