Wideband Low-Directivity Cavity-Backed Yagi-Uda Dipole Antenna for Electrically Large Laptops

To avoid co-channel interference and the uncertainty of multipath-induced incoming waves, mobile antennas pursue low-directivity radiation. The European Telecommunications Standards Institute (ETSI) specifies an upper limit for the equivalent isotropic radiated power (EIRP) in wireless fidelity (Wi-Fi) bands within ETSI EN 300 328 V1.9.1. Achieving low directivity on electrically large platforms presents a significant challenge, especially across a wide frequency range. This communication analyzes the key factors affecting the directivity in the laptop environment and demonstrates that directing the main radiated energy of the antenna to a large angle can effectively reduce the directivity, with the ideal angle being the full space. Based on this, a cavity-backed Yagi-Uda dipole is introduced into the laptop hinge region, allowing the control of the main radiated energy to distribute more evenly in full space, thereby reducing the directivity across the Wi-Fi band. The measured directivity and total efficiency of the proposed antenna are 7.0 to 7.6 dBi and −2.6 to −2.0 dB, respectively, across 5.15–5.85 GHz. The average directivity is reduced by 2.8 dB compared to the traditional inverted-F antenna (IFA) scheme. To the best of the authors’ knowledge, this is the first realization of a low-directivity antenna on electrically large platforms.