SE1930232A1 - A dual polarized antenna - Google Patents

Abstract

ABSTRACT A dual polarized antenna (100) comprising a distribution layer (110)with transmission lines based on ridge waveguide technology, RGW, a cavity layer (120), and a radiatinglayer (130). (Fig. 1)

Description

A :|:45° Dual-Polarized Antenna for 5G mmWaveApplications Based on Gap Waveguide Technology Alireza Bagheri*l, Julius Petersson*, Abolfazl Haddadi*, and Andrés Alayón Glazunovlï*Gapwaves AB, Gothenburg, SwedenlUniversity of Twente, Enschede, NetherlandsïChalmers University of Technology, Gothenburg, Sweden Abstract-A :|:45° dual-polarized antenna is designed based onthe gap waveguide technology which offers a low loss and easy-to-manufacture solution at the mmWave frequencies. Dual-polarizedantennas help to increase the capacity and coverage of a wirelesssystem and also decrease the overall cost. Two parallel arrays of8 slots each are employed to create the orthogonal polarizations.The antenna operates in the 24.25 - 27.25 GI-Iz frequency band.The simulated average gain of each polarization is 14.5 dBi whileachieving a cross-polarization isolation of at least 15 dB.

I. INTRODUCTION The rising demand for higher data rates is pushing commu-nication systems to employ the millimeter-wave (mmWave)frequency bands due to the availability of larger spectrumchunks. Large bandwidth in mmWaves has been used inradar and automotive applications, added to Sth generationof communication systems (SG) [1], [2]. Using orthogonallypolarized antennas is a well-known technique to increasethe capacity and the reliability of a wireless system andcombat multipath fading as compared to single-polarized an-tenna systems [3]. In addition, lower fabrication costs maybe achieved by making the antennas more compact. Manydual-polarized antennas based on planar technologies such assubstrate integrated waveguide (SIW) have been proposed sofar for mmWaves applications [4], [5]. However, they sufferfrom high losses and consequently low total efficiency due topresence of substrate.

As well known, traditional technologies, such as planartransmission lines and hollow waveguides, lose their advan-tages at the mmWaves by incurring high losses and a complexmanufacturing process, respectively [6]-[8]. Currently, re-search efforts have intensified to produce antenna technologiesallowing for easy manufacturing, low loss and high antennaefficiency. The gap waveguide technology has emerged asa candidate for providing a fair trade-off between cost andmanufacturing flexibility of electromagnetic components [9].So far, manufactured and reported antennas based on thegap waveguide technology have mainly focused on linearpolarization. The only dual-polarized antenna based on thistechnology is reported in [10]. It uses a circular apertureas the radiation element which are fed orthogonally by twocylindrical cavities. Given the resonant nature of the antennathis leads to a lirnited bandwidth within 29.5 - 31 GHz (5%).

Slant polarized antennas, i.e., producing :|:45° linear po-larization, offer lower side lobe levels compared to those Distribution layer Cavity layer Radiating layerY Fig. 1: Exploded view of the antenna. with horizontal and/or vertical polarization [8]. 45° linearpolarized antennas are good candidates for collision avoidanceautomotive radar systems, due to minimum interference fromthe radars with orthogonal polarization mounted in the carscoming from opposite direction [l1], [12]. In this paper, anantenna based on the gap waveguide technology is designedproviding two orthogonal linear polarizations with similarradiation patterns for both polarizations over a wide frequencyband. The frequency band of the antenna is 24.25-27.25 GHz,which complies with the 5G mmWave frequency bands in EU[13].

II. ANTENNA DESIGN The antenna consists of three layers, the distribution layercontaining the ridge gap waveguide (RGW) transmission lines,the cavity layer, and the radiating layer shown in Fig. 1. Thedistribution layer is fed from the middle (in y-axis direction)with two double ridge waveguides that each feed two RGWs inthe opposite direction. Three columns of pins are used to stopany leakage from the RGWs. The pins are designed so thattheir stop-band covers the operational frequency bandwidth ofthe antenna. The fields from the RGWs are coupled through 16vertical slots to the cavity layer. The cavity layers slots are intwo columns and they are separated with Åg / 2 vertical distance TABLE I: Co-polarization and cross-polarization unit vectorsfor the waves generated by each port.

| Port | Co-polarization | Cross-polarization | P1 ëüflï) ëü-ü)P2 ñm-y) ñmflâ) (y-axis direction). The slots in each column have electric fieldswith same phase, magnitude and direction (x-axis direction). _ \ _5rad,P1 Q 'K e [dB] f [aim I 3: Radiation (Crad,P11erad,P2) and total (etot,P1vetot,P2)efficiencies of the antenna.

Each column of cavities changes the direction of electricfields in the vertical slots to create two orthogonal polar-izations. There are two pins in each cavity to transforrn thefield direction. The transformed fields excite the slots in theradiating layer. The fields in the radiating layer for eachcolumn of slots also have the same phase, magnitude anddirection and finally, they create two waves with orthogonalpolarizations. The co-polarization and cross-polarization unitvectors of each port are shown in Table I.

III. RESULTS The designed antenna is simulated and optimized using theCST MWS softwave. Fig. 2 shows each ports return losses and G9 [clßij G0 ldßi] aa .a - x _“ '_\\\\\\ _ \\ -š x* ~* 'via i. \-~ '\\vi t.

