volume | PIER Journals

2009-12-16

A Broadband Quadrature Hybrid Using Improved Wideband Schiffman Phase Shifter

Eslam Jafari,

Dr. Eslam Jafari

Department of Electrical Engineering

Iran University of Science and Technology (IUST)

Iran

Homepage

Farrokh Hojjat-Kashani,

Professor Farrokh Hojjat-Kashani

Iran University of Science and Technology (IUST)

Iran

Homepage

Reza Rezaiesarlak

Dr. Reza Rezaiesarlak

Department of Electrical Engineering

Iran University of Science and Technology

Iran

Homepage

Progress In Electromagnetics Research C, Vol. 11, 229-236, 2009

doi:10.2528/PIERC09112101 | Google Scholar

Abstract

In this paper, a broadband quadrature hybrid is presented. The hybrid comprises a Wilkinson divider, followed by an improved Schiffman phase shifter. An improved wideband Schiffman phase shifter on a single layer printed circuit board is accompanied by a lumped capacitor between two coupled lines. Lumped capacitor is in parallel with the odd-mode capacitance of the two coupled lines, hence, the odd-mode capacitance is increased and consequently the odd-mode impedance is decreased. Therefore, by this method we can control the ratio of the even mode impedance to the odd mode impedance which is critical in Schiffman phase shifter design. Compared with the cascading Microstrip multi-section coupled lines, our proposed single layer phase shifter is smaller in size. Also, the proposed phase shifter has the greater bandwidth compared to the patterned ground plane Schiffman phase shifter and its realization is simpler because of its single layer structure. As an example, a Schiffman phase shifter at frequency f₀ =650 MHz is designed and simulated. With the proposed phase shifter a 90°hybrid is designed, simulated, fabricated and measured. Exprimental results show that the amplitude and phase imbalance between two paths at worth case are within 0.75 dB and 5°, respectively, over the frequency band from 362 MHz to 891 MHz, or around 84% bandwidth. The measured return loss is better than -10.8 dB over the operating frequency band.

Download Full Article (326) View Full Article volume

Citation

Copy Export

Eslam Jafari, Farrokh Hojjat-Kashani, and Reza Rezaiesarlak, "A Broadband Quadrature Hybrid Using Improved Wideband Schiffman Phase Shifter," Progress In Electromagnetics Research C, Vol. 11, 229-236, 2009.
doi:10.2528/PIERC09112101

References

1. Chiu, L. and Q. Xue, "Wideband parallel-strip 90°hybrid coupler with swap," Electronics Letters, Vol. 44, No. 11, 687-688, May 22, 2008.
doi:10.1049/el:20080975 Google Scholar

2. Tang, C. W., M. G. Chen, Y. S. Lin, and J. W. Wu, "Broadband microstrip branch-line coupler with defected ground structure," Electronics Letters, Vol. 42, No. 25, Dec. 2006.
doi:10.1049/el:20063025 Google Scholar

3. Levy, R. and L. F. Lind, "Synthesis of symmetrical branch-guide directional couplers," IEEE Transactions on Microwave Theory and Techniques, Vol. 19, No. 2, Feb. 1968.
doi:10.1109/TMTT.1968.1126612 Google Scholar

4. Schiffman, B. M., "A new class of broad-band microwave 90-degree phase shifters," IRE Trans. Microwave Theory Tech., 232-237, Apr. 1958.
doi:10.1109/TMTT.1958.1124543 Google Scholar

5. Quirarte, J. L. R. and J. P. Starski, "Synthesis of Schiffman phase shifters," IEEE Transactions on Microwave Theory and Techniques, Vol. 39, No. 11, 1885-1889, Nov. 1991.
doi:10.1109/22.97492 Google Scholar

6. Guo, Y.-X., Z.-Y. Zhang, and L. C. Ong, "Improved wide-band Schiffman phase shifter," IEEE Transactions on Microwave Theory and Techniques, Vol. 54, No. 3, Mar. 2006. Google Scholar

7. Jafari, E., F. Hodjatkashani, and R. Rezaiesarlak, "A wideband compact planar balun for UHF DTV applications," Journal of Electromagnetic Waves and Applications, Vol. 23, No. 14-15, 2047-2053, 2009.
doi:10.1163/156939309789932566 Google Scholar