Signal amplification performs two important functions:
• Increases the resolution of the inputted signal
• Increases it's signal-to-noise ratio
Operational amplifiers over the years have proven to be the best choice
for signal amplifications because of the following characteristics offered
by Operational amplifiers over other kinds of amplifiers
• High open-loop gain
• High Bandwidth
• High input impedance
• Low/Non offset voltage
• Fast/High slew rate
• Low output impedance
• Low noise
Saturday, October 31, 2009
Introduction To Filter
What is a filter?
A filter is a device that passes electric signals at certain frequencies or frequency ranges while
preventing the passage of others.
Applications:
• Filter circuits are used in a wide variety of applications.
• In the field of telecommunication, band-pass filters are used in the audio frequency
range (0 kHz to 20 kHz) for modems and speech processing.
• High-frequency band-pass filters (several hundred MHz) are used for channel
selection in telephone central offices.
• Data acquisition systems usually require anti-aliasing low-pass filters as well as lowpass
noise filters in their preceding signal conditioning stages.
• System power supplies often use band-rejection filters to suppress the 60-Hz line
frequency and high frequency transients.
• In addition, there are filters that do not filter any frequencies of a complex input
signal, but just add a linear phase shift to each frequency component, thus
contributing to a constant time delay. These are called all-pass filters.
• At high frequencies (> 1 MHz), all of these filters usually consist of passive
components such as inductors (L), resistors (R), and capacitors (C). They are then
called LRC filters.
• In the lower frequency range (1 Hz to 1 MHz), however, the inductor value becomes
very large and the inductor itself gets quite bulky, making economical production
difficult.
• In these cases, active filters become important. Active filters are circuits that use an
operational amplifier (op amp) as the active device in combination with some
resistors and capacitors to provide an LRC-like filter performance at low frequencies.
Application as Interface Circuit:
That connects the real world analog signal to the digital signal processor and provides band
limiting before the signal can be sampled for further processing with the digital technique and
reconstruction back to the analog world.
Why We Use Analog Filter?
• The practical active filter makes use of operated amplifier together with capacitor and
resistor is known as Analog filters.
• Many filtering applications are now handle with digital signal processing techniques
and digital filters.
• Analog continues time filter provides a more economical solution.
• For analog filter we must consider such factors as:
Factor considered while filter designing:
1. Technology derived for the system implementation.
2. Availability of DC supplies for the active devices and power
consumption.
3. Availability of voltage source for Op-Amp.
4. Cost.
5. Range of frequency of operation.
6. Sensitivity to parameter changes and stability.
7. Weight and size of the implemented circuit.
8. Noise and dynamic range of the realize filter.
These factors are to choose an analog or digital filter for a particular application.
Introduction to Filter Design:-
• The filter design is a special case of electric wave’s filter which makes the properties of
the Op-Amp.
• Such filter are sometimes called Active filter, currently called Analog Filter.
• In modern integrated circuits technology both analog and digital filter may be
implemented on the same chip.
Circuit Diagram:-
• If we know the circuit and the form of input then we may determine the output V2, this is
known as Circuit Analysis.
• If we know the input and the output or the ration that is |T| then we found the response in
the circuit is known as Circuit Designing.
• We have to design a circuit therefore we concern with designing in the filter Analysis.
• The circuit that we have design for the variation of the magnitude, phase or related
quantities they are known as Filter.
• In electrical engineering we filter the signal in terms of voltages at a specified frequency.
If a signal is made up of 2 tones, one at high frequencies called Piccolo and other is low
frequency called Tuba, imagine a filtering action by which one tone or the other is
suppressed.
A filter is a device that passes electric signals at certain frequencies or frequency ranges while
preventing the passage of others.
Applications:
• Filter circuits are used in a wide variety of applications.
• In the field of telecommunication, band-pass filters are used in the audio frequency
range (0 kHz to 20 kHz) for modems and speech processing.
