Annular Ring Patch Research Articles

Crosspolar performance of annular-ring microstrip antenna with novel mode suppression

The crosspolarisation of annular-ring microstrip patches resonating in the TM12 mode is discussed. It is shown that circumferential slots within the rings can suppress other modes and improve the radiated crosspolarisation levels.

A wider band microstrip antenna for circular polarization

Circular polarization is achieved by separating two degenerate orthogonal modes in an annular ring patch antenna, by using an ear at the outer periphery. The analysis of such a structure is performed by using the generalized transmission line model. It is found theoretically that this structure can be used to generate circular polarization over a wider frequency range than other structures. An annular ring is designed and its performance is evaluated. Good agreement between the theory and the experiment is obtained. It is also found that the axial ratio bandwidth is higher for the TM/sub 12/ mode than the TM/sub 32/ mode of operation in an annular ring antenna.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Method of reducing mode-degeneracy problem in annular-ring patch antennas

The annular-ring patch antenna with an extended ear at its outer periphery is analysed. A mode matching technique (MMT) is utilised and is improved by incorporating the mutual coupling effect between the two radiating edges. The formulations for the wall admittances including the extended ear are also developed. The analysis shows that for an annular bandwidth of the TM12 mode is increased by increasing its inner radius. It also moves the resonant frequency of the TM02 mode towards that of the TM12 mode, overlap-ping their bandwidths and causing mode degeneracy. The addition of an extended ear separates the mode resonances and removes their degeneracy and, therefore, the usable range of frequency for a particular mode is increased. An annular ring with the extended ear is fabricated and tested. The numerical results of the improved MMT agree more closely with the experimental data than those obtained using the conventional MMT used in the literature.