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What is the need of non uniform quantization?
problem with uniform quantisatonis 1.real audio signal is concentrated near zero 2.human ear is more sensitive to quantisaton error at small value using non-uniform quantisaton quantisaton intrval smaller near zero Non uniform quantization reduces the signal-noise ratio at low signal levels.
What are the different types of noise in communication systems?
There are a number of ways to classify noise. It can be subdivided according to type, source, effect, or relation to the receiver, depending on circumstances. In order to make the classification more compact, noise sources can be divided into two main groups: • Noise whose sources are external to the receiver (External Noise) and • Noise source created within the receiver itself (Internal Noise). types include: Shot noise; Johnson noise and Partition noise.In electrical terms, noise is defined as the unwanted form of energy which tends to interface with the proper reception and the reproduction of transmitted signals. Electronic Devices unwanted random addition to the signal are considered as Noise.Classification of Noise:There are several way to classify Noise, but conveniently Noise is classified as1) External Noise2) Internal NoiseExternal Noise:External noise is defined as the type of Noise which is general externally due to communicationsystem. External Noise are analysed qualitatively. Now, External Noise may be classified asa) Atmospheric Noise : Atmospheric Noise is also known as static noise which is the natural source of disturbance caused by lightning, discharge in thunderstorm and the natural disturbances occurring in the nature.b) Industrial Noise : Sources of Industrial noise are auto-mobiles, aircraft, ignition of electric motors and switching gear. The main cause of Industrial noise is High voltage wires. These noises is generally produced by the discharge present in the operations.c) Extraterrestrial Noise : Extraterrestrial Noise exist on the basis of their originating source. They are subdivided intoi) Solar Noiseii) Cosmic NoiseInternal Noise:Internal Noise are the type of Noise which are generated internally or within the Communication System or in the receiver. They may be treated qualitatively and can also be reduced or minimized by the proper designing of the system. Internal Noises are classified as1) Shot Noise : These Noise are generally arises in the active devices due to the random behaviour of Charge particles or carries. In case of electron tube, shot Noise is produces due to the random emission of electron form cathodes.2) Partition Noise : When a circuit is to divide in between two or more paths then the noise generated is known as Partition noise. The reason for the generation is random fluctuation in the division.3) Low- Frequency Noise : They are also known as FLICKER NOISE. These type of noise are generally observed at a frequency range below few kHz. Power spectral density of these noise increases with the decrease in frequency. That why the name is given Low- Frequency Noise.4) High- Frequency Noise : These noises are also known TRANSIT- TIME Noise. They are observed in the semi-conductor devices when the transit time of a charge carrier while crossing a junction is compared with the time period of that signal.5) Thermal Noise : Thermal Noise are random and often referred as White Noise or Johnson Noise. Thermal noise are generally observed in the resistor or the sensitive resistive components of a complex impedance due to the random and rapid movement of molecules or atoms or electrons.Get more details from http://blog.oureducation.in/types-of-noise/
Why coaxial cable not used in low frequency?
Coax is normally used in high frequency applications due to its ability to shield the signal. The coax construction prevents radiation, while at the same time prevents noise pick up. It is the shielding that makes coax a better choice at higher frequency, however coax can be used as low as audio frequencies. Lower frequency systems do not need the shielding due to the long rise times. They are not as sensitive to noise pick up and generally do not radiate.
What is the voltage level of noise signal?
Electrical noise amplitude depends on:1. source impedance, and2. Bandwidth.Approximately, at 50 ohms, you get around one nanovolt with one hertz bandwidth, increasing at the square root of frequency, at the square root of impedance.
What is circular complex Additive White Gaussian Noise?
"Circular" means the variance of the real and imaginary parts are equal. "White" refers to the fact that the power spectral density of the noise is flat across the whole frequency spectrum. This means that its autocorrelation is a Dirac-delta at t=0 (so its covariance matrix will show noise powers on the diagonal elements and zeros elsewhere). "Gaussian" means the probability distribution of the amplitudes of the noise samples is Gaussian.
Sampling frequency doubles then quantization noise?
quantisation noise decrease and quantization density remain same.
Suppose that the quality of a phone signal degrades due to quantization noise once it is digitized?
assigning too few quantization intervals during sampling of the signal
What is the relationship between quantisation noise and bandwidth in pcm systems?
Quantization noise is a model of quantization error introduced by quantization in the analog-to-digital conversion(ADC) in telecommunication systems and signal processing.
What are the goals of signal processing?
Signal processing's goals include many things, most importantly: sampling, quantization, noise reduction, image enhancement, image understanding, speech recognition, and video compression.
What is logarithmic quantizer or quantization?
In logarithmic quantization, one does not quantize the incoming signal but log of it to maintain signal to noise ratio over dynamic range. Dr Inayatullah Khan
What types of noise are frequency independent?
noise are assumed frequency independent......
Why is amplitude modulation susceptible to noise but not frequency modulation?
because noise usually changes the amplitude not frequency.
Differentiate between natural sampling and flat-top sampling?
The natural sampling is one which can be represented with respect to amplitude of the analog signal.The flat top sampling is the one which can be represented in only a particular amplitude which cannot be changed with respect to the analog signalthis is true but let me add another difference that Is The Noise ...In Natural sampling : the sample take the top signals shape ( respect to amplitude of the analog signal ) which mean if there is noise above signal , when it will be demodulate with LBF (low pass filter ) it will cut from the original signal ,,,, We cant do that ...but In Flat-Top sampling : the sample shape will be lated so if there is noise we can remove it easily and the signal we be like it transmitted without any noise ...
Which noise becomes a great importance at high frequency?
SHOT Noise
What is the meaning of quantization noise of Pulse-code modulation?
In source coding (analog-to-digital conversion and compression), the difference between the actual analog value and quantized digital value due is called quantization error. This error is due either to rounding or truncation
What happens to noise when frequency of the wave decreases?
When the frequency of the wave decreases, the pitch of the noise decreases, making it sound lower. The noise may also become more rhythmic or repetitive as the frequency decreases. Additionally, lower frequency noises can travel further distances and penetrate obstacles more effectively.
Which type of noise has sound at every frequency within the range of human hearing?
White noise
