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A simple method to achieve multi-focus and pattern manipulation in antenna near field (NF) is proposed in this study, whose effectiveness is then validated by measurements based on different transmit-array antennas. The radiating aperture is divided into several regions and each region corresponds to one assigned focal point, thus achieving multi-focusing performance. Then, the superposition principle is employed and constrains the multiple foci into a certain area to get a contoured pattern. Three examples are investigated. Ant-A presents four balanced focal spots simultaneously, while Ant-B presents two unbalanced foci. A square flat-top field pattern is obtained for Ant-C. Three-dimensional printing technology is employed to fabricate these lenses, resulting in a low cost and light weight. Measured results coincide well with the numerical design and simulation. The proposed method provides a simple and effective alternative for NF power redistribution and owns great value in such applications as radio-frequency identification, wireless power transmission, millimetre-wave imaging etc. [ABSTRACT FROM AUTHOR]

The authors propose the design of a compact mechanically frequency and pattern reconfigurable patch antenna. The frequency tuning is achieved by changing the positions of two adjustable shorting screws which are used to modify the length of the antenna radiating patch. Simulated and measured results are carried out to validate the proposed approach. When the screws are symmetrically positioned, the measured operating frequency can be tuned from 2.95 to 5.16 GHz without degrading the radiation characteristics over the entire comparatively wide measured tuning range of 54.5%. The antenna main radiating beam can be tilted from θ = 0° to θ = 30° when the screws are asymmetrically positioned. The measured gains and efficiencies range from 3.01 to 5.53 dBi and 68 to 74%, respectively. The overall antenna size is only 0.39λ0 x 0.39λ0 x 0.02λ0. [ABSTRACT FROM AUTHOR]

A compact dual-band patch antenna with independent tuning of both frequencies is introduced. The frequency agility is achieved by inserting two varactor diodes into the radiating patch, while the antenna miniaturisation is realised by shorting one patch edge using metallised vias. Simulated and measured results are in good agreement. Measurements reveal that the two operating bands can be tuned separately without any frequency shifting and with high stability and similar unidirectional radiation patterns during the tuning process. The measured tunable ranges of the lower and upper bands are 27.95% (from 2.4 to 3.18 GHz) and 28.27% (from 4.1 to 5.45 GHz), with measured peak gains and efficiencies of [3.23 dBi, 65%] and [3.42 dBi, 62%], respectively. The antenna presents comparatively wide tuning ranges with similar unidirectional radiation patterns, has a miniaturised size, and uses a simple direct current bias circuit. Thus, it can be easily integrated and used in different wireless systems. [ABSTRACT FROM AUTHOR]

An efficient method is presented to design the evanescent wave amplification exactly by cascading two layers of periodic series-shunt capacitors and inductors, which simulate a bilayer of magnetic and electric plasmas. Based on the presented method, equivalent lumped parameters of circuit structures are retrieved, from which the evanescent-wave amplification (EWA) is obtained at a designed frequency. Full-wave simulations show that the relative offset of the EWA frequency is less than 0.1%. The structure has been fabricated and measured, and the measurement results have good agreements with the simulation results. The proposed method can be used to design other periodic circuit structures, and the exact design of EWA can be used in the fabrication of novel components. © Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1870–1873, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23501 [ABSTRACT FROM AUTHOR]

An analogue phase shifter with a constant low insertion loss (IL) and compact size is proposed. It consists of two quarter wavelength transmission lines and three tunable reflective loads. The theoretical analysis to maximise the relative phase shift, reduce the IL and the IL variation of the phase shifter is presented explicitly, which provides performance estimation and design guidance for this class phase shifter. A circuit with a size of 0.12λg × 0.21λg is designed and fabricated to verify the theory. The simulated and measured results are in good agreement. The measurement shows that the relative phase shift of the proposed phase shifter is 186° at 1.97 GHz. The average IL is 0.79 dB with a very small IL variation which is just 0.02 dB. [ABSTRACT FROM AUTHOR]

A modulatable electromagnetically induced transparency (EIT) is achieved using a slotted circle ring structure. The circle ring structure is used to induce a polarisation-independence resonance with a low Q factor, while the slot is etched to obtain a polarisation-dependence resonance with a high Q factor. The EIT effect is obtained when the two resonances have nearby resonant frequencies but with different Q factors. As both resonant modes are excited by the external field independently, different coupling strength is achieved simply by adjusting the polarisation angle. Then the transmission of EIT is successfully modulated. The design concept is well validated both by simulation and measurement. [ABSTRACT FROM AUTHOR]