## 3 Experimental Results, Verification, and Discussion
Based on our calculations, the ENOBs of channel 1 and channel 2 are 4.7417 and 4.3042 bits, respectively, with average peak-to-peak values of 1658 and 1660, indicating that the signal power of channel 2 is slightly higher, but the difference is quite small. Figure 7(a2,b2) depict the detailed raw data collected within the first 20 ns, making it easier to observe the peak jitter of channel 2. Figure 7(a3,b3) show the data and corresponding fitted trigonometric signals within the first 20 ns after implementing the PLM and normalization processing, represented by solid blue dots and solid red lines respectively. It can be observed that the peak jitter has been improved, and the original data match the fitted signal well. Based on our calculations, the ENOBs of the two channels are 4.7418 and 4.3229 bits, respectively, which are higher than the values of the original data, and the improvement in the ENOB of channel 2 is more significant. Figure 7(a4,b4) illuminate the normalized power spectrum information. The top three frequencies and power information with the strongest power are marked. It can be observed that the strongest frequency in both channels is 200 MHz, which is consistent with the test signal frequency, i.e., the main frequency. However, the power of channel 2 is higher than the other frequency, which is consistent with the test signal frequency, i.e., the main frequency is higher than the other frequency. 1 is slightly lower than that of channel 2, indicating that the main frequency intensity of channel 2 is relatively larger, but the difference is not significant, consistent with the findings in Figure 7(a1,b1). In addition, the power levels of the second- and third-strongest spectra are similar, but it is evident from the graph that the power heights of 400 MHz and 600 MHz relative to noise base in channel 1 are higher than those in channel 2, indicating that the noise base of channel 1 is relatively low. The blue solid horizontal lines in the graph indicate the average peak values of the noise base, which are approximately \(-74\) dB and \(-66\) dB, respectively. Therefore, compared to channel 1, the low ENOB in channel 2 is mainly caused by noise, and the impact of nonlinear distortion is relatively small. Figure 7(c1) shows the result of directly synthesizing the two channels after using the PLM and normalization treatment within the first 20 ns, and it can be found that the intensity non-uniformity has been improved. Figure 7(c2,c3) depict the fitted signals according to the data in Figure 7(c1) by the frequencies 200 MHz and 5.0 GHz, respectively. The solid blue dots represent the directly synthesized data, and the solid red lines represent the fitted signal. It can be observed that the collected data do not match the fitted signal very well for Figure 7(c2), with the corresponding ENOB is only \(-3.1627\) bits. For Figure 7(c3), the collected data are relatively consistent with the fitted signal. Based on our calculation,  
Figure 7: Experimental results of 200 MHz collected by the PADC system. (**a–d**) Data of channel 1, data of channel 2, synthesized signal directly, and synthesized signal after shift correction. its ENOB reaches 2.5268 bits, indicating that the main frequency of the directly synthesized signal is no longer 200 MHz but rather, 5.0 GHz. Figure 7(c4) shows the power spectrum information of the directly synthesized signal after applying the PLM and normalization. The top four frequencies and power information with the strongest power are marked in the figure. Among them, the power at 5.0 GHz is the highest, followed by 200 MHz, which is 17.26 dB lower than the maximum power. Therefore, the data collected in Figure 7(c3) are more consistent with the fitted signal. The frequencies with higher powers are 4.6 GHz and 600 MHz. Thus, there is a significant nonlinear distortion for the directly synthesized signal. Additionally, it can be observed that the average peak value of the noise base is approximately \(-\)70 dB.