диафрагмированные волноводные фильтры / 162dedbc-facd-440e-9661-726fb894f0f8

Abstract – A waveguide-based magic-tee integrated with bandpass filter is proposed. To increase the compactness of the magic-tee, the E-plane arm is folded to parallel with the H-plane arm. An inverted funnel-shaped stub is designed to achieve a good impedance matching. Each arm of the magic-tee is connected to a waveguide bandpass filter consisting of three resonator sections. As the structure is too complicated to be fabricated by traditional machining methods, a 3-D printing technique is suitable to realize the proposed magic-tee without intricate assembly process, especially after it is integrated in a RF system.

Index Terms — Folded magic-tee, bandpass filter, 3-D printing.

I.INTRODUCTION

High-level of system integration becomes more and more important in current advanced RF applications as diverse as satellite communication, radar systems and on-the-move system. For the RF system alone, it requires not only the compactness of the front-end antenna, but also a commensurate size of the RF circuit in the rear. In waveguide-based structures, most of the designs have to split into different parts before machining fabrication, and the post-assembly processes are necessary [1-3]. Such “multiple jointing” structure cannot avoid potential impedance mismatch and power loss in the connection parts. Traditionally, different waveguide components have to join with each other via connectors or transformers. Therefore, it is always expected all these connectors and joints can be removed so that the whole design including different waveguide components can be built up in one piece of metal. In this paper, a compact magic-tee integrated with bandpass filter (BPF) is proposed, avoiding any electrical contact reflection.

II. DESIGN AND FABRICATION

The proposed magic-tee structure integrated with waveguide bandpass filter is shown in Fig. 1. The magic-tee is of traditional-type but an inverted funnel-shaped stub is incorporated at the center, helping to achieve a better matching performance. The bandpass filter attached to each arm is a three-resonator-section configuration, separated by four septum windows [4]. Port 1, 2, and 3 form the H-plane T-junction of the magic-tee and Port 4, 2 and 3 form the E-

Fig. 1. Sketch of the 16-way power combiner.

plane T-junction. In order to achieve a compact and lowprofile structure, the E-plane arm (Port 4) is folded to parallel with the H-plane arm (Port 1). As can be seen in Fig.1, the overall structure becomes overly complicated after linking all the components together. It is hard to be realized by traditional machining and assembly approach. However, the complete design is feasible to be realized by 3-D metal printing technique without need for any assembly process [5- 7].

In this work, a 3-D printing technique called Direct Metal Laser Sintering is chosen for fabricating the proposed magictee combiner after considering the cost, printing precision, and material availability and properties. This technique enables one to fabricate extremely complicated and intricate geometries of waveguide structure. Within the printing system’s capability, the printing precision of the object depends on the design specifications of the material. Here, an aluminum alloy AlSi10Mg is chosen for this application, which is a metallic alloy that has a combination of good strength, good hardness and light weight with good electrical conductivity.

III. RESULTS

This paper reports preliminary results obtained from numerical analysis, as shown in Fig. 2 and Fig. 3. It can be seen in Fig. 2 that, after applying the bandpass filters at each waveguide arm, all the ports can cover a fractional bandwidth of 3% (Reflection Coefficient ≤ -20 dB) in the pass-band. Power division is stable at around (3.00±0.03) dB in the operational bandwidth, indicating the in-band insertion loss is

TH3B_04

Fig. 2. Bandwidth performance.

Fig. 3. Isolation between Port A and Port B.

2016 IEEE 5th Asia-Pacific Conference on Antennas and Propagation (APCAP)

around 0.03 dB. Fig. 3 shows the isolation between Port 1 and Port 4, Port 2 and Port 3 is higher than 40 dB and 25 dB, respectively. More details will be shown in the conference.

IV. CONCLUSION

A magic-tee integrated with waveguide bandpass filter is proposed in this work. The aim is to integrate two different waveguide components into a compact structure without any assembly process. Preliminary electrical performance is presented. The relatively complicated design can be realized by 3-D metal printing technique, avoiding disadvantages of the traditional machining methods.

REFERENCES

[1]O. A. Peverini, G. Virone, G. Addamo, and R. Tascone, “Development of passive microwave antenna-feed systems for wide-band dualpolarisation receivers,” IET Microwaves, Antennas & Propagation, vol. 5, no. 8, pp. 1008-1015, June 6 2011.

[2]J. A. Ruiz-Cruz, M. M. Fahmi, S. A. Fouladi, and R. R. Mansour, “Waveguide Antenna Feeders With Integrated Reconfigurable Dual Circular Polarization,” IEEE Transactions on Microwave Theory and Techniques, vol. 59, no. 12, pp. 3365-3374, Dec. 2011.

[3]S. Srikanth and M. Solatka, “A compact full waveguide band turnstile junction orthomode transducer,” URSI General Assembly and Scientific Symposium, pp. 1-4, Istanbul, 2011.

[4]M. Martínez-Mendoza, D. Cañete-Rebenaque, A. Alvarez-Melcon, and R. Cameron, “Complex waveguide filter topologies employing inductive windows and dielectric objects,” IET Microwaves, Antennas & Propagation, vol. 8, no. 15, pp. 1305-1312, 12 9 2014.

[5]Guan-Long Huang, Shi-Gang Zhou, Tan-Huat Chio, and Tat-Soon Yeo, “Fabrication of a High-Efficiency Waveguide Antenna Array via Direct Metal Laser Sintering,” IEEE Antennas and Wireless Propagation Letters. Available online.

[6]Guan-Long Huang, Shi-Gang Zhou, Tan-Huat Chio, and Tat-Soon Yeo, “3-D metal-direct-printed wideband and high-efficiency waveguide-fed antenna array,” IEEE MTT-S International Microwave Symposium, pp. 1-4, Phoenix, USA, 17-22 May 2015.

[7]Guan-Long Huang, Shi-Gang Zhou, Tan-Huat Chio, and Tat-Soon Yeo, “Design of a wideband and low-profile monopulse array fabricated by 3-D metal printing technique,” IEEE International Symposium on Antennas and Propagation, pp. 322-323, Vancouver, Canada, 19-24 July 2015.