• High-frequency band-pass filters (several hundred MHz) are used for channel
selection in telephone central offices.
• Data acquisition systems usually require anti-aliasing low-pass filters as well as lowpass
noise filters in their preceding signal conditioning stages.
• System power supplies often use band-rejection filters to suppress the 60-Hz line
frequency and high frequency transients.
• In addition, there are filters that do not filter any frequencies of a complex input
signal, but just add a linear phase shift to each frequency component, thus
contributing to a constant time delay. These are called all-pass filters.
• At high frequencies (> 1 MHz), all of these filters usually consist of passive
components such as inductors (L), resistors (R), and capacitors (C). They are then
called LRC filters.
• In the lower frequency range (1 Hz to 1 MHz), however, the inductor value becomes
very large and the inductor itself gets quite bulky, making economical production
difficult.
• In these cases, active filters become important. Active filters are circuits that use an
operational amplifier (op amp) as the active device in combination with some
resistors and capacitors to provide an LRC-like filter performance at low frequencies.
Application as Interface Circuit:That connects the real world analog signal to the digital signal processor and provides band
limiting before the signal can be sampled for further processing with the digital technique and
reconstruction back to the analog world.
Why We Use Analog Filter?
• The practical active filter makes use of operated amplifier together with capacitor and
resistor is known as Analog filters.
• Many filtering applications are now handle with digital signal processing techniques
and digital filters.
• Analog continues time filter provides a more economical solution.
• For analog filter we must consider such factors as:
Factor considered while filter designing:
1. Technology derived for the system implementation.
2. Availability of DC supplies for the active devices and power
consumption.
3. Availability of voltage source for Op-Amp.
4. Cost.
5. Range of frequency of operation.
6. Sensitivity to parameter changes and stability.
7. Weight and size of the implemented circuit.
8. Noise and dynamic range of the realize filter.
These factors are to choose an analog or digital filter for a particular application.
Introduction to Filter Design:-
• The filter design is a special case of electric wave’s filter which makes the properties of
the Op-Amp.
• Such filter are sometimes called Active filter, currently called Analog Filter.
• In modern integrated circuits technology both analog and digital filter may be
implemented on the same chip.
Circuit Diagram:-
• If we know the circuit and the form of input then we may determine the output V2, this is
known as Circuit Analysis.
• If we know the input and the output or the ration that is |T| then we found the response in
the circuit is known as Circuit Designing.
• We have to design a circuit therefore we concern with designing in the filter Analysis.
• The circuit that we have design for the variation of the magnitude, phase or related
quantities they are known as Filter.
• In electrical engineering we filter the signal in terms of voltages at a specified frequency.
If a signal is made up of 2 tones, one at high frequencies called Piccolo and other is low
frequency called Tuba, imagine a filtering action by which one tone or the other is
suppressed.
Filter Terminologies
Brief definitions of terms related to filter design:
Convolution
Neighborhood operation in which each output pixel is a weighted sum of neighboring input
pixels. Image processing operations implemented with convolution include smoothing,
sharpening, and edge enhancement.
Correlation
Neighborhood operation in which each output pixel is a weighted sum of neighboring input
pixels. Correlation is closely related mathematically to convolution.
Bandwidth - few terms in signal processing have more definitions than this one. We'll define
bandwidth as the frequency width of the passband of a filter. For a low-pass filter, the bandwidth
is equal to the cutoff frequency. For a bandpass filter, the bandwidth is typically defined as the
frequency difference between the upper and lower -3 dB points.
Attenuation - an amplitude loss, usually measured in dB, incurred by a signal after passing
through a filter.
Cascaded filters - the implementation of a filtering system where multiple individual filters are
connected in series. That is, the output of one filter drives the input of the following filter.
Center Frequency (fo) - the frequency lying at the midpoint of a bandpass filter.
Cutoff Frequency - the upper passband frequency for low-pass filters, and the lower passband
frequency for highpass filters. A cutoff frequency is determined by the -3 dB point of a filter
magnitude response relative to a peak passband value.
