A compact shared-aperture dual-band 28/39 GHz endfire antenna phased array for 5G-enabled IoT systems

Modern communication systems strategically leverage multi-spectral bands to enable diverse service scenarios, ensuring seamless connectivity with enhanced reliability and throughput. Millimeter-wave (mmWave) 5G New Radio (NR) is essential to meet the escalating data demands of massive IoT deployments while maintaining stringent quality-of-service (QoS) requirements for real-time emerging applications. In this paper, we present a dual-band endfire phased array antenna for 5G NR IoT applications. A novel radiating aperture array, based on an open-ended substrate-integrated waveguide (SIW) horn antenna, is introduced to enable wide dual-band operation with vertically polarized (VP) and symmetric endfire radiation. The antenna is fed by the open-ended SIW, which functions as a backed cavity loaded with parasitic elements to generate multi-mode operation. To meet 5G system requirements, a 4-element antenna array is simulated, fabricated, and tested. The simulated and measured impedance bandwidth achieves –10 dB dual-band operation of 17% (25.2–29.9 GHz) in the lower band and 12.71% (36.1–41 GHz) in the upper band, covering 5G NR bands n257, n260, and n261, with isolation levels better than 15 dB across the operating bands. The measured realized gain reaches 9.4 dBi in the lower band and 11.25 dBi in the upper band. The array offers beam scanning of ± 48°at 28 GHz and ± 36°at 39 GHz, achieving a realized endfire gain exceeding 6.5 dBi and 9 dBi, respectively. These results confirm its feasibility for mass integration in future IoT ecosystems.