Introduction to Signal and Signal Processing : Introduction to Signal and Signal Processing
Digital Signal Processing (DSP) is one of the most powerful technologies that will shape science and engineering in the twenty first century. : Digital Signal Processing (DSP) is one of the most powerful technologies that will shape science and engineering in the twenty first century.
While starting study of DSP first we have to see the basic terms involving DSP that is ‘Signal’ and ‘Signal Processing’. : While starting study of DSP first we have to see the basic terms involving DSP that is ‘Signal’ and ‘Signal Processing’.
Signal :Signals plays a major role in electronics and in our daily life also.A word ‘Signal’ comes from latin ‘Signum’ which means ‘Sign’.In simple words we can define a signal, as ‘A signal is anything that serves to indicate, warn or direct.’ Information is the key concept. Every signal must consist of some useful information, otherwise it can be considered as a noise. : Signal :Signals plays a major role in electronics and in our daily life also.A word ‘Signal’ comes from latin ‘Signum’ which means ‘Sign’.In simple words we can define a signal, as ‘A signal is anything that serves to indicate, warn or direct.’ Information is the key concept. Every signal must consist of some useful information, otherwise it can be considered as a noise.
The term ‘signal’ can also defined as below: Ø “ A signal is a function or a data set, representing a physical quantity or variable.” Or Ø “ A signal is a function carrying information about the behavior of a physical phenomenon.”Or Ø “ A signal is a quantity or effect such as current or voltage that can be varied in such a way as to convey information.”OrØ “ A signal is defined as a mathematical function that conveys information about the state or behavior of a physical system.” : The term ‘signal’ can also defined as below: Ø “ A signal is a function or a data set, representing a physical quantity or variable.” Or Ø “ A signal is a function carrying information about the behavior of a physical phenomenon.”Or Ø “ A signal is a quantity or effect such as current or voltage that can be varied in such a way as to convey information.”OrØ “ A signal is defined as a mathematical function that conveys information about the state or behavior of a physical system.”
In general a signal can be a function of time, distance, position, temperature, frequency or any other independent variable. : In general a signal can be a function of time, distance, position, temperature, frequency or any other independent variable.
Examples of Signal :Some examples of signals are electrical current, voltage, force, speed, speech, music, picture and video signals etc. : Examples of Signal :Some examples of signals are electrical current, voltage, force, speed, speech, music, picture and video signals etc.
Digital signal :It is a special form of discrete time signal which is discrete in time and amplitude.A digital signal is acquired by representing the sampled analog value into a finite set of values (quantization).These signals are called digital because the samples are represented by digits. : Digital signal :It is a special form of discrete time signal which is discrete in time and amplitude.A digital signal is acquired by representing the sampled analog value into a finite set of values (quantization).These signals are called digital because the samples are represented by digits.
Digital Signal Processing:Digital signal processing is nothing but application of mathematical operations to digital signals. : Digital Signal Processing:Digital signal processing is nothing but application of mathematical operations to digital signals.
Signal Processing:We know that every signal consist of some information, but to obtain useful information from that signal, signal processing is required. “ Signal processing is a method of extracting information from the signal.”It depends upon the type of signal and the nature of information it carries.Signal processing is concerned with representing signal in mathematical terms. By carrying out algorithmic operations on the signal, information can be extracted. : Signal Processing:We know that every signal consist of some information, but to obtain useful information from that signal, signal processing is required. “ Signal processing is a method of extracting information from the signal.”It depends upon the type of signal and the nature of information it carries.Signal processing is concerned with representing signal in mathematical terms. By carrying out algorithmic operations on the signal, information can be extracted.
Basic elements of DSP: : Basic elements of DSP: 1. Input Signal:
It is the signal generated from some transducer or some communication system.It may be biomedical signal like ECG or EEG. Generally it is analog in nature. It is denoted by x(t).
2. Anti Aliasing Filter: This is basically a low pass filter. It is used for the following purposes. ( A ) It removes the high frequency noise contained in input signal. ( B ) As the name indicates, it avoids aliasing effect. That means it is used to band limit the signal. : 2. Anti Aliasing Filter: This is basically a low pass filter. It is used for the following purposes. ( A ) It removes the high frequency noise contained in input signal. ( B ) As the name indicates, it avoids aliasing effect. That means it is used to band limit the signal.
3. Sample and hold circuit:This block takes the samples of input signal and keeps the voltage level of input signal relatively constant which the requirement of ADC. : 3. Sample and hold circuit:This block takes the samples of input signal and keeps the voltage level of input signal relatively constant which the requirement of ADC.
4. Analog to digital converter This block is used to convert analog signal into digital form. This is required because digital signal processor accepts the signal which is digital in nature. : 4. Analog to digital converter This block is used to convert analog signal into digital form. This is required because digital signal processor accepts the signal which is digital in nature.
5. Digital Signal Processor:It processes input signal digitally. In a simple language processing of input signal means modifying the signal as per requirement. For this purpose DSP processors like ADSP2100 or TMS 320 can be used. : 5. Digital Signal Processor:It processes input signal digitally. In a simple language processing of input signal means modifying the signal as per requirement. For this purpose DSP processors like ADSP2100 or TMS 320 can be used.