Decibels (dB) - a logarithmic unit of attenuation, or gain, used to express the relative voltage or
power between two signals. For filters we use decibels to indicate cutoff frequencies (-3 dB) and
stopband signal levels (-20 dB)
Digital filter- computational process, or algorithm, transforming a discrete sequence of numbers
(the input) into another discrete sequence of numbers (the output) having a modified frequency
domain spectrum. Digital filtering can be in the form of a software routine operating on data
stored in computer memory or can be implemented with dedicated digital hardware.
Filter Coefficients - the set of constants, also called tap weights, used to multiply against
delayed signal sample values within a digital filter structure. Digital filter design is an exercise in
determining the filter coefficients that will yield the desired filter frequency response. For an FIR
filter, the filter coefficients are, by definition, the impulse response of the filter.
Filter Order - a number describing the highest exponent in the numerator or denominator of the
z-domain transfer function of a digital filter. For FIR filters, there is no denominator in the
transfer function and the filter order is merely the number of taps used in the filter structure. For
IIR filters, the filter order is equal to the number of delay elements in the filter structure.
Generally, the larger the filter order, the better the frequency magnitude response performance of
the filter.
Frequency Magnitude Response - a frequency domain description of how a filter interacts with
input signals.
Impulse Response - a digital filter's time domain output sequence when the input is a single
unity-valued sample (an impulse) preceded and followed by zero-valued samples. Using perhaps
the most powerful principle in signal processing, we can say that a linear digital filter's frequency
domain response can be calculated by taking the discrete Fourier transform of the filter's time
domain impulse response.
Linear Phase Filter- a filter that exhibits a constant change in output phase angle as a function
of frequency. The resultant filter phase plot vs frequency is a straight line. As such, a linear
phase filter's group delay is a constant. In order to preserve the integrity of their informationcarrying
signals, linear phase is an important criteria for filters used in communication systems.
Phase Response - the difference in phase, at a particular frequency, between an input sinewave
and the filter's output sinewave at that frequency. The phase response, sometimes called phase
delay, is usually depicted by a curve showing the filter's phase shift vs frequency.
Ripple - Ripple refers to fluctuations (measured in dB) in the passband, or stopband, of a filter's
frequency magnitude response curve.
Rolloff - a term used to describe the steepness, or slope, of the filter response in the transition
region from the passband to the stopband.
Transfer Function - a mathematical expression of the ratio of the output of a filter over the
input of the filter. Given the transfer function we can determine the filter's frequency magnitude
and phase responses.
Transition Region - the frequency range between the passband and the stopband of a filter.
Passband - that frequency range over which a filter passes signal energy.
Stopband - that band of frequencies attenuated by a digital filter
Convolution
Neighborhood operation in which each output pixel is a weighted sum of neighboring input
pixels. Image processing operations implemented with convolution include smoothing,
sharpening, and edge enhancement.
Correlation
Neighborhood operation in which each output pixel is a weighted sum of neighboring input
pixels. Correlation is closely related mathematically to convolution.
Bandwidth - few terms in signal processing have more definitions than this one. We'll define
bandwidth as the frequency width of the passband of a filter. For a low-pass filter, the bandwidth
is equal to the cutoff frequency. For a bandpass filter, the bandwidth is typically defined as the
frequency difference between the upper and lower -3 dB points.
Attenuation - an amplitude loss, usually measured in dB, incurred by a signal after passing
through a filter.
Cascaded filters - the implementation of a filtering system where multiple individual filters are
connected in series. That is, the output of one filter drives the input of the following filter.
Center Frequency (fo) - the frequency lying at the midpoint of a bandpass filter.
Cutoff Frequency - the upper passband frequency for low-pass filters, and the lower passband
frequency for highpass filters. A cutoff frequency is determined by the -3 dB point of a filter
magnitude response relative to a peak passband value.
