02-10-2012, 05:05 PM
Digital Signal Processor
Digital_Signal_Processor.doc (Size: 105 KB / Downloads: 21)
ABSTRACT
Digital signal is a numerical representation of the analog signal. It may be easier and more cost effective to process these signals in the digital world. One of the main advantages of digital signal is that it can be stored and manipulated easily. To do this several processes are in use. Of these, Digital Signal Processor plays a leading role.This is used in various applications like instrumentation & measurement, communications , audio & video processing ,graphics , image enhancement , navigation , radars ,control-robotics, machine vision ,guidance etc.
The objective is to encrypt the speech signal. That is to convert the speech signal into an unknown form and then the scrambled speech signal is transmitted. The person who know, how the speech signal is encrypted can decrypt (i.e.,converting the scrambled speech signal into original signal) the signal. Thus security of sending speech message is done.
For encryption and decryption of the signal, we develop a software program in assembly language programming techniques of ADSP 2181. In this paper, encryption and decryption of the speech signal is done using the Digital Signal Processor ADSP 2181.
INTRODUCTION
In recent trends, cell phone, voice chat, etc., is the main topic of the communication. But it is not possible to speak secretly through them. Our objective is to speak secretly, i.e., to maintain security of certain important information. So for that we are going for a technology using digital signal processor.
Our paper also deals with storing and retrieval of speech signal using digital signal processor.
We have used ADSP processor 2181. This is 16 bit fixed point processor.
Here the voice signals is acquired and then digitally coded and stored in the memory of processor. Using FFT (Fast Fourier Transform) and IFFT (Inverse Fast Fourier Transform) techniques, speech signal is scrambled. Then it is decoded to obtain the same speech signal and now the original speech is confused. Then it is transmitted using transmitter. The coding and decoding is done with CODEC.
In the receiver side, if the receiver knows how the speech signal is scrambled, then the receiver would descramble the scrambled signal and get the original speech signal. The programming is done on the assembly language of the ADSP 2181 processor
DIGITAL SIGNAL PROCESSING:
In general signal carries information, and the objective of signal processing is to extract this information.
Signal processing is the method of extracting information from the signal. Thus signal processing is concerned with representing in mathematical terms and extracting the information by carrying out algorithmic operations on the signal.
Analog signal are real world signals that you and I experience everyday- sound, light, temperature, pressure. A digital signal is a numerical representation of the analog signal. We can convert the analog signal into digital signal through our analog to digital conversion process, process the signals, and if needed, bring the signal back out to analog world through the digital to analog converter.
The basic explanation of DSP is the processing of signal by digital systems, to improve the signal. The improvement may be clearer sound, sharper images, or faster data. The digital systems are software and hardware. In digital processing of signal consists of a number of mathematical operations as specified by a software program.
DIGITAL SIGNAL PROCESSOR:
A digital signal processor is a type of microprocessor that is incredibly fast and powerful. They are specifically designed to handle digital processing tasks. As a broad generalization, traditional microprocessors, such as the Pentium, primarily directed at data manipulation. Similarly, DSPs are designed to perform the mathematical calculations needed in digital signal processing.
A DSP is unique because it processes data in real time. To start we need to distinguish between offline and real time processing.
OFFLINE PROCESSING:
In this processing, the entire input signal resides in the computer at the time of manipulation, for example, in medical imaging such as tomography, the data is acquired while the patient is inside the machine, but the image reconstruction may be delayed until a later time. The key point is all the information is simultaneously available to the processing program.
REAL TIME PROCESSING:
Signal is produced at the same time that the input signal is being acquired. This real time capability makes the DSP perfect for applications that cannot tolerate any delays. For example, did you ever talk on a cell phone where two people couldn’t talk at once? You had to wait until the other person finished talking. If you both spoke simultaneously, the signal will be cut. You couldn’t hear the other person. With today’s digital cell phones, which use DSP, you can talk normally. The DSP processors inside cell phones process sounds so rapidly you hear them as quickly as you can speak in real time.
FAST FOURIER TRANSFORM:
It is an algorithm for computing DFT with reduced number of calculations. The computational efficiency is achieved by a divide and conquer approach, which is based on the decomposition of N-point DFT into successively smaller DFT’s. In an N-point sequence if N=rm , then the sequence can be decimated into r-point sequences. Here ‘r’ is called the radix. If r=2 it is called radix-2 FFT. The decimation can be done in two ways namely Decimation In Time (DIT) and Decimation In Frequency (DIF). Here we use Radix-2 DIT FFT algorithm.
CONCLUSION :
We can use this technique in military for sending secret messages. We can use this technique wherever we want security. What we have done is storing the speech signal for a period of few milli seconds. This can be increased if we extend the memory size and select that through a decoding switch.
