Wideband Slot Array Antenna Fed by Gap Waveguide with Right-Handed Circular Polarization and High Gain

This paper presents a circularly polarized (CP) monopulse slot array antenna based on gap waveguide (GWG) technology. The proposed monopulse antenna is composed of a 4 × 4 array antenna fed by the monopulse comparator network in a compact three-layer structure. To achieve a broad axial ratio (AR) bandwidth of right-handed circular polarization (RHCP) in the sum radiation pattern, a septum polarizer is used in the radiating aperture. Based on this approach, horizontal transition structures are used to excite the radiating array from the WR-28 waveguide to the GWG, which helps to reduce the reflection loss and expand the impedance bandwidth. Experimental results show that the impedance bandwidth is 30.5 GHz to 40 GHz, which is 27.1%. The 3 dB AR bandwidth is 31%. The measured null depth is −40 dB, and the maximum measured gain in the sum pattern is 22 dBi at 34 GHz, while the antenna efficiency is greater than 86%. The advantages of low loss, broad bandwidth, and compact structure make the proposed antenna a competitive candidate for millimeter-wave (mmWave) monopulse direction-finding applications.

In this paper, a planar single layer circular polarized array antenna is proposed using sequential-phased feeding network in V-band frequency range based on gap waveguide technology. The antenna used a 2×2 elements with 45-degree tilted slots to provide proper electrical field distribution in the slots to produce circular polarization. To excite slots, a feeding network based on combination of E-plane groove and ridge gap waveguide is utilized. To realize 90-degree phase rotation between slots, ridge waveguides are inversely shifted. The proposed antenna presents 14% impedance bandwidth below -10 dB and 8% axial ratio bandwidth under 3 dB.

This paper proposed a wideband, efficient, and high gain circularly polarized (CP) array antenna based on the gap waveguide technology for 30 GHz frequency band applications. The antenna subarray is a 2 × 2 slot groove gap waveguidebased 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 subarrays. The planar 16-way feeding network based on RGW is utilized to feed the subarrays. The feeding network is multilevel 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 paper presents a feed network for a high gain array antenna capable of 1D beam scanning up to 60 degrees without grating lobes. The feed network uses a layered design where the use of gap waveguide technology enables the layers to be assembled without good electrical contact. Each layer constitute one section of a vertical corporate feed network ending in a horizontal series feed, allowing for a compact design and integration of electronic components inside the antenna. To enable this, a periodic pin structure has been designed together with two vertical power dividers, one in ridge gap waveguide and one from microstrip to ridge gap waveguide. The structure is designed for Ka-band at 27.5-30 GHz and results show a 10 dB return loss bandwidth of 10 %. The array size is 40x8 elements which fits in a volume of 59.2x242.9x13.1 mm, while the boresight realized gain is 28 dBi.

An ultrawideband circularly polarized (CP) planar array antenna built by new radiation elements, the bold-C spiral elements, in millimeter-wave band is presented in this article. Using the tightly coupled array (TCA) technique, the embedded CP bold-C spiral element in the infinite array has achieved both impedance bandwidth and 3 dB axial ratio (AR) bandwidth of 50.7% covering 18.1-30.4 GHz for the fixed broadside beam. Then, a feeding network is designed by using the dielectric-based inverted microstrip gap waveguide (DIMGW) technology in order to have a compact layout. An 8×8 CP planar array based on the proposed radiating element and the feeding network is designed and prototyped. The measured results show that the impedance bandwidth of the whole array for the reflection coefficient below -10 dB is 49% from 18.2 to 30 GHz, and 3 dB AR bandwidth is 44.9% covering 19-30 GHz.

In this paper, a high gain circularly polarized (CP) aperture-coupled magneto-electric (ME) dipole antenna array excited by the air cavity in gap waveguide (GWG) feeding technology in W-band is proposed. This antenna array is composed of two layers, upper CP ME-dipole antenna subarrays and lower metallic GWG feeding networks. The planar antenna array structure is realized by the high mode air cavity feeding network, which is realized by extending the 1×2 cavity to 3×2 cavity using more shorted pins to split the electromagnetic field. The whole single-layer GWG feeding network is composed of a ridge gap waveguide (RGWG) transmission structure and short-ended vertical polarized groove gap waveguide (VP-GGWG) high mode air cavities. The transmission loss caused by the coupling and the fabrication tolerance can be reduced by combining the RGWG and GGWG in the same layer. In addition, the feeding network is fabricated all in metal with no substrate loss. Transverse slots are etched at the right position of the printed circuit board (PCB) backside to excite the CP ME-dipoles. The antenna element has stable radiation patterns and wide axialratio (AR) bandwidth. The proposed 3×8 planner antenna array has a maximum boresight gain of 22 dBi and an AR bandwidth of 10.8% for AR <;; 3 dB. In the frequency band from 87.7 to 97.7 GHz, a boresight gain above 20 dBi is achieved.

