## 1 Introduction  
Recently, various countries have been creating and enforcing energy-related regulations to reduce environmental pollution caused by fossil fuels [1; 2; 3]. In addition, there is increasing concern regarding the depletion of fossil fuels, and research is underway on various renewable energy sources to replace them. Energy harvesting converts natural energy into electrical energy. Among the various energy harvesting methods, the use of a mechanical vibration component is a typical power generation method [4; 5; 6; 7; 8]. However, energy harvesting is mainly used for low-power generation because of irregular power generation conditions such as wind or waves [9; 10]. To solve these problems, many studies have been conducted to utilize resonance phenomena in energy harvesting. A representative case study is the wingless wind turbine presented by [PERSON] et al. [11] The generator is in the form of a cantilever beam fixed vertically to the floor, and it harnesses the force of the turbulence generated by natural wind passing through the pillars. The energy from the force of the turbulent flow generated at this time is dispersed over a wide low frequency band. Permanent magnets were installed on both sides of the outer wall and a nonlinear resonance frequency model was used to generate power over the widest possible frequency band. In another study using pendulum resonance, [PERSON] et al. [12] proposed a pendulum resonance generator model in which the frequency of an artificial pool for collecting wave energy matches the resonance frequency of the pendulum. [PERSON] et al. [13] proposed a model in which a pendulum is installed on a rotating body and the rotational vibration component is used for power generation. In addition, [PERSON] et al. [14] presented an extremely low frequency generator model that collects the energy generated when a person moves using a double pendulum structure and used the motion of the pendulum for generation. Energy harvesting devices usinghigh frequencies, such as radio frequency (RF), have been studied, not in low-frequency power generation environments such as wind or waves. [PERSON] et al. [15; 16; 17; 18] researched a high-frequency broadband RF energy harvesting device using a metamaterial with resonant frequency. [PERSON] et al. [19] studied broadband planar antennas by using H-shaped Resonators (HSRs). [PERSON] et al. [20] reproduced an antenna structure that can utilize resonance from 3.5 GHz to 5 GHz by placing 3D MIMO nano-cells in an array structure. Research on power generation using resonance has also been conducted out using piezoelectric elements or linear electromagnetic induction methods. [PERSON] et al. [21] advanced the research on generating energy by attaching a piezoelectric element to the hanger structure. [PERSON] et al. [22] installed two permanent magnets facing the same pole, constructed a nonlinear resonance frequency model, and proceeded with research on generating energy through electromagnetic induction in the case-surrounding coil. Research has also been conducted to utilize the pendulum as a medium for power generation. [PERSON] et al. [23] presented a generator model that utilizes the resonant frequency of the pendulum's rotational motion by suspending the pendulum at the end of a cantilever beam. [PERSON] et al. [24] presented a spring-type pendulum using a clip, and a power generation model with piezoelectric elements attached to each clip. [PERSON] [25] presented a model in which a vertically moving vibration absorber was installed on the main body and electricity was generated using magnets and coils at the ends of the vibration absorber. The above studies presented various generator models using resonance, and defined forces used for resonance, such as turbulence owing to wind and wave force.