An Independently Tunable Dual-Band 360° Reflection-Type Phase Shifter With High Cross-Band Isolation

In this article, an independently tunable dual-band reflection-type phase shifter with 360° and high cross-band isolation is proposed. In this design, a new topology of the independently tunable dual-band phase shifters (DBPSs) is proposed. The independently tunable DBPS topology addresses the cross-band coupling and below 360° phase shift in existing DBPSs. To the best of our knowledge, it provides the first full 360° independently dual-band phase shift with the highest cross-band isolation. The phase shift in one band is highly transparent to the counterpart in the other band. The proposed new independently tunable DBPS topology involves an independent dual-band decoupled hybrid coupler (DDHC) and two sets of tunable loads. First, we propose a novel topology of the DDHC to provide a high cross-band isolation for the proposed DBPS. The DDHC leverages low-band and high-band decoupled networks to generate the hybrid coupler response in each band, which splits signals operating in dual bands to separate ports effectively. In addition, a general theoretical analysis and simplified design method are concluded in this article, providing explicit guidance for the independently tunable DBPSs and DDHCs. Second, the tunable parallel <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</i>–<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</i> loads are adopted. The proposed load method provides a full 360° phase shift for the independently tunable DBPS. Using the two-step phase extraction method, the DBPS is designed and measured with reduced traversal states from <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2^{2n}$</tex-math> </inline-formula> to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2^{{n}+1}$</tex-math> </inline-formula> for n-bit varactors. To validate the principle, our proof-of-concept design is fabricated and measured. It is observed that an over 360° phase shift with high cross-band isolation is obtained in the independently tunable DBPS. Compared with the existing literature, the maximum cross-band phase and magnitude errors are decreased by over ten times and four times. Thus, the proposed independently tunable DBPS is a promising candidate for dual-band scenarios such as baseband and satellites.