Frequency-Adjustable Planar Folded Slot Antenna Using Fully Integrated Multithrow Function for 5G Mobile Devices at Millimeter-Wave Spectrum

This article describes a low-profile frequency-adjustable planar folded slot antenna (PFSA) system that is applicable to real-life smartphone platforms at the millimeter-wave (mmWave) 5G spectrum. Critical challenges that are attributed from the frequency discrepancy between sub-6 GHz and mmWave 5G are discussed. The multithrow topology is used to minimize the distortion of the far-field radiation pattern due to the beam squint while adjusting the resonant frequency between 27.95 and 28.65 GHz. The presented methodology entails using a multithrow switch chip directly on the transmission line, which enables a bistate function. The proposed methodology is exemplified into a 28 GHz 1 x 4 subarray. Measured and simulated results confirm that the frequency-adjustable PFSA features a 2.6-time enhanced impedance bandwidth and an average peak gain of 6.3 dBi while maintaining identical antenna volume in comparison to the previously reported PFSA.