A Quasi-1/2 rule for quick estimation on the upper limit of the antenna efficiency

A simple, useful, and interesting rule named quasi-1/2 rule is presented to enable a quick estimation on the upper limit of the antenna efficiency. The studied upper limit of the antenna efficiency is based on assumptions that the antenna's power confinement in the near field and the related losses, such as the conductor losses and the substrate losses, can be ignored. In other words, all the received power by the antenna is radiated to the far field. The proposed quasi-1/2 rule is hence purely according to the VSWR (Voltage Standing Wave Ratio) values; therefore, it is an easy way to do a quick and helpful estimation and guidance without dimensions, structures, materials, etc., involved or known, which is especially beneficial to the antenna designers of cellular phones because of the complexity and uncertainty of the practical antenna environment in cellular phones. Moreover, the final result of the quasi-1/2 rule is just a single number, 1/2, which is very easy, simple, and straightforward to be memorized and applied.