4 × 4
Magneto-Electric Dipole Array with
Single-Layer Corporate-Feed Ridge Gap
Waveguide for mmWave Applications
Wai Yan Yong
1∗, Thomas Emanuelsson
2, and Andr´es Alay´on Glazunov
1,31
Department of Electrical Engineering, University of Twente, 7522NB, Enschede, The Netherlands.
2GAPWAVES AB, Gothenburg, Sweden.
3
Department of Electrical Engineering, Chalmers University of Technology, Gothenburg, Sweden.
∗Corresponding author, email: w.y.yongwaiyan@utwente.nl
Abstract—This paper presents simulations results of a 4 × 4 magneto-electric dipole (MED) array antenna fed by a single-layer corporate-feed ridge gap waveguide (RGW) for millimeter wave applications. The designed antenna model consists of two unconnected metal layers: the top radiating layer and the bot-tom corporate-feed RGW layer. Hence, the antenna profile can be lowered since no intermediate cavity layer is required. The MED radiating element shows a larger impedance bandwidth compared to the conventional single layer array antenna. The S11 ≤ −10 dB bandwidth of the simulated antenna is from
24 − 29 GHz, resulting in a 18.9% impedance bandwidth. The realized antenna gain is greater than approximately 19.6 dBi.
Keywords—Array antenna, AMC, single-layer, gap waveg-uide, metamaterial, millimeter wave
I. INTRODUCTION
The gap waveguide (GW) technology offers promising performance in the design of millimeter wave (mmWave) high gain array antennas due to its low losses, simple assembling and self-packaging properties. To date, a number of antennas have been built based on the GW technology [1]–[3]. In order to obtain wideband performance, and have ample space for the distribution networks and AMC pins, these antennas are often backed with cavities where four slots are excited using one cavity [1]. Although these antennas provide sufficient bandwidth performance, still production costs and design complexity can be reduced by reducing the number of layers. In addition, compact antenna structures are preferred in many applications due to obvious reasons. Single-layer-feed array antennas based on serial-feed net-works have been suggested to address these issues. However, the studies presented so far show poor bandwidth perfor-mance with a −10dB impedance bandwidth around 10% [4]. Recently, few models of GW-based single-layer corporate-feed array antennas have been successfully implemented . Also, the design proposed in [5] shows limited bandwidth performance, i.e., 5%. To address the narrow bandwidth performance, [6] proposed to modify the traditional slot into an “8-shaped” slot with a bandwidth of around 17%. Thus far, many of these GW-based array antenna have proposed designs utilizing conventional slots as the radiating
Fig. 1: Distributed view of the proposed 4 × 4 MED array antenna fed by single-layer corporate-fed RGW.
element, which has restricted the bandwidth performance the GW-based array antennas. In this paper, we suggest an alternative approach for the design of wide-band single-layer corporate-feed array antennas based on the ridge gap-waveguide (RGW). Moreover, the magneto-electric dipole (MED) is proposed as the radiating element. In the proposed design, there is no need for backed-cavities for excitation, while maintaining a similar bandwidth to the cavity-backed array designs. The proposed MED antenna is realized using two pairs of pins and is surrounded by a cavity forming a radiating structure with a wider bandwidth compared to single-layer corporate-feed antennas.
II. MED ARRAYANTENNADESIGN AND SIMULATION RESULTS
As can be seen from Fig 1 the proposed 4 × 4 MED array antenna fed by RGW comprises two layers: the radiating layer and the feeding layer. The radiating layer contains the MED antenna elements consisting of four metallic pins surrounded by a rectangular cavity, and connected to the ground. To avoid grating lobes, while providing sufficient spacing for the corporate-feed network, the proposed unit cell antenna is 0.9λ0× 0.9λ0 in size, where λ0 is the
free-space wavelength at 29 GHz. To achieve effective radiation from the electric dipole, the height of the pin dipole is approximately a quarter-wavelength at 26 GHz. In addition
Fig. 2: Simulated input reflection coefficient, S11 and
real-ized gain of the proposed 4 × 4 MED array antenna fed by single-layer RGW.
, it is observed that in the configuration of the proposed MED antenna, the distance between the left- and the right-column pins, and the length of the pins greatly affect the bandwidth efficiency of the proposed MED antenna. The design principle of the proposed MED is similar to the techniques proposed in [7]. The proposed MED antenna is excited with the slot-coupled technique which is widely used to excite the antenna in the mmWave band [7]. The wave propagating in the RGW is coupled to the proposed MED antenna by means of the proposed “I-shaped” slot etched on the ground of the MED antenna. The ”I-shaped’ slot is used because it acts as a multi-level ridge slot enabling the frequency of the dominant mode to be lowered and the frequency of the next higher-order slot modes to be increased [3]. Hence, the energy propagating from the RGW to the MED antenna to be combined over a wide bandwidth in a small area.
As can be seen from Fig 2, the impedance bandwidth computed from the S11 of the simulated design is 18.9%
from 24 − 29 GHz. Our proposed design offers a bandwidth that is 13.9% and 2% greater than the designs presented in [5] and [6], respectively. In addition, the simulated gain is more than 19.6 dBi from 24 − 29 GHz.
Fig 3 shows a comparison of the simulated normalized far-field radiation pattern of the antenna in E-, H- and D-planes at 24, 26 and 28 GHz. The side lobe level for the proposed array antenna is below −10 dBi for all three frequencies in both the E-, the H- and the D-planes. In addition, the relative cross-polar (X-Pol) level is below −35 dB for both E-, H-plane and D-H-plane.
III. CONCLUSION
In this paper, we have proposed a 4 × 4 magneto-electric dipole (MED) array antenna fed by a single-layer corporate-feed network designed based on the gap waveguide (GW) technology. The antenna is composed of only two uncon-nected metal layers. Compared to the current single-layer corporate-feed array antenna, the numerical results of the proposed solution demonstrates a wider impedance band-width of approximately 18.9% (24 − 29 GHz). The proposed array antenna shows stable co-polar radiation patterns with relative side lobe levels of less than −10 dB for both E-,
H-(a) (b)
(c)
Fig. 3: Simulated radiation pattern of the proposed 4×4 MED array antenna fed by single-layer RGW for (a) E-plane, (b) H-plane and (c) D-plane.
and D-planes. The corresponding relative cross-polar level is less than −35 dB. Future research will focus on the analysis of the impact manufacturing tolerance on fabricated array antenna prototypes.
ACKNOWLEDGMENTS
This project has received funding from the European Union Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement No. 766231 — WAVECOMBE — H2020-MSCA-ITN-2017.
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