# An Intelligent DOA Estimation Error Calibration Method Based on Transfer Learning
## 4 Simulation and Result Analysis  
* **Experiment environment. ** The ideal array signal sample is a five-element uniform circular array signal with a frequency range of 100 MHz-200 MHz, signal-to-noise ratio set to 0-25 db, angle range of 0-360\({}^{\circ}\), and interval of 1\({}^{\circ}\). The actual signal sample is a five-element uniform circular array signal collected in the actual environment, with a frequency range of 150 MHz-200 MHz, an angle range of 0-360\({}^{\circ}\), and an interval of 5\({}^{\circ}\). **Collection of actual signals. ** We use a circular array of five-channel ultrashortwave correlation interferometer direction finding equipment to collect the actual signal samples, and the data obtained is the phase difference data of the actual signal. The receiving antenna array of the ultrashort wave direction-finding equipment we used to collect actual signal samples is five-element uniform circular array. The antenna array is divided into upper and lower layers. The upper layer is used to receive ultrashort wave spatial signal source and the working frequency band is vertical polarization 800-3000 MHz. The lower layer is used to collect a short-wave spatial signal source and the working frequency band is vertical polarization 30-800 MHz. We use the five-element uniform circular array of the lower layer to collect the actual signal samples. Figure 8 shows the positions of the five elements, the five antenna elements are evenly distributed on the circumference with radius \(r=0.75\) m, and the included angle between adjacent elements is 72\({}^{\circ}\). The frequency range is 151-200 MHz, the azimuth range is 0-360\({}^{\circ}\), the angle step is 5\({}^{\circ}\), and the frequency interval is 1 MHz. A total of 3600 samples of actual signal samples were collected, and some of them are shown in Table 1, where \(\theta_{ij}\) represents the phase difference between the array element \(i\) and array element \(j\). **Generation of simulation signals. ** We generate the simulation signal samples of a five-element uniform circular array with radius \(r=0.75\) m by computer. The frequency range is 100-200 MHz, the azimuth range is 0-360\({}^{\circ}\), the angle step is 1\({}^{\circ}\), and the frequency interval is 0.5 MHz, and the signal-to-noise ratio is 0-25 db. A total of 72,000 samples of actual signal samples were generated. * **Evaluation metrics. ** There are four evaluation metrics for the intelligent DOA estimation model: average absolute angle error (MAE), root mean square angle error (RMSE), maximum absolute angle error (MAXE), and the ratio of absolute angle error less than 1\({}^{\circ}\) (Ratio-1). The MAE is calculated as follows: \[\text{MAE}=\frac{1}{N}\sum_{i=1}^{N}|\theta_{test}-\theta_{label}|\] (28) The RMSE is calculated as follows: \[\text{RMSE}=\sqrt{\frac{1}{N}\sum_{i=1}^{N}(\theta_{test}-\theta_{label})^{2}}\] (29) The MAXE is calculated as follows: \[\text{MAXE}=MAX\{|\theta_{test}-\theta_{label}|\}_{i=1}^{N}\] (30) The Ratio-1 is calculated as follows: \[\text{Ratio-1}=\frac{num(|\theta_{test}-\theta_{label}|<1^{\circ})}{N}\] (31) Among them, \(\theta_{test}\) is the test angle, \(\theta_{label}\) is the actual angle, \(N\) is the number of test samples, and \(num\) is the operation of counting quantity.