Design of a Compact Band‐Pass Filter With an Inclined Phase Shift

This paper presents a design for a band‐pass filter (BPF) with a desired phase shift at the inclined frequency in the passband. This design is achieved by combining a right‐handed transmission line (RHTL), which exhibits positive phase propagation and works as a low‐pass filter (LPF), and a left‐handed transmission line (LHTL), which exhibits negative phase propagation and works as a high‐pass filter (HPF). The proposed BPF simultaneously realizes a desired frequency filtering and phase shifting by cascading proper unit cells of RHTL and LHTL. To verify our proposed idea, we designed four BPFs with similar passband frequencies but different phase delays at a certain frequency in the passband. In the actual experiment, phase delays of 0°, +90°, −90°, and 180° were used, and the phase deviations from the designed phase shift were less than 9.59° at 600 MHz for all four phase delays. The insertion losses were maintained below 1.31 dB. As the RHTL and LHTL were synthesized with lumped elements only, the circuit is compact and applicable to monolithic microwave integrated circuit design.