김영민 *, 정용선 *, 노재우 *, 장리검 *, 안병철 ** 요약 Abstract This paper presents a broadband orthomode transducer (OMT) operating at 7-87GHz. The proposed OMT consists of a T-shaped bifurcation structure, a polarization divider section and three input/output ports. In the initial design step, the dimensions for the T-shaped bifurcation and the polarization divider section are derived from the theoretical approach method. Next, the optimized dimensions of the OMT are acquired by using the parametric-sweep methods. The final model of the OMT is finally designed by adapting low-loss waveguide transitions at each input/output port. The optimally designed OMT is fabricated by three split blocks and measured by using the WR-12 waveguide calibration kits. The fabricated OMT shows that it has a reflection coefficient of less than -17dB, a transmission coefficient of larger than -.5dB and an isolation of less than -33dB over 7-87GHz. Keywords wideband OMT, T-shaped bifurcation junction, polarization divider section, split blocks for fabrication ž Received: Apr. 28, 215, Revised: July 16, 215, Accepted: July 19, 215 ž Corresponding Author: Bierng-Chearl Ahn Director of Applied EM Lab, Chungbuk National University, 52 Chungdae-ro 1, Seowon-gu, Cheongju City, Chungbuk Province, 361-763, Korea Tel.: +82 43 261-3194, Email: bician@cbu.ac.kr
44 7/8GHz.,,, [1].... (Orthomode Transducer; OMT),,... T- - [2], [3], folded tumstile [4]-[6], [7]-[9]. T- 7-8GHz.. 1 (OMT).,,. T-. WR-12. 1. 7-87 GHz -15dB.5dB. 3dB. Circular to rectangular waveguide transition Side port (vertical polarization) T-shaped cross section Mitered bend Straight port (horizontal polarization) Common port Vertical polarization Horizontal polarization 2-step transition Polarization separating junction
2. CST Microwave Studio TM v. 212. WR-12 a = a 1=3.1mm, b = b 1=1.55mm. (d) (a 6 b 6). (d) (7-87 GHz) TE11 3.1mm. TE11 56.7GHz. (a 6 b 6 ) TE 1 (7GHz).9. spike. spike. (a 6 b 6) 2.36 2.36mm. T- (a 16) (b 16). (a 16) spike a 6 2.86mm (b 16 ) 1/5. T- (a 13, a 14, a 15) a 16. (b 14 ) -. (α) 45 (b 13) λ g/5 1.3mm.. (b 2 - b 6). (b 2) b 6 1/2. (l 2. - l 6) λ g/4 3. (a) 45 (b 13, b 14 ) h c [1]. hc 1.7mm.. parametric-sweep.
46 7/8GHz T-,,. (l 3 ). l 3 (b 2 ). l 3 =.9mm, b 2 =1.6mm. (l 9 ).29mm. T-... T- (l 5 ). (b 4 ). T-. T- (b 5 ) (a 6 ).. 4. T- WR- 12.. -25dB, -3dB, - -35dB. 2. α
Journal of KIIT. Vol. 13, No. 7, pp. 43-5, July 31, 215. pissn 1598-8619, eissn 293-7571 47. 표 2와 같이 최적 설계된 직교모드 변환기는 성 능 확인을 위해 제작 측정하였다. 7-8 GHz 대역 직교모드 변환기는 표 2에 제시된 것과 같이 모든 치수가 매우 작다. 직교모드 변환기는 정밀한 가공 을 위해 그림 5와 같이 3개의 split 블록으로 나누어 제작하였다. 각 split 블록은 가이드 핀과 볼트로 결 합된다. 그림5에서 OMT part I/II는 서로 대칭적으 로 설계되었고 다른 블록은 원형-정사각 도파관 변 환부이다. 그림 6은 개별적으로 제작된 3개의 split 블록을 조립한 상태와 공용 포트용 정합 부하이다. 제작된 직교모드 변환기의 성능은 회로망 분석기 를 이용하여 측정하였다. 