29-09-2012, 12:18 PM
DEVELOPMENT OF ADAPTIVE EQUALIZER FOR m-PSK & m-QAM RECEIVERS
[attachment=34795]
Tasks carried out to achieve set of objectives
1. To generate a baseband digital modulated signal with in-phase and quadrature phase(i+j) signals
2. Creating multipath Rayleigh fading channel to the input baseband signal
3. Using LMS algorithm adjusts the filter coefficients in order get the desired response
Introduction to equalizer
In a communication system, the information is transmitted over a RF channel
RF channel distorts the transmitted signal
Amplitude, frequency ,phase are changed
A receiver should compensate the distortions to recover the transmitted signal
Channel equalization is the compensation of the distortions in the transmitted signals
M-PSK AND M-QAM SIGNALS
In Adaptive Filter an FIR filter is used for filtering process, because it is inherently stable
It structure involves forward paths only
So for this kind of filter we use digital modulation techniques for change in signal variation amplitude, frequency & phase.
m-PSK
m-QAM
Equalizer
The equalizer is a device that attempts to reverse the distortion incurred by a signal transmitted through a channel.
To adapt the coefficients to minimize the noise & intersymbol interference it depends upon the type of equalizer in the output.
Equalizer reduce intersymbol interference to allow recovery of the transmit symbols by using an complex algorithm
Adaptive Equalization
For a time varying channel , an adaptive equalizer is needed to track the channel variations
Adaptive equalizers compensate for signal distortion
attributed to intersymbol interference (ISI), which is
caused by multipath within time-dispersive channels.
LMS(Least mean square):
The LMS (least mean squares) algorithm is an approximation of the steepest descent algorithm which uses an instantaneous estimate of the gradient vector of a cost function.
The difference between the reference signal and the actual output of the transversal filter is the error signal
[attachment=34795]
Tasks carried out to achieve set of objectives
1. To generate a baseband digital modulated signal with in-phase and quadrature phase(i+j) signals
2. Creating multipath Rayleigh fading channel to the input baseband signal
3. Using LMS algorithm adjusts the filter coefficients in order get the desired response
Introduction to equalizer
In a communication system, the information is transmitted over a RF channel
RF channel distorts the transmitted signal
Amplitude, frequency ,phase are changed
A receiver should compensate the distortions to recover the transmitted signal
Channel equalization is the compensation of the distortions in the transmitted signals
M-PSK AND M-QAM SIGNALS
In Adaptive Filter an FIR filter is used for filtering process, because it is inherently stable
It structure involves forward paths only
So for this kind of filter we use digital modulation techniques for change in signal variation amplitude, frequency & phase.
m-PSK
m-QAM
Equalizer
The equalizer is a device that attempts to reverse the distortion incurred by a signal transmitted through a channel.
To adapt the coefficients to minimize the noise & intersymbol interference it depends upon the type of equalizer in the output.
Equalizer reduce intersymbol interference to allow recovery of the transmit symbols by using an complex algorithm
Adaptive Equalization
For a time varying channel , an adaptive equalizer is needed to track the channel variations
Adaptive equalizers compensate for signal distortion
attributed to intersymbol interference (ISI), which is
caused by multipath within time-dispersive channels.
LMS(Least mean square):
The LMS (least mean squares) algorithm is an approximation of the steepest descent algorithm which uses an instantaneous estimate of the gradient vector of a cost function.
The difference between the reference signal and the actual output of the transversal filter is the error signal