GQ (c) Fig. 4: Co-polar and cross-polar radiation patterns of theantenna in the mz-plane for different frequencies: (a) 24.25GHz, (b) 25.75 GHz and (c) 27.25 GHz. G0 and 9 stand forantenna gain and polar angle, respectively co-polar - Pl,---- cross-polar - P1, ~ ~ ~ co-polar - P2 and - ~ ~ cross-polar- P2). their mutual coupling. The results show that the antenna coversthe frequency band 24.25 - 27.25 GHz (BW= 11.6%). In thisband, reflection coefficient for both ports and their mutualcoupling are less than -10 dB and -19 dB, respectively.Total efficiency of the antenna is more than -0.5 dB foreach polarization, which is depicted in Fig. 3. Co-polarizationand cross-polarization radiation patterns of the antenna inhorizontal plane (æz-plane) are shown in Fig. 4, for three different frequencies. In the broadside direction (0 = 0), eachpolarization has a 14.5 dBi gain with maximum -15 dB cross-polarization level in the frequency band of interest.

IV. CoNcLusroN A slant dual-polarized antenna design based on the gapwaveguide technology is presented in this paper. The twoorthogonal polarizations are produced by two arrays consistingof 8 radiating slots with slant polarizations. The antenna coversthe frequency band 24.25 to 27.25 GHz, which makes itsuitable for 5G applications in mmWave frequencies. Eachpolarization have 14.5 dBi gain on average with maximum-15 dB lower cross-polarization level in the operationalfrequency band of the antenna.

AC KNOWLEDGMENT This project has received funding from the European UnionHorizon 2020 research and innovation program under theMarie Sklodowska-Curie grant agreement No. 766231 WAVE-COMBE H2020-MSCA-ITN-2017.

REFERENCES [1] T. S. Rappaport, S. Sun, R. Mayzus, H. Zhao, Y. Azar, K. Wang, G. N.Wong, J. K. Schulz, M. Samimi, and F. Gutierrez, “Millimeter wavemobile communications for Sg cellular: It will work!,” IEEE access,vol. 1, pp. 335-349, 2013. [2] J. Choi, V. Va, N. Gonzalez-Prelcic, R. Daniels, C. R. Bhat, and R. W.Heath, “Millimeter-wave vehicular communication to support rnassiveautomotive sensingf' IEEE Communications Magazine, vol. 54, no. 12,pp. 160-167, 2016. [3] B. Lindmark and M. Nilsson, “On the available diversity gain fromdifferent dual-polarized antennasf' IEEE Journal on Selected Areas inCommunications, vol. 19, no. 2, pp. 287-294, 2001. [4] Y. Yu, W. Hong, Z. H. Jiang, and H. Zhang, “E-band low-profile,wideband 45° linearly polarized slot-loaded patch and its array formillimeter-wave communicationsf' IEEE Transactions on Antennas andPmpagation, vol. 66, no. 8, pp. 4364-4369, 2018. [5] S. Park, Y. Okajirna, J. Hirokawa, and M. Ando, “A slotted post-wallwaveguide array with interdigital structure for 45° linear and dualpolarizationf” IEEE Transactions on Antennas and Propagation, vol. 53,no. 9, pp. 2865-2871, 2005. [6] A. Vosoogh, P.-S. Kildal, and V. Vassilev, “Wideband and high-gain corporate-fed gap waveguide slot array antenna with etsi classii radiation pattern in v-bandf' IEEE Transactions on Antennas andPropagation, vol. 65, no. 4, pp. 1823-1831, 2016. [7] J. Zhu, S. Liao, S. Li, and Q. Xue, “60 ghz substrate-integratedwaveguide-based monopulse slot antenna arrays,” IEEE Transactions onAntennas and Propagation, vol. 66, no. 9, pp. 4860-4865, 2018. [8] T. Tomura, Y. Miura, M. Zhang, J. Hirokawa, and M. Ando, “A 45°linearly polarized hollow-waveguide corporate-feed slot array antennain the 60-ghz band,” IEEE Transactions on Antennas and Pmpagation,vol. 60, no. 8, pp. 3640-3646, 2012. [9] P.-S. Kildal, E. Alfonso, A. Valero-Nogueira, and E. Rajo-Iglesias,“Local metamaterial-based waveguides in gaps between parallel metalplates,” IEEE Antenna: and Wireless Prapagation Letters, vol. 8, pp. 84-87, 2009.

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[12] H. lizuka, T. Watanabe, K. Sato, and K. Nishikawa, “Millirneter-wavemicrostrip array antenna for automotive radars,” IEICE transactions oncommunications, vol. 86, no. 9, pp. 2728-2738, 2003.

[13] EU Radio Spectrum Policy Group, “Strategic spectrum roadmap towards5g for europe." https://circabc.europa.eu/sd/a/fela3338-b75 l-43e3-9ed8-a5632f05 1d1f/RSPG18-005final-2nd_opinion_on_5G.pdf, 2018. [On-line].

Claims (6)

1. A dual polarized antenna (100) comprising; a distribution layer (1 10) with transmission lines based on ridge waveguide technology,RGW, a cavity layer (120), anda radiating layer (130).

2. The dual polarized antenna (100) according to claim 1, wherein thedistribution layer (110) is arranged to be fed from the middle, in y-axis direction, with two double ridge waveguides that each feed two RGWs in opposite direction.

3. The dual polarized antenna (100) according to any previous claim,wherein columns of pins are configured to stop or attenuate leakage from the RGWs.

4. The dual polarized antenna (100) according to any previous claim,wherein the distribution layer comprises pins configured so that their stop-band coversan operational frequency bandwidth of the antenna.

5. The dual polarized antenna (100) according to any previous claim,wherein the fields from the RGWs are coupled through 16 vertical slots to the cavity layen

6. The dual polarized antenna (100) according to any previous claim,wherein the cavity layers slots are in two columns and are separated by half of theoperational wavelength vertical distance.