Ridged Cross-Junction Power Divider for the Center Feed in a Single-Layer Slotted Waveguide Array

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1 Rige Cross-Junction Power Divier for the Center Fee in a Single-Laer Slotte Waveguie Arra # Yasuhiro Tsunemitsu 1, 2, Jiro Hirokawa 1, Makoto Ano 1, an Naohisa Goto 3 1 Department of Electrical an Electronic Engineering, Toko Institute of Technolog C 2-1-S3-19, O-okaama, Meguro-ku, Toko, , JAPAN tsunemitsu@antenna.ee.titech.ac.jp 2 Laborator, Japan Raio Co., Lt, 1-1, Shimorenjaku 5 chome, Mitaka-shi, Toko, 18151, JAPAN tsunemitsu.asuhiro@jrc.co.jp 3 Raial Antenna Laborator, No Nishisinjuku Shinjuku-ku Toko 163 JAPAN n.goto@m.ieice.org Abstract The center fee in a single-laer te waveguie arra [1,2] is the one of the ke component of ual polariation fie wireless access sstem. Two center fee single laer te waveguie arras with orthogonal polariation in eactl the same frequenc are use for transmission an reception, respectivel. Each arra has bore sight beam. This antenna has etremel high XPD (almost 5B in measurement) an high isolation (over 8B in measurement) between two arras orthogonall arrange sie-b-sie. On the other hans, the blocking area at the center of the antenna causes the high sielobe level. The reucing blocking area is require. The rige cross-junction power ivier is propose to solve above problem. 1. INTRODUCTION Fie Wireless Access (FWA) sstems in the 26 GH ban have been commercialie in Japan for high-spee Internet connections between subscribers an base stations [3]. Compact an low-cost user terminals are realie b aopting alternating-phase fe single-laer waveguie arras [4].As the unique structure of alternating phase fe arras, it consists of two parts, a plate an a base plate with corrugations screwe to each other as shown in fig.1, which ispenses with electrical contact in the strict sense [5]. To ouble the frequenc efficienc, we have propose a ual polariation sstem that utilies high XPD of te waveguie arras [6]. A single laer te waveguie arra has been one of the ke components in this sstem, since it has high efficienc an a mass proucible structure. This arra, in its original form, has the cascae fee at one en of the aperture with travelling wave operation. It suffers the frequenc epenent beam shift as is usual the case with the travelling wave arras an brings about the fatal ifficult in ual-polariation FWA sstems where a terminal consists of two linearl-polarie arras arrange orthogonall. To solve this problem, authors have evelope H-plane cross-junction multiple wa power ivier [7] an E- to H-plane crossjunction multiple wa power ivier [8,9] for feeing the arra from the center of the aperture, which still lie in the same laer as the raiating waveguies. The E- to H-plane cross-junction power ivier is solve the problem of the blocking area as shown in fig.2. The istance is the spacing of between the center of the first s across the crossjunction. But this fee waveguie can not be the ais of smmetr of arra. So the isolation is almost (6B) in the case of two arra arrange orthogonall sie-b sie. This sstem is require higher isolation an the reucing blocking area to ecrease sielobe. This paper emonstrates the preicte characteristics of a rige cross-junction an a linear arra with this crossjunction. The reflection an the ivie power can be esigne. The sielobe is confirme as the avantage of the fee with rige cross-junction. Base plate Slot arra Input Slotte plate Raiating waveguie Cross-junction power iviers (Fee waveguie) Fig. 1: The structure of the center-fee in a single-laer te waveguie arra. 1

2 (a) large smmetr The arra with H-plane cross-junction power ivier. Post = length of blocking area (a) A H-plane cross-junction (conventional) small not smmetr (b) The arra with E- to H-plane cross-junction power ivier. = length of blocking area Reflection canceling wall (b) A E- to H-plane cross-junction (conventional) small smmetr (c) The arra with rige cross-junction power ivier. Raiating waveguie Fee waveguie Port3 Cp C Coupling winow 3mm Cl 4.5mm Port4 8mm 3mm = length of blocking area (c) A rige cross-junction (propose) Fig. 2: The ifference of the blocking area an smmetr of the arras. 2. STRUCTURE Three tpes of a cross-junction are shown in Fig.3. Fig.3 (a) is a H-plane cross-junction. The cross-junction has four inuctive posts to control ivision to two raiating waveguies an to suppress the reflection. The broa wall of the fee waveguie is set 9.mm so that the spacing of the raiating waveguie is an half of the guie wavelength of the fee waveguie. This moel realies the center-fee in a single-laer te waveguie arra. Though, the blocking area of the antenna aperture is relativel large (2.1 ). This space causes the high sielobe in H-plane raiation pattern an the aperture efficienc egraation. To suppress a blockage in the antenna aperture, a novel unit structure of the E- to H-plane cross-junction is propose in Fig.3 (b). Fig. 3: Structure of a cross-junction The narrow wall of the fee waveguie is embee on the top instea of the broa wall in the conventional H-plane cross-junction, in orer to reuce the blocking area of the arra in Fig.2 (b). A unit cross-junction has a wall at the bottom of the fee waveguie to suppress the reflection an two winows to control ivision to two raiating waveguies. The ivision is controlle b the with of the coupling winows. The reflection is controlle b the height of the wall an its position from the center of the cross-junction. The wall an the winows can be fabricate with the groove fee waveguie simultaneousl. It is suppresse below -3B at 25.3GH in the esign. The broa wall of the fee waveguie is set 7.2mm so that the spacing of the raiating waveguie is an half of the guie wavelength of the fee waveguie. The narrow wall with of the fee waveguie is chosen 3.6mm, which is an half of the broa wall with. This moel can reuce the blocking area. The sielobe is achieve less than -13B an improve antenna efficienc. But the 2 International Smposium on Antennas an Propagation ISAP 26

