The Launch Waveform Optimization Based On Meteorological Radar

At present Doppler weather radar has been widely used for meteorological observation in our country. The electromagnetic wave that launched by the Doppler radar is the single frequency pulse waveform routine. Because of the waveform is relatively simple, the range resolution relative to other modulation signal waveform is smaller, while The detection speed and range resolution not be taken into account when the radar transmit power is fixed. It shows certain limitations on the development of radar meteorology. With the development of radar technology, multi modulation technology develops rapidly. Compared with the traditional radar, the information provided by these new modulation signal radar for meteorological radar detection are more accurate. It makes a great contribution to the development of meteorological radar. Therefore, the waveform optimization of weather radar is very important.The paper is based on the theory of software radio and radar detection based on principle and use microwave signal generators, spectrum analyzer and computer etc. To built a small radar system, in order to realize radar detection process. This paper analyzes the four kinds of radar waveform signal from the signal processing point of view.The other three kinds of waveform signals used in this experiment were:linear FM signal, the13bit Barker code signal, the13bit Barker code modulation and linear frequency modulation combined waveform signal. These three signals are large time width and bandwidth product signal and all need the echo pulse compression to the corresponding. Compared to the traditional single frequency pulse signal, the three kinds of signals have good range resolution and velocity resolution. And it could balance the relationship between emission energy and the detection distance, and get the weather echo signal in higher meteorological sounding, so that the signal received by the instrument are more real and accurate after the filtering processing. At the same time it also can calculate a series of parameter information of accurate weather intensity and distance. Due to the compression processing method and Doppler sensitivitypulse of the three signals is different, so the process of these three signals is not the same. The three kinds of the echo signal under the same power conditionis different. The paper make a distinction between Doppler sensitivity and pulse compression processing methods.Due to the Doppler’s effect is larger, from meteorological observation, so we need to make a compensation to the13bit Barker code waveform signal Doppler and the process is more complex. The linear frequency modulation signal waveform and combined waveform signal is low sensitivity to Doppler, it can be directly used to matched filter processing in pulse compression processing. Since the spectrum signal has no zeros, It decided by13bit Barker code sidelobe pulse compression in the remaining time after weighted. When the sidelobe is still high, we can also do a weighted processing, processing after the sidelobe performance is better than the linear frequency modulation signal. Although the three wave would cause a loss of signal to noise ratio to some extent in pulse the compression process, but in the meteorological sounding those are acceptable.Small radar system built in this experiment was used Perl and MATLAB language program, LAN network system consists of a switch and a crossover cable through the computer to realize the program control. This study conducted a survey on the actual rainfall, waveform signal through different signal source, a spectrum analyzer to receive data, use MATLAB the software processing, the transceiver and data processing were controlled by computer.