RADAR

 

RADAR Signal Processing

Basic Principles

■ Radar is an acronym for RAdio Detection And Ranging;

 ■ An object detection system that transmits electromagnetic (EM) waves and analyses the echoes coming from the objects;

■ Why use radar?

– Radar can operate in any weather conditions (e.g. darkness, fog, rain);

– Radar can perform its function at long and short ranges;

– Radar can provide measurements in high accuracy

 

 

2. Radar Signal Transmission

 

Radar technology has been extensively used in practical applications owing to its signal has the characteristics of large bandwidth and time-width for the complex modulation to enhance the antijamming ability of the signal , whose signal transmission processes are displayed in Figure 2. The stability and reliability of signals can be optimized and improved from the multidisciplinary aspects of signal generation, amplification, reception, processing, and detection.

        

As a special equipment, Radar’s daily work is carried out with the help of a certain amount of information. Signal reflection can play a role in recognizing objects, which is also the focus of the development of radar technology in the current era. Normalized signal application will exert tremendous influence in practice. Especially in complex combat environment, once the problem of nonstandardized signal recognition is encountered, it will directly restrict radar synthesis ability. The quality of radar signal depends on the signal transmission loss, the interference degree of other signals, and the influence of transmission mode 

 

3. Radar Signal Design and Classification

 

In the field of modern radar signal utilization, the requirements of signal ability and function compatibility are increasingly stringent, which demands not only a large amount of data information but also a good system compatibility timely and punctual. The comprehensively used multidisciplinary radar signal design methods are shown in Figure. The design targets include the frequency division multiplexing, stealth targets, polyphase, analog, GSM-based passive, and waveform design. The corresponding objectives are different, and different design methods can be adopted with their respective design focus and highlights.

           

RS should be based on high range and speed of the resolution and then be designed with multidisciplinary algorithms. The radar signal characteristics and performance of various design methods are synthesized as shown in Table. Overall, high-performance radar signals processed by multidisciplinary hybrid algorithm are available.

 

3.3. Classification of Signal

Potential applications requiring classification of unknown radar signals include maritime barrier operations aimed at preventing illegal immigration , arms and drug smuggling , illegal fishing, and piracy . RS classification method is based on diverse radar signals which has been extensively studied and applied in the field of signal classification. Radar signal classification mode is illustrated in Figure. which includes the methods of the neural network , cluster method , similitude entropy , support vector machine, time-scale characteristics , modulation domain , basis function neural networks , Rihaczek distribution and Hough transform, frequency estimation , pulse repetition interval , bispectrum two dimensions , and so on. These classification methods synthesize the research methods of many disciplines, such as system control , heat transfer , and mathematics . These radar classification methods also reflect the integration of multidisciplines which is helpful to improve the performance of radar signals.

 

4. Radar Signal Processing Technology

 

The characteristics of radar signal include carrier frequency , its variation characteristics and pulse repetition frequency  and its variation characteristics, pulse width and its variation characteristics , antenna scanning type, antenna scanning period, signal spectrum, and signal azimuth, and there are a large number of intravenous characteristics of signals . The extraction of features from radar signals is influenced by many factors, which leads to the existence of subjectivity, speculation, and a certain degree of disordered distribution of the extracted features . There are many methods for radar signal processing including the application of single method  and the combination of multidisciplinary and multimethod (as shown in Figure). In order to eliminate the subjectivity of feature extraction and improve the accuracy of radar signal sorting, recognition, and processing, effective multidisciplinary and multimethods are needed to perform signal processing work .

 

5. Diversification of Signal Processing Technology

In addition to conventional processing methods such as correlated/uncorrelated processing, signal processing technology includes space-time adaptive (STAP), multiple-input multiple-output (MIMO), synthetic aperture (SAR/ISAR/CSAR), synthetic pulse and aperture (SIAR), and adaptive/cognitive radar signal processing technology based on artificial intelligence.

6. Research Challenges

Significant changes have taken place in the targets observed by radar, and the electromagnetic environment of radar work has deteriorated seriously, which has a tremendous impact on the development of radar.

 

6. Conclusion

With the increasing energy shortage, pollutant generation, and the rapid development of large-scale integrated circuits, the application of radar has gradually changed from military to civilian. It has been found that the development of radar in the field of industrial products is unprecedented in our daily life, covering transportation, search and tracking, navigation, and so on. Direct or indirect acquisition of high-quality and stable radar signals is the main research focus of researchers. Radar signal, as a special signal, has opened up new research fields and methods for meteorology, exploration, flight, and autopilot and even opened up new horizons. In this review, the design and classification of the radar signal are introduced by this blog primarily to reflect signal’s differences and advantages according to radar signal respective characteristics. And then the multidisciplinary processing technology of the radar signal is classified and compared in details referring to adaptive radar signal process, pulse signal management, digital filtering signal mode, Doppler method, and high frequency. It can be concluded that radar signals will become more common and stable in future applications.