Internally loaded cross-coupled open-loop resonators for a miniaturized bandpass filter using integrated passive device technology

In this article, an open-loop resonator with internally loaded side-coupled double open-loops is proposed for use in the design of a compact bandpass filter with high selectivity and improved out-of-band rejection characteristics. The outer main open-loop resonators are designed to operate at the center frequency of 7.7 GHz. In addition, side-coupled double open-loops are used to enhance electromagnetic coupling to provide high selectivity response and suppressed harmonics with an additional transmission zero at the bandstop region. The operating frequency shifting is performed by tuning the electromagnetic coupling strength without changing the configuration of the outer main open-loops. To achieve a miniature size with high selectivity, the integrated passive devices semiconductor fabrication technology is implemented to achieve a compact size of 2.2 × 4.98 mm², which is a compact size for X-band downlink satellite communication applications.