Decibels (dB) - a logarithmic unit of attenuation, or gain, used to express the relative voltage or
power between two signals. For filters we use decibels to indicate cutoff frequencies (-3 dB) and
stopband signal levels (-20 dB)
Digital filter- computational process, or algorithm, transforming a discrete sequence of numbers
(the input) into another discrete sequence of numbers (the output) having a modified frequency
domain spectrum. Digital filtering can be in the form of a software routine operating on data
stored in computer memory or can be implemented with dedicated digital hardware.
Filter Coefficients - the set of constants, also called tap weights, used to multiply against
delayed signal sample values within a digital filter structure. Digital filter design is an exercise in
determining the filter coefficients that will yield the desired filter frequency response. For an FIR
filter, the filter coefficients are, by definition, the impulse response of the filter.
Filter Order - a number describing the highest exponent in the numerator or denominator of the
z-domain transfer function of a digital filter. For FIR filters, there is no denominator in the
transfer function and the filter order is merely the number of taps used in the filter structure. For
IIR filters, the filter order is equal to the number of delay elements in the filter structure.
Generally, the larger the filter order, the better the frequency magnitude response performance of
the filter.
Frequency Magnitude Response - a frequency domain description of how a filter interacts with
input signals.
Impulse Response - a digital filter's time domain output sequence when the input is a single
unity-valued sample (an impulse) preceded and followed by zero-valued samples. Using perhaps
the most powerful principle in signal processing, we can say that a linear digital filter's frequency
domain response can be calculated by taking the discrete Fourier transform of the filter's time
domain impulse response.
Linear Phase Filter- a filter that exhibits a constant change in output phase angle as a function
of frequency. The resultant filter phase plot vs frequency is a straight line. As such, a linear
phase filter's group delay is a constant. In order to preserve the integrity of their informationcarrying
signals, linear phase is an important criteria for filters used in communication systems.
Phase Response - the difference in phase, at a particular frequency, between an input sinewave
and the filter's output sinewave at that frequency. The phase response, sometimes called phase
delay, is usually depicted by a curve showing the filter's phase shift vs frequency.
Ripple - Ripple refers to fluctuations (measured in dB) in the passband, or stopband, of a filter's
frequency magnitude response curve.
Rolloff - a term used to describe the steepness, or slope, of the filter response in the transition
region from the passband to the stopband.
Transfer Function - a mathematical expression of the ratio of the output of a filter over the
input of the filter. Given the transfer function we can determine the filter's frequency magnitude
and phase responses.
Transition Region - the frequency range between the passband and the stopband of a filter.
Passband - that frequency range over which a filter passes signal energy.
Stopband - that band of frequencies attenuated by a digital filter
Significance of 3dB Frequency
• The 3dB frequency is the frequency at which the power is reduced by one half.
• Another way of saying it is the frequency at which the voltage is reduced to 70.7% of its full
value.
• An audio amplifier will have a lower and an upper 3dB frequency, so will a bandpass filter.
• A high‐pass filter will have only one 3dB frequency, that of the lowest frequency for which it is
much use; and conversely for a low‐pass filter.
• A power ratio of 2 is equal to 3 dB. ( take the log of 2 check above equation) Conversely, a
power ratio of 1/2 is equal to ‐3 dB. (NOTE: The ‐3 dB point is often referred to as a "half‐power
point," as when describing, say, a frequency response curve)
• A voltage or current ratio of 2 is equal to 6 dB. Conversely, a voltage or current ratio of 1/2 is
equal to ‐6 dB. Since power is E^2/ R.
• The 3dB point, or 3dB frequency, is the point at which the signal has been attenuated by 3dB (in
a bandpass filter). This is generally considered the point for determining the filter's bandwidth.
The bandwidth is defined as the difference between the upper and lower 3dB points.
• For example, if you have a filter which has a lower 3dB point of 720 MHz, and an upper 3dB
point of 730 MHz, you have a bandwidth of 10 MHz.
