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A novel compact ring monopole antenna with double meander lines is proposed for wireless local area networks (WLAN) applications in IEEE 802.11b/g/a systems. The designed antenna, fed by a 50 Ω microstrip transmission line, is only 32 mm in height and 16 mm in width. By introducing a horizontal and a vertical branched strips to a closed rectangular strip ring, the proposed antenna can generate two separate impedance bandwidths. Prototypes of the proposed antenna have been constructed and tested. The obtained impedance bandwidths reach about 12% for the 2.4 GHz band and 45.3% for the 5 GHz band, which meet the required bandwidth specification of 2.4/5 GHz WLAN standard. Also, good radiation performance and antenna gain over the two frequency ranges have been obtained.

A new method to improve the gain of patch antenna with metamaterial composed of ring aperture lattice is presented. The influences of the number of metamaterial layers and a comparison of electromagnetic characteristics between the conventional patch antenna and the new metamaterial patch antenna are studied by using numerical simulation method. Then, a patch antenna with the metamaterial is fabricated and measured. The simulation and experimental results show that this method is effective and this structure can realize congregating the radiation energy, thus the gain of the antenna with metamaterial can greatly increase when compared with the conventional one. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 456–459, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22146

A novel multilayer bidirectional linear array with the same sense circularly polarised (CP) radiation patterns are proposed. The CP resonant unit consists of a pair of loops and two square patches added on their opposite corners. With a feeding slotted substrate integrated waveguide (SIW) sandwiched between two back-to-back mirror rotated resonant units, a radiating element is designed, and same sense bidirectional CP waves are generated. Along the longitude direction, the radiating elements are arranged alternately from the centre line of the slotted SIW. Then, an 8-element linear array with uniform distribution is designed. Identical right-hand CP waves are achieved in both front and back directions. The array is fabricated, and measured results are in good agreement with simulated ones.

A novel directive dual-band and dual-polarized microstrip antenna with ZIM is presented. An averaging effect over constituent materials of the metamaterial structure yields an effective permittivity that approaches zero at dual band with different polarizations, and then it results in a metamaterial with zero index of refraction and the radiation energy of this antenna is congregated. The experimental results show that this method is effective, and this structure can greatly increase the gain at dual frequencies. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2902–2904, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23855

In this paper, a novel compact printed monopole antenna with multiband operation for wireless local area networks (WLAN) is presented. A simple C-shaped strip and a straight strip of this antenna provide two resonant paths to achieve 2.4-, 5.2-, and 5.8-GHz multiband operation. Good similar omnidirectional radiation patterns in the azimuth plane of the proposed antenna with compact radiator size of 11.5 × 8.5 mm2 in the desired frequency bands have been achieved. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 365–367, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23078

A novel wideband slot-fed cylindrical dielectric resonator antenna (DRA) is proposed in this paper. The dielectric resonator is lifted from the ground plane to form an isolated dielectric resonator (DR) and an equivalent air-dielectric DR. The hybrid structure is excited by a slot-fed mechanism to obtain a smooth transition between each resonant mode. It is found that the bandwidth of the proposed antenna can be greatly enhanced by using the hybrid DRA structure instead of the case mounted on the ground plane. A comprehensive parametric study is carried out using HFSS to optimize the bandwidth of the proposed antenna. Measured results demonstrate that the proposed DRA has a 10 dB impedance bandwidth of 76% from 2.63 GHz to 5.86 GHz and the radiation pattern is stable through the operating frequency.

In this paper a reconfigurable microstrip-fed slot antenna for 2.4/5.2 GHz band applications is proposed. The design of these slots that form several "island-like" metal blocks in the ground are based on the use of space-filling curves, which endow the antenna with broadband performance, and here some modifications are implemented. By connecting several "islands" with some circuits to build bridge between them, the radiation properties can be changed, including the resonant frequency and radiation patterns. Here, a switch is added to achieve a reconfigurable antenna, and with the switch state changing, the radiation properties can be altered. The antenna structure proposed could be reconstructed in several manners, and in this paper, we give an easy way to realize the frequency hopping for 2.4/5.2 GHz band systems. The design and analysis for this antenna are accomplished by using HFSS (high frequency structure simulator), and its performance is calculated. Then the antenna prototype is fabricated and measured, the calculated and measured results show good agreements, which implies that such a type of antennas can achieve our design requirements.

A 2.4 GHz power divider with harmonic suppression is presented. It comprises two sets of hook-shaped resonators in each branch. By adjusting the widths and lengths of the hook-shaped strips, it is convenient to control the third and fifth harmonic suppression separately without affecting the passband performance. Experimental results show insertion losses of 3.453 and 3.341 dB, the return loss of 19.3 dB and better than 14 dB isolation at the centre frequency. Furthermore, excellent out-of-band rejection can be observed, including 46.2 dB suppression for the third harmonic and 37.35 dB suppression for the fifth harmonic.

As a very powerful optimisation approach, differential evolution algorithm for continuous optimisation problems has been applied to electromagnetic (EM) design problems. However, the optimisation of a thinned array can be formulated as a discrete-variable optimisation problem with solutions encoded as binary strings. Here, a Boolean differential evolution (BDE) algorithm for 0–1 integer programming problems is proposed to design planar thinned arrays with minimum sidelobe levels. The BDE algorithm with only one control parameter is easily implemented. Meanwhile, a fast Fourier transform is employed to speed up the calculation of the pattern. Numerical experiments show that the BDE algorithm is an effective technique.