그림 7의 WR-12 도파관 보정세트(Short, Offset Short, 정합 부하)를 이용하여 회로망 분석기를 보정하였다. -5 Reflection coefficient (db) Ⅲ 직교모드변환기 제작 및 실험 -1-15 -2-25 -3-35 -4-45 -5 68 7 72 74 76 78 8 82 84 86 88 9 92 94 (a) 공용포트-수직편파 (Common port-vertical pol.) Reflection coefficient (db) -5-1 -15-2 -25-3 -35-4 -45-5 68 7 72 74 76 78 8 82 84 86 88 9 92 94 (b) 공용포트-수평편파 (Common port-horizontal pol.) -5 Reflection coefficient (db) 그림 5. 직교 모드 변환기의 제작 모델 Fig. 5. Fabrication models of the OMT -1-15 -2-25 -3-35 -4-45 -5 68 7 72 74 76 78 8 82 84 86 88 9 92 94 (c) 측면포트 (Side port) Reflection coefficient (db) 그림 6. 조립된 OMT와 공용 포트용 정합부하 Fig. 6. Assembled OMT and a load -5-1 -15-2 -25-3 -35-4 -45-5 68 7 72 74 76 78 8 82 84 86 88 9 92 94 (d) 직선포트 (Straight port) 그림 8. 제작된 교차모드변환기의 반사계수 Fig. 8. Reflection coefficient of the fabricated orthomode transducer 그림 7. WR-12 도파관 보정 세트 Fig. 7. WR-12 waveguide calibration kit
48 7/8GHz 8... 7-87GHz -17dB. Insertion loss (db) Insertion loss (db) Isolation loss (db). -.2 -.4 -.6 -.8-1. 68 7 72 74 76 78 8 82 84 86 88 9 92 94. -.2 -.4 -.6 -.8-1. 68 7 72 74 76 78 8 82 84 86 88 9 92 94-1 -2-3 -4-5 -6-7 68 7 72 74 76 78 8 82 84 86 88 9 92 94 9. - -.5dB. 1-33dB. 7/8-GHz,. T-. T-,..,,. 3 split. OMT WR-12.., -.5dB -33dB.,. [1] M. A. Meyer and H. B. Goldberg, "Applications of the turnstile junction", IEEE Trans. Microwave Theory Tech., Vol. 3, No. 6, pp. 4-45, Dec. 1955. [2] A. Dunning, S. Srikanth, and A. R. Kerr, "A simple orthomode transducer for centimeter to submillimeter wavelenghts", Proc. Int. Symp. Space Terahertz Tech., 2-22 Apr. 29. [3] L. Salghetti, R. Vallauri, P. Besso, and M.
Mongiardo, "A manufacturing-oriented 9GHz ortho-mode transducer for a polarimetric experiment", Proc. 32nd European Microwave Conf., pp. 1-4, Sept. 22. [4] J. A, Ruiz-Cruz, J. R. Montejo-Garai, and J. M. Rebollar, "Full-wave modeling and optimization of Bøifot ortho-mode transducers", Int. J. RF Microw. Comp.-Aided Eng., Vol. 18, Issue 4, pp. 33-313, July 28. [5] Bøifot. A. M., E. Lier, and T. Schaug-Pettersen, "Simple and broadband orthomode transducer", IEE Proc. H, Microw. Antennas Propagat., Vol. 137, No. 6, pp. 396-4, Dec. 199. [6] Moorey. G., R. Bolton, A. Dunning, R. Gough, H. Kanoniuk, and L. Reilly, "A 77-117GHz cryogenically cooled receiver for radioastronomy", Proc. Workshop on the Applications of Radio Science, 15-17 Feb. 26. [7] A. Dunning, "Double ridged orthomode mode transducer for the 16-26GHz microwave band", Proc. Workshop on the Applications of Radio Science (WARS 22), 2-22 Feb. 22. [8] D. I. L. Villiers, P. Meyer, and K. D. Palmer, "Design of a wideband orthomode transducer", Proc. IEEE ARFRICON, pp. 1-6, Sep. 29. [9] G. M. Coutts, H. Dinwiddle, and P. Lilie, "S-band octave-bandwidth orthomode transducer for the extended very large array", Dig. IEEE 29 Antennas Progat. Soc. Int. Symp. (APSURSI '9), pp. 1-4, June 29. [1] Ki-Rock Kim, Byung-kook Joo, Jae-Hoon Bang, Bierng-Chearl Ahn, and Jong-Hun Chun, "Optimal Design and Fabrication of a Stepped Waveguide Bend at Ka-Band", JKIIT, Vol. 7, No. 6, pp. 69-73, Dec. 29. 김영민 (Young-Min Kim) 정용선 (Yong-Sun Jung) 노재우 (Jae-Woo Noh) 장리검 (Li-Jian Zhang)
5 7/8GHz 안병철 (Bierng-Chearl Ahn)