Method And Implementation Of Non-Cooperative FSK And CPM Signal Demodulation

The signal demodulated by the receiver with unknown modulation informations is the so-called blind demodulation of non-cooperative signal. There has been a lot of research on the issue of non-cooperative blind demodulation of the FSK signal. Modulation and demodulation algorithm parameter estimation are mature. In order to avoid producing large spectral side lobes in the switching of FSK oscillator, the continuous phase FSK keying (CPFSK) evolved by FSK. FSK is also the precursor of the subsequent CPM signal.The significant characteristics of Continuous phase modulation (CPM) contains: continuous phase, constant modulus, attractive spectral and power efficiency. CPM is a non-liner modulation scheme. Meanwhile, CPM signals are a huge family. With different modulation parameters, such as, the modulation index, frequency shaping pulse, various CPM signals exhibit different properties. So the analysis of demodulation technique of non-cooperative CPM signal has important research value.This thesis divide blind demodulation of CPM signals into modulation estimation Parameter algorithms and demodulation algorithms.Then they are deeply studied. The main contents are listed as fol lows.1. Analyze the cyclic-spectrum characteristics of CPM signal and cost function feasible to the carrier frequency, modulation indexes and symbol period estimation algorithm. The study the modulation index and is then adjusted to lay the foundation for. The simulation proves the performance of the algorithm. It shows that the algorithm estimates stable performance.2. The binary representation of the decimal CPM-signal and its frequency-domain relationship with binary CPM-signal are deduced. Computer Simulation proves that the modulation order estimation algorithm based on the cyclic-spectrum characteristics of CPM is not limited by the signal modulation order and the frequency-shaping pulse.3. Analyze the internal relationship between the length of CPM-signal frequency-shaping pulse and auto-correlation functions. Computer simulation has been done with the previously estimated modulation order. And it proves the correlation length estimation algorithm applicable to any modulation index.That indicates the algorithm facilitates hardware implementation and has high estimation accuracy.4. Analyze coherent and non-coherent demodulation algorithm of CPM-signal comprehensively. Demodulation algorithm based on composite trellis diagram of CPM-signal is deeply studied. The algorithm not only introduces multiple component trellis diagram and state coupling transitions, but also achieves effective tracking of Doppler frequency shifting. Theoretical analysis and simulation show that the number of root trellis diagram over than 4, the non-coherent demodulation algorithm appropriating to the best demodulation situation. At the same time, it has the advantage of anteing the initial phase and tracing the frequency shifting.5. After that, a blind demodulator structure of non-coherent CPM-signal is designed. Then this paper divided the module of the blind demodulator. This paper gives the program processes and optimization methods of the algorithm code which realized DSP. The complex between the Vitoria algorithm and the coupling algorithm in the demodulation algorithm based on composite trellis diagram are also analyzed. Finally, demodulation scheme of composite trellis diagram based on multi-core DSP is composed. This kind of scheme can achieve large amounts of data parallel processing by multi-core parallel processing.