Introduction
- Digital signal processing is concerned with the representation of signal by sequence of number or signal and the processing of these sequences. There are three main points in these sentence signals, representation of signals and processing of these signals. So the signal defines as a signal can be define as a function that conveys information generally about the state or behavior of a physical system.
- Mathematically, signals are represented as function of one or more independent variable. If you take the same example of audio signals the amplitude of my voice can be plotted as a function of time that is if we take time on the x-axis and on the y-axis if you plot the corresponding amplitude at each instance of time we get signal. Here the independent variable is time t and the signal which is my voice is plotted as a function of time. If you see this signal is defined continuously in time also it has continuous amplitude so this is an analog signal.
- Another form of signals are discrete signals their signals. They are signals that a defined only at discrete units of time to obtain discrete signals all we have to do is sample the analog Signals at discrete units of time. For instance let’s sample this analog signal for that first let us split the time axis into discrete units that is we mark the x axis at equal distances then we obtain the amplitude of signal at this discrete time. Now if we plot only these points we get a discrete signal. Now many people often confused analog signals with continuous time signals. Analog Signals and continuous time signals are not the same.
- Another common misconception is that discrete Signals and digital signals are the same even the name of this course Digital Signal Processing is based on that misconception but understand that digital signals and discrete signals are not the same so the true name of this course should be discrete signal processing as we are only dealing with discrete signal throughout the course but since universities around the world name it as digital signal processing.
- Now the signal processing involves analyzing, modifying and synthesizing signals to put or extract meaning of it. Signal Processing can be broadly classified into analog Signal Processing and digital signal processing as you can guess analog Signal Processing deals with transformation of analog Signals and the processing is done using electrical networks consisting of active and passive elements that is op-amps resistors, capacitors and inductors etc. On the other hand Digital Signal Processing deals with the processing of discrete signals here the processing is done by general purpose computer or by Digital circuit such as ASICs, FPGAs, or specialized DSP chips.
- Now let us understand the block diagram of a DSP Systems. There are mainly 5 blocks in the diagram they are input filter, analog to digital converter or ADC, DSP or digital signal processors DAC or digital to analog converters and output filter. This input filter is usually a low pass filter and is used to filter out unwanted high frequency components from the row analog input signal. For example if we are processing audio signals we only need frequencies in the range of 20 Hz to 20 kHz and this input filter will filter out any frequencies above 20 kHz as they can cause noise.
- Next the ADC will convert analog signal to digital signals then these signals are fed to the DSP where it is analyzed and processed and the synthesized output is fed to the DAC. The DAC converts digital signals back into analog Signals and finally this output filter is used to filter out any unwanted high frequency components in the generated analog signal. Now most often we also provide an amplifier at the beginning and at the end this is to amplify the incoming and outgoing signals.
Applications of Digital signal processing(DSP) system
- We use Digital Signal Processing in many areas it is used to process speech and audio this involves speech recognition, analysis, noise filtering echo cancellation etc.
- It is also used to process image and video this involves compression, enhancement, reconstruction and Restoration of images and videos.It also involve face detection like in the case of face unlock in fonts.
- DSP also used in military and telecommunication applications for example sonar and navigation radar tracking modulation and demodulation etc.
- Next application is in biomedical and health care sector for example analysis of ECGs, EEGs and x-ray signals
- Another application is consumer electronics most digital equipments in your home like smart phones, television, digital camera etc have a DSP embedded in it to accelerate its performance.
