Millimeter wave communication systems require many innovative antennas adapted for the future application scenarios such as the upcoming 5G cellular networks. Due to the strong path loss in free space at millimeter wave frequency range, high gain and low cost antennas are of great demand. Also, advanced features such as multi-beam for multiple user, dual-pol or even complete phased arrays with enormous degrees of freedom in beamforming are some of the key research lines for antenna designers nowadays. In this paper an overview of a new type of family of low loss antennas and components based on the recently developed gap waveguide technology is presented. With the advent of new millimeter wave applications, this low cost and low loss waveguide technology can be considered as a good candidate to be used as the core RF building block.Index Terms-Gap waveguide Technology, millimeter wave antennas, millimeter wave components.

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This paper describes an 8×8 fully-metallic highefficiency dual-polarized array antenna working at Ka-band, based on Gap Waveguide concept. The radiating element is a circular aperture backed by two stacked cylindrical cavities, which are fed orthogonally to achieve a dual-polarized performance. Both feeding layers consist of a gap waveguide corporate network to reach all the cavities backing each radiating element. Cavities are naturally integrated within the bed of nails hosting grooves and ridges for guiding EM field, leading to a low-profile dualpolarized array in Ka-band. Experimental results present good agreement with simulations. Measured radiation patterns agree well with simulation and the antenna provides an average gain over 27 dBi within its operating bandwidth (29.5 to 31 GHz).

This paper presents an 8×8 dual-band sharedaperture array antenna operating in K (19.5-21.5 GHz) and Kaband (29-31 GHz) using Gap Waveguide technology. Radiating elements consist of circular apertures located on the top plate of the antenna and excited by two stacked cavities with different diameters for dual-frequency operation. A waffle grid is used on top to increase the effective area of apertures and reduce grating lobes. Each stacked cavity is fed by its appropriate corporate-feeding network: the upper feeding layer operates at 20-GHz band and the lower one at 30-GHz band. As a result, the antenna presents two ports, one for each band, which radiate a directive farfield pattern with linear polarization, orthogonal to each other. Experimental results show impedance and radiation pattern bandwidths larger than 1.5 GHz in both bands.

Achieving a functional antenna for mobile SATCOM terminals in Ka band is probably one of the most challenging tasks in current antenna engineering. Even more if this terminal has to exhibit a low profile and be "affordable". This quest is involving many companies in the field. Our contribution represents one of such efforts. The antenna is based on slotted waveguide array technology to maximize efficiency and it features a number of novel solutions, going from its robust polarization switching mechanism, to the use of a thin wideband polarizer and the utilization of groove gap waveguides. This paper reports the measured data of a fully functional prototype to validate its novel contributions.

A V-band single-layer low-loss slot-array antenna is presented in this paper. Radiating slots are backed by coaxial cavities which are fed through a Groove Gap Waveguide (GGW) E-plane corporate feed network. Cavity resonances are created by shortening nails with respect to the surrounding ones. This fact enables a compact single-layer architecture since coaxial cavities and feeding network can share the same bed of nails. A 16×16 array is designed, constructed and measured to demonstrate the viability of this concept for high-gain single-layer slot-array antennas. In addition, this solution can be extended to circular polarization by seamlessly adding a polarizer above the slots without changing the feeding network piece. Measurements show a relative bandwidth of 10% with input reflection coefficient better than −10 dB and a mean antenna efficiency above 70% within the operating frequency band (57-66 GHz).

Institute of Electrical and Electronics Engineers (IEEE)FerrandoThis article has been accepted for publication in a future issue of this journal, but has not been fully edited. Content may change prior to final publication. Abstract-This paper demonstrates experimentally the improvement in axial ratio performance when a slot is combined with a set of three parasitic dipoles instead of one. The analysis is performed in the context of slotted waveguide arrays and SATCOM applications in Ka band, where a bandwidth specification as wide as 7.5% can be demanded.

This paper proposes a novel all-metal mechanical phase shifter in gap waveguide technology. The phase shifter is aimed at providing beam-scanning capabilities to conventional slot array antennas along the elevation plane. To validate experimentally the beam-steering functionality, a 4×8 slot-array antenna has been designed and fabricated, along with the phaseshifting mechanism. The whole antenna consists of two pieces: a lower rotatable block, which changes the length of concentric Groove Gap Waveguides, and an upper fixed block, where the slot-array antenna is placed. Experimental results validate the proposed concept, having obtained steering angles of up to 25 • , with gain levels around 20 dBi with an antenna efficiency close to 90%. A reflection coefficient below −10 dB is achieved for a wide range of rotation angles from 29.5 GHz to 30.5 GHz. The proposed phase shifter is completely scalable to any array size and its true-time-delay nature enables wide steering ranges for closely-spaced slot arrays with wideband radiation performance.