## 3 Experiments and Results
According to the equation \(SE=20\times\log_{10}(E_{0}/E_{s})\)[22], in which \(E_{0}\) and \(E_{s}\) represent the electric field intensities in open environment and covered with the resonator sample, respectively, the measured shielding effectiveness can exceed 33 dB,  
Figure 5: **(a)** Power frequency electric field shielding performance measurement setup. **(b)** Measured photograph when the electric wire is close to the sensor. **(c)** Measured electric field intensities at different distances (black dots). The red line indicates the fitting curve. Measured photographs when the electric wire is close to the **(d)** permalloy lid and **(e)** cross-meandering resonator sample. which is comparable to that observed in previous works [26; 28] (Table S1 of the Supplementary Materials). Hence, the proposed cross-meandering resonator could find potential applications in power frequency electromagnetic field shielding of UHV power grids. In addition to testing the shielding performance of the power frequency electromagnetic field, we also studied the transmission of wireless communication signals by the cross-meandering resonator sample. Herein, an air pressure sensor (Figure 6a) composed of a MEMS piezoresistive pressure sensor, temperature sensor, and integrated narrow-band Internet of Things (NB-IoT) communication module was independently developed. The sensor can send barometric data to the software platform via a 900 MHz wireless communication signal. By utilizing the low power technology and temperature compensation algorithm, the air pressure sensor monitoring system has the advantages of low power consumption, low cost, high accuracy, and online monitoring. As in the previous experiment, the air pressure sensor is suspended in the open-sided shielding box, as depicted in Figure 6b. Three controlled experiments--the whole device in an open condition (Figure 6b), with the permalloy lid on (Figure 6c) and covered with the cross-meandering resonator sample (Figure 6d) were also performed. It should be noted that the sample in Figure 6d is the same as that in Figure 5e, and the difference in color is caused by different ambient light. If a barometric value is displayed in the online post-processing platform, the wireless communication signal transmitted by the air pressure sensor passed smoothly through the cross-meandering resonator sample and was successfully received by the NB-IoT base station. In this case, we used the symbol of \"\(\sqrt{\text{\text{\text{\text{\text{\text{\text{\text{\text{\text{\text{ \text{\text{\text{\text{\text{\  
When the shielding box was open, the wireless communication signal was effectively received by the NB-IoT base station. The probability is not 100% because the communication signal transmitted between the self-developed sensor and the base station was unstable. As a contrast, the wireless communication signal was completely blocked by the permalloy lid. When the shielding box was covered by the cross-meandering resonator sample, the chance of the signal being received by the NB-IoT base station was about 53%. The low probability was attributed to the instability of the communication signal and resonant frequency deviations. To remove the instability of the communication signal between the sensor and NB-IoT base station, a 2.4 GHz wireless communication module (left part in Figure 7a) and the signal receiving module (right part in Figure 7a) were brought from Shenzhen Ruidilai Technology Company Limited (Shenzhen, China). By adjusting the structural parameters of the cross-meandering resonator, the resonance frequency shifted to near 2.4 GHz. The fabricated resonator sample composed of the permalloy material is displayed in Figure 7b. Then the communication module was placed in the shielding box, and the receiving module was inserted into a computer.