A Compact $\mathbf{1}\times \mathbf{4}$ Antenna Array with Steerable Beam for 5G Millimeter-Wave Smartphone Applications

The paper introduces a compact 28GHz <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$1\times 4$</tex> antenna array designed on a multi-layer organic substrate, allowing for a broad bandwidth in a compact Antenna-in-Package (AiP) module. The novel design incorporates shorted parasitic elements to address size constraints without compromising performance. The beamformer IC is used TSMC 90 technology and consists of LNA, <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$4\times 4$</tex> Butler matrix, Coupler, and Switch to form a beamforming circuit network. The paper also discusses the design of an integrated socket and load board for active testing, as well as a four-channel transmit beamforming array front-end module. Additionally, an antenna measurement method using a test socket is presented, which can reduce time-consuming sample changing and alignment during R&D phase. The paper concludes by showcasing the 2D beam steering capabilities of the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$1\times 4$</tex> antenna array at 28 GHz, achieving a peak gain of 11 dBi in the primary beam direction and a steering range of approximately 70 degrees. The compact antenna design offers both bandwidth and size advantages, making it suitable for 28GHz mmWave bands in mobile devices.