线性调频信号的另一个缺点可以从图3.6中看出。其输出波形的主瓣两边存在

Another shortcoming of the chirp signal can be seen in Figure 3.6. There are many side lobes on both sides of the main lobe of the output waveform, just like the side lobes of the antenna pattern. Its value is similar to that of the antenna with constant amplitude feed. The first side lobe is about -14 dB. In order to have good performance to avoid distance side lobe interference, the first side lobe needs to be reduced to -25 dB or -30 dB. This shortcoming can be solved by applying the same principle of reducing antenna side lobes, that is, using a compensation filter that reduces side lobes after matching the filters, or combining the two in one filter. The frequency-weighted reduction of side lobes essentially introduces a little mismatch consciously, so it will make the main lobe slightly wider and the action distance slightly reduced, as shown in Figure 3.6. By comparison, the ratio of the main and side lobes after windowing becomes larger, the side lobes decrease to below, but the width of the main lobe increases, about 1.5 times that without the window, and the main lobe also has a certain loss

Another drawback of the linear FM signal can be seen in Figure 3.6. There are many side lobes on both sides of the main flap of the output waveform, like the side lobe of the antenna orientation map, with a value similar to that of the antenna of the isometric feed, with the first side lobe being about -14 decibels. In order to have good performance to avoid distance sidelobe interference, the first side lobe needs to be reduced to -25 decibels or -30 decibels. This disadvantage can be solved by using the same principle of reducing the antenna side lobe, i.e. using a compensation filter to reduce the side lobe after matching the filter, or combining the two in one filter. The frequency-weighted reduction sidelobe essentially introduces a little mismatch, thus making the main lobe slightly wider and slightly smaller, as shown in Figure 3.6. Through comparison, it is known that the main side valve ratio after the window becomes larger, the side lobe is reduced to the following, but the width of the main flap has increased, about 1.5 times when the window is not added, the main flap also has a certain loss.

Another disadvantage of the LFM signal can be seen in Figure 3.6. There are many side lobes on both sides of the main lobe of the output waveform. Like the side lobe of the antenna pattern, its value is similar to that of the antenna fed with constant amplitude. The first side lobe is about - 14 dB. In order to avoid range sidelobe interference, the first sidelobe should be reduced to - 25 dB or - 30 dB. This shortcoming can be solved by using the same principle of reducing antenna sidelobe, that is, a compensation filter with reduced sidelobe is used after the matched filter, or the two can be combined in one filter. A slight decrease in the width of the main lobes slightly reduces the width of the main lobe as shown in Fig. 3. The results show that the ratio of the main lobe to the side lobe increases and the side lobe decreases to below, but the width of the main lobe increases, which is about 1.5 times of that without windowing<br>