Filters classification:
Filters can be categorized in numerous ways either by technology, topology or design methodology. Classification of filters by technology separates them in passive filters, active filters and digital filters.
Passive Filters:
Passive filters are linear networks that are created out of combinations of Inductors, Capacitors and Resistors. They don't have any active component like transistors or valves; neither do they need external power supply.
Passive filters are further categorized by electrical topology in single element filters, L-filters, T-filters and π -filters. Number of circuit elements in each of the sub classifications of passive filters is simply determined by number of inductors and capacitors that make up filter except when the Inductor-Capacitor pair forms the resonant tank circuit in which case pair is treated as the single circuit element. Multiple element Passive Filters generally have the ladder topology that can be viewed as replication of L-filter, T-filter and π -filter sections.
Active Filters:
Family of filters expressed as Active Filters are the combination of passive and active components. Active filters need the power source and frequently use high gain Operational amplifiers in designs to attain very high Q factors. It becomes possible with Active filters to get particularly modified response curves that are only restricted by bandwidth of amplifiers utilized in design.
Digital Filters:
Digital methods are utilized to process both digital and analogue signals that have been converted to appropriate digital form which computers programs can operate upon.
Powerful algorithms implemented in hardware for fast processing calculate output for particular filter response curves in frequency domain. The practical application of this in audio is tone control through digital equalizer.
Passive filters:
Passive Analogue Linear Filters that are built with only resistors, capacitors and inductors, and are known as RC and RL filters single-pole filters.
Realize that Multipole LC filters also exit with well documented and well understood features.
Passive Filter is frequency-selective as it filters out unwanted frequencies and circuit passes to output only those input signals which fall within the desired frequency range. This is known as Pass band.
Region outside Pass band is referred to as Stop Band and amplitude of signals within Stop band are really attenuated. In analyzing Passive Filter, signal source must have very low internal impedance while load must present very high impedance. This allows us to concentrate Voltage transfer function while ignoring Current Transfer Function as current is kept to a minimum.
In practical filters, pass and stop bands are not evidently stated but differs continuously from its maximum toward zero and cut-off frequency is stated as frequency at which amplitude is decreased to 0.7 of its maximum value. This corresponds to signal power being reduced by half.
This is given below.
In Low Pass Filter:
Voltage Transfer Function; ratio of output to input voltage is
V0/Vi = R/(R + jωL) = 1/(1+ j(ωL/R))
Cutoff frequency at which Transfer Function degenerates to 0.7 is
ωc = R/L
By substituting above Transfer Function is rewritten as:
H(jω) = 1/(1 + jω/ωc)
Input Impedance is:
Zi = Vi/Ii = jωL + R
While the output impedance is stated as
Z0 = jωL||R
Active filter:
Filters of all type find application over the broad spectrum of frequencies ranging from sub-audio applications through microwave frequencies. At frequencies higher than 1 Megahertz, filters comprise approximately completely of passive components like Inductors, Capacitors and resistors. In certain situations are hybridizations where parasitic effects of real world component imperfections are capitalized on like parasitic inductance of leads of a capacitor; to attain these filters.
At sub-one-megahertz frequency range though, physical values of some passive filter components become prohibitively high and components themselves turn out to be bulky and expensive rendering production of filters difficult and uneconomical. All these situations that plague Passive Filter implementation at lower frequencies encourage use of Active Filters.
Active Filters are circuits which use operational amplifier as the active device in combination with resistors and capacitors to give LRC-like filter performance; and can usually be referred to as Network Synthesis Filters.
The family of network Synthesis Filters includes Butterworth filter, Tschebyscheff filter, Elliptic filter that is also known as Cauer filter, Gaussian filter, Bessel filter, Linkwitz-Riley filter and Optimum L filter derived from Legendre filter. Three main optimizations of Active filters are Butterworth, Tschebyscheff and Bessel filters. All active filters find application in high-pass, low-pass, band-rejection, band-pass, and all-pass filters.
Other filter methods - hum injector filter:
More than one offending frequency is present that needs numerous notch filters to be cascaded and if desirable frequency lies near one of the offensive frequencies, useful frequency will be eradicated and offensive one. This impossible condition arises when it is desirable to filter out 50 Hertz. Hum without affecting signal at exactly same frequency.
Obvious solution would be to use conventional notch filter in which input signal suffers the phase shift of 1800at some specified frequency, relative to input and when input and output signals are combined; null in response is created at that frequency.
Phase-shifted signal is utilized to oppose original input, and if two signal levels are accurately equal the result is complete cancellation. In cancelling 50 Hertz hum, opposing frequency need not be deduced from original signal, but instead is derived from sample of actual power line, and it can be utilized to exactly balance any hum in output without influencing desired range of helpful signal frequencies. This however should be done in real time, so that hum source and cancellation signals will be synchronized.
The higher the frequency, the more diminished in amplitude the harmonic amplitude and in this particular circuit, it was not necessary to have more than four stages. You should recognise this method of filtering out an undesirable frequency through cancellation as a very effective method which precisely cancels out the offending signal frequency while leaving desirable signal at that same frequency untouched.
Tutorsglobe: A way to secure high grade in your curriculum (Online Tutoring)
Expand your confidence, grow study skills and improve your grades.
Since 2009, Tutorsglobe has proactively helped millions of students to get better grades in school, college or university and score well in competitive tests with live, one-on-one online tutoring.
Using an advanced developed tutoring system providing little or no wait time, the students are connected on-demand with a tutor at www.tutorsglobe.com. Students work one-on-one, in real-time with a tutor, communicating and studying using a virtual whiteboard technology. Scientific and mathematical notation, symbols, geometric figures, graphing and freehand drawing can be rendered quickly and easily in the advanced whiteboard.
Free to know our price and packages for online physics tutoring. Chat with us or submit request at [email protected]
tutorsglobe.com structure of a prokaryotic cell assignment help-homework help by online prokaryotes tutors
tutorsglobe.com prophylaxis of diphtheria assignment help-homework help by online corynebacterium diphtheria tutors
www.tutorsglobe.com offers ionic compound homework help, ionic compound assignment help, online tutoring assistance, inorganic chemistry solutions by online qualified tutor's help.
tutorsglobe.com non-contagious diseases assignment help-homework help by online dairy tutors
TutorsGlobe.com Periodic Table-Gradations of Atomic properties Assignment Help-Homework Help by Online Access Chemistry Tutors
tutorsglobe.com united nations assignment help-homework help by online humanities tutors
tutorsglobe.com blood cells assignment help-homework help by online circulation tutors
tutorsglobe.com sexual reproduction assignment help-homework help by online reproduction biology tutors
organic spectroscopy tutorial all along with the key concepts of interaction of light and matter, properties of light, infrared absorption spectroscopy, infrared light absorption and molecular structure, determination of molecular structure, nuclear magnetic resonance spectroscopy
Algebra math tutors are helping students in algebra assignment help, algebra homework help, solutions to math problems,
tutorsglobe.com catabolism of the carbon skeleton of amino acids assignment help-homework help by online metabolism of proteins tutors
tutorsglobe.com function of treasury management assignment help-homework help by online treasury management tutors
Most large businesses are busy in a number of dissimilar operations, with each containing its own levels of profitability, growth and risk.
What is Issue Control? explain Pricing of Issues, A Material Requisition Note is prepared through the department that is in requirement of the material and sent to the stores department.
tutorsglobe.com muscle tone assignment help-homework help by online muscles tutors
1962421
Questions Asked
3689
Tutors
1465271
Questions Answered
Start Excelling in your courses, Ask an Expert and get answers for your homework and assignments!!