Project Highlight

Antenna Group

Optimization design of wire loaded antenna

Wire antennas have been extensively used for communication since the early days of radio transmission, and they still remain one of the most popular options for a variety of communication systems, especially at high frequency band. Beside the broadband requirements, antennas should be compact or minimization enough to be placed within a limited space. Since the characteristics of an antenna are obviously determined by the current distributions on the structure, we can improve their performance by controlling the current value on the antenna. For HF to VHF bands, loading with lumped parallel or series resistor–inductor–capacitor (RLC) circuits are adopted. In the analysis of wire antennas with loading, the Method of Moment (MoM) is widely used, with results of good accuracy. Matching network can be designed for the loaded antenna to reduce in-band VSWR.

Designing a broad-band antenna to meet certain specifications is a nonlinear optimization problem. The solution procedure carries out a search for the optimal set of parameters. Genetic Algorithm (GA) is a stochastic optimization algorithm, which is as robust as it is versatile. The algorithm repetitively applies three stochastic operators on a population of designs, viz., "reproduction," “crossover," and "mutation." The GA has the desirable attribute by operating on a large population of designs, and by implementing stochastic transition rules; it avoids getting trapped into a local minimum. Another attractive feature of this algorithm is it can generate a number of distinct and high performance designs, and offers the designer a number of candidates for the final design. The GA optimization process guides the population of potential designs toward better solutions through a repetitive application of genetic operators. This evolution process continues until an antenna-matching network system satisfying the design goals is found.

Based on the MoM and GA, the optimization design code is developed. The optimized parameters include all the Rs, Ls, Cs, the locations of the loadings, and the matching network. HF band antenna (2MHz to 30GHz) and VHF (30MHz to 100MHz) band antenna have been designed by using the effective code.