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A novel MIMO sharp band-notched antenna with high isolation for UWB applications is presented. The antenna consists of two antenna elements with an overall area of 18 × 36 mm 2. A T-shaped stub is extruded in the ground plane to improve isolation and an L-shaped stub to introduce band-notched function C-band (3.62-4.77 GHz). The designed antenna possesses a low mutual coupling of <−20 dB over the operating band from 2.9 to 20 GHz. The performance of this antenna is studied in terms of isolation between the two ports, radiation pattern, efficiency, realised gain, and envelope correlation coefficient. Conclusion: We have proposed enhanced bandwidth, compact, MIMO antenna with band-notched characteristics for modern wireless UWB applications. The proposed MIMO antenna offers an impedance bandwidth of 17.1 GHz (from 2.9 to 20 GHz) with a good impedance matching and good isolation over the operating band with band notched at C-band.

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It is worth to note that a maximum possible number of strain sensors depend on a dynamic measurement range of the OTDR and a discrimination range of the strain sensor. If it is assumed that the commercial OTDR has the dynamic measurement range of 30 dB and while each of sensors based on SMS fiber structure has the discrimination range of 0.5 dB, therefore the maximum number of sensor can be used in this system is about 60 sensors. This feature is useful for quasi-distributed strain measurement in many applications such as to monitor strain in the bridges, buildings or others civil structures.Further investigation on a temperature-dependence on the optical fiber strain sensor needs to be carried out. It is well known that the temperature variations can induce strain measurement errors. According to the references, an accurate strain measurement in the SMS fiber structure sensor can be carried out when the ambient temperature is known using either an external temperature sensor or a self-temperature sensor as reported in Ref. 4, or other technique can be used by choosing core and cladding material with opposite thermo-optic coefficients [8].The proposed strain measurement system offers low cost and simple fabrication process of the sensor based on SMS fiber structure. The interrogator of OTDR is widely used to inspect the optical fiber network in the field makes the proposed strain measurement system is suitable to be developed. Moreover, the quasidistributed strain measurement can also be easily implemented. CONCLUSIONThe SMS fiber structure sensor and the OTDR interrogator for the strain measurement was investigated and proposed. Depending on the MMF length of the SMS fiber structure, the strain sensor characteristic can be varied. It is found that the strain measurement with a range of 0-1000 le with a resolution less than 10 le can be achieved. It is demonstrated as a proof of principle, the quasi-distributed strain measurement using the proposed method. Depending on the dynamic measurement range of the OTDR, tens of sensors can be used simultaneously to perform the quasi-distributed strain measurement for applications such as a structural health monitoring system. ABSTRACT: The analysis of TEM three-section symmetrical directional couplers with tightly coupled section realized as a tandem connection of two coupled-line sections has been shown. The design equations allowing for calculating the required even-mode characteristic Key words: broadband coupled-line couplers; tandem connection of coupled-line couplers; symmetrical couplers ACKNOWLEDGMENT INTRODUCTIONMultisection coupled-line directional couplers are commonly used in modern microwave electronics because they offer very wide bandwidth and relatively small size. They can be realized in either asymmetric or symmetrical structures [1,2]. The major advantage of symmetrical multisection couplers over asymmetric ones is that they provide constant 90 differential phase over entire frequency range. However, it is known that they require much stronger coupling...

A novel microstrip‐line fed beak‐shaped monopole‐like slot UWB antenna is proposed for enhanced ultrawideband, bluetooth, GPS, and GSM applications. In which, a beak‐shaped radiating patch is fed by a microstrip‐line and a square ground plane is defected by etching a hexagonal slot. Two triangular slots in the beak‐shaped radiator and hexagonal‐shaped defect in the ground plane are used to obtain GPS (1520–1590 MHz), GSM (1770–1840 MHz), and bluetooth (2385–2490 MHz). Furthermore, the bandwidth of an antenna is increased by etching a triangular slot at the junction of patch and feeding line. The antenna is fabricated on 1.6 mm thick commercial available FR4 material. The antenna offers an enhanced bandwidth of 24.26 GHz from 0.24 to 24.5 GHz with the voltage standing wave ratio <2. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2624–2628, 2014