An Engineered Conductor for Gain and Efficiency Improvement of Miniaturized Microstrip Antennas

This paper reviews the concept of an engineered conductor, introduced by the authors in order to reduce ohmic losses of miniaturized microstrip antennas [1-4]. Because of the miniaturization, the ohmic losses of microstrip antennas increase, which essentially significantly reduces their gain and efficiency. By the use of the engineered conductor concept, these two important parameters of such antennas can be improved without altering the antenna's geometry. The concept is based on using multiple laminated thin conductors, rather than one thick conducting layer, to form the microstrip antenna. The technique is applied to several miniaturized microstrip antennas in order to reduce their ohmic losses. The concept is explained using a microstrip line to demonstrate that the conductor loss can be reduced by increasing the number of layers in the lamination, while keeping the total thickness constant. Using conventional metallized substrates, the lamination reduces the thickness of each conductor layer to approximately or less than the skin depth in that conductor. Studies of two miniaturized antennas - namely, the square-ring antenna and the modified open-ring antenna - have respectively provided about 4.6 dB and 1.5 dB improvements in the gain, and from 30% to 40.7% improvement in the efficiency. Experimental investigations are also presented that confirmed the simulated results.