The simulation and the realization of the digital filter
With the information age and the advent of the digital world, digital signal processing has become one of today's most important disciplines and door technology. Digital signal processing in communications, voice, images, automatic control, radar, military, aerospace, medical and houhold appliances, and many other fields widely applied. In the digital signal processing applications, the digital filter is important and has been widely applied.
1、figures Unit on :
Analog and digital filters
In signal processing, the function of a filter is to remove unwanted parts of the signal, such as random noi, or to extract uful parts of the signal, such as the components lying within a certain frequency range.
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The following block diagram illustrates the basic idea.
There are two main kinds of filter, analog and digital. They are quite different in their physical makeup and in how they work. An analog filter us analog electronic circuits made up from components such a
羊毛大衣怎么洗s resistors, capacitors and op amps to produce the required filtering effect. Such filter circuits are widely ud in such applications as noi reduction, video signal enhancement, graphic equalirs in hi-fi systems, and many other areas. There are well-established standard techniques for designing an analog filter circuit for a given requirement. At all stages, the signal being filtered is an electrical voltage or current which is the direct analogue of the physical quantity (e.g. a sound or video signal or transducer output) involved. A digital filter us a digital processor to perform numerical calculations on sampled values of the signal. The processor may be a general-purpo computer such as a PC, or a specialid DSP (Digital Signal Processor) chip. The analog input signal must first be sampled and digitid using an ADC (analog to digital converter). The resulting binary numbers, reprenting successive sampled values of the input signal, are transferred to the processor, which carries out numerical calculations on them. The calculations typically involve multiplying the input values by constants and adding the products together. If necessary, the results of the calculations, which now reprent sampled values of the filtered signal, are output through a DAC (digital to analog converter) to convert the signal back to analog form.
Note that in a digital filter, the signal is reprented by a quence of numbers, rather than a voltage or current.
The following diagram shows the basic tup of such a system.
Unit refers to the input signals ud to filter hardware or software. If the filter input, output signals are parated, they are bound to respond to the impact of the Unit is parated, such as digital filters filter definition. Digital filter function, which was to import quences X transformation into export operations through a ries Y.
According to figures filter function 24-hour live respon characteristics, digital filters can be divided into two, namely, unlimited long live long live the corresponding IIR filter and the limited respon to FIR filters. IIR filters have the advantage of the digital filter design can u simulation results, and simulation filter design of a large number of tables may facilitate simple. It is the shortcomings of the nonlinear pha; Linear pha if required, will u the entire network pha-correction. Image processing and transmission of data collection is required with linear pha filters identity. And FIR linear pha digital filter to achieve, but an arbitrary margin characteristics. Impact from the digital filter respon of the units can be divided into two broad categories : the impact of the limited respon (FIR) filters, and unlimited number of shocks to (IIR) digital filters.
FIR filters can be strictly linear pha, but becau the system FIR filter function extremity fixed at th
爱情片大全e original point, it can only u the higher number of bands to achieve their high lectivity for the same filter design indicators FIR filter called band than a few high-IIR 5-10 times, the cost is higher, Signal delay is also larger. But if the same linear pha, IIR filters must be network-wide calibration pha, the same ction also increa the number of filters and network complexity. FIR filters can be ud to achieve non-Digui way, not in a limited precision of a shock, and into the homes and quantitative factors of uncertainty arising from the impact of errors than IIR filter small number, and FIR filter can be ud FFT algorithms, the computational speed. But unlike IIR filter can filter through the simulation results, there is no ready-made formula FIR filter must u computer-aided design software (such as MATLAB) to calculate. So, a broader application of FIR filters, and IIR filters are not very strict requirements
on occasions.
Unit from sub-functions can be divided into the following four categories :
(1) Low-filter (LPF);
(2) high-filter (HPF);
(3) belt-filter (BPF);
(4) to prevent filter (BSF).
