## 3 Method for Beam Steering  
### Phase Calculation for Electronic Beam Steering  
In the previous section, we designed the antenna for the radar system. In this section, we will design a power divider. In a radar system, each element of the antenna array must be supplied with the same power to minimize mutual interference and improve accuracy. In a radar system that is actually in operation, a power amplifier exists for each channel. Through this, the same power is supplied. Additionally, the amplitude can be adjusted for beam steering. However, since this paper will conduct a simple beam steering test, a power divider that can apply the same voltage to each antenna element is sufficient. The designed power divider must minimize the phase difference between each output port. If you use such a carefully designed power distributor, you can secure an ideal beam pattern during frontal steering. Basically, the power divider is designed in the form of a power of 2 to make it easier to match the impedance of the feed line and is widely used as a method of minimizing the phase difference between output ports. Additionally, because the voltage is divided in half, there is almost no voltage difference between each port. To ensure smooth impedance matching between the input and output of the power divider, the power divider was designed considering the Quarter Wave Transformer (QWT). QWT was inserted into the part where each feed line is divided into two branches. Since the antenna array of the radar system covered in this experiment is 4 \(\times\) 4, a 16-channel power divider was designed. The designed power divider is shown in Figure 7(a). The power divider actually manufactured based on this is shown in Figure 7(b). Figure 6: S-parameter measurement setup: (**a**) block diagram, (**b**) the free space measurement system. Figure 7: Comparison of the simulated and measured results: (**a**) \(S_{11}\) (**b**) \(S_{21}\). First, a simulation was performed to measure the phase of each port. The phase of each port is shown in Figure 9a. At 3.0 GHz, the phase difference between ports was approximately 0.5\({}^{\circ}\), which was almost non-existent. The phase difference of the actually manufactured power divider is shown in Figure 9b. The phase differences between the simulation results and the actually measured power distributor ports are all about 0.5\({}^{\circ}\), which is similar to the simulation results. The gain (dB) of the measured output ports can be obtained through simple calculation by extracting the real and magnitude values separately. Figure 10a is the result of simulating the gain of each port. It can be seen that the remaining values, except for \(S_{11}\), have the same power distribution of approximately \(-12.7\) dB. Figure 10b is the result of actually measuring the gain of each port. Likewise, it can be seen that the power is distributed almost equally for the remaining values, except for \(S_{11}\), at about \(-12.8\) dB. Figure 8: A 16-channel power divider: (**a**) simulation, (**b**) fabricated. Figure 9: Phase difference for each port: (**a**) simulation, (**b**) measured. ### Phase Calculation for Electronic Beam Steering  
There are two primary methods for beam steering in radar systems: mechanical beam steering and electronic beam steering. Mechanical beam steering involves physically rotating the antenna to align it with the desired beam steering angle. However, this method requires separate manufacturing of rotating components, leading to increased system size and slower mechanical movement. On the other hand, electronic beam steering adjusts the beam pattern by applying varying phase and amplitude differences to each element of the array antenna. This method enables faster beam steering compared to mechanical methods, and since the antenna remains fixed, there is no need for additional mechanical parts. Consequently, electronic beam steering offers the advantage of reducing system size and enabling real-time beam steering.