Quasi-log-periodic microstrip antenna with closely coupled elements

Abstract

This paper proposes a method of constructing a log-periodic microstrip antenna. Log-periodic technique is considered to be useful for improving the characteristics of a microstrip antenna (MSA) which is narrow band in nature, without giving up the advantages of low profile and light weight. The radiating elements are coax-fed and arranged on one side of the common feed line behind the ground plane. This arrangement necessarily decreases the element spacings, and increases the mutual coupling between elements. The coupling effect has acted to fill up the inactive frequency regions. Larger coupling between elements due to the necessarily dense arrangement enables obtaining wide-band frequency characteristics. An example five-element case proves that the present method is useful, giving a gain of 6 to 10 dBi over a bandwidth of about 20%. © 2000 Scripta Technica, Electr Eng Jpn, 132(2): 58–64, 2000