Improved wide-band Schiffman phase shifter

• Published in: IEEE transactions on microwave theory and techniques Vol. 54; no. 3; pp. 1196 - 1200
• Main Authors: GUO, Yong-Xin, ZHANG, Zhen-Yu, LING CHUEN ONG
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01-03-2006; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Applied sciences; Capacitors; Circuit properties; Circuits of signal characteristics conditioning (including delay circuits); Conductors; Coupled lines; Dielectric, amorphous and glass solid devices; Electric, optical and optoelectronic circuits; Electromagnetic measurements; Electronic circuits; Electronic equipment and fabrication. Passive components, printed wiring boards, connectics; Electronics; Exact sciences and technology; Frequency bands; Frequency measurement; Ground plane; Impedance; Microstrip; Microwave circuits, microwave integrated circuits, microwave transmission lines, submillimeter wave circuits; Microwaves; Noise levels; patterned ground plane; Phase measurement; phase shifter; Phase shifters; Printed circuits; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Shiffman phase shifter; Simulation; Software measurement; wide-band phase shifter; Wideband; Performance evaluation; Return loss; Coupled line; Printed circuit board; Electromagnetic wave; Phase shifter; Microstrip line; Shiffman phase shifter; wide-band phase shifter; Frequency band; Wide band; Coupled lines; patterned ground plane; Software; Printed circuit; Impedance; Capacitor; Planar technology
• ISSN: 0018-9480; 1557-9670
• DOI: 10.1109/TMTT.2005.864105

In this paper, one improved wide-band Schiffman phase shifter is presented by modifying the ground plane underneath the coupled lines. In this new design, with the ground plane under the coupled lines removed, the even-mode impedance will be increased substantially. Meanwhile, we propose that one additional isolated rectangular conductor is placed under the coupled lines to act as one capacitor so that the odd-mode impedance is decreased. The proposed new design was simulated by the full-wave electromagnetic software IE3D and validated by the measurement. Compared with the cascading microstrip multisection coupled-line configuration, our newly proposed planar one with a patterned ground plane is small in size and, meanwhile, has a good performance. As an example, one Schiffman phase shifter on a double-sided printed circuit board is designed, simulated, fabricated, and measured. The measured amplitude and phase imbalance between the two paths are within 0.5 dB and 5/spl deg/, respectively, over the frequency band from 1.5 to 3.1 GHz, or around 70% bandwidth. The measured return loss is found to be better than -12 dB over the operating frequency band.