Research And Application Of Direct Digital Synthesis Technology

Frequency source is an important component of modern large-scale electronic equipment and plays a significant role in the system performance. Beginning in the 30's of the 20th century, frequency synthesis theory is essentially one kind of frequency simulation (digital) computation technologies, which obtains a lot of high stability frequencies by implementing adding, reducing, multiplying, dividing(mixing, frequency multiplication, frequency division and so on) of the oscillating source's frequency, applies artificial or automatic control method (program control), realizes each type of frequency transformation and synthesizes each type of different signals.This thesis carries on a fundamental study on frequency synthesis technology and its applications, especially to the associated problems of noise interference signal's synthesis, major work includes:1. Based on the development history of frequency synthesis technology, the work principle, performance analysis and actualizing method of direct frequency synthesis, indirect frequency synthesis and direct digital frequency synthesis are summarized; the work principle, output characteristic and mixed discrete performance of the direct digital frequency synthesis technology rapidly developed in recent years are also discussed in depth in the thesis.2. The noise interference signal form and realization mode required by enveloped interference are analyzed and discussed. Based on the demand of electronic countermine, especially radar electronic field for noise signal, combining with the characteristics and advantage of direct digital frequency synthesis technology, the realization method of total digital noise source is proposed for the first time, which uses direct digital frequency synthesis technology as the hardware base and Monte Carlo method to produce random data sequence, controls the output amplitude, frequency and phase of DDS directly, and obtains the noise signal amplitude modulation, frequency modulation and phase modulation. The characteristics of this type of noise source are simple system structure, convenient producing debug, low cost, multi-style modulation mode realized without hardware circuit change, and change of the noise distributed performance.3. The production of random sequence is the key of digital noise source. The production method of random sequence is discussed in depth in this thesis, RAND function in ANSIC language is analyzed and validated and the function is used to produce random sequence in practical application.4. Based on the principle idea of digital noise source proposed above, combining with the fact of our radar army, the design, facture and field debugging of certain meter wave radar interferometer are finished and the method of total digital noise source may produce the needed noise disturbing in practical application, which actualizes expected disturbing effect, has broad application fields and high value in practical applications, and gained third-class award of advancement of Military Science & Technology in 2006.5. Aiming at encryption failure incidents caused by filching secret information by using computer radiation, also applying the principle idea of digital noise source, inner-installed computer interferometer is designed, which may produce electromagnetic radiation of wide-band enveloped interference signal of 0～1000MHz to prevent encryption failure. The interferometer has been authenticated with Military's B-level by Chinese People's Liberation Army Information Authentication Center and produced for thousands of army equipment.6. In order to fully utilize the technique advantages of our army's active duty meter-radar, meter-radar self-adaptive stable local oscillator system based on DDS technology and digital frequency measurement method is designed, debugged and finished, which may solve such technical difficulties as digital frequency measurement, DDS output mixed-discrete restrain, system anti-jamming, and greatly improve the tactical technology level of active duty meter-radar. 7. In the national 863 project"Research of key technology and equipment of low cost, high performance vacuum fuse-welding sealing", the quartz crystal oscillator test system is designed by using high frequency pixels provided by DDS and may accurately measure the change of resonance impedance of quartz crystal, which may implement the measurement of the vacuum level in a MEMS package through the theory that its resonance impedance changes with the change of vacuum level. Then it has been found that vacuum level in a MEMS package is not that in the inner cavity of package equipment as we always think. Furthermore the improvement plan for package is proposed.