Digital_Signal_Processor.doc (Size: 105 KB / Downloads: 21)
ABSTRACT
Digital signal is a numerical representation of the analog signal. It may be easier and more cost effective to process these signals in the digital world. One of the main advantages of digital signal is that it can be stored and manipulated easily. To do this several processes are in use. Of these, Digital Signal Processor plays a leading role.This is used in various applications like instrumentation & measurement, communications , audio & video processing ,graphics , image enhancement , navigation , radars ,control-robotics, machine vision ,guidance etc.
The objective is to encrypt the speech signal. That is to convert the speech signal into an unknown form and then the scrambled speech signal is transmitted. The person who know, how the speech signal is encrypted can decrypt (i.e.,converting the scrambled speech signal into original signal) the signal. Thus security of sending speech message is done.
For encryption and decryption of the signal, we develop a software program in assembly language programming techniques of ADSP 2181. In this paper, encryption and decryption of the speech signal is done using the Digital Signal Processor ADSP 2181.
INTRODUCTION
In recent trends, cell phone, voice chat, etc., is the main topic of the communication. But it is not possible to speak secretly through them. Our objective is to speak secretly, i.e., to maintain security of certain important information. So for that we are going for a technology using digital signal processor.
Our paper also deals with storing and retrieval of speech signal using digital signal processor.
We have used ADSP processor 2181. This is 16 bit fixed point processor.
Here the voice signals is acquired and then digitally coded and stored in the memory of processor. Using FFT (Fast Fourier Transform) and IFFT (Inverse Fast Fourier Transform) techniques, speech signal is scrambled. Then it is decoded to obtain the same speech signal and now the original speech is confused. Then it is transmitted using transmitter. The coding and decoding is done with CODEC.
In the receiver side, if the receiver knows how the speech signal is scrambled, then the receiver would descramble the scrambled signal and get the original speech signal. The programming is done on the assembly language of the ADSP 2181 processor
DIGITAL SIGNAL PROCESSING:
In general signal carries information, and the objective of signal processing is to extract this information.
Signal processing is the method of extracting information from the signal. Thus signal processing is concerned with representing in mathematical terms and extracting the information by carrying out algorithmic operations on the signal.
Analog signal are real world signals that you and I experience everyday- sound, light, temperature, pressure. A digital signal is a numerical representation of the analog signal. We can convert the analog signal into digital signal through our analog to digital conversion process, process the signals, and if needed, bring the signal back out to analog world through the digital to analog converter.
The basic explanation of DSP is the processing of signal by digital systems, to improve the signal. The improvement may be clearer sound, sharper images, or faster data. The digital systems are software and hardware. In digital processing of signal consists of a number of mathematical operations as specified by a software program.
DIGITAL SIGNAL PROCESSOR:
A digital signal processor is a type of microprocessor that is incredibly fast and powerful. They are specifically designed to handle digital processing tasks. As a broad generalization, traditional microprocessors, such as the Pentium, primarily directed at data manipulation. Similarly, DSPs are designed to perform the mathematical calculations needed in digital signal processing.
A DSP is unique because it processes data in real time. To start we need to distinguish between offline and real time processing.
OFFLINE PROCESSING:
In this processing, the entire input signal resides in the computer at the time of manipulation, for example, in medical imaging such as tomography, the data is acquired while the patient is inside the machine, but the image reconstruction may be delayed until a later time. The key point is all the information is simultaneously available to the processing program.
REAL TIME PROCESSING:
Signal is produced at the same time that the input signal is being acquired. This real time capability makes the DSP perfect for applications that cannot tolerate any delays. For example, did you ever talk on a cell phone where two people couldn’t talk at once? You had to wait until the other person finished talking. If you both spoke simultaneously, the signal will be cut. You couldn’t hear the other person. With today’s digital cell phones, which use DSP, you can talk normally. The DSP processors inside cell phones process sounds so rapidly you hear them as quickly as you can speak in real time.
FAST FOURIER TRANSFORM:
It is an algorithm for computing DFT with reduced number of calculations. The computational efficiency is achieved by a divide and conquer approach, which is based on the decomposition of N-point DFT into successively smaller DFT’s. In an N-point sequence if N=rm , then the sequence can be decimated into r-point sequences. Here ‘r’ is called the radix. If r=2 it is called radix-2 FFT. The decimation can be done in two ways namely Decimation In Time (DIT) and Decimation In Frequency (DIF). Here we use Radix-2 DIT FFT algorithm.
CONCLUSION :
We can use this technique in military for sending secret messages. We can use this technique wherever we want security. What we have done is storing the speech signal for a period of few milli seconds. This can be increased if we extend the memory size and select that through a decoding switch.