In this study, two compact ultra‐wideband (UWB) frequency selective surface (FSS) reflectors, which combine the branch loading method with the design of the traditional FSS, are proposed for antenna gain enhancement application. The working mechanism of the proposed FSS reflectors is analysed by the equivalent circuit model. The first FSS reflector, which is a 10 × 10 array with 8.25 mm × 8.25 mm unit size, not only enhances the gain of the UWB antenna, but also guarantees a constant gain with only 0.5 dB variation across the whole operation band. To further reduce the reflector size, a more compact FSS reflector with 6.25 mm × 6.25 mm unit size is designed by printing similar patterns on both sides of a single‐layer dielectric slab. Compared to the first structure, the second reflector can realise a 25% size reduction and the same gain variation in the entire UWB frequency range. The only compromise is a 0.5 dB gain decrease. Finally, a good agreement between the measured and simulated results proves the feasibility of the authors’ design.
Lateral flow assay (LFA) has played pivotal roles in many emergency public safety incidents, such as coronavirus disease diagnostics; however, the present double-line (test and control line) design strategy for LFA strips greatly restricts their applications in high-throughput quantitative analysis because the limited sample diffusion distance on the strips constrains the number of test/control lines. Herein, a novel single-line-based LFA (sLFA) strip, which combines test and control line, is developed by exploiting an orthogonal emissive upconversion nanoparticle (UCNP) as a signal reporter on the test line, where one emission can be used as a reporting signal and the other as a calibrating signal. This UCNP-based test line with an interior reference also can play a validating role as a control line, and hence capturing antibodies are not needed for control lines, greatly saving fabrication costs. As a proof-of-concept, this novel sLFA strip is successfully explored to accurately and rapidly detect aflatoxin B1. Moreover, due to the removal of control lines, such a novel strategy greatly reduces the strip size, facilitating the design of a testing array for multiple detections of different samples. The test line herein is designed in a ring shape, and several test rings are assembled to be a chip for the testing of multiple samples. To our knowledge, this is the first demonstration of single-line-based LFA strips, which will significantly improve the detection capacities and accuracies and reduce the testing costs of LFA strips in real sample applications ranging from food analysis to in vitro diagnostics.
A compact printed reconfigurable monopole antenna with switchable band-notches is designed and manufactured. The proposed antenna mainly consists of a disc-like radiator with two pairs of T-shaped strips protruded inside a rectangular aperture. Five PIN diode switches are employed to bridge or open the slots, which allow the antenna to be configured into three different structures functioning as an ultra-wideband (UWB) antenna, or an antenna with notched frequencies at WLAN or WiMAX band. Design and optimization of the antenna are done using CST Microwave Studio. After fabrication on an FR4 substrate with dimensions of 35 mm (width) × 41 mm (length) × 1.5 mm (thickness), numerical and experimental results of the proposed reconfigurable antenna are presented and discussed. The experimental results confirm the design as a good candidate for UWB applications.
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