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Filtering antennas or filtennas realize both antennas and filter functions in a single structure with the sole purpose of reducing losses and size in the design of a radio system. This article presents a comprehensive view of various filtennas design techniques and their types, satisfying the requirements of different wireless communication standards. The codesign and synthesis approaches and multilayer structure, slot/slit, and parasitic elements are the frequently used techniques reported in the literature to date for the filtennas design. The codesign and synthesis approaches need an extra filter in the filtenna's design, thus making it more complex. Whereas multilayer, slot, and parasitic elements do not require additional filters, and help the radio design become compact in size. The individual elements, that is, filter and antenna used in the filtenna are designed by cutting slots, stacking, resonators, or metamaterial structures. There are two broad categories of filtennas, namely, planar and nonplanar. Most of the papers covered in this article are planar, whereas, under the nonplanar category, horn filtennas are analyzed. Performance in each case is compared in terms of size, complexity, and cost. Considering filtennas frequency of operation, they are classified as a single band, multiband, ultra‐wideband, and their MIMO configurations are analyzed to improve the reliability of the wireless radio system. Finally, various types of filtennas are compared, and the design guidelines are elaborated, mainly focusing on their application aspect to achieve more compact radio design solutions. The different techniques related to designing filtennas have been compared, and their glance details are provided for a more realistic assessment of individual techniques used till date. Thus, the authors believe that this review article presents a helpful guiding platform for researchers working on filtenna design. [ABSTRACT FROM AUTHOR]

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 @ S 11 = −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. [ABSTRACT FROM AUTHOR]

A miniaturized quad-band patch antenna for WiMAX/WLAN/GSM applications is presented in this paper. The proposed antenna structure consists two L-slots and a slit in the patch. The longer between two slots, resonates at 1.74 GHz (1.8 GHz band), whereas the shorter at 2.58 GHz (2.4/2.5 GHz band). The third and fourth resonances at 3.6 GHz (3.5 GHz band) and 5.6 GHz (5.2/5.5/5.8 bands) are due to the slit and length of the patch, respectively. A detail parametric analysis is carried out by varying the length of the slots (i.e. L-slots and slit) to achieve the desired frequency bands. An equivalent circuit model of the antenna is developed and the various antenna performances are analyzed. The antenna simulated results for return loss and 2D radiation patterns are experimentally verified. [ABSTRACT FROM AUTHOR]