Dajian Zhang

Application of Smart Antenna Interference Suppression Techniques in TD-SCDMA Systems

The quality of mobile communications have been severely affected by interference among users in TD-SCDMA, in allusion to this problem, the smart antenna adaptive beam-forming algorithm are researched deeply in the thesis. According to the technical features that smart antenna can adaptive track the user signals realize the design and simulation of smart antenna in interference suppression, and compare and analyze the result then prove the advantage and disadvantage of two algorithms. We simulates the adaptive filter with MATLAB, the results prove that it can suppression interference in TD-SCDMA system with the effectiveness.

Analyze Electromagnetic Compatibility of High Frequency Switching Power Supply by Finite Element Method of Harmonic Balance

This article offers the analysis of electromagnetic compatibility of high frequency switching power supply by finite element method of harmonic balance theoretically. Finite element method of harmonic balance is different from traditional time-domain finite element method and transient analysis method. Finite element method of harmonic balance produces solution using linear synthesis of sine function and represents wave figure using coefficient of sine function. It combines steady-state response of finite element method directly in frequency domain solution electromagnetic field. The experiment has proved finite element method of harmonic balance is generally more effective than traditional time-domain method.

Suppression of radiated emission in fiscal taxi meter

This paper is based upon National Standards for EMC. For the problem that the intensity of electromagnetic radiation in the meter with the THG at 36MHz is seriously more than National Standards, by studying the theory of radiation emission and analyzing the formation mechanism of electromagnetic radiation interference, it proposes three restrain measures: 1.the improvement of the Crystal oscillators grounding measure; 2.adding a RC filter circuit to the Crystal oscillator circuit; 3.the improvement of the taxs communication cable, solving the problem that radiation harassment the taxi meter seriously exceeds. The experimental result demonstrates that the radiation intensity of tax meter improved with the general measures meet the requirements of the national standard, making more than 32000 taxes in Tianjin install this green meter, protecting the safety of staff and normal operation of the surrounding equipment.

Electromagnetic inhibition of high frequency thermal bonding machine

The traditional high frequency thermal bonding machine had serious radiation problems at dominant frequency, two times frequency and three times frequency. Combining with its working principle, the problems of electromagnetic compatibility were studied, three following measures were adopted: 1.At the head part of the high frequency thermal bonding machine, resonant circuit attenuator was designed. The notch groove and reaction field can make the radiation being undermined or absorbed; 2.The electromagnetic radiation shielding was made for the high frequency copper power feeder; 3.Redesigned the high-frequency oscillator circuit to reduce the output of harmonic oscillator. The test results showed that these measures can make the output according with the national standard of electromagnetic compatibility (GB4824-2004-2A), the problems of electromagnetic radiation leakage can be solved, and good social, environmental and economic benefits would be brought.

Communication design of automatic test system based on VC

The design of automatic test system based on VC++ implemented the communications between the spectrum analyzer and PC. USB-GPIB Interface board is used, USB with its unique advantages of strong anti-interference?high speed and easy to use make the application of automated test system based on GPIB more extensive and flexible. This paper describes the working principle of the test system and the design of hardware as well as software. And complete the procedures of host computer for spectrum analyzer automated test system in VC + +6.0 environments.

The data processing system of spectrum analyzer based on VC

Spectrum analyzer system function is shown in the frequency domain where the spectral characteristics of the signal can be real-time signal analysis, but results of the analysis can not be saved. To solve this problem, the system based on VC + + object-oriented programming design method, using VC + +6.0 is generated to achieve the advantages of friendly interface in the instrument data processing, graphical display and preservation functions, experimental results show that The system has good stability, easy operation, has greatly enhanced the use of the instrument, the application prospect is broad.

Error analysis of pseudo single point position date range on account of kailman filtering

GPS with a global, all-weather, continuous real-time three-dimensional navigation and positioning capabilities, has a broad application value and development potential. GPS receiver with C / A code has advantage of cheap, small, easy to carry, from the results of position by C / A code GPS receiver outputting, researching the C / A code GPS receiver static positioning accuracy, has important practical value‥ Kalman filtering is a linear unbiased minimum variance estimation theory pushdown obtained a recursive filtering method, which introduces the concept of the state space, using the system state transition equation of state of the previous one moment of valuation and the current moment observed value estimated that the new state of Recursive valuation. Experiments show that the Kalman filter introduced into the positioning data as a post-processing tool, which greatly improves the positioning accuracy.

Simulation for Doppler signal Periodogram Spectral estimation methods

With the rapid development of modern intelligent traffic, the speed-testing radar becomes a kind of essential equipment, which measures speed through the acquisition of the moving target signal frequency deviation according to Doppler principles. Traditional method uses analog filtering, whose measurement accuracy is low and the measured speed is slow. Obviously, its difficult to meet the need of the modern intelligent transportation management. Speed radar signal processing generally uses the power spectrum estimation method. Periodogram Spectral estimation (using Hamming window periodogram method) considers for different signal to noise ratio of the data spectral estimation, and finally receives the largest frequency error to meet the system requirements for measurement accuracy.

VRS technology based on multi-base station network and its error analysis

The existing problems of conventional RTK in actual applications specifically indicate that the difference technology can only eliminate the public error between base station and subscriber station under certain conditions. With the increases of baseline length (more than 20 km), the correlation of errors between tropospheric and ionospheric weakens or even disappears such that, the differential GPS technology loses its theoretical foundation. The experimental analysis shows that in network RTK, the Virtual Reference Station RTK technology enables VRS technology to extend the effective distance from 15 km to 50 km or more, and thus, to greatly enhance the relative positioning accuracy in medium-baseline and long-baseline (20∼50km).

Discrete Chaotic Synchronization and Secure Communication Design

In resent years, secure communication is becoming one of the researching hotspots in information safety. Some problems of chaotic synchronization and its application in communication are studied on the bases of the theory of nonlinear dynamics. It is a mode of correspondence, which transmits the desired information in the channel by means of encrypting, and then decrypts them at the receiving end. Chaos encryption is to encrypt the plaintexts and utilize random-like characteristics of chaos signal to secure the real-time communication. This paper bases on nonlinear dynamics theory and Starts from stability theory of dynamic system , In addition, it adopts Logistic mapping of discrete chaotic system and uses modular operation to design the synchronization and secure communication. This design is easily realization and has stronger anti-interference ability, and then the secure capacity of secure communication system is nice.