A Compact Ultra-Wideband Power Divider withHigh Isolation

Liang Liu, Ronghong Jin, Hangchen Yu, Xianling Liang, Junping Geng, Xudong Bai*Department of Electronics EngineeringShanghai Jiao Tong University (SJTU)

Shanghai, 200240, Chinaliangliu247@sjtu.edu.cn, baixudong@sjtu.edu.cn

Abstract—Power divider is widely used in the phased antennaarray. In this paper, a novel ultra-wideband divider with highisolation is proposed, which bases on the multi-section transmis-sion line theory to extend the bandwidth of the power divider andthe multilayer technique to reduce the size of the power divider.The simulated isolation of power divider is almost 25 dB from3.1 GHz to 10.6 GHz, and the insertion loss is about 3.5 dB.

I. INTRODUCTION

Power divider is frequently used in the phased antennaarrays and other communication systems. In order to reducethe coupling between the array elements, high isolation of thepower divider is always needed. On the other hand, with theneed and the development of the high rate data transmission,bandwidth of the component becomes more and more wide.Although the Wilkinson power divider was proposed in theearly 1960s [1], due to the narrow fractional bandwidth, itcan’t fulfill the need of Ultra-Wideband (UWB) application inmodern communication. Thus, considerable efforts were focuson the improvement of the bandwidth of the power dividerwith high isolation. Multi-section Wilkinson power dividerwas researched extensively but leads to the large size [2]–[6]. Coupled strip line was used to better the performance ofhigh frequencies in power divider in [6], which was the subtledistinction from other multi-section power divider. Recently,multilayer techniques were researched to realize the compactsize. In [7], broadband coupling via multilayer microstripand slot transition of elliptical shape was utilized to achievea compact UWB power divider. A novel UWB multilayerslotline power divider for two ports was also presented in [8].In [9], reduced size can be realized by the use of the OMMICtechniques, which based on the theory of dual-band transmis-sion line transformer and lump-distribute techniques. UWBpower divider based on micro-coaxial impedance transformerwas also proposed in [10].

In this paper, a novel wideband power divider is proposedbased on the multi-section impedance transformer and threelayers structure. With this structure, compact size and highisolation is achieved across wide bandwidth. Compared withthe conventional multi-section divider, the proposed powerdivider adopts the multilayer structure to make the componentmore compact. On the other hand, wideband power dividerrealized by multistage transmission line is well understoodcomparing with other ultra–wideband power divider.

II. THE DESIGN OF THE POWER DIVIDER

Fig. 1. Circuit of proposed wideband power divider.

Fig. 2. 3D structure of proposed wideband power divider.

The schematic figure of the proposed power divider isshown in Fig. 1, which has three ports with standardimpedance Z0 = 50Ω. In the figure, the solid line denotesthat the transmission lines and components are on the toplayer, while the dashed lines represent that they are on thebottom layer, the internal layer is the ground. And at theintersection between the dashed line and the solid line, viasare utilized to connect the top layer and the bottom layer.The three-dimensional structure is shown in Fig. 2, where, thered part is on the top layer, the green part is on the bottomlayer. All characteristic impedances of the transmission lineshown in Fig. 1 are 2

√2Z0, and the electrical lengths of the

transmission lines satisfy the following relation to keep the

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Fig. 3. Simulated insertion loss and isolation.

insertion loss minimum:

θ1 + θ2 + θ3 = θ4 + θ5 + θ6. (1)

where, θ1, θ2, · · ·, θ6 are the electrical lengths of the trans-mission lines. R1, R2, R3, and R4 are resistors used for theisolation between the port 2 and the port 3.

By using the classical analysis method of even and oddmodes, we can easily get that the isolation between the twooutput ports is mainly subjected to the electrical length ofeach section transmission line and the value of the resistors.Thus, dividing every port into two parts and constructing thepower divider with different electric lengths respectively, betterisolation can be got because of the two different classes ofelectrical length and resistors.

III. SIMULATION AND DISCUSSION

By choosing proper electrical length of the transmissionlines and the value of resistors listed in the table I, goodisolation can be achieved. It is noted that all of the electricallengths in the table I are normalized at the frequency 3.1 GHz.The simulation results in Advanced Design System (ADS) areshown in Fig. 3 and Fig. 4. From the simulated results, wecan see that, in the UWB frequency range from 3.1 GHz to10.6 GHz, the insertion loss is about 3.5 dB and isolation isalmost 25 dB. The return loss of both input port and outputsare near 10 dB. The total electrical length at 3.1 GHz is about153.5o. Compare Fig. 3 with Fig. 4, the frequency of bestisolation differs with the frequency of good return loss, whichis attributed to the difference of electrical lengths in the toplayer and in the bottom layer.

TABLE IPARAMETERS OF SIMULATION.

Length θ1 θ2 θ3 θ4 θ5 θ6degree 56.4 59.5 37.6 94.8 48.8 9.9

Resistor R1 R2 R3 R4

ohm 30 549 47.9 407.3

IV. CONCLUSION

A novel ultra-wideband power divider with high isolationis proposed and simulated, which incorporates the advantages

Fig. 4. Simulated return loss of port 1 and port 2.

of multistage power divider and multilayer power divider.From the simulation result we can see that, the isolationof power divider is almost 25 dB from 3.1 GHz to 10.6GHz, the return loss is about 10 dB, which can be furtherimproved by replacing the uniform transmission line with thestep impedance transmission line in the future work.

ACKNOWLEDGEMENT

This work was supported by the National Science andTechnology of Major Project (2011ZX03001-007-03), the Na-tional Natural Science Foundation (61201058), the Researchand Innovation Project of Shanghai Education Commission(12Z112030001), and the Scientific Research Foundation forReturned Overseas Chinese Scholars, State Education Min-istry, the Project of SMC Excellent Young Faculty.

REFERENCES

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[4] Homayoon Oraizi, and Ali-Reza Sharifi, “Design and optimization ofbroadband asymmetrical multisection Wilkinson power divider,” IEEETransaction on Microwave Theory and Techniques, vol. 54, no. 5, pp.2220–2231, May 2006.

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[6] P. O. Afanasiev, V. A. Sledkov, and M. B. Manuilov, “A novel designof ultra-wideband strip-line power divider for 2–18 GHz,” Intertionalconference on Antenna theory and techniques, pp. 323-325, 2013.

[7] Amin M. Abbosh, “A compact UWB three-way power divider,” IEEEMicrowave and Wireless Components Letters, vol. 17, no. 8, pp. 598–600, Aug 2007.

[8] Kaijun Song, and Quan Xue,“Novel ultra-wideband multilayer slotlinepower divider with bandpass response”, IEEE Microwave and WirelessComponents letters., vol. 20, no. 1, pp. 13–15, Jan 2010.

[9] Zhang Yaqiong, Tang Xinyi, Fan Yijing, Ooi Ban Leong, Leong MookSeng, and Koen Mouthaan, “A miniaturized wideband Wilkinson powerdivider,” 10th Electronics Packaging Technology Conference., pp. 271–274, 2008.

[10] N. Ehsan, K. Vanhille, S. Rondineau, E. D. Cullens, and Z. B. Popovic,“Broadband micro-coaxial wilkinson dividers,” IEEE Trans. Microw.Theory Tech., vol. 57, no. 11, pp. 2783–2789, 2009.

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