The Study Of The Theory Of The Three Dimensional Modems

Based on the mathematical description of the space electromagnetic field, a novel approach to the three-dimensional modulation by the signal amplitude, polarization angle and polarization phase angle of an electromagnetic signal in wireless communication is presented in this paper. The model of the three-dimensional modulation signal is first given. Then, the transmission implementation of the three-dimensional modulation signal is discussed by a vector antenna.With the different antenna number and locations of the transmitting and receiving antennas, the different demodulation methods for the single-source single vector antenna, single-source vector antenna array, and multi-source vector antenna array cases are respectively studied to demodulate the received three-dimensional modulated signal. When the transmitting and receiving antennas are aligned or when the direction of arrival is known, a least squares demodulation method is presented. The total least squares demodulation method is given to the situation where the direction of arrival is unknown. The weighted least squares demodulation method is used to handle the antennas components with different noises. An ESPRIT decoupling based least squares demodulation method is proposed to the multi-source input case. Furthermore, the symbol error probability and the performances of all the proposed demodulation methods mentioned as above are analyzed in this paper. Both the analysis and the simulation results show that a high information transmission rate and a low symbol error probability can be simultaneously obtained by the proposed three-dimensional modulator and demodulator. Meanwhile, how to select the appropriate demodulation method under different cases is also given.A lattice theory approach to the construction of novel three-dimensional signal constellations is reported. The constructed three-dimensional hexagonal constellation is shown having the highest coding gain and the minimum average transmit power. The calculation methods of the basic coding gain, forming gain, average power and symbol error probability of the proposed three-dimensional constellations are also given. By means of these given calculation methods, we compare the novel three-dimensional constellation with the existing three-dimensional constellation. The analytical results show that our three-dimensional constellation approaches to the lowest symbol error probability and the minimum average transmit power. The power spectrum characteristics of the three-dimensional modulation signal corresponding to the three-dimensional constellation are derived. The suppression methods of the discrete spectral components of the three-dimensional hexagonal constellation are given. How to design the three-dimensional constellation which does not contain the discrete spectral components and form the pulse signal is discussed. Both the analysis and the simulation results show that the discrete spectral components in the power spectrum can be controlled.The implementation techniques of the three-dimensional modulator are studied. The model and the circuit of the three-dimensional modulator are implemented by the software SystemView. The simulation results of the signal waveform, the distribution of constellation points, the power spectral density curve and the symbol error probability performance are given. The simulation results verify the correctness of the analytical results.