This manuscript proposes a Filtenna operating in the frequency range of 5.15-5.35 GHz for possible application in wireless local area network (WLAN). Initially, a monopole antenna consisting of a square loop radiating patch is designed at 5.2 GHz and is integrated into a bandpass filter (BPF) with centre frequency of 5.2 GHz. Within the proposed frequency band of operation, the filtenna exhibits omni-directional radiation pattern, good selectivity and low reflection loss. Also, the VSWR observed is less than 2 and peak antenna gain is approximately 2.5 dBi within the frequency range. A consistency is obtained between the simulation and the experiment.

This manuscript proposes a triple band filtering antenna operating in the frequency range of 2.4 to 2.484 GHz, 4.2 to 4.5 GHz, and 5.15 to 5.825 GHz for possible application in WLAN and aeronautical radio navigation. Initially, a conventional square shaped monopole antenna is designed at 4 GHz, in which staircases are introduced at the edges to enhance bandwidth. Later, a triangle shape is carved out of square patch and cascaded at the junction to generate the proposed sunflower shaped fractal filtenna. Also, the ground plane is modified to further enlarge the bandwidth. By inserting C shaped complimentary split ring resonator slot on the feed line, a stop band is created at 3.5 GHz. Within the proposed frequency band of operation, the filtenna depicts omni‐directional radiation pattern, good selectivity, and low insertion loss. Also, the VSWR observed is less than 2 and peak antenna gain is 3.5 dBi. A good uniformity is achieved between the simulation and the experimental.

In this work, a switchable bandstop filter is used as a decoupling structure for developing a miniaturized reconfigurable multiple input multiple output (MIMO) antenna. Initially, a dual band ((2.43-2.60 GHz and 3.51-3.79 GHz)) single monopole antenna structure is developed on FR4 substrate. Then the single monopole antenna and its replica are accommodated in a small space with an edge to edge separation distance of 11 mm to form a 2 port MIMO antenna. Now, a switchable bandstop filter is used as a decoupling network between two closely spaced monopole antenna elements to prevent mutual coupling and reconfigure the antenna characteristics. The dual pole switchable bandstop filter is configured in such a way that one of its poles lies at 2.5 GHz in one state (Mode 1) and at 3.68 GHz in another state (Mode 2) under the switching action of two PIN diodes. Controlling the ON/OFF states of the PIN diodes in the bandstop filter, high isolation is achieved alternately in lower (2.43-2.60 GHz) and upper (3.51-3.79 GHz) frequency bands of the MIMO antenna. Also, stub network is used to improve impedance matching in the upper frequency band. The proposed isolation technique helps the antenna to yield high isolation (>30 dB), fair gain (>2.97 dBi), reasonable radiation efficiency (>86.8 %), low envelope correlation coefficient (<0.16), high diversity gain (DG >9.88 dB), low Mean effective gain ratio (MEG 1/MEG 2 <0.05 dB) and low channel capacity loss (CCL <0.06 bits/s/Hz) for both the operating frequency bands. The overall dimension of the antenna is restricted to 44mm × 22mm (0.36λ o × 0.18λ o ) for its easy integration in compact wireless devices. This type of reconfigurable MIMO antenna is best suited for cognitive radio communication, which promotes efficient spectrum utilization.

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A new antenna structure comprising of multiple radiating microstrip patches, representing a figure of digit eight, proximity fed by a microstrip line is proposed. On a double-layered substrate of FR4, this antenna achieves multiband functionality in the range of 3.81-12.42 GHz, which covers IEEE 802.11a standards and is suggestive of reconfigurability in frequency and pattern. Details of the antenna design, measured and simulation results are presented.