Frequency reconfigurable dual-band filtenna

Abstract

In this paper, a compact size frequency reconfigurable dual-band filtenna (Filter + Antenna) is proposed for WLAN, WiMaX and C-band applications. The filtenna is designed by a switchable SRR (i.e. Two switches are used in inner and outer split rings) band pass filter (BPF) and a CSRR based antenna. In the process of filtenna design synthesis process is used. The advantages of the reconfigurable filtenna structure are to reduce undesired frequency interference to the system and controllable bandwidth. The antenna is resonated at three frequencies with the bandwidth @ S11 = −10 dB i.e. 2.4 GHz (2.05–2.86 GHz), 3.46 GHz (3.4–3.55 GHz) & 4.36 GHz (4.19–4.65 GHz), whereas the filter is resonated at two frequencies i.e. 2.42 GHz (2.36–2.48 GHz) and 4.41 GHz (4.16–4.77 GHz), When both the designs (i.e. antenna & filter) are combined (i.e. Filtenna), then the joint structure allow only two resonance frequencies i.e. 2.42 GHz (2.37–2.47 GHz) and 4.41 GHz (4.24–4.69 GHz) to pass through and 3.46 GHz frequency is rejected. The rejection is occurred due to dual band filter. Due to the filteration the in band gains are 2.14 dBi and 3.39 dBi, whereas the out of band gain is −4.23 dBi, which justify its rejection behavior and does not effect system performances. Furthermore, the resonances of the resonating structures (SRR and CSRR) are justified by the lump components of the structure.In order to make the filtenna operation re-configurable, PIN diodes with DC block capacitors are connected in the inner and outer split rings of the SRR band pass filter and appropriate dc bias is applied across the PIN diodes to perform either ‘ON’ or ‘OFF’ operation. When inner ring PIN diode is ‘ON’ and outer one is ‘OFF’ then filtenna operates at 2.58 GHz (2.5–2.67 GHz). Similarly, when outer ring PIN diode is ‘ON’ and inner one is ‘OFF’ then the frequency of operation is shifted to 4.45 GHz (4.26–4.85 GHz) band. The realized filtenna at each resonance frequency exhibits bi-directional radiation pattern in E-plane and omni-directional in the H-plane. The simulated performances of the proposed filtenna is verified using the experimental results.