Sai Ho Yeung

Jumping Genes Multiobjective Optimization Scheme for Planar Monopole Ultrawideband Antenna

A planar ultrawideband (UWB) monopole antenna is proposed in this paper. It has a planar multiple-trapezoidal monopole with adjustable dimensions. The proposed antenna is incorporated with the rectangular/rounded-corner ground plane to further improve the monopole performances such as impedance bandwidth. The geometric complexity of the antenna configuration is not easily devisable when the UWB performance criteria such as low voltage standing wave ratio (VSWR), minimal antenna size, omni-directional and uniform radiation pattern, and relatively constant gain over the ultrawide frequency band are to be simultaneously met. In this paper, all of these requirements can now be easily accomplished by making use of the recently developed jumping genes (JGs) multiobjective optimization scheme. A vivid demonstration of this approach of UWB design is to select an antenna configuration from the thoroughly investigated results and come up with the ultimate recommendation of hardware prototype fabrication. This way not only confirms both the simulated and measured results are all in good agreement but also indicates that the proposed methodology is sound for the design of UWB antenna.

A Trapeizform U-Slot Folded Patch Feed Antenna Design Optimized With Jumping Genes Evolutionary Algorithm

A novel design of trapeizform U-slot folded patch feed antenna is presented in this paper. It is optimized by an evolutionary based optimization scheme which is capable of producing an antenna design that has a wide impedance bandwidth but small in dimension size. The optimized design was also experimentally verified by its hardware prototype in which 101.3% measured impedance bandwidth was obtained compared with its simulated bandwidth of 104%. Also, both the effectiveness of the optimization methodology and the proposed antenna configuration have been justified through comparison results.

Computational Optimization Algorithms for Antennas and RF/Microwave Circuit Designs: An Overview

This paper provides an overview of optimization algorithms for antennas and radio frequency (RF)/microwave circuit designs. The significance of wireless communication to our daily lives and industrial engineering will first be discussed. Antennas and circuits used in wireless communication will then be introduced followed by a discussion on the need for optimization. After that, this paper will focus on three widely used optimization algorithms for antennas and RF/microwave circuit design. A survey of the optimization of antennas and microwave devices available in the literature will be presented and will include the use of other optimization algorithms. For illustration purposes two optimization examples with measurement results will be given.

Circularly Polarized Reconfigurable Crossed-Vagi Patch Antenna

A reconfigurable crossed-Vagi patch antenna (CYPA) that yields a circularly polarized pattern is proposed, and optimized by a novel Jumping-Genes Genetic Algorithm. This antenna is formed by two identical orthogonal reconfigurable linear Vagi patch arrays, around a single driven patch element. The main lobe of the reconfigurable crossed-Yagi patch antenna covers the elevation angles from 0° to 47° with a peak gain of 8.68 dBi. Full azimuthal coverage can be achieved by switching among the four antenna modes. The design justification has been duly demonstrated based on fabricated prototypes. The effect of a MEMS switch on the reconfigurable Vagi antennas is investigated. The reactance introduced by the switch can be offset by modifying the dimensions of a loaded slot. Due to the distinctive features of this antenna, satellite communications and global positioning systems would be the most suitable targets for application.

Dual-Band Rectangular Patch Hybrid Coupler

This paper presents, for the first time, the design of a rectangular patch hybrid coupler that can operate at two arbitrary frequency bands with the same quadrature phase relation between the two outputs. The design procedure of the hybrid coupler is presented. For demonstration, a dual-band rectangular patch hybrid coupler is designed to operate in the 2.4- and 5-GHz bands corresponding to the IEEE 802.11 a/b/g bands. The measured result shows 9.3% and 18.2% bandwidth for the lower and upper frequency bands.

A Bandwidth Improved Circular Polarized Slot Antenna Using a Slot Composed of Multiple Circular Sectors

A circular polarized (CP) slot antenna is designed with a slot composed of multiple circular sectors (MCS). The design has advantages of having a wide 3 dB axial ratio (AR) bandwidth of 57.4%, achieving a good AR smaller than 2 dB in most areas of the frequency range. The design of the antenna follows a multi-objective optimization procedure that applies computational power rather than human tuning. A comparison of the optimized antenna design with other wideband CP antennas in the literature shows that it has advantages of having a smaller physical size in the cross-sectional area than the antennas with multiple feeding structures and a wider operating bandwidth than all the compared antennas.

Size-Reduced Rectangular Patch Hybrid Coupler Using Patterned Ground Plane

This paper presents, for the first time, the design of a size-reduced rectangular patch hybrid coupler. Different types of compact rectangular patch hybrid couplers with different ground plane patterns are described. For demonstration, two compact rectangular patch hybrid couplers are designed to operate at 3.5 GHz. They are measured to have 30.1% and 33.3% bandwidth with 67.3% and 72.3% size reduction compared with the optimized one without patterned ground plane.

Design of Broadband Hybrid Coupler With Tight Coupling Using Jumping Gene Evolutionary Algorithm

This paper presents the design procedure for complex RF circuits using the Jumping Genes Evolutionary Algorithm (JGEA). Due to the complex and stringent requirements for industrial environments, it is not an easy task to obtain a good design in which irregular structures are always needed. In this paper, JGEA has, however, demonstrated its excellent ability in practical RF circuit design compared with other algorithms. For demonstration, it was used in the design of a slot-coupled 3-dB hybrid coupler operating in the popular Industrial, Scientific and Medical application frequency band with small amplitude imbalance, low cost, and small size.

Design and Testing of a Single-Layer Microstrip Ultrawideband 90 ° Differential Phase Shifter

This letter proposes a design of single-layer microstrip ultrawideband (UWB) 90^° differential phase shifter. The operating bandwidth covers the UWB frequency range from 3.1-10.6 GHz. The design is optimized using a transmission line model and an electromagnetic model, and have been fabricated using a plotter dealing with generation of printed circuits. The measured <i>S</i>₁₁ is better than -10 dB and <i>S</i>₂₁ is better than -0.96 dB within the UWB frequency range. The simulated and measured phase deviation of the differential phase shift are 90^°±5.23^° and 90^°±9.02^°, respectively. The advantages of the proposed design are the simple fabrication, low insertion loss, and broad bandwidth.

The Multiple Circular Sectors Structures for Phase Shifter Designs

Two phase shifters are proposed using a multiple circular sector structure. Advantages of the design include low insertion losses and small phase variations over a wide range of operating bandwidths. The design process follows a multiobjective optimization procedure that applies computational power for circuit tuning. Performance of the phase shifters are analyzed, after fabricating and measuring for verification. The phase shifter performances are compared with other existing phase shifter configurations in terms of insertion losses and phase variations.