K. Vasudevan

CPW-Fed Koch Fractal Slot Antenna for WLAN/WiMAX Applications

A dual wide-band CPW-fed modified Koch fractal printed slot antenna, suitable for WLAN and WiMAX operations, is proposed in this paper. Here, the operating frequency of a triangular slot antenna is lowered by the Koch iteration technique resulting in a compact antenna. Studies on the impedance and radiation characteristics of the proposed antenna indicate that a modified Koch fractal slot antenna has an impedance bandwidth from 2.38 to 3.95 GHz and 4.95-6.05 GHz covering 2.4/5.2/5.8 GHz WLAN bands and the 2.5/3.5/5.5 GHz WiMAX bands. The antenna exhibits omnidirectional radiation coverage with a gain better than 2.0 dBi in the entire operating band. Empirical relations are deduced and compared with the results.

A New Compact Microstrip-Fed Dual-Band Coplanar Antenna for WLAN Applications

A novel compact microstrip fed dual-band coplanar antenna for wireless local area network is presented. The antenna comprises of a rectangular center strip and two lateral strips printed on a dielectric substrate and excited using a 50 Omega microstrip transmission line. The antenna generates two separate resonant modes to cover 2.4/5.2/5.8 GHz WLAN bands. Lower resonant mode of the antenna has an impedance bandwidth (2:1 VSWR) of 330 MHz (2190-2520 MHz), which easily covers the required bandwidth of the 2.4 GHz WLAN, and the upper resonant mode has a bandwidth of 1.23 GHz (4849-6070 MHz), covering 5.2/5.8 GHz WLAN bands. The proposed antenna occupy an area of 217 mm2 when printed on FR4 substrate (epsivr=4.7). A rigorous experimental study has been conducted to confirm the characteristics of the antenna. Design equations for the proposed antenna are also developed

DESIGN OF COMPACT RECONFIGURABLE DUAL FREQUENCY MICROSTRIP ANTENNAS USING VARACTOR DIODES

The design of a compact, single feed, dual frequency dual polarized and electronically reconfigurable microstrip antenna is presented in this paper. A square patch loaded with a hexagonal slot having extended slot arms constitutes the fundamental structure of the antenna. The tuning of the two resonant frequencies is realized by varying the effective electrical length of the slot arms by embedding varactor diodes across the slots. A high tuning range of 34.43% (1.037–1.394 GHz) and 9.27% (1.359–1.485 GHz) is achieved for the two operating frequencies respectively, when the bias voltage is varied from 0 to −30 V. The salient feature of this design is that it uses no matching networks even though the resonant frequencies are tuned in a wide range with good matching below −10 dB. The antenna has an added advantage of size reduction up to 80.11% and 65.69% for the two operating frequencies compared to conventional rectangular patches.

Design of a Compact Semi-Elliptic Monopole Slot Antenna for UWB Systems

A printed semi-elliptic monopole slot antenna for use in ultrawideband (UWB) communication systems is presented. The antenna features a coplanar waveguide signal strip terminated with a semi-elliptic stub and a modified ground plane to achieve wide bandwidth from 2.85-20 GHz. An exhaustive study of the radiation characteristics of this antenna in the frequency and time domains are presented. Design equations are derived and experimentally validated. Transient analysis indicates linear phase response and minimum dispersion to the transmitted pulse. The proposed radiator is omnidirectional with appreciable gain throughout the band.

An Electronically Reconfigurable Microstrip Antenna With Switchable Slots for Polarization Diversity

An electronically reconfigurable microstrip antenna with circular and linear polarization switching is presented. The prototype fabricated on a substrate of dielectric constant (εr) 4.4 and height (h) 1.6 mm is fed by a proximity feed fabricated using the same substrate. By controlling the bias voltage of two PIN diodes, the polarization of the antenna can be switched between three states; two states for linear polarization (horizontal and vertical) and one state for circular polarization (RHCP). Simulation and experimental results show that the proposed antenna has a cross polar level better than 10 dB in the linear polarization state and 18 MHz axial ratio bandwidth in the circular polarization state. The frequency and polarization diversities of this design could potentially improve the reliability of wireless communication systems.

Compact dual band slot loaded circular microstrip antenna with a superstrate

Design of a compact dual frequency microstrip antenna is presented. The structure consists of a slotted circular patch with a dielectric superstrate. The superstrate,not only acts as a radome, but improves the bandwidth and lowers the resonant frequency also. The proposed design provides an overall size reduction of about 60% compared to an unslotted patch along with good efficiency,gain and bandwidth. The polarization planes at the two resonances are orthogonal and can be simultaneously excited using a coaxial feed. Parametric study of this configuration showed that the frequency ratio of the two resonances can be varied from 1.17 to 1.7 enabling its applications in the major wireless communication bands like AWS, DECT,PHS,Wi.Bro,ISM,and DMB. Design equations are also deduced for the proposed antenna and validated.

A Compact Dual-Band Planar Antenna for DCS-1900/PCS/PHS, WCDMA/IMT-2000, and WLAN Applications

A compact dual-band planar antenna developed for DCS-1900/PCS/PHS, WCDMA/IMT-2000, and WLAN applications is presented. The proposed antenna consists of a flared monopole with an additional sleeve for dual-band applications. The overall size of the antenna is 40 mm times 25 mm times 1.6 mm including the Finite Ground CPW feeding mechanism. The antenna operates in two frequency bands from 1.83 to 2.34 GHz and 3.23 to 5.76 GHz covering DCS-1900/PCS/PHS, WCDMA/IMT-2000, and WLAN bands. Simulation results along with measurements of the prototyped antenna are presented and discussed.

Wideband Printed Microstrip Antenna for Wireless Communications

A simple electromagnetically coupled wideband printed microstrip antenna having a 2:1 VSWR bandwidth of 38% covering the 5.2/5.8-GHz WLAN, HIPERLAN2, and HiSWANa communication bands is presented. The large bandwidth is obtained by adding a rectangular metal strip on a slotted square microstrip antenna. The antenna occupies an overall dimension of 42 times 55 times 3.2 mm3 when printed on a substrate of dielectric constant 4. It exhibits good radiation characteristics and moderate gain in the entire operating band. Details of the design along with experimental and simulation results are presented and discussed.

Chipless RFID Tag Using Multiple Microstrip Open Stub Resonators

A novel compact RFID tag employing open stubs in a microstrip transmission line is proposed. The prototype of the tag is fabricated on a substrate of dielectric constant 4.4 and loss tangent 0.0018. The tag consists of microstrip open stub resonators and cross polarized transmitting and receiving disc monopole antennas. A prototype of 8 bit data encoded tag is demonstrated in this communication. Method for enhancing the performance of the RFID tag is also proposed. Magnitude or group delay response can be used to decode the tag informations.

A Compact UWB MIMO Antenna With Reflector to Enhance Isolation

A compact ultrawideband (UWB) multiple-input multiple-output (MIMO) antenna, with high isolation, is proposed for portable UWB MIMO systems. Two coplanar stripline-fed staircase-shaped radiating elements are connected back-to-back. The prototype is designed on a substrate of dielectric constant 4.4 with an overall dimension of 25 mm × 30 mm × 1.6 mm. This antenna configuration with an isolating metal strip placed in between the two radiating elements ensures high isolation in the entire UWB band. The proposed antenna exhibits a good 2:1 VSWR impedance bandwidth covering the entire UWB band (3.1-10.6 GHz) with a high isolation better than 20 dB, peak gain of 5.2 dBi, peak efficiency of 90%, and guaranteed value of envelope correlation coefficient (ECC) ≤0.1641.