3 arra oes not smmetr in the center line on the fee waveguie. So this structure cannot obtain high isolation in the case of arrange orthogonall sie-b-sie. The measure isolation is almost 6B. To obtain the high isolation (over 8B) must nee smmetr of arras. So cross-junction is require to istribute the electric fiel of E component in same phase to each raiating waveguies. From this point of view, rige cross-junction is propose as shown in fig.3 (c). A unit cross-junction has a rige structure to reuce the area of the broa wall on the antenna aperture. The structure of the cutting rige can prouce a wave to suppress the reflection from the coupling winows. Two coupling winows control the ivision to two raiating waveguies. The reflection is controlle b the length Cl of the cutting rige, the epth C of cutting rige, an its position Cp from the center of the cross-junction. It is suppresse below -3B at 25.3GH in the esign. The broa wall epth of the fee waveguie is set 4.5mm an height of the rige structure is set 2.5mm. This moel can reuce the blocking area. The smmetr arra on the ais of fee waveguie is obtaine using this cross-junction. An reuce the blocking broa wall area from 9.mm to 3.mm compare with conventional H-plane cross-junction. The istance between first an coupling winow of crossjunction is also important to reuce blocking area on the aperture. Net we iscuss the each power ivier istribution characteristics an evaluate the reucing blocking area using the raiation pattern with 1 s arra each raiating waveguies. 3. ANALYSIS A. Characteristics of each Cross-junctions First, we compare the characteristics of each cross-junction. The amplitue of reflection an istribution in each moel are shown in Fig.4. Reflection ( S11 ), transmission ( S21, S31, S41 ) characteristics are evaluate b the commercial Finite Element Metho (FEM) software Ansoft HFSS TM (High- Frequenc Structure Simulator). Fig.4 shows the reflection an ivie amplitue of the junctions in Fig.3 where the total couple power to the two raiating waveguies is 5% as an eample. The esign frequenc is 25.3GH. The reflection cancelling using 4 posts is relativel narrow ban in H-plane cross-junction power ivier as shown in fig.4 (a). On the other han, E- to H-plane cross-junction an rige cross-junction have more wie ban characteristics ( S11 is less than B range) Amplitue [B] Amplitue [B] Amplitue [B] -3 S21 =-3.2B (2/4) S31 =.2B (1/4) S41 =.3B (1/4) S11 =7.6B -5 Frequenc [GH] -3 (a) H-plane cross-junction (conventional). S21 =.95B (2/4) S31 =.9B (1/4) S41 =.8B (1/4) S11 =-37.1B -5 Frequenc [GH] -3 (b) E- to H-plane cross-junction (conventional) S21 =-3.8B (2/4) S31 =.B (1/4) S41 =.B (1/4) S11 =-32.B -5 Frequenc [GH] (c) Rige cross-junction (propose). Cl=1.2mm, C=1.5mm, Cp=.8mm. Fig. 4: The amplitue of reflection an ivie power. International Smposium on Antennas an Propagation ISAP 26 3

