suitable to describe the singular behavior of the spatial GF. In its turn in the improved version the analytical part derived in the explicit form provides with this behavior. It can be easily derived from Fig. 2 that the numerical part (dash-point line) of the improved GF gives a considerably smaller contribution in the vicinity of the origin than the analytical one. This numerical part can be calculated with guaranteed accuracy. The real part of the plotted GF is not singular at the origin and its values calculated with and without the analytical extraction coincide. V. CONCLUSIONIn this paper, a rigorous way to extract the singularity of the spatial GFs for a sheet electric current over a dielectric coated cylinder is proposed. The spatial GFs are required to analyze cylindrical microstrip antennas. Up to now the direct rigorous numerical calculation of the spatial GFs using the IFT in practice was not possible because of the hidden singularity. The singular part of the spatial GFs is derived in an analytical form. The remaining part of the spatial GFs is calculated numerically with guaranteed accuracy. The proposed spatial GFs can be effectively used in the moment method formulation for cylindrical microstrip antennas. Thus, our approach allows extending the concept of the mixed-potential formulation, which proved its efficiency for planar structures, to cylindrical structures. REFERENCES

Abstract-A dual-band R-shaped planar inverted-F antenna is proposed for vehicular application. Utilization of this unique geometry dual-frequency operation is achieved with a single feed. The proposed antenna operates in the 225-and 450-MHz bands. Input impedance and return loss data as function of various antenna parameters are presented, which show that parameters can be adjusted in order to obtain optimum tuning. Radiation pattern data for the antenna mounted on the roof of two types of vehicles are given. The pattern in the low-frequency band is essentially omnidirectional while that in the high-frequency band is directional and normal to the antenna surface. With proper scaling, this antenna may be suitable for dual-band GSM 900/1800-MHz phone applications.

No abstract

This paper presents unequal microstrip power divider designs using the hierarchal genetic algorithm (HGA). The dividing ratio and return loss are the design specifications leading the evolution direction. By employing the HGA chromosome formulation, the system structure and its associated parameters can be minimized in a simultaneous manner. The INTRODUCTIONPower dividers are extensively used in RF/microwave power amplifier, linearizers, and antenna arrays. The equal microstrip power divider is very simple to design and realize. On the contrary, power dividers with unequal power division are more restrictive in the design process. Impedance-matching techniques are introduced to solve this problem and some "general design equations" were derived to guide the design procedures [1][2][3]. However, compared to the full-wave numerical analysis, the circuit theory design model is too crude and the design based on impedance-matching techniques may be difficult to realize in practice [4]. Moreover, the massive parameters and complex design specifications are major obstacles to achieving the successful design by following the circuit theory design model.The hierarchal genetic algorithm (HGA) is an emerging optimization algorithm, which has the capacity of optimizing the system structure and its parameters in a simultaneous fashion [5]. The precise divider characteristics of dividing ratio and return loss obtained by the full-wave numerical analysis are converted into the fitness value based on the design specification. Following the rule of "survival of the fittest," HGA can search more than one solution whose characteristics also match the required design criteria. The realization of the optimal microstrip divider profile demonstrates its efficiency and success.In this paper, the design and measured performance of the 3:1 and 3:2 unequal microstrip power dividers are presented. The full-wave numerical analysis, incorporating the HGA optimization scheme, is carried out on a parallel computing platform to form a practical proposition for engineering uses. HIERARCHICAL GENETIC ALGORITHMHGA has a newly formulated chromosome structure inspired by the complex hierarchical chromosome structure in nature. The hierarchical chromosome consists of two gene levels, namely, the control genes and parametric genes. It can provide a unique solution for simultaneous parametric and system structural search.For the unequal microstrip power divider design, the profile is divided into four parts: three arms and one connection, whose width and length are the parameters taken into optimization in the design. To represent the arm profile, binary strings with the same binary bits construct the grids to depict the arm profile, in which '1' implies the presence of the conducting trace on the substrated and '0' otherwise, as shown in Figure 1. The successive '1' implies the continuous conducting trace profile of the arm. However, additional binary string is used to eliminate the possibility of disjointed arm profile representation. As ...

A wideband microstnp patch antenna has been analyzed, designed, fabricated, and measured for wireless local area network (LAN) applications in the 5-6 GHz frequency range. The antenna is internal to the housing of a personal digital assistant (PDA), such as a PALM organizer and has the dimensions of 28 mm by 9 mm by 3 mm on FR4 substrate. The antenna meets or exceeds the bandwidth requirements for the dual-band IEEE 802.1 l a wireless local area network (WLAN) applications (5.15-5.35 GHr and 5.725-5.825 GHz) within 2:l VSWR.