No abstract

In this study, a Koch snowflake frequency reconfigurable antenna for wideband applications is presented including experimental verification. The frequency reconfigurable approach is obtained for UHF band using RF PIN diodes, lumped capacitor and inductors. Proposed antenna is compact, therefore, it can be used as an array element. It has three measured frequency bands. These bands are: case I, 3.34– 4.52 GHz (30%); case II, 2.2–3.4 GHz (43%); and case III, 1.45–4.1 GHz (95.49%). In cases I and II, two different bands are obtained and case III covers almost the frequency band of case I and case II. Thus, the impedance bandwidth of the proposed antenna provides continuous wideband frequency coverage from 1.45 to 4.52 GHz (103%). In addition, the measurements are carried out to validate the performance of the antenna. The proposed antenna has good agreement between simulated and measured results with reasonably low cross polarisation.

A microstrip line feed modified Sierpinski square fractal antenna for ultra-wide band (UWB) with band notch characteristics is presented. UWB operation (3.1-10.6 GHz) is achieved by increasing the numbers of iteration and rectangular grooved ground plane. The band rejection characteristic is realised by a ∩ -slot in the feed line. The proposed antenna has a volume 34 × 34 × 1.6 mm 3 with a square shape structure and shows omnidirectional radiation patterns. The measurement results indicate that the antenna offers UWB operation and a notch at 5.5 GHz (5-6 GHz) for a reflection coefficient below −10 dB which covers the wireless local area network band. Acceptable agreement is obtained between the simulated and measured antenna performance parameters. These characteristics demonstrate that the proposed antenna is an attractive candidate for UWB applications.

A compact size hybrid fractal antenna is proposed for the application in wideband frequency range. The proposed antenna structure is the combination of Koch curve and self-affine fractal geometries. The Koch curve and self-affine geometries are optimized to achieve a wide bandwidth. The feed circuit is a microstrip line with a matching section over a rectangular ground plane. The measured impedance matching fractal bandwidth (S11 ≤ −10 dB) is 72.37% from 1.6 to 3.4 GHz. An acceptable agreement is obtained from the simulated and measured antenna performance parameters.

No abstract

In this article, a circular microstrip tunable wideband frequency and polarisation reconfigurable antenna are investigated. The wideband tunability is achieved by placing the four varactor diodes between circular microstrip patch and circular ring. The impedance bandwidth of 2.09–2.96 GHz (34.52%) is realised by tuning the capacitance value from 4.15 pF (0 V) to 0.94 pF (6 V). Both frequency tunability and polarisation reconfigurability are controlled in the antenna using the proposed cascaded branch line coupler feed network. The four single pole double throw and two dual in‐line package switches are used in the feed network to control the tunable impedance bandwidth of the antenna over a wideband from 1.25 to 2.95 GHz. The vertical linear polarisation and horizontal linear polarisation (H‐LP) are achieved by any one of the feed port excited in the antenna. Similarly, the right‐hand circular polarisation and left‐hand circular polarisation are realised by exciting both the feed ports in the antenna with±90° phase difference. The impedance bandwidth of proposed feed network is well matching with the tunable bandwidth of the patch antenna. Simulated and experimental verification results show good agreement.

A sectoral Sierpinski Gasket fractal (SSGF) antenna is proposed for dualband operation with wide-bandwidth covering GPS, DCS-1800, PCS-1800, UMTS, IMT-2000, Wireless broadband Internet Services (WiBro), Bluetooth, and WLAN bands. The SSGF antenna consists of volume 65.5 Â 27 Â 1.6 mm 3 . To analyze its performance, measurements are carried out. The proposed antenna model exhibits resonances in 1.51-3.39 GHz (2:1 VSWR BW 76.6%) and 5.31-6.32 GHz (2:1 VSWR BW 17.3%) bands with 2.5-5 dBi gain. Very good agreement is obtained between simulation and experimental results.

Dual-frequency operation of antenna has become a necessity for many applications in recent wireless communication systems, such as GPS, GSM services each operating at two different frequency bands. A new technique to achieve dual band operation from different types of microstrip antennas is presented here. An evolutionary design process using a particle swarm optimization (PSO) algorithm in conjunction with the method of moments (MoM) is employed effectively to obtain the geometric parameters of the antenna performance.