CYLINDRICAL MICROSTRIP ARRAY ANTENNAS WITH SLOTTED STRIP-FRAMED PATCHES

A cylindrical microstrip array antenna with 5 pairs of coupled slotted strip framed patches is analyzed. The patches are proximity-fed by a cylindrical microstrip line. In order to extract the reflection coefficient from the standing wave pattern on the microstrip line, its length is about 5 wavelengths. To the best of the authors' knowledge proximity-fed cylindrical arrays have not been analyzed before using a rigorous MOM model that takes into account all electromagnetic couplings between patches and feeding line. The paper consists of three parts. The first part describes a plane wave excitation of the cylindrical microstrip structure. It introduces some innovating theoretical developments, like the improvement of the asymptote for the spectral Green's function and the explicit surface wave contribution. The second part calculates the radar cross section of the cylindrical microstrip structure with single and coupled slotted strip framed patches. The resonant frequencies, and the amplitude and phase of the current distribution are analysed. The third part describes a design for a proximity-fed array of 5 coupled slotted strip framed patches. It gives the reflection coefficient, current distribution on the patches, and radiation pattern. A very low level of cross polarization (< -40 dB) is achieved. It is shown that the resonant frequencies of the cylindrical array and its planar analogue lie very close to each other. This is due to the common nature of the low frequency slot resonance for the slotted strip framed patch.