Novel factor of merit for center‐frequency tunable bandpass filters comparison

Abstract

fifth harmonic signal is also suppressed and suppressed level at the fifth harmonic of 10 GHz is 30 dB. The measurements show similar fundamental responses while the proposed hybrid achieves a suppression improvement of 22 dB at the third harmonic frequency and 27 dB at the fifth harmonic frequency. The sizes of the conventional and second proposed hybrids are commeasurable. The phase difference between Port 2 and Port 3 is 88.8°at fundamental frequency. CONCLUSIONSTwo improved quadrature hybrids with the harmonic suppression are proposed. In comparison to the conventional quadrature hybrid, the proposed quadrature hybrid with the third harmonic suppression achieves not only a 29.5% size reduction but also a 18-dB suppression at the third harmonic frequency, and the other proposed quadrature hybrid achieves a 23-dB suppression at the third harmonic frequency and a 30-dB suppression at the fifth harmonic frequency. The proposed hybrids do not need lumped elements or via-hole grounding, which leads to low cost, simple fabrication process, and excellent design accuracy. ACKNOWLEDGMENTS