Bandwidth reconfigurable antenna with a fixed lower and a variable upper limit

This paper presents a frequency bandwidth reconfigurable antenna capable of gradually varying its bandwidth from 43 to 76% by keeping the lower band limit fixed and varying the upper one. The antenna consists of a disc-monopole antenna with four vertical slot lines and a via-shorted slot ring incorporated in its ground-plane. To vary the bandwidth, the first slot line is used to create a new resonance below the operating band of the monopole, which is used as the fixed lower band limit. The next two slots are used to vary the upper limit while adjusting the middle resonance in order to maintain a good impedance-matching over the bandwidth. The fourth slot line and the shorted slot ring are used together to suppress high frequencies. In addition to this gradual bandwidth reconfiguration, the proposed antenna has the potential to offer several different modes of operation; however for concise reasons, only two other modes corresponding to a single-band and a dual-band narrowband, modes are presented here. To validate the proposed bandwidth reconfiguration approach, simulated and measured results are provided and a good agreement is achieved. The antenna is potentially suitable for applications needing to adjust the frequency bandwidth such as cognitive radios.