6. Digital to analog converter (DAC):The output of digital signal processor is digital in nature but the required final output is analog. So to convert digital signal into analog signal DAC is used. : 6. Digital to analog converter (DAC):The output of digital signal processor is digital in nature but the required final output is analog. So to convert digital signal into analog signal DAC is used.
7. Reconstruction Filter:Output signal of DAC is analog, that means it is a continuous signal. But it may contain high frequency components which are unwanted. To remove these components, reconstruction filter is used. : 7. Reconstruction Filter:Output signal of DAC is analog, that means it is a continuous signal. But it may contain high frequency components which are unwanted. To remove these components, reconstruction filter is used.
Advantages of DSP:1.VersatilityDigital systems can be reprogrammed for other applications ( where programmable DSP chips are used). Moreover, digital systems can be ported to different hardware. : Advantages of DSP:1.VersatilityDigital systems can be reprogrammed for other applications ( where programmable DSP chips are used). Moreover, digital systems can be ported to different hardware.
2. RepeatabilityDigital systems can be easily duplicated. These systems do not depend upon component tolerances and temperature. : 2. RepeatabilityDigital systems can be easily duplicated. These systems do not depend upon component tolerances and temperature.
3. SimplicityIt is easy to built any digital system as compared to an analog one.4. AccuracyTo design an analog system, analog components like resistors, capacitors and inductors are used. The tolerance of these components reduce accuracy of the system. While in case of DSP; much better accuracy is obtained. : 3. SimplicityIt is easy to built any digital system as compared to an analog one.4. AccuracyTo design an analog system, analog components like resistors, capacitors and inductors are used. The tolerance of these components reduce accuracy of the system. While in case of DSP; much better accuracy is obtained.
5. Remote ProcessingAnalog signals are difficult to store because of problems like noise and distortion. While digital signal can be easily stored on storage media like magnetic tapes, disks etc. Thus as compared to analog signals digital signals can be easily transposed. So remote processing of digital signal can be done easily. : 5. Remote ProcessingAnalog signals are difficult to store because of problems like noise and distortion. While digital signal can be easily stored on storage media like magnetic tapes, disks etc. Thus as compared to analog signals digital signals can be easily transposed. So remote processing of digital signal can be done easily.
6. Implementation of algorithms The mathematical processing algorithms can be easily implemented in case of digital signal processing.But such algorithms are difficult to implement in case of analog signals. : 6. Implementation of algorithms The mathematical processing algorithms can be easily implemented in case of digital signal processing.But such algorithms are difficult to implement in case of analog signals.
7. Easy UpgradationsBecause of the use of software,digital signal processing systems can be easily upgraded as compared to analog systems. : 7. Easy UpgradationsBecause of the use of software,digital signal processing systems can be easily upgraded as compared to analog systems.
8.CompatibilityIn case of digital systems, generally all applications needs standard hardware. Thus operation of DSP system is mainly dependent on software. Hence universal compatibility is possible as compared to analog systems.9. CheaperIn many applications, the digital systems are comparatively cheaper than analog systems. : 8.CompatibilityIn case of digital systems, generally all applications needs standard hardware. Thus operation of DSP system is mainly dependent on software. Hence universal compatibility is possible as compared to analog systems.9. CheaperIn many applications, the digital systems are comparatively cheaper than analog systems.
Limitations of Digital Signal Processing : The DSP systems have many advantages. Even though there are certain disadvantages as follows: 1. System Complexity DSP system needs use of converters like ADC and DAC. This increases the system complexity compared to analog systems. Similarly in many applications, the time required for this conversion is more. : Limitations of Digital Signal Processing : The DSP systems have many advantages. Even though there are certain disadvantages as follows: 1. System Complexity DSP system needs use of converters like ADC and DAC. This increases the system complexity compared to analog systems. Similarly in many applications, the time required for this conversion is more.
2.Bandwidth LimitationIn case of DSP system, if input signal is having wide bandwidth then it demands for high speed ADC. This is because to avoid aliasing effect, the sampling rate should be at least twice the bandwidth. Thus such signals require fast digital signal processors. But always there is practical limitation in the speed of processors and ADC. : 2.Bandwidth LimitationIn case of DSP system, if input signal is having wide bandwidth then it demands for high speed ADC. This is because to avoid aliasing effect, the sampling rate should be at least twice the bandwidth. Thus such signals require fast digital signal processors. But always there is practical limitation in the speed of processors and ADC.
3. Power ConsumptionA typical digital signal processing chip contains more than 4 lakh transistors. Thus power dissipation is more in DSP systems as compared to analog systems.4. For small applications digital signal processing systems are expensive as compared to analog systems. : 3. Power ConsumptionA typical digital signal processing chip contains more than 4 lakh transistors. Thus power dissipation is more in DSP systems as compared to analog systems.4. For small applications digital signal processing systems are expensive as compared to analog systems.
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