人生路经典短句子The following chart dotted line for the ideals of the filter frequency characteristics :
A
1(f) A
2
(f)
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f
(a) (b)
A
3(f) A
4
(f)
f f
(c) (d)
(a)LPF (b)HPF (c)BPF (d)BSF
2、MATLAB introduced
降格的意思
MATLAB is a matrix laboratory (Matrix Laboratory) is intended. In addition to an excellent value calculation capability, it also provides professional symbols terms, word processing, visualization modeling, simulation and real-time control functions. MATLAB as the world's top mathematical software applications, with a strong engineering computing, algorithms rearch, engineering drawings, applications development, data analysis and dynamic simulation, and other functions, in aerospace, mechanical manufacturing and construction fields playing an increasingly important role. And the C language function rich, the u of flexibility, high-efficiency goals procedures. High language both advantages as well as low level language features. Therefore, C language is the most widely ud programming language. Although MATLAB is a complete, fully functional programming environment, but in some cas, data and procedures with the external environment of the world is very necessary and uful. Filter design using Matlab, could be adjusted with the design requirements and filter
characteristics of the parameters, visual simple, greatly reducing the workload for the filter design optimization.
In the electricity system protection and condary computer control, many signal processing and analysis are bad on are certain types Yeroskipou and the cond harmonics of the system voltage
and current signals (especially at D process), are mixed with a variety of complex components, the filter has been installed power system during the critical components. Current computer protection and the introduction of two digital signal processing software main filter. Digital filter design using traditional cumbersome formula, the need to change the parameters after recalculation, especially in high filters, filter design workload. Us MATLAB signal processing boxes can achieve rapid and effective digital filter design and simulation.
MATLAB is the basic unit of data matrix, with its directives Biaodashi mathematics, engineering, commonly ud form is very similar, it is ud to solve a problem than in MATLAB C, Fortran and other languages End precision much the same thing. The popular MATLAB 5.3/Simulink3.0 including hundreds of internal function with the main pack and 30 types of tool kits (Toolbox). kits can be divided into functional tool kits and disciplines toolkit. MATLAB tool kit ud to expand the functional symbols terms, visualization simulation modelling, word processing and real-time control functions. professional disciplines toolkit is a stronger tool kits, tool kits control, signal processing tool kit, tool kits, etc. belonging to such communications
MATLAB urs to open widely welcomed. In addition to the internal function, all the packages MATLAB tool kits are readable document and the document could be amended, modified or urs th
rough Yuanchengxu the construction of new procedures to prepare themlves for kits.
3、Digital filter design
素馅水饺Digital filter design of the basic requirements
Digital filter design must go through three steps :
补脾中药
(1) Identification of indicators : In the design of a filter, there must be some indicators. The indicators should be determined on the basis of the application. In many practical applications, digital filters are often ud to achieve the frequency operation. Therefore, indicators in the form of general jurisdiction given frequency range and pha respon. Margins key indicators given in two ways. The first is absolute indicators. It provides a function to respond to the
demands of the general application of FIR filter design. The cond indicator is the relative indicators. Its value in the form of answers to decibels. In engineering practice, the most popular of such indicators. For pha respon indicators forms, usually in the hope that the system with a linear pha frequency bands human. Using linear pha filter design with the following respon to the indicators strengths：①it only contains a few algorithms, no plural operations；
②there is delay distortion, only a fixed amount of delay; ③the filter length N (number of bands for N-1), the volume calculation for N/2 magnitude.
(2) Model approach : Once identified indicators can u a previous study of the basic principles and relationships, a filter model to be clor to the target system.
(3) Achieved : the results of the above two filters, usually by differential equations, system function or pul respon to describe. According to this description of hardware or software ud to achieve it.
4、Introduced FPGA
Programmable logic device is a generic logic can u a variety of chips, which is to achieve ASIC ASIC (Application Specific Integrated Circuit) mi-customized device, Its emergence and development of electronic systems designers u CAD tools to design their own laboratory in the ASIC device. Especially FPGA (Field Programmable Gate Array) generated and development, as a microprocessor, memory, the figures for electronic system design and t a new industry standard (that is bad on standard product sales catalogue in the market to buy). Is a digital system for microprocessors, memories, FPGA or three standard building blocks constitute their integration direction.
Digital circuit design using FPGA devices, can not only simplify the design process and can reduce the size and cost of the entire system, increasing system reliability. They do not need to spend the traditional n a lot of time and effort required to create integrated circuits, to avoid the investment risk and become the fastest-growing industries of electronic devices group. Digital circuit design system FPGA devices using the following main advantages
(1)Design flexible
U FPGA devices may not in the standard ries device logic functional limitations. And changes in system design and the u of logic in any one stage of the process, and only through the u of re-programming the FPGA device can be completed, the system design provides for great flexibility.
