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1.
Virtual Instrument has become an important direction of instrument development, now it has been widely used in many fields. FFT analysis is a widely used method in mechanical engineering, fault detection and many other fields. However, the traditional FFT analyzer is expensive and is not easy to upgraded. The birth of virtual FFT Spectrum Analyzer gets rid of the limit of traditional FFT analyzer, and paves the way for the application of FFT analyzer. The uses of DSP technology make the future broadened of Virtual Instrument. This article ,based on the deep study of DSP system, designs a virtual FFT Spectrum analyzer based on DSP technology. The design is new and of great practicality, which indicates the important role of Virtual Instrument in the development of instruments. 相似文献
2.
Ding KangXie Ming 《保鲜与加工》1992,(2):51-57
FFT(Fast Fourier Transform)is the basis of spectrum analysis. This paper gives out a method which can improve the speed and accuracy of FFT. The spectrum analysis based on the proposed method is of a high level: the amplitude error of spectrum is less then 1 % , the time of completing 1024 compler points FFT and 32 segments spectrum analysis is less then 250ms and only 5 seconds respectively. 相似文献
3.
Using studied ECG sampling system, the analog signals of electrocardiograph is magnified and filtered,sending into the sampling card in computer, the sampling frequence is 1 000 Hz, the 5 minutes sampling signal is saved to hard disk. Using modern spectrum analysis method and FFT, the specific value VLF/HF of Heart Rate Variability (HRV)of 19 healthy individuals and 10 hyperthyroid is analysed .It is found that the significant difference of the specific value VLF/HF between the healthy individuals and hyperthyroid.There are no especial advantage and distinctness by using the modern spectrum analysis method or FFT to study balance the specific value VLF/HF between the healthy individuals and hyperthyroid. The result shows that the spectrum analysis method is relly an effective measure to analyze independence nerve abnormalities of hyperthyroid. 相似文献
4.
The sole note is a regular cyclical signal. The best frequency domain resolution can be gotten with FFT. However, the harmonic components of the note are extremely rich, so FFT is unable to examine the fundamental frequency accurately. DWT can decompose the signal to low pass rapidly,and has a smooth low frequency approximation. This article brings forward DWT and FFT union musical note recognition method, which realizes the precise frequency recognition of the musical note and is an expected method. 相似文献
5.
Synthetic aperture radar (SAR) raw signal generation and SAR image simulation of typical targets are very significant for the validation of SAR imaging algorithms, the interpretation of SAR images, and automatic target recognition of SAR images. Based on analysis of the existing SAR raw signal generation and SAR image simulation methods, a new method for SAR raw signal generation and SAR image simulation is proposed. This method combined the curved surface pixel method (CSPM) and the two dimensional FFT (2DFFT) based SAR raw signal generation model. CSPM is used to calculate the target reflectivity, while the 2DFFT method is employed to obtain the raw signal. The simulations are carried out, and the effectiveness of this method is validated by the results of simulating some typical targets. 相似文献
6.
The architecture of scalable length and high speed FFT processor based on CPLD(Complex Programmable Logic Device) is proposed, including the pipeline architecture of the radix mixed FFT algorithm, the address regularity of the read-then-write RAM, the array architecture of short-length FFT and the pipeline complement architecture of CORDIC(Coordinate Rotation Digital Computer) algorithm. If the input-data velocity is 20 MHz,the time expended on 1024-point FFT is 50 us. 相似文献
7.
In order to accelerate the working speed of a FFT processor, this paper presents a hardware structure of a FFT processor, which is suitable for CPLD , and the 128-point FFT single-chip processor is realized by means of FLEX10K CPLD and MAX+PLUS II software. The calculation time of the processor is less than 230uS. The research proves that the combination of CPLD and FFT increases the working speed of FFT processors and raise the level of application . 相似文献
8.
This paper has explained the characteristics,virtue of sound intensity measurement and the principle. And compare with traditional sound pressure measurement. The principle and composing of virtual sound intensity measurement system based on two-channel FFT analysis are researched. The sound power of large turbogeneratorin operating site is determined by means of sound intensity measurement and sound pressuremeasurement. Itis demonstrated that the method of sound intensity measurement of engine is practicable and the measuring data are valid and the method conquers the problems of traditional method of sound pressure measurement which is apt to environmentinfluence and sound power measurement need to especially acoustic environment. It is proved that the sound intensity method is especially suited to determine highaccuratelythe sound Power level of the electrical machines operating in situated conditions especially in case of acoustically worst environments or on loadand themethod is so superiorityin noise measurement. 相似文献
9.
Traditional noise octave analyzers consist of filter network and weight network based on hardware. In order to realize a noise octave analysis by software, a digit weight method based on FFT is proposed. Using the method, digit weight and digit system error modification for virtual noise octave analyzer can be realized. Because of digit weight and digit system error modification, precision and stability of the instrument can be improved greatly. As an application, which combines the method of digit weight with the technique of digit system error modification, a low cost and high precision virtual real time noise octave analyzer is developed. 相似文献
10.
The accuracy of modal parameters identification has the influence on the quality of dynamic characteristics analysis of mechanical structure directly. And the precision of the frequency response function estimation has the great influence on the accuracy of modal parameters identification. In the engineering the frequency response function can be estimated by the average power spectrum and cross-power spectrum with the hel Pof FFT. As the result of limited frequency resolution in the course of FFT and the noise, the accuracy of modal parameters identification is influenced by the frequency response function estimation. This paper has put forward a least-square-based optimization of frequency response function estimation in modal parameters identification. According to the optimized frequency response function, the peak value can be searched to identify the damped natural frequencies and damping ratio directly. An experiment has been made to validate the proposed method. The result indicates that the damped natural frequencies and damping ratio identified by the optimized frequency response function are closer to the true results than which without the optimized frequency response function. So the accuracy of modal parameters identification can be improved by adopting the proposed method. 相似文献
11.
