A Review on Improved Design Techniques for High Performance Planar Waveguide Slot Arrays

Planar waveguide slot arrays (WSAs) have been used since 1940 and are currently used as performing antennas for high frequencies, especially in applications such as communication and RADAR systems. We present in this work a review of the most typical waveguide slot array configurations proposed in the literature, describing their main limitations and drawbacks along with possible effective countermeasures. Our attention has been focused mainly on the improved available design techniques to obtain high performance WSAs. In particular, the addressed topics have been reported in the following. Partially filled WSAs, or WSAs covered with single or multilayer dielectric slabs, are discussed. The most prominent second-order effects in the planar array feeding network are introduced and accurately modeled. The attention is focused on the T-junction feeding the array, on the effect of interaction between each slot coupler of the feeding network and the radiating slots nearest to this coupler, and on the waveguide bends. All these effects can critically increase the first sidelobes if compared to the ideal case, causing a sensible worsening in the performance of the array.

Ka-band planar slotted waveguide array based on groove gap waveguide technology with a glide-symmetric holey metasurface

The design of a planar slot array in groove gap waveguide technology implemented by glide-symmetric holes as Electromagnetic Band Gap structure is here presented. Despite the advantages of using holes instead of pins in terms of manufacturing simplicity and cost,the larger size of the holes compared to pins needs to be considered when designing slot arrays without grating lobes. A 1 to 4 corporate feed network is designed using this technology as well. Corrugations are included to further reduce the grating lobes. Experimental results support the viability of the proposed concept for designing glide-symmetric planar arrays of any size.

Advanced high-gain slot antenna arrays for 5G and radar applications

This paper presents an advanced design of high-gain slot antenna array at K-band using slots as radiating elements serially fed by coplanar waveguide (CPW). The arrays consist of identical slots of rectangular shape positioned symmetrically relative to the CPW feeding line. Firstly, the linear arrays of 14 slots are examined considering mainly their bandwidth and radiation characteristics. In addition, two identical linear sub - arrays of 14 slots are investigated when they have separate feeding in the form of two generators for each sub - array. Last, a CPW T-junction is employed to feed the antenna consisting of 2 x 14 slots which resulted in a wide operating bandwidth and maximum gain of 21.0 dBi which proved to be 2.25 dB less gain than with independent feeding. In order to enhance the antenna gain, both arrays are terminated with open-circuited stubs, so that the energy remaining after the last array element is reflected from the stub and re-radiated through the slot arrays. The length of the stubs is optimized to provide that the reflected wave is in phase with the forward-traveling waves at all the slot locations. In that way, very little energy is wasted and consequently the antenna gain is increased. The feed simplicity and uniplanar configuration of the slot arrays, designed for the frequency range 24.25-27.5 GHz, makes them attractive for radar sensors and high capacity 5G technology applications.