Bidirectional rod antenna composed of narrow patches

A collinear antenna, which is a familiar rod antenna, is widely used because of its inconspicuous shape. The radiation pattern of such an antenna in the H-plane is omni-directional. Its gain can be increased by using linear arrays. However, the gain is not proportional to the number of elements because the loss of the feeding network increases. Gain is more effectively increased by creating a directional pattern in the H-plane than by increasing element number. The bidirectional narrow patch antenna (BNPA), which has narrow patches on both sides of a narrow dielectric substrate fed by a parallel strip line, is a bidirectional antenna in the H-plane. This is easily fabricated by printing patches and the feeding network on a substrate, and this can form the bidirectional rod array antenna (BIRA) by orienting several BNPAs in the E-plane. However, BNPAs with a thin substrates have low radiation efficiency. The paper first clarifies the dependency of a BNPA´s radiation efficiency on the thickness of the dielectric substrate by the FDTD method. In order to improve the radiation efficiency, the authors add two opposing parasitic patches to a BNPA to form the BNPA-P. It is shown that a BIRA formed with several BNPA-Ps has higher gain than a collinear antenna of the same length.<>