Abstract-A reconfigurable stacked microstrip patch antenna is proposed. The antenna operates at an upper frequency f u with a broadside pattern, 7.5-dBi right-hand circularly polarized gain, and 15.8% bandwidth. At a lower frequency f l , the antenna operates as a planar inverted-F antenna (7.3% bandwidth and 3.9-dBi peak gain) with the main beam directed close to the horizon. Switching between the two regimes of operation is achieved using p-i-n diodes. Antenna operation in the upper frequency band is suitable for low-earth-orbit or medium-earth-orbit satellite communications, and in the lower frequency band, the antenna is useful for terrestrial land-mobile or other wireless applications.Index Terms-Reconfigurable antenna, satellite link, stacked patch antenna, terrestrial link.

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 ...

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