• Another way of saying it is the frequency at which the voltage is reduced to 70.7% of its full
value.
• An audio amplifier will have a lower and an upper 3dB frequency, so will a bandpass filter.
• A high‐pass filter will have only one 3dB frequency, that of the lowest frequency for which it is
much use; and conversely for a low‐pass filter.
• A power ratio of 2 is equal to 3 dB. ( take the log of 2 check above equation) Conversely, a
power ratio of 1/2 is equal to ‐3 dB. (NOTE: The ‐3 dB point is often referred to as a "half‐power
point," as when describing, say, a frequency response curve)
• A voltage or current ratio of 2 is equal to 6 dB. Conversely, a voltage or current ratio of 1/2 is
equal to ‐6 dB. Since power is E^2/ R.
• The 3dB point, or 3dB frequency, is the point at which the signal has been attenuated by 3dB (in
a bandpass filter). This is generally considered the point for determining the filter's bandwidth.
The bandwidth is defined as the difference between the upper and lower 3dB points.
• For example, if you have a filter which has a lower 3dB point of 720 MHz, and an upper 3dB
point of 730 MHz, you have a bandwidth of 10 MHz.
Wide area network
A wide area network (WAN) is a computer network that covers a broad area (i.e., any network whose communications links cross metropolitan, regional, or national boundaries [1]). This is in contrast with personal area networks (PANs), local area networks (LANs), campus area networks (CANs), or metropolitan area networks (MANs) which are usually limited to a room, building, campus or specific metropolitan area (e.g., a city) respectively.
WANs are used to connect LANs and other types of networks together, so that users and computers in one location can communicate with users and computers in other locations. Many WANs are built for one particular organization and are private. Others, built by Internet service providers, provide connections from an organization's LAN to the Internet. WANs are often built using leased lines. At each end of the leased line, a router connects to the LAN on one side and a hub within the WAN on the other. Leased lines can be very expensive. Instead of using leased lines, WANs can also be built using less costly circuit switching or packet switching methods. Network protocols including TCP/IP deliver transport and addressing functions. Protocols including Packet over SONET/SDH, MPLS, ATM and Frame relay are often used by service providers to deliver the links that are used in WANs. X.25 was an important early WAN protocol, and is often considered to be the "grandfather" of Frame Relay as many of the underlying protocols and functions of X.25 are still in use today (with upgrades) by Frame Relay.
Academic research into wide area networks can be broken down into three areas: Mathematical models, network emulation and network simulation.
Performance improvements are sometimes delivered via WAFS or WAN optimization.
Several options are available for WAN connectivity:Saturday, October 24, 2009
Local area network
A local area network (LAN) is a computer network covering a small physical area, like a home, office, or small group of buildings, such as a school, or an airport. The defining characteristics of LANs, in contrast to wide-area networks (WANs), include their usually higher data-transfer rates, smaller geographic area, and lack of a need for leased telecommunication lines.
ARCNET, Token Ring and many other technologies have been used in the past, and G.hn may be used in the future, but Ethernet over twisted pair cabling, and Wi-Fi are the two most common technologies currently in use.
As larger universities and research labs obtained more computers during the late 1960s, there was increasing pressure to provide high-speed interconnections. A report in 1970 from the Lawrence Radiation Laboratory detailing the growth of their "Octopus" network[1][2] gives a good indication of the situation.
Cambridge Ring was developed at Cambridge University in 1974[3] but was never developed into a successful commercial product.
Ethernet was developed at Xerox PARC in 1973–1975,[4] and filed as U.S. Patent 4,063,220. In 1976, after the system was deployed at PARC, Metcalfe and Boggs published their seminal paper, "Ethernet: Distributed Packet-Switching For Local Computer Networks."[5]
ARCNET was developed by Datapoint Corporation in 1976 and announced in 1977.[6] It had the first commercial installation in December 1977 at Chase Manhattan Bank in New York.[7]
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