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FIR Filter

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Published in: Networking
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Digital FIR Filter and it's specifications

Najeemullah B / Hyderabad

8 years of teaching experience

Qualification: M.Tech (Moguls Institute of learning - 2007)

Teaches: Algebra, Computer Science, Mathematics, Physics, B.Tech Tuition, Electronics, M.Tech Tuition, Railways Exams, RRB, Sub-Inspector Exam, UGC Exams, Chemical, Electrical, Embedded Systems, Hardware Training, Informatica, MCA Subjects

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  1. Introduction In signal processing, the function of a filter is to remove unwanted parts of the signal, such as random noise, or to extract useful parts of the signal. A filter will not add new frequencies to the input signal, nor will it change the component frequencies of that signal, but it will change the relative amplitudes of the various frequency components and/or their phase relationships. Raw Signal (unfiltered) Filtered Signal FILTER Figure 1.1 A block diagram of a basic filter-
  2. Types of Filters There are two main kinds of filter, Analog and Digital filter. An analog filter uses analog electronic circuits made up from components such as resistors, capacitors and op amps to produce the required filtering effect. Advantages: Simple and consolidated methodologies of plan. Fast and simple realization. Disadvantages: Little stable and sensitive to temperature variations. Expensive to realize in large amounts.
  3. A digital filter uses a digital processor to perform numerical calculations on sampled values of the signal. The processor may be a general purpose computer such as a PC, or a specialised DSP (Digital Signal Processor) chip. unfiltered analog signal digitally filtered signal filtered analog signal digitised signal Block diagram of digital filter.
  4. The following list gives some of the main advantages of digital over analog filters. A digital filter is programmable, i.e. its operation is determined by a program stored in the processor's memory. This means the digital filter can easily be changed without affecting the circuitry (hardware). An analog filter can only be changed by redesigning the filter circuit. Digital filters are easily designed, tested and implemented on a general purpose computer or workstation. The characteristics of analog filter circuits (particularly those containing active components) are subject to drift and are dependent on temperature. Digital filters do not suffer from these problems, and so are extremely stable with respect to both time and temperature.
  5. FIR Filter Finite impulse response (FIR) filters are digital filters that have a finite impulse response. FIR filters operate only on current and past input values and are the simplest filters to design. FIR filters also are known as non recursive filters. FIR filters provide a linear phase response. IIR filters provide a nonlinear phase response. FIR filters are always stable because they are implemented using an all zero transfer function. FIR filters are used for applications that require linear phase responses like high quality audio systems.
  6. IIR Filter ' Infinite impulse response (IIR) filters, also known as recursive filters operate on current and past input values and current and past output values. Theoretically, the impulse response of an IIR filter never reaches zero and is an infinite response. ' IIR filters are used for applications that do not require phase information, such as signal monitoring applications. ' Compared to IIR filters, FIR filters sometimes have the disadvantage that they require more memory and/or calculation to achieve a given filter response characteristic.
  7. Field-Programmable Gate Arrays Logic blocks to implement combinational and sequential logic Interconnect wires to connect inputs and outputs to logic blocks I/O blocks special logic blocks at periphery of device for external connections
  8. FIR Filter Design Start Performance specification Calculation of filter Realization structuring Finite •svorldlength effects analysis H/ XV or S/W implementation Stop Summaty ofdesign stage for digital filter
  9. Filter specification: This may include stating the type of filter, for example low pass filter, the desired amplitude and/or phase responses and the tolerances, the sampling frequency, the word length of the input data. Pass band edge frequency = 1.5KHZ Stop band attenuation > 50dB Transition width = 0.5KHZ Sampling frequency = 8KHZ