4 B. Raiation pattern in H-plane (incluing blocking area) Net, we iscuss the effect of reucing the blocking area using propose moel. Each raiating waveguie has 1 s, each of which with a reflection-canceling sie wall as shown in Fig.5. The total number of the s in the arra is 2 (12). The arra is esigne to ecite uniforml. The esign frequenc is 25.3GH. Fig.6 shows the results of preicte raiation pattern of the H- plane which has blocking area in the center. The preicte raiation pattern, this arra uses H-plane moel, E- to H- plane moel, an rige moel, has the first sie-lobe level is almost -11B(=2.1 ) as shown in Fig.6(a), - 12B(=1.7 ) as shown in Fig.6 (b), an -13B (=1.6 ) as shown in Fig.6 (c) respectivel. In first esign, each first ege is positione 5.mm from cross-junction s coupling winows to neglect mutual coupling inner fiel. The istance between each first s is important. So, net step the arra move towar to cross-junction s coupling winows. The H-plane moel an rige moel is nee 2mm between an cross-junction for maintain s ecitation phase. If the istance is less than 2mm, each first s is ecite ifferent phase. So the first sielobe is increase. H-plane crossjunction moel is achieve onl B (=1.6 ) as shown in Fig.6 (a). Rige cross-junction moel can be obtaine almost -13B (=1.1 ) of uniform amplitue arra as shown in fig.6 (c). So this arra is smmetr in cross-junction, the high isolation will be obtain in the case of orthogonall arrange two arras sie-b sie. This was improve at a point of the first sie-lobe level in comparison with the antenna which uses conventional H-plane cross-junction. E- to H-plane cross-junction moel can be obtaine less than - 13B (=1.1 ) as shown in Fig.6 (b). This time, arra onl move to cross-junction power ivier, in future stu the first can be revise for eciting phase an amplitue. 4. CONCLUSION (a) H-plane moel (b) E- to H-plane moel (c) Rige moel Fig.5 A cross-junction power ivier with arra. The istance is the spacing of between the center of the first s across the cross-junction. We have propose the rige cross-junction for the fee waveguie in a center-fee single-laer waveguie. This fee waveguie is avantageous in terms of reucing blocking area an smmetr arra to obtain high isolation. The calculate sielobe level of the propose cross-junction is almost -13B in H-plane at 25.3GH. Our future stu is to arra cross-junctions to use planar antenna fee structure. 4 International Smposium on Antennas an Propagation ISAP 26

5 Relative Amplitue [B] Relative Amplitue [B] Relative Amplitue [B] =2.1 = Angle [eg] (a) Linear arra with a H-plane cross-junction =1.7 =1.1 = Angle [eg] (b) Linear arra with an E- to H-plane cross-junction =1.6 = Angle [eg] (c) Linear arra with a rige cross-junction Fig.6 Raiation pattern in H-plane (ZX-plane). ACKNOWLEDGEMENT This stu is partl supporte b the Strategic Information an Communications R&D Promotion Programme (SCOPE) in the Japan Ministr of Internal Affairs an Communications. REFERENCES [1] Sehun Park, Yasuhiro Tsunemitsu, Jiro Hirokawa, Makoto Ano, Center Fee Single Laer Slotte Waveguie Arra, IEEE Trans. Antennas Propag., vol. 54, no5, pp , Ma 26. [2] Yasuhiro Tsunemitsu, SeHun Park, Jiro Hirokawa, Makoto Ano, Yohei Miura, Yasuhiro Kaama, an Naohisa Goto, "Reflection Characteristics of Center-Fee Single-Laer Waveguie Arras," IEICE Transactions on Communications, Vol.E88-B, No.6, pp , June 25. [3] 26GH FWA [4] Naohisa Goto, A waveguie-fe printe antenna, IEICE Technical Report, AP89-3, Apr [5] Yuichi Kimura, Yohei Miura, Jiro Hirokawa, an Makoto Ano, "A LOW-COST AND COMPACT WIRELESS TERMINAL WITH AN ALTERNATING PHASE FED SINGLE-LAYER WAVEGUIDE ARRAY FOR 26GH FIXED WIRELESS ACCESS SYSTEMS," JINA, Nov. 22. [6] Yasuhiro Tsunemitsu, Yohei Miura, Yasuhiro Kaama, SeHun Park, Jiro Hirokawa, Makoto Ano, an Naohisa Goto, "Polariation Isolation between Two Center-Fee Single-Laer Waveguie Arras Arrange Sie-b-sie," IEEE Antenna an Propagation Societ International Smposium an USNC/URSI National Raio Science Meeting, Session:86, Vol.3, pp , Montere, CA, June 26, 24. [7] Se-Hun Park, Jiro Hirokawa, an Makoto Ano, "A Planar Cross-Junction Power Divier for the Center Fee in Single-Laer Slotte Waveguie Arras," IEICE Trans. Communication, Vol.E85-B, No.11, pp , November 22. [8] Yasuhiro Tsunemitsu, Jiro Hirokawa an Makoto Ano, "Center-Fee comprise of E to H-plane Cross-Junctions in an Alternating-Phase Fe Single-Laer Slotte Waveguie Arra," IEEE Antenna an Propagation Societ International Smposium an USNC/URSI National Raio Science Meeting, Session:P65.6, Vol.3A, pp , Washington DC, USA, Jul 3, 25. [9] Yasuhiro Tsunemitsu, Jiro Hirokawa an Makoto Ano, "Characteristics of E- to H-Plane Multiple Wa Power Divier for the center fee in alternating phase fe Single-Laer Slotte Waveguie Arra," 25 INTERNATIONAL SYMPOSIUM ON ANTENNAS AND PROPAGATION (ISAP25), FD3-3, Vol.3, pp , Seoul, KOREA, August 3-5, 25. International Smposium on Antennas an Propagation ISAP 26 5