Design of wideband microstrip array antennas using the coupled lines

A variety of single layer wideband microstrip antenna designs (e.g., parasitic structure, embedding slot, reactive loading, etc.) have been reported. The wideband impedance matching technique can also increase the bandwidth of microstrip antenna on a single layer, but this technique has a complicated design procedure and the disadvantage of increasing the coplanar size of the antenna due to the wideband impedance matching section. If the wideband impedance matching technique is applied to antenna arrays, the enlargement of coplanar size can be overcome by the inherent space between the array elements. In this article, we present two different designs of wideband microstrip array antennas using the coupled lines that are a kind of wideband impedance matching technique and are adequate for array antennas. Antenna designs and details of the experimental results are described and discussed.