Signal Processing
Question 24 on math from GATE (Graduate Aptitude Test in Engineering) 2012 Electronics and Communication Engineering paper.
(A) 3/4
(B) 9/16
(C) 1/4
(D) 2/3
Question 25 on math from GATE (Graduate Aptitude Test in Engineering) 2012 Electronics and Communication Engineering paper.
(a)
(b)
(c)
(d) 1
Question 6 on digital circuit from GATE (Graduate Aptitude Test in Engineering) 2012 Electronics and Communication Engineering paper.
In this circuit, the race around
(A) does not occur
(B) occurs when CLK=0
(C) occurs when CLK=1 and A=B=1
(D) occurs when CLK=1 and A=B=0
In typical wireless system simulations, there is a need to model the phase noise profile of the local oscillator. For eg, the phase noise profile of the oscillator can be of the shape described in the post on Phase Noise Power Spectral Density to Jitter. While looking around for example Matlab code, found two references [1, 2] which uses the approach of defining the phase noise profile in frequency domain, and then using ifft() to convert to the time domain samples. This post gives a brief overview of the modeling and provides an example Matlab/Octave code.
Continue reading “Modeling phase noise (frequency domain approach)”
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Those visiting the blog might have noticed a fresh look to the dspLog. This new feel is thanks to the Thesis Magazine Skin provided by FourBlogger Skins.
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The earlier posts on phase noise discussed about phase noise in oscillators, conversion of phase noise profile to jitter and the impact of phase noise on the error vector magnitude (evm). This post discuss the impact of phase noise on the spectrum of the transmit waveform. A simple random QPSK modulated symbols, oversampled and passed through a root raised cosine filtering is used for the simulation. Continue reading “Transmit spectrum with phase noise”
The previous post on phase noise discussed about finding the root mean square phase noise for a given phase noise profile. In this post let us discuss about the impact of phase noise on the error vector magnitude (evm) of a transmit symbol.
Following a brief discussion with my friend Mr. Rethnakaran Pulikkoonattu on phase noise profiles, he pointed me to his write up on Oscillator Phase Noise and Sampling Clock Jitter . In this post, we will discuss the math behind integrating the phase noise power spectral density (in dBc/Hz) to find the root mean square jitter value.
Oscillators are used in typical radio circuits to drive the mixer used for the up-conversion or down-conversion of the passband transmission. Ideally, the spectrum of the oscillator is expected to have an impulse at the frequency of oscillation with no frequency components else where. However the spectrum of practical oscillators do have spectrum skirts around the oscillation frequency caused due to phase noise. This post discuss about the phase noise of oscillator and the metrics used to specify it.
This post discuss about the thermal noise in RC low pass filter. Using the noise equivalent model using resistor with a voltage source, which gets passed through a no noise RC low pass filter. The noise power at the output is computed by integrating the output voltage spectral density over all frequencies.
Following the discussion on thermal noise and it’s modeling and noise figure computation for a simple resistor network, in this article let us discuss the Noise Figure of cascaded stages.
The post on thermal noise described the noise produced by resistor ohms over bandwidth
at temperature
Kelvin. In this post, let us define the noise voltage at the input and output of a resistor network and further use it to define the Noise Figure of such a network.
After 6 months, 2 cube’s and countless twists and turns, extremely glad to reach here.
Will enjoy the beauty of the solved cube for couple of days before breaking it and going over the whole journey again….
(Thanks dear Kunju for introducing me to the cube)
Disclosure :
After solving the first two layers, going got really tough. Couple of pointers from Rubik’s original website helped me proceed.
A friend called me up couple of days back with the question – How white is AWGN? I gave him an answer over phone, which he was not too happy about. That got me thinking bit more on the topic and the result is this post – brief write up on thermal noise and it’s modelling as Additive White Gaussian Noise aka AWGN.
