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The simulated and measured port-to-port isolation performance levels are shown in Figs. 5 and 6, respectively. The simulated and measured results also agree very well. The measured isolation is better than -10 dB over entire working band from 4.5 to 11.2 GHz except for S32 and S52, whose -10 dB isolation bandwidth is about 3.2 GHz.

HMSIW Methods Make Broadband Dividers, Fig. 5

HMSIW Methods Make Broadband Dividers, Fig. 6

As Fig. 7 shows, two power dividers were fabricated and connected back-to-back with 18-mm-long microstrip lines to form a power combiner. The unit’s frequency response is shown in Fig. 8. The measured return loss is better than -10 dB from 4.8 to 11 GHz. The measured magnitude of S21 is from 0.8 dB to 1.9 dB in the same frequency band. The maximum potential combining efficiency (eff) can be estimated by Eq. 3:

eff = [|S21|2/(1 - |S11|2)]0.5 x 100%   (3)

Figure 9 shows the calculated results from Eq. 3 for the structure of Fig. 7. From these results, it is clear that combining efficiency from 82.5% to 92.5% can be achieved for a wide frequency range. Considering the loss of the vertical microstrip lines, the combining efficiency is even better. Wideband fluctuations in S21 are caused by return loss and isolation, as indicated by Eq. 1. In a power-combining system, such fluctuations can be alleviated by optimizing the input matching network of the power amplifier in the system.

HMSIW Methods Make Broadband Dividers, Fig. 7

HMSIW Methods Make Broadband Dividers, Fig. 8

HMSIW Methods Make Broadband Dividers, Fig. 9

The HMSIW power divider achieves low insertion loss and good input return loss over a wide frequency range from 4.8 to 11.0 GHz. Its performance makes it a promising building block for broadband power dividing and combining networks that require high efficiency.

Lei Zhang, Associate Professor

Xiaowei Zhu, Professor

Ling Tian, Associate Professor

Jiafeng Zhai, Associate Professor

State Key Laboratory of Millimeter Wave, School of Information Science and Engineering, Southeast University, Nanjing, 210096, People’s Republic of China.

Acknowledgments

This work was supported in part by National Science and Technology Major Project 2013ZX03001017-003 and 2008ZX03005-001, and the National Natural Science Foundation of China under Grant No.60702163.

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