A wideband high-gain high-efficiency 16 × 16-element slot antenna array is presented for 60-GHz band applications. The antenna is designed based on gap waveguide technology. The most important advantage of using this technology is its ability to decrease complexity and cost of fabrication because there is no requirement of electrical contact between the three layers of the antenna structure. The three layers are a corrugated metal plate with radiating slots, a subarray cavity layer, and a ridge gap waveguide (RGW) feed network layer. The corporate feed network is realized by a texture of pins and guiding ridges in a metal plate. Also, in order to excite the antenna with a standard V-band rectangular waveguide, a transition from RGW to WR-15 is designed. The radiating elements, corrugations, cavity layer, power dividers, and transition are designed and optimized to suppress the reflection coefficient at the input WR-15 port over the desired frequency range from 57 to 66 GHz. Finally, the 16 × 16-element slot antenna array is fabricated by the standard milling technology. The measured results demonstrate about 16% of reflection coefficient bandwidth (|S ₁₁ | <; -10 dB) covering the 56-65.7-GHz frequency range, and the measured gain is larger than 32.5 dBi over the band with more than 70% antenna efficiency.

A wideband 8 ×8-element slot antenna array based on ridge gap waveguide feeding network has been proposed for mmWave applications. The antenna sub-array consists of four radiating slots which are excited by a groove gap cavity layer. Compared with previously published works, the proposed planar antenna array has quite wide impedance bandwidth. The antenna covers a wide band of 50-67.8 GHz with 30% impedance bandwidth (VSWR < 2). Also, the antenna has only 2.5 dB gain variation over the entire bandwidth which implies also good radiation characteristics for the proposed antenna. The maximum measured gain value is about 27.5 dBi with a total efficiency of 80% for the proposed antenna within the band of interest. With this performance, the proposed antenna array is a promising candidate for millimeter-wave communication systems.

Wideband design of power dividers, T-junctions, and transitions based on groove gap waveguide (GGW) technology is presented in this paper with the goal to use these components in high-gain millimeter-wave antenna array design at 60-GHz frequency range. Since this GGW technology does not require electrical contact between the different metal layers of a complex 3-D waveguide structure, the fabrication cost and mechanical complexity are decreased. The designed T-junctions and different power dividers exhibit wide operational bandwidth and low output power and phase imbalance over the 60-GHz frequency band. Also, two transitions from GGW to a standard rectangular waveguide have been designed. To validate the performance of the designed components, a 64-way power divider in combination with 256 radiating slots is designed, prototyped, and measured at 60-GHz band. Measurement results agree well with the simulated performance of the complete array antenna, and the antenna gain is more than 32.5 dBi. The total radiation efficiency is more than 80% over the operating frequency range from 57 to 67 GHz. Also, the measured sidelobe levels are found to be agreeing well with the simulated level.

This paper proposed a wideband, efficient and high gain circularly polarized (CP) array antenna based on gap waveguide technology for 30 GHz frequency band applications. The antenna sub-array is a 2 ×2-slot groove gap waveguide (GGW)-based cavity-backed antenna. The antenna is fed by a ridge gap waveguide (RGW). Two corners of the radiating slots are truncated to obtain CP radiation and some corrugations are introduced to the radiating layer to suppress the surface waves between neighbor sub-arrays. The planar 16-way feeding network based on RGW is utilize to feed the sub-arrays. The feeding network is multi-level sequential phased with a quadrature phase shift. To validate the array antenna performance, a prototype of the antenna has been manufactured using standard milling technology. The measured reflection coefficient bandwidth is about 22 % covering from 28.3 to 35.3 GHz and a measured 3-dB axial ratio bandwidth of about 21.8 % is achieved from 27.8 to 34.6 GHz. The maximum measured gain is 23.5 dBi which is occurred at 30.75 GHz.

This communication presents a wideband aperture-coupled patch antenna array based on ridge gap waveguide feed layer for 60-GHz applications. The novelty of this antenna lies in the combination of relatively new gap waveguide technology along with conventional patch antenna arrays allowing to achieve a wideband patch antenna array with high gain and high radiation efficiency. An 8 × 8-element array antenna is designed, fabricated, and tested. Experimental results show that the bandwidth of VSWR . 2 is up to 15.5% (57.5-67.2 GHz). More than 75% efficiency and higher than 21.5-dBi gain are achieved over the operational bandwidth. The results are valuable for the design and evaluation of wideband planar antenna arrays at millimeter-wave frequencies.

This work presents a high gain D-band slot array antenna with a corporate-fed distribution network designed by the gap waveguide. The gap waveguide technology is employed for overcoming the challenge of appropriate electrical contact related to the mechanical assemblage of the antenna feed network and the radiation layer. The antenna includes 24×16 slots and the basis of the antenna interdigital feeding network includes the ridge and groove gap waveguides. A standard WR-6 waveguide flange at the bottom is used to excite the presented antenna. To understand the fabrication challenges and tolerance issues around 140GHz, an antenna prototype was made by standard CNC milling techniques. The results show that an impedance bandwidth of 5.5% (141.8-149.8 GHz), efficiency higher than 78%, and a peak gain of 33.8 dBi are achieved for the proposed 24×16-element array antenna. According to the results, the presented planar array is a good option for D-band applications and can be used as the building block to develop high efficiency and high gain upper mm-wave antennas.