Radial Guided 4-Way Power Divider Using Substrate Integrated Waveguide for Satellite Communication
Tae-Yoon Seo, Dong-yeon Kim, Jae W. Lee, and Choon Sik Cho School of Electronics, Telecommunication and Computer Engineering, Korea Aerospace University, Goyang-city, Gyeonggi-do, Korea E-mail:
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Introduction As a key component in microwave applications such as antenna feeding network, power distribution network, and array systems requiring beam forming network(BFN) in satellite communication, the power divider/combiner is widely designed and implemented by using various analysis methods[1,2] and various integration method[6-8]. In array systems employing microstrip feeding network, the beam forming network(BFN) becomes more complicated as a number of array element increases, resulting in a significant radiation loss caused by the conductor in microstrip line. In order to overcome the radiation loss problem on the transmission line, many researchers have studied on the novel feeding network with waveguide- or cavitytyped closed boundary structure. Especially, the radial waveguide structure having low insertion loss characteristic has been adopted in many array systems[3-5]. Hence, in this paper, substrate integrated waveguide(SIW) as a highly-integrated microwave component is employed for the design of low-loss radial-guided power divider/combiner. At this time, the side walls in regular rectangular waveguide have been replaced by metalized via arrays with optimized diameters of vias and separation between the nearest vias[9]. Design Procedure A multi-port power divider employing SIW is shown in Fig. 1 with integrable single radiating antenna element. It is seen from Fig. 1 that the proposed power divider can be integrated and designed in a single substrate with via arrays. A. Coaxial cable at input Generally, the signal excitation of radial waveguide is accomplished by using a current probe from a coaxial cable. The height of inserted current probe inside waveguide plays an important role in the smoothly transition from current probe to regular radial waveguide. However, the proposed structure in this paper provides a direct connection between the current probe and upper ground plane because of the difficulties in the control of height in the SIW structure. At this time, in order to improve return loss characteristic, we should optimize the other parameters of radial waveguide.
B. Guiding posts for equal power division As a key structure in the proposed power divider, the guiding posts located in front of each SIW play an important role in both making higher resonant frequency and smooth energy transition from TEM-mode(generated by coaxial feeding) to TE10-mode which is a fundamental mode in dielectric-filled rectangular waveguide using SIW. Simulation and Measured Results The total power divider structure using SIW have been designed by employing a RT/Duroid 5880 substrate as a single layer, which relative permittivity is 2.2 and substrate thickness is 1.57 mm. The occupying areas of radial SIW power divider with and without waveguide-to-microstrip transition are 30 ൈ 30 mm2 and 50 ൈ 50 mm2, respectively. It is conjectured from Fig. 2 that a smooth energy transition in the neighborhood of guiding posts occurs with the help of the boundary condition between the current probe and SIW. It is seen from Fig. 3 that the output magnitudes of all ports are exactly equal to each other. There is a little deviation 0.83 dB from the perfect power divider due to a microstrip transition loss at all powers. As shown in Fig. 3, the input impedance bandwidth amounts to about 3.5 GHz under the criterion of –10 dB in simulation. Also, Fig. 3 shows a good agreement between simulated and measured data. Conclusion In this paper, a 4-way SIW power divider operating at X-band with guiding posts has been designed, simulated, and measured to verify the accuracy of the design method. It is predicted from the configuration and electrical performances that this power divider has advantages of easy implementation and connection with other structures such as SIW antenna or phase shifter in a single substrate. References [1] E. L. Holzman, “An eigenvalue equation analysis of a symmetrical coax line to n-way waveguide power divider,” IEEE Trans. Microwave Theory Techniques, vol. 42, no. 7, July 1994. [2] V. Volski and G. A. E. Vandenbosch, “Modeling of a cavity filled with a plane multilayered dielectric using the method of auxiliary sources,” IEEE Trans. Microwave theory and techniques, vol. 54, no. 1, pp. 235-239, Jan. 2006. [3] K. Song, Y. Fan, and Z. He, “Broadband radial waveguide spatial combiner,” IEEE Microwave and Wireless Comp. Letters, vol. 18, no. 2, Feb. 2008. [4] K. Song, Y. Fan, and Y. Zang, “Radial cavity power divider based on substrate integrated waveguide technology,” Electron. Lett., vol. 42, no. 19, Sep. 2006.
[5] K. song, Y. Fan, and Y. Zang, “Eight-way substrate integrated waveguide power divider with low insertion loss,” IEEE Trans. Microwave Theory and Techniques, vol. 56, no. 6, June 2008. [6] L. Pazin and Y. Leviatan, “Design of a radial waveguide feed network for a pin-fed array antenna,” Proc. Inst. Elect. Eng., vol. 153, no. 1, pp. 38-42, 2006. [7] H. Nakano, H. Takeda, Y. Kitamura, H. Mimaki, and J. Yamauchi, “Lowprofile helical array antenna fed from a radial waveguide,” IEEE Trans. Antennas Propag., vol. 40, no. 3, pp. 279-284, Mar. 1992. [8] M. E. Bialkowski and P. Kabacik, “An electromagnetic-field method modeling of a radial line planar antenna with coupling probes,” IEEE Trans. Antennas Prolag., vol. 51. No. 5, pp. 1114-1120, May 2003. [9] F. Xu and K. Wu, "Guided-wave and leakage characteristics of substrate integrated waveguide," IEEE Trans. Microwave theory and Techniques, vol. 53, no. 1, pp. 66-73, Jan. 2005.
Figures
(a) (b) Fig. 1. Configuration of suggested power divider (a) application of power divider with radiating element, (b) detailed description.
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Fig. 2. E-field distribution of SIW power divider at phase of (a) 45°, (b) 90°, (c) 135°, and (d) 180°.
Fig. 3. Simulated and measured results of the proposed SIW power divider.