In the field of signal analyies for time frequency, the DFT is a familiar term. Especially,when its efficient algorithm FFT given, the other operations in signal analyses are also usually translated to DFT as soon as possible so as to enhance the calculating speed. But in our exploning the virtual instrument for time frequency analyzing, two sorts of formulas to calculate DFT and its inverse transform (IDFT) are found. These results are in different value of operation from different signal analysts or from different instruments for time frequency analyzing, their physical meaning are also not clear enough.The period extent theory some previous document based on when defined DFT is firstly expatiated. Then, separately with future defining coefficient method and analogy evolvement method, the authors argue that, based on the period extent theory, it is more rational to calculate DFT with the formula given. A shortage is pointed out and corrected is appeared in some previous documents when having given the formula of DFT. The improper view is also clarified that the reason why there are two sorts of formulas is make by custom.The rationality of the authors view with three examples is visually verified in the end. 相似文献
12.
A pipelined FFT processor designed for fast and real-time requirements with FPGA is introduced. This FFT processor can be used to real-time frequency analysis and its working frequency can reach to 75 MHz. The leakage error is reduced through multiply the sampled signal by a weighting window. In order to improve FFT's working frequency and economize FPGA resources, an algorithm of 1024-point complex to compute 2048-point real data is adopted. In addition, an approximate algorithm to compute module value of complex number is introduced. 相似文献
13.
Skin electrode unit is a channel through which energy can be transferred to the implanted device by volume conduction. The unit can be equivalent to lumped circuit, but so far there are no appropriate calculation methods of these circuit parameters, so variable load method based on field-circuit coupled is proposed. A skin electrode unit field circuit coupled model is established to obtain the relationship of the network parameters between voltage and current at electrode port, and the amplitude and phase of the power signal is extracted by the use of all phase FFT spectrum analysis. On this basis, equivalent circuit impedance parameters of the skin electrode unit under various conditions are obtained by the application of variable load method and the validity of the method is verified. As a result, the equivalent circuit impedance parameters obtained in this way can be used for the circuit analysis and optimization of the volume conduction energy transfer system. 相似文献
14.
The performance requirements of marine gear box are much higher than that of other gear boxes due to its special working conditions. The structure and transmission principle of a high-power marine gearbox are analyzed, and the experimental test is carried out for the analysis and calculation of its vibration characteristics and intensity. Measured by FFT analysis of vibration signals, the main peak is caused by its octave and the engagement frequency of input stage and middle-class transmission. The vibration severity of high-power marine gearbox reached 4.47 mm/s. In addition, the calculated structure noise of the measuring points is at the 1/3 octaves, and the largest structure noise is 131.27 dB which occurred in the frequency of 329 Hz. 相似文献
15.
Transient analysis of transmission line has recently been received more attention because operating speeds in high-speed digital electronics are increasing. Transmission line equations are hyperbolic partial differential equations, firstly this paper deduces how to change transmission line equations into quasilinear differential equations , thus the transmission line equation numerical result is gotten by computing the differential formation of quasilinear differential equations. The constraint of voltage and current is be considered and lumped equivalent circuit mode at boundary network collaborated at the same time in finding boundary conditions. Finally the paper computes transient response of transmission line with two typical boundary conditions. Numerical result shows that this approach is an effective way. It is explicit algorithm with less CPU consumption which can get time field response directly. The agree-upon effective way does be frequency field method, however it could not get time response unless the numerical inverse laplace transformation (NILT) be introduced. Thus this approach is more effective than FFT algorithm. 相似文献
16.
A lot of information needs processing in time in dynamic balance testing, but the current intelligent dynamic balance instruments and the controlling box of dynamic balance machines made up ofsinglemicrocontroller do not meet the request.A method isgioen that the DSP-Microcontroller will be useddiredtlyinthe system of the intelligent dynamic balance instrumentby using embedded design technique. A principal and subordinate control system compose of DSP and microcontroller. The Microcontroller the system as a principal controller and the DSP implements digital filtering and FFT in dynamic balanc by means of its fast operation. The system develoyed according tothe method can do more analysisin time areaand frequency area. 相似文献
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18.
This paper presents a method of tamping for improving unconsolidated sand and gravel foundation backfilled on the flood land,and introduces the principles of soil improvement with some engineering cases. Results from the field tests show that this method is reliable,economical and feasible.It provides reliable basis for applying this method on other similar engineering projects hereafter. 相似文献
19.
Orthogonal frequency division multiplexing (OFDM) is sensitive to the in-phase and quadrature-phase (IQ) imbalance induced by the direct conversion architectures. A compensation scheme of IQ imbalance exploiting null subcarriers in OFDM symbols is presented. The proposed algorithm is with high bandwidth utilization because the training symbols are not required. The effect of IQ imbalance on OFDM systems is studied, and the mirror relationship between the FFT of a sequence and that of its conjugate is employed to estimate and compensate the IQ imbalance. This method can be applied to multiple input multiple output (MIMO) OFDM systems with space time block code (STBC). Performance analysis shows that the proposed algorithm is asymptotically unbiased. The variance is inversely proportional to the number of OFDM symbols, null subcarriers, the SNR and the channel frequency response, and proportional to the IQ imbalance. Simulation results demonstrate that this scheme can obtain almost the optimal bit error rate (BER). 相似文献
20.
应用竞争酶联免疫法(ELISA)能够快速对动物性食品中的恩诺沙星残留进行检测筛选。与其他检测方法相比,ELISA具有适用范围宽、样品预处理简单、批处理量大、检测速度快、准确性高和重复性强的特点,特别适用于基层大规模筛选和现场监控。 相似文献