| Because of the increasing numbers of electronic equipment having been used in modern electronic warfare, radar communication integration equipment is the trend of the electronic equipment at the present, and even in the future. The signals of a radar communication integration equipment have both the features of radar signals and communication signals, an integration equipment modulates the communication information onto the carrier wave of a radar signal, it finishes sending and receiving of communication signals by radar transceiver, then compounding or decomposing radar signals and communication signals by software radio. Therefore, the radar communication integration equipment not only improves the confidentiality and the capability of anti-jamming, but also realizes the automation and networking of the radar and communication system. Aiming at the technical problems of the radar signal recognition, this paper improved the existing key radar signal recognition algorithms, and researched the recognition of the radar signals and communication signals by analyzing the features of radar signals and communication signals. The specific studies are described below: 1. In the electronic scout, the PRI recognition is processed after sorting, and the result of sorting directly determines the accuracy of the PRI recognition. Because of the harmonic interference and the error of parameter measurement, the pulse signal exists different proportions of spurious pulses after sorting, and the rate of PRI recognition is not high. Thus, this paper proposed an algorithm of PRI recognition based on symbolic method for the typical six PRI modes. Through symbolizing the sequence of PRI and DPRI and encoding the symbolic sequence, we can extract four parameters. The four parameters are F, H, C and P. Then, we can identify the six modes of PRI by comparing the four parameters with corresponding threshold respectively. The simulated results show that: the recognition rate is up to 95% when the proportion of spurious pulses is from 0 to 20%.2. Modern new system of radar signals have strong stability, namely the property of coherence. Currently, the most effective anti-jamming recognition method is the time-domain autocorrelation. But, this algorithm doesn’t identify the coherence automatically, because only through observing image can it identify the property. Thus, this paper proposed an improved time-domain autocorrelation. This new algorithm can process the signals which have non-fixed PRI mode by improving delayer, and we can symbolize the filtered pulse signal and encoding the symbolic sequences. Then we can distinguish coherence and non-coherence signals by extracting H1 from the encoding sequences. This paper did comparative experiments under the condition that the mode of PRI is fixed or sliding up and the modulation is convention or LFM. The simulated results show that: when signals have different modes of PRI and modulation and the SNR is greater than or equal 5dB, the recognition rate is up to 95%. 3. The most essential distinction between radar signals and communication signals is the difference in modulation. This paper selected NM, LFM, SFM and 4PSK as the modulation of a radar signal and selected MSK as the modulation of a communication signal to study. Then, the author corrected the Fast Discrete Fractional Fourier Transform and proposed an algorithm to identify the five modulations based on FRFT. We can extract H2, H3 from the p-v curve which achieved by FRFT transformation to identify different modulations. The simulated results show that: when the noise is Gaussian white noise and the SNR is greater than or equal 5d B, the recognition rate is up to 95%. |
