A Broadband Digital Phase Shifter Using Phase-Slope Tuning Properties of Microstrip to Slotline Transition and Microstrip-Loaded Slotline Structure

• Published in: IEEE transactions on microwave theory and techniques 2024-04, Vol.72 (4), p.1-11
• Main Authors: Liu, Fang, Xu, Jin, Zhou, Guo-Qing, Pu, Jia-Yang, Zhu, Lei
• Format: Article
• Language: English
• Subjects: <inline-formula xmlns:ali="http://www.niso.org/schemas/ali/1.0/" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"> <tex-math notation="LaTeX"> lambda </tex-math> </inline-formula>/4 short-circuit microstrip line; Broadband; Broadband communication; Design methodology; Design parameters; Design techniques; digital phase shifter (PS); Impedance; Insertion loss; Microstrip; microstrip to slotline transition; Phase error; Phase shifters; phase slope; Power transmission lines; Short circuits; Slot lines; Transmission lines; Tuning
• ISSN: 0018-9480; 1557-9670
• DOI: 10.1109/TMTT.2023.3312970

This article presents a design method for broadband digital phase shifter (PS). In this design, the phase-slope tuning properties of microstrip to slotline transition and \lambda /4 short-circuit microstrip-loaded slotline structure are researched and exposed. Equivalent transmission line models and a set of closed-form equations for both structures are presented for the purpose of revealing the mechanism of phase-slope tuning properties while predicting their transmission and matching characteristics. Design methods and specific design parameters for 11.25 ^{\circ} , 22.5 ^{\circ} , and 45 ^{\circ} PSs are provided, for the case where two structures are used independently. Combining two structures for PS designs with larger phase shift range (PSR), such as 90 ^{\circ} PS, has likewise been investigated to improve the flexibility of the proposed design method. In order to verify the correctness and practicality of the theoretical analysis, 11.25 ^{\circ} , 22.5 ^{\circ} , 45 ^{\circ} , 90 ^{\circ} , and 180 ^{\circ} single-bit PSs and a 5-bit 360 ^{\circ} broadband digital PS are designed and fabricated. From measurement, the operating bandwidth, return loss (RL), maximum root mean square (rms) phase error, and maximum rms amplitude error of this 5-bit PS are 2.55-4.5 GHz (55%), 10 dB, 4.5 ^{\circ} , and 0.35 dB, respectively. The average insertion loss (IL) at the center frequency is 5.7 dB. The measured results demonstrate the usefulness of the proposed two structures with phase-slope tuning property for broadband PS design.