An Oscillation-Based Bandpass Filter With a Structure of Two Magnetically Coupled Orthogonal Cantilevers

Abstract

In this article, an oscillation-based bandpass filter with a structure of two magnetically coupled orthogonal cantilevers was proposed for the first time. Two magnetically coupled orthogonal cantilevers with a frequency ratio of 1:2 was adopted, including an input cantilever and an output cantilever. When the input cantilever was driven to resonance directly by a sweep periodic excitation force, a rectangular-like <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$A$ </tex-math></inline-formula> – <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$f$ </tex-math></inline-formula> curve was observed in response to the output cantilever theoretically because of internal resonance, which showed great potential for bandpass filter applications. A macro prototype with a center frequency of 73.1 Hz and a 3 dB bandpass width of 6.2 Hz was developed for experimental verification. The experimental results showed that the output signal in the passband was generally linearly related to the input signal as the voltage of the input signal was in the range of 200–600 mV. In addition, the passband ripple could be greatly improved by limiting the deviation of modal frequency ratio by adjusting the center distance of the two magnets in the range of 7.5–8.0 mm. The proposed oscillation-based bandpass filter provided a new idea for the design of filters. Compared to some conventional electronic filters, it possesses a higher reliability and is immune to electromagnetic noise, which is capable of filtering signals in extreme environments, such as high-temperature environment and strong-electromagnetic-noise environment.