S. W. Cheung

A Novel Technique and Soldering Method to Improve Performance of Transparent Polymer Antennas

A novel technique and a nonthermal soldering method to improve the performance of AgHT-8 transparent polymer antennas are proposed in this letter. The proposed technique involves the removal of the coating layer at areas on the coplanar waveguide (CPW) ground and feed line where the connectors of the coaxial feed or legs of the SMA connectors will be attached and applying a coat of silver paint on the exposed areas before cold-soldering the coaxial connections or SMA connector legs. The nonthermal or cold soldering using electrically conductive paste enables direct soldering of the coaxial feed points or connector legs, which cannot otherwise be done with hot or thermal soldering. This type of connection greatly enhances the performance of the AgHT-8 polymer antennas compared to coaxial feed point connections through hot-soldered copper pads glued to the surface of the polymer coating. The proposed technique also gives a stronger connection bond than directly cold-soldering the feed points or connectors to the smooth surface of the AgHT-8 material. Furthermore, the copper pad connection technique also introduces additional losses contributed by the adhesive properties of the glue used. This proposed novel technique and soldering method may be extended to enhance antenna performance made from other similar transparent conductive polymers like ITO.

UWB antenna with single or dual band-notched characteristic for WLAN band using meandered ground stubs

The paper proposes to use meandered grounded stubs to design single or dual band-notched planar-monopole antennas for ultrawide band (UWB) applications. The center-notch frequencies and notch bandwidths of the UWB antennas can be adjusted by using the dimensions of the meandered grounded stubs. Two prototype antennas are designed, fabricated and studied. One has a single band notch in the wireless area network (WLAN) band from 5.15 GHz to 5.825 GHz and the other one has two sets of dual-band notches at the lower WLAN band (5.15–5.35 GHz) and higher WLAN band (5.725–5.825 GHz). The band-notched characteristics, radiation patterns and peak gains of the antennas are studied using computer simulation and measurements.

Triple band-notched UWB antenna using meandered ground stubs

In this paper, three pairs of meandered ground stubs are used to create a triple band-notched characteristic for a compact planar-monopole antenna used in the ultrawide band (UWB). The three band notches include the IEEE 802.16 (WiMax) band (3.3–3.6 GHz), the lower wireless area network (WLAN) band (5.15–5.35 GHz) and the higher WLAN band (5.725–5.825 GHz). The center frequencies and bandwidths of the notches can be adjusted using the dimensions of the meandered ground stubs. Prototype of the proposed antenna is designed and fabricated. The band-notched characteristics, return loss, radiation patterns, peak gains and efficiencies of the antenna are studied using both computer simulation and measurements.

An antenna for UWB and Bluetooth standards with band-notched characteristic

This paper presents the design and results of a small size, integrated Bluetooth and Ultrawideband (UWB) planar monopole antenna with a band-notched characteristic in the WLAN band. The antenna consists of a dual-ring radiator as the primary radiation element for the Bluetooth and UWB bands and a complementary split-ring resonator (CSRR) to produce a notched characteristic at the center frequency of 5.5GHz. The return loss, voltage-standing-wave ratio (VSWR), radiation pattern and peak gain of the antenna are studied by computer simulation and verified by measurements which agree well with the simulation results.

Effects of ground-plane size on planar UWB monopole antenna

Planar monopole antennas have found widespread applications in wireless communication systems. Their advantages of compact size, omnidirectional radiation pattern and wide impedance bandwidth make them good candidates for the designs of ultra-wideband (UWB) antennas. This paper investigates the effects of the dimensions of the rectangular ground-plane on the return loss and efficiency of an elliptical planar monopole antenna for UWB applications. Computer simulation and measurement are carried out on a group of nine antennas with different rectangular ground plane sizes. The simulated and measured results on return loss agree well. However, the simulated and measured efficiencies do not agree well in the lower UWB band. The measured efficiency shows that the efficiency is affected more by the width rather than by the length of the ground plane while the length of the ground plane affects the lower cutoff frequency.

Ultrawideband antenna using CPW resonators for dual-band notched characteristic

This paper presents the design and results of a compact Ultrawideband (UWB) monopole antenna with a dualband notched characteristic. The antenna consists of a semicircular radiator and a dual-coplanar-waveguide (CPW) resonator to produce two notched bands at the center frequencies of 3.5 and 5.5 GHz in the UWB region. The computer simulation results of the Voltage-Standing-Wave Ratio (VSWR), radiation pattern and peak gain of the antenna agree well with the measurements.

A compact and UWB time-delay line inspired by CRLH TL unit cell

This paper presents the design of compact and ultra-wideband (UWB) time-delay lines inspired by the use of composite right/left-handed transmission line (CRLH TL) unit cell. A conventional CRLH TL unit cell is used as the basic elements for the design of time-delay lines and a rotated version of the unit cell is used to achieve ultrawide bandwidth operation. Time-delay lines for large time delays are designed by cascading the proposed unit cells, optimized using computer simulation and then fabricated on PCBs. A compact UWB time-delay line is designed by bending the time-delay line in a meander. For comparison, the time-delay line using the right-handed transmission line (RH TL) is also fabricated. Simulation and measurement results show that our proposed time-delay lines have ultrawide bandwidth operation and much longer time delays than that of the time-delay line based on RH TL. They also have the advantages of high return losses and low insertion losses.

A fast-decodable code structure for linear dispersion codes

This paper proposes the design of a new family of fast-decodable, full-rank, flexible-rate linear dispersion codes (LDCs) for MIMO systems with arbitrary numbers of transmit and receive antennas. The codewords of LDCs can be expressed as a linear combination of certain dispersion matrices and, in this new family of LDCs, we propose to have orthogonal rows in as many dispersion matrices as possible. We show that, with the proposed code, the number of levels in the tree search and hence the complexity of the sphere decoder (SD) at the receiver can be substantially reduced. Monte Carlo computer simulation has shown that the LDCs with and without the orthogonal structure have nearly identical bit-error-rate (BER) performances. However, the complexity of the SD used for decoding the proposed family of LDCs is substantially reduced.