A small size microstrip antenna having a partial short circuit

Two special configurations of partially shorted microstrip antennas are studied experimentally. In the first configuration, the shorted portion of the partially shorted edge is formed in one continuous section centered around the central line of the antenna, on which the feed point is located. The different widths of the shorted section and the corresponding resonant frequencies and the feed locations that provide 50 ohms input impedance are shown. In order to satisfy the required input impedance of 50 ohms, the feed point should be moved closer to the partially shorted edge as the width of the shorted section of that edge decreases. In the second configuration the short circuited portion comprises two equal sections at the outer ends of the partially shorted edge. In such a case, any point on the central line of the antenna, including the feed point, will always be far enough from the shorted sections of the partially shorted edge. Hence, the variation of the input impedance along the central line of the antenna is much smaller than the first configuration