Miniaturized dielectric-loaded rectangular waveguides for use in multi-frequency arrays

There is an increasing interest in combining several antennas into a multi-function system, thus incorporating multiple frequency bands into a single antenna. Multi-band phased arrays are potential candidates for this purpose, allowing several frequency bands to operate from the same array aperture, i.e. aperture reuse. Such arrays may be realized by using compact narrowband elements in an array sufficiently sparse for intermediate compact elements operating at other frequencies to be embedded or superposed over the same array aperture. Hence, there is a need for miniaturized elements that are very small in terms of wavelength. The paper investigates miniaturized open-ended rectangular waveguides for use as array elements. We show that operating dielectric-loaded rectangular waveguide elements of an infinite planar array within the vicinity of the TEM frequency gives rise to the best transmission. In addition, it is seen that miniaturization in E-plane is better than in H-plane. For a large degree of miniaturization, the reflection coefficient is large and needs to be reduced by incorporating matching layers or similar. The results have been verified by using two independently developed codes. One of these has also been validated in other works.