A New Design Method for Frequency-Reconfigurable Antennas Using Multiple Tuning Components

Frequency-reconfigurable antennas seem a viable solution to achieve better performance and increased flexibility for integrated mobile phone antennas. Due to the lossy nature of many tunable components, the use of multiple combined tuning components in a single design seems attractive, as it can distribute the current over the components. However, many combinations of individual tuning component settings can result in an acceptable input match, while they will significantly vary in terms of radiation efficiency. It is challenging to distinguish between these radiating and nonradiating tuning component settings during the design procedure. In this paper, we propose a method to determine the component settings with the highest efficiency at a desired operating frequency. The method uses a single full-wave simulation, which is combined with circuit-level calculations. We discuss how to apply the method in detail and demonstrate its functionality with an inverted-L antenna sporting three tunable barium-strontium titanate capacitors. It is shown that the method can successfully predict tuning component settings for high antenna efficiency over a 1.4–2.8 GHz tuning band, with total efficiencies up to 35% and radiation efficiencies up to 50%. The method can easily be applied to any desired antenna geometry.