AMCs, EBGs and other surface-based metamaterials are known to have narrow bandwidths. However, when they are used to generate stopbands for parallel-plate modes, the bandwidth can be very large. This characteristic is used in the gap waveguide technology that was invented in 2008, based on old research on soft and hard surfaces. The gap waveguide technology can be used to package microstrip and CPW circuits, but can also with advantage replace such standard technologies and in particular above 30 GHz. The gap waveguides can have similar lowloss performance as solid rectangular waveguides, but they can be realized in a much better way. Rectangular waveguides are normally realized by split blocks which are screwed tightly together to ensure good conductive contact, whereas gap waveguides can be realized between parallel plates without metal connection. This paper overviews how the gap waveguide technology has been explored during the passed five years including: demonstrations of the wideband lowloss guiding characteristics up to 260 GHz, demonstrations of packaging in different frequency ranges with different AMCs or EBGs, and demonstrations of filters, transitions, MMIC packaging, corporate distribution networks, and slot and horn array antennas. The technology demonstrators cover the three different versions of gap waveguides: groove gap waveguide, ridge gap waveguides and microstrip gap waveguides.

In this work, we present a wideband gap waveguide planar array antenna for millimeter wave point to point communication systems. The proposed antenna is designed using ridge gap waveguide technology and the design is based on the cavity-backed slots as the core radiating elements. There exists a coupling slot in the cavity layer which allows the excitation of the radiating slot elements using ridge gap waveguide feeding section. The designed antenna have 8×8 radiating slot elements and the antenna operate over 15% relative bandwidth from 50–67GHz frequency range with −11 dB reflection coefficient. The measured gain for the slot array is about 27 dBi at the center of the band.

© 2017 IEEE. In this work, we present wideband gap waveguide planar array antenna for millimeter wave point to point backhauling systems. The proposed antenna is designed using ridge gap waveguide technology and the design is based on the cavity-backed slots as the core radiating elements. There exists a coupling slot in the cavity layer which allows the excitation of the radiating slot elements using ridge gap waveguide feeding section. The designed antennas have 8×8 or 16×16 radiating slot elements and the antenna operate over 15% relative bandwidth from 56-67GHz frequency range with -11 dB reflection coefficient. The measured gain for the slot arrays are within the range from 27 dBi-33dBi at the center of the band.

Circularly polarized (CP), beam steering antennas are preferred to reduce the disruptive effects such as multi-path fading and co-channel interference in wireless communications systems. Nowadays, intensive studies have been carried out not only on the specific antenna array design but also their feeding networks to achieve circular polarization and beam steering characteristics. A compact broadband CP antenna array with a low loss feed network design is aimed in this work. To improve impedance and CP bandwidth, a feed network with modified Butler matrix and a compact ultra-wideband square slot antenna element are designed. With this novel design, more than 3 GHz axial ratio BW is achieved. In this study, a broadband meander line compact double box coupler with impedance bandwidth over 4.8-7 GHz frequency and the phase error less than 3° is used. Also the measured impedance bandwidth of the proposed beam steering array antenna is 60% (from 4.2 to 7.8 GHz). The minimum 3 dB axial ratio bandwidth between ports, support 4.6–6.8 GHz frequency range. The measured peak gain of the proposed array antenna is 8.9 dBic that could scan solid angle about ∼91 degree. © 2015 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:146–153, 2016.

