The Cpld Technology Applied Research, In The Dense Frequency Than The Wide Area Broad-spectrum Pseudo-random Signal

Pseudo-random multi-frequency (PRMF) signal is invented and named by academician He Jishan. The bandwidth of PRMF signal is controllable, it's energy concentrates on several frequencies, which are equally spaced on log scale coordinates. It is ideal excitation source for electrical exploration such as Induced Polarization method and Controlled Source Electromagnetic method.In this dissertation, the device structure of complex programmable logic device LC4256V-100T from Lattice semiconductor is introduced by the numbers. High density in-system programmable logic device, include CPLD and FPGA, has integrated numerous logic functions into a single chip. It is easy to develop a System-on-Chip by using this device. They are the one's that can be programmed and reconfigured the logic functions while on the system board which is suitable for faster prototyping.Hardware description language VHDL is very powerful for the application design of programmable logic device. It can produce square waveform arbitrarily by using Finite State Machine in VHDL. In this paper, the binary sequence is constructed based on the time domain expression of pseudo-random multi-frequency waveform. Using Finite State Machine, the binary sequence is converted into pseudo-random multi-frequency signal.A new signal generation cell is designed in this paper, carried on the complex programmable logic device LC4256V-100T from Lattice semiconductor and developed with the tool of hardware description language VHDL. It can produce sixteen different waveforms, and has twenty-five frequency options which divided from four dense frequency ratio initial frequencies. The generated pseudo-random multi-frequency signal contains up to thirteen frequencies. Its frequency can be more higher rather than low which is generated by the control of microprocessor 8031. The design reduced the number of discrete components and power costs effectively, and enhanced the system more robuster. The working frequency of this design can be up to 80MHz and the signal frequency range from 2-20Hz to 110KHz can be generated.It is a feasible design tested by carrying out water tank experiments.