диафрагмированные волноводные фильтры / a4afa09c-e6b7-4b9a-b37c-f2efd561f151

Abstract—In this paper, a coupled resonator waveguide diplexer operating in frequency range 11.5-14 GHz is presented. The diplexer structure consists of a waveguide E-plane T- junction and two waveguide cavity filters whose center frequency are 12.375 GHz and 13.125 GHz. The simulation results show that over the operating band of the two filters the return loss is better than -18 dB and the the insertion loss is lower than 0.05 dB. the out-band rejection is higher than 30 dB at the suppression frequency band of 11.75 GHz to 12 GHz and 13.5 GHz to 13.75 GHz

Keywords—E-plane; T-junction; diplexer; filter

I.INTRODUCTION

Diplexers are widely used in many microwave and millimeter communications systems to separate or combine two frequency channels which have the same input port. In many microwave and millimeter applications, return loss, insertion loss and power handling are requirements that need to be considered. In order to improve the diplexer’s performance, waveguide technology is especially needed because of its capability of handling high power and lower insertion loss compared with the micro-strip devices. However, the waveguide implementation makes the diplexer one of the most cumbersome structures of the whole RF equipment. Therefore, geometrical and size constraints are further fundamental requirements [1].

Typical diplexer architectures employ a three-port junction between two separately designed filters [2]. Several H-plane and E-lane three-port junctions have been proposed [3]-[6], each of them having its specific properties in terms of electrical and mechanical features. Uwe Rosenberg and his team proposed a waveguide diplexer which has extreme broadband [7]. Talal Skaik proposed a micromachined WR-3 band waveguide diplexer based on Coupled Resonator Structures [8]. Their design gives good return loss but high insertion loss of 8 dB.

This letter will show how to simultaneously achieve a waveguide diplexer with 18 dB reflection serving two operating bands (12.25 GHz to 12.5 GHz and 13 GHz to 13.25 GHz).The design of the waveguide diplexer is shown in 3D model Figure 1. According to this design , a sample diplexer with simulation results is presented, whose out-band rejection is more than 30dB and the insertion loss is lower than 0.05 dB.

Fig. 1. The 3D model of the proposed waveguide diplexer

II.DIPLEXER DESIGN AND SIMULATION RESULTS

A.T-Junction Design

The T-Junction is a three-port waveguide device that be

used to connect the two filters together in the diplexer. In our design process, we use the well-known commercial simulator Uwave for original structure’s building and further optimization of the building parameters. At first we design an original three-port junction which providing a compact solution for rectangular waveguide diplexers. The structure of the proposed junction is shown in Figure 2, which is essentially an typical E-plane T-junction with WR75 standard waveguide output port(a =19.050 mm, b =9.05 mm). Thus the proposed junction can easily be used in connection with most waveguide filter architectures which have the same waveguide ports.

Fig. 2. The 3D model of the proposed E-plane T-junction

B. Filter Design

The two filters have different design requirements that need to be design separately. Waveguide cavity filters are easy to be design and fabricated so we chose this method to design the filters to meet the particular passband and rejection demands. For the first filter whose operating band is 12.25 GHz to 12.5 GHz, we design five cavities to achieve the goal of 18 dB reflection and 30 dB out-band rejection. As to the other filter which has higher operating band of 13 GHz to 13.25 GHz we just need use four cavities to get the same results. In order to make it easy to connect with the T-junction and other waveguide devices, we set the input and output ports of the two filters equal to the standard waveguide port WR75. The 3D model of the two filters are shown in Figure 3.

C. Diplexer Design

To finish the design of the diplexer we combine the proposed E-plan T-junction and the two different filters together for further optimization. After the parameters optimization, the final result of the diplexer is shown in Figure 5 .

Fig. 3. The 3D model of the proposed cavity filters

After the structures of the two cavity filters have been building, we start to optimize the building parameters for good results. The final simulation results of the two cavity filters are shown in Figure 4.

(a)

(b)

Fig. 4. The simulation results of the two filters

Fig. 5. The simulation results of the proposed diplexer

III. CONCLUSION

A waveguide diplexer using E-plane T-junction for connecting has been proposed, which has 18 dB reflection over the operating band of the two filters. From the results,we can know that the insertion loss is lower than 0.05 dB in the passband and the out-band rejection is higher than 30 dB at the suppression frequency band of 11.75 GHz to 12 GHz and 13.5 GHz to 13.75 GHz. The main properties and modeling have been described, with special emphasis on the structure and electrical properties.

References

[1]S. Bastioli, L. Marcaccioli and R. Sorrentino, “An Original Resonant Y- Junction for Compact Waveguide Diplexers,” Microwave Symposium Digest, 2009. MTT '09. IEEE MTT-S International

[2]J. Uher, J. Bornemann, U. Rosenberg, Waveguide Components for Antenna Feed Systems: Theory and CAD, Artech House, Boston – London, 1993.

[3]Y. Rong, H.-W. Yao, K. A. Zaki, T. G. Dolan, “Millimeter-wave Kaband H-plane diplexers and multiplexers,” IEEE Trans. Microwave Theory & Tech.,vol. 47, no. 12, Dec. 1999.

[4]J. M. Rebollar, J. R. Montejo-Garai, A. Ohoro, “Asymmetric Hplane T- junction for broadband diplexer applications,” IEEE AP-S Int. Symp. Dig., pp. 2032-2035, July 2000.

[5]Ke-Li Wu, H. Wang “A rigorous modal analysis of H-plane waveguide T-junction loaded with a partial-height post for wideband applications,” IEEE Trans. Microw. Theory & Tech., vol. 49, no. 5, May 2001.

[6]T. Shen, K.A. Zaki, T.G. Dolan, “Rectangular waveguide diplexers with a circular waveguide common port”, IEEE Trans. Microw. Theory & Tech., vol. 51, no. 2, pp. 578-582, Feb. 2003.

[7]U. Rosenberg, A. Bradt, M. Perelshtein and P. Bourbonnais “Extreme Broadband Waveguide Diplexer Design for High Performance Antenna Feed Systems ,”Microwave Conference (EuMC), 2010 European

[8]T. Skaik, M. Lancaster, Maolong Ke and Yi Wang “A Micromachined WR-3 band Waveguide Diplexer based on Coupled Resonator Structures,” Microwave Conference (EuMC), 2011 41st European