A single‐layered W band circularly polarised (CP) antenna array fed by a sequential feeding network using compact gap waveguides (GWs) with reduced pins is presented. The radiating element consists of a pair of cross slots and an open‐ended rectangular cavity integrated into the top metal plate of the GW. A sequential rotation network (SRN) consisting of hybrid groove gap waveguide (GGW) and ridge gap waveguide (RGW) structure is presented. Due to the fact that conventional GWs with multiple rows of pins occupy large lateral size, thus making them difficult to realise a single‐layered CP array fed by SRN. Compared with conventional GW with multiple rows of pins, compact GGW with a single row of pins is deployed here to make the presented SRN more compact, thus combining SRN and multiple CP radiators in the same layer. Particularly, a comprehensive investigation on the choice of the GGW groove depth is carried out. The groove depth is designed carefully such that the electric‐field energy is more confined along the GGW line, and less rows of pins are required. For proof‐of‐concept demonstration, the proposed array has been fabricated and measured, exhibiting an overlapped bandwidth of 10.64% (89–99 GHz) and a peak gain of 19.48 dBi at 94 GHz. It presents a promising candidate for W band wireless applications.

Dual circular polarization 2 × 2 slot array antenna based on printed ridge gap waveguide technology in Ka band

On the base of gap waveguide (GWG), a transition is designed between microstrip line (MSL) and waveguide at W-band in this paper. The proposed MSL to waveguide transition consists of MSL, groove GWG, ridge GWG and WR-10 waveguide. The electromagnetic waves propagate from MSL to substrate integrated waveguide (SIW), then the energy transfer from SIW to groove GWG by two metallic pins to coupled electromagnetic waves. Then, the groove GWG is connected to the ridge GWG. Finally, the ridge GWG probe is applied for WR-10 waveguide transition. For the groove GWG and ridge GWG, ball-grid-array (BGA) play a significant role of improving performance, and limit the energy transmission over the path we have designed. The simulated results show the operating frequencies of the proposed transition are from 85.5 to 104 GHz. The proposed transition has advantages of light weight and low profile, and has potential applications in antenna in package.

In this article, a double-layer 1-D multibeam antenna based on gap waveguide (GWG) technology is proposed. The bottom layer is the beamforming network (BFN), which is composed of four cruciform couplers and two −45° phase shifters realized by groove GWGs. Four output ports of the BFN are connected to the slot arrays on the top layer through 180° E-plane bends. The output amplitudes of the BFN are −6.3 ± 0.5 dB and the phase errors are within ±14° from 26 to 32 GHz with a bandwidth of 20%. To relieve the grating lobe problem, groove GWGs are transited to ridge GWGs on the top layer and the slot array is fed from ridge GWGs. Due to the topology of the BFN, the slot array is oriented along the diagonal plane and as a result, the multibeam antenna is 45° linearly polarized. To handle the dip emerging in the side beam caused by the finite ground of the BFN, several metal fences working as a soft surface are applied to suppress the edge diffractions. Besides, the gain is increased by 0.78 dB compared to the case without metal fences at 29 GHz. Thanks to the low-loss property of GWG technology, high gain, and high radiation efficiency are obtained. The maximum gain is 17.46 dBi with the beam direction at −11° for Port 1 and 16.51 dBi with the beam direction at 37° for Port 2. The simulated radiation efficiency is above 97% for both Port 1 and Port 2.

A 1 × 8 circularly polarized (CP) aperture-coupled magneto-electric (ME) dipole antenna array excited by low-loss gap waveguide (GWG) feed network is proposed in this study. This linear antenna array is composed of two layers, upper CP ME-dipole printed circuit board (PCB) antenna subarrays and a lower metallic GWG feed network. The proposed compact GWG feed network with wideband impedance matching is composed of a ridge gap waveguide (RGWG) transmission structure and two short-ended vertical polarized groove gap waveguide (VP-GGWG) cavities. The transmission loss of this feed network caused by transition, such as coupling and fabrication tolerance between two layers, can be reduced by combining RGWG and VP-GGWG in the same layer. In addition, this feed network is fabricated all in metal with no substrate loss. Transverse slots are etched at the right position of the upper PCB layer above VP-GGWG cavities to excite the CP ME-dipole antennas. The antenna element has stable radiation pattern and wide axial-ratio (AR) bandwidth, which is desirable for CP antenna array. The proposed 1 × 8 linear antenna array has been simulated and fabricated to validate our design. Measured results show that antenna array achieves a maximum boresight gain of 18 dBi and an AR bandwidth of 14.5% from 89 to 103 GHz for AR <; 3 dB, with a boresight gain above 16.5 dBi.