Abstract:
There is an increasing need for ultra-wideband antennas with higher gain yet smaller in size. Few kinds of antennas can help us in these situations. TEM horn antenna has been a candidate to have relatively smaller size while supports high gain and bandwidth [1-2]. In order to design a high gain and broadband antenna with a small size, we face fundamental limitations and tradeoffs between size and bandwidth and also size and gain. Chu and Wheeler have illuminated the problem for the first limitation [3, 4], and Schantz [5] for the second. As it is obvious, one should compromise between these three requirements when all are of interest. Combining the idea of TEM horn and V-conical [6-7] antennas we introduce a new kind of wire antenna with special advantages named porcupine antenna due to its unusual shape. The antenna is illustrated in Fig. 1. In the main part of the antenna, a number of diverging metallic rods thickened gradually with stepped increase are elevated from horizon. Each rod somewhat looks like a V-conical antenna owing to its gradual thickening. These rods are connected in the base and positioned to form a conical section. In order to increase the gain of the antenna, a small half circle metallic plate is located behind the main structure. All of the mentioned parts are above the ground. The coaxial feed is inserted between the base of metallic rods and the ground.