A Compact High Out of Band Rejection Filter With High Power Capacity

A compact high out-of-band rejection filter with high power capacity is designed. The filter adopts a 7th-order cavity structure, consisting of seven coupling units and two taps arranged in a linear distribution. Each coupling unit comprises one metal resonant rod, three metal resonant plates, one dielectric resonant column, and one metal tuning screw. By reducing the height of the metal resonant rod to decrease inductive effects and introducing three metal resonant plates to enhance capacitive effects, the resonant frequency is adjusted to a very low range, achieving miniaturization. Introducing dielectric material around the metal tuning screw enables significant adjustments in Sparameters within a small insertion depth range. Electromagnetic simulation results demonstrate that the filter achieves a voltage standing wave ratio (VSWR) <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\leq 2$</tex> and an insertion loss <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\leq 0.5 ~\text{dB}$</tex> within the passband of 0.63 GHz to 0.79 GHz. Out-of-band rejection exceeds 30 dB in the ranges of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$0.2 \text{GHz}-0.57 \text{GHz}$</tex> and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$0.88 \text{GHz}-1.1 \text{GHz}$</tex>, with rejection reaching 109 dB at 1.1 GHz. In the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$1.1 \text{GHz}-6 \text{GHz}$</tex> range, rejection remains <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\geq 109 ~\text{dB}$</tex>, peaking at 155 dB at 1.21 GHz. These results highlight exceptional out-ofband rejection capabilities, significantly enhancing system antiinterference performance.