Papers by Keyword: Direct Digital Synthesis

Abstract: Wireless anti-jamming data link was widely applied in modern electronic warfare environment recently. Anti-jamming function of wireless data link was realized by constantly changing the signal carrier frequency according to a specific pseudo-random sequence. Frequency switching time and bandwidth were the main factors of frequency hopping anti-jamming performance. With the development DDS technology, frequency switching time and bandwidth had been improved significantly. The hardware of anti-jamming data link node in this paper was composed of frequency synthesizer module and FPGA control module taking advantage of both DDS technology and FPGA. Frequency synthesizer module was under the control of FPGA to output appropriate frequency carrier signal. FPGA control module is designed in Quartus II software development platform environment. The frequency tuning and control of frequency synthesizer module output signal were operated through serial or parallel I/O ports. Two kinds of configuration mode were designed in FPGA control module: serial configuration mode and parallel configuration mode. Digital signal data process in serial configuration logic and parallel configuration logic of FPGA control module were studied especially. The main function of serial configuration logic and parallel configuration logic were realized to process the digital signal data under appropriate time sequence correctly. By the correct time sequence of reading and writing function, frequency synthesizer module worked well with FPGA control module. Simulation and experiment results showed that anti-jamming data link node outputted stable frequency carrier signals by the excellent processing of digital signal data transferred between FPGA control module and frequency synthesizer module.

Abstract: A new quadrature signal generator based on Direct Digital Synthesis (DDS) algorithm for digital demodulation of MEMS gyroscope was proposed in this paper. To avoid quantization error, the dual-accumulator with signal-ROM structure was adopted. This signal generator was realized in FPGA chip, which could be quit compact to realize all digital demodulation in one chip. Simulations and tests of the generator were carried out. The test results demonstrate that the signal generator achieves high stability. The standard deviation of the frequency is 0.075Hz and the standard deviation of the amplitude is 0.037mV.

Abstract: A method to simulate the Doppler frequency shift of high dynamic signals of Global Navigation Satellite Systems (GNSS) is provided in this paper. The methodology of the method based on third-order Direct Digital Synthesis (DDS) is introduced and the efficient implementation architecture is proposed. The design criteria of the DDS are investigated according to the precision and dynamic range of the Doppler shift. The simulation results are also demonstrated, which indicate that the method is available for the high precision Doppler shift simulation of GNSS signals.

Abstract: As the key junction between the ground and underground, hoisting systems as well as mines themselves are of vital importance to coalmine production. Laser ranging method is studied as a new solution of getting the real-time position directly. Furthermore, multi-scale phase based laser ranging principles are utilized in the system. The paper is aimed to conduct research into the problems existing in standard signal generating while using laser to locating the hoisting container, and to design standard sine generator circuits with DDS technology and DDS devices AD9850 to generate multiple frequency standard signals. In view of the serious noise disturbance in high frequency output, 4-order Chebyshev low-pass filter is designed, by using the integrated analog filters LT 6600-15, to filter the sine signals from AD9850 and to effectively weaken the noise disturbance. The established practical circuits are tested, obtaining trillion level high frequency and low frequency sine signals and fulfilling the requirements for the location system of hoisting containers.

Abstract: A signal generator with adjustable frequency, phase and duty cycle is designed in this paper. The design of this signal generator is based on the technology of direct digital synthesis (DDS).The classic structure of DDS is presented and its principles are introduced in detail. The key modules of the design such as phase accumulator and pulse width processing are implemented by verilog HDL language. With suitable FPGA, the designed signal generator and all modules of the design are simulated successfully in Quartus II.

Abstract: When designing signal generator with adjustable frequency based on direct digital synthesis technology (DDS), it is very important to calculate the frequency control word. To address the shortcoming of large computation, low efficiency of frequency setting, more storage space occupied or significant cumulative errors of frequency setting when calculating frequency control word with traditional methods, a novel calculation way for frequency control word is researched in this paper. This new method does not need large computation and more space and simultaneously it can decrease the error greatly, which plays an important role in improving the frequency setting speed and precision in signal generator.

Abstract: A direct digital synthesis (DDS) waveform generator for electromagnetic non-destructive testing (NDT) is presented in order to improve the measurement quality. The advantage and disadvantage of analogue and digital circuit waveform generators are analyzed. The DDS technique is preferred. The principle of DDS technique is introduced and the hardware and software design of a DDS waveform generator is described. The characteristics of the waveform generator based on a DDS chip AD7008 are that the signal frequency is of high stability, high precision and high resolution. Furthermore, the amplitude, frequency and phase can be continuously adjusted. An experimental electromagnetic NDT system is built and the testing results are analyzed. The system uses digitally generated sine waves as exciting, reference and demodulation signals. Experimental results show that the DDS waveform generator improves the signal-to-noise ratio. This kind of wave generation circuit is used not only in NDT but also in other instruments, such as electrical impedance tomography (EIT), which need signals with high stability, high precision and high resolution.