Lewis Kelsey
  • Member for 3 years, 2 months
  • Last seen this week
  • United Kingdom
Ambiguity in the IFFT process in OFDM
Accepted answer
1 votes

The answers to this are now on my site, which I'm not going to keep updating into this answer when I modify it

View answer
Why is the relationship between Es/N0 and SNR different for complex and real signals?
0 votes

Ignoring quantisation noise, if you anti alias filter a signal at 2x the nyquist rate and then sample at 2x the nyquist rate then you capture twice the bandwidth of thermal noise. The discrete signal ...

View answer
Proper meaning (and origin) of PCM (pulse code modulation)?
0 votes

In the end, I worked out that PCM is a function that multiplies a signal with a Dirac comb, rounds them to a quantisation level, and takes the discrete data points as samples and stores them in memory ...

View answer
Why is the Dirac delta used when sampling continuous signals?
0 votes

If you decided to represent a time domain sample as an infinitesimal width sinc with main lobe width of $\frac{\pi}{T}$ at a fixed height $A$ centered at $t=0$, instead of a Dirac delta $A\delta(t)$, ...

View answer
Understanding the Matched Filter
0 votes

I feel like the other answers don't state succinctly the step by step process of how the matched filter is used on a concrete example, and what it actually consists of, and why it is needed and how it ...

View answer
How does companding compress dynamic range?
0 votes

Companding implies that there is a decompression operation, whereas compression implies that it is lossy compression and the final product, which is just used to compress in a way that cannot be ...

View answer
What's the impact of aliasing in the time domain?
0 votes

If a piece of music is sampled at 32,000 samples per second (Hz), any frequency components at or above 16,000 Hz (the Nyquist frequency for this sampling rate) will cause aliasing when the music is ...

View answer
Are capacity and spectral efficiency identical for a dicrete-time digital signal?
0 votes

In the end I came to the conclusion that the maximum spectral efficiency a channel allows with its SNR is $\log_2(1+\frac S N)$. This is a property of an analogue channel with an SNR and is measured ...

View answer
Sequence expansion by zeros and interpolation - does it insert additional frequencies?
0 votes

Zero stuffing does not insert additional frequencies and the frequencies above the original signal frequency are not present in the original signal; however, because the signal is a set of samples, ...

View answer
Autocorrelation function and correlation integral
0 votes

I think $$R_{xx}(\tau) \triangleq \int_{-\infty}^\infty x(t)x(t+\tau)dt$$ Is just for a continuous signal $X$ that isn't a stochastic process. When it becomes a stochastic process, the expected value ...

View answer
Isn't the rect pulse filter implicit at the transmitter?
Accepted answer
0 votes

This has been resolved. It was due to a misunderstanding of what a pulse filter was. It's used on the ZOH output of the DAC to convolve it, which is a multiplication in the frequency domain, i.e. it's ...

View answer
What is the difference between continuous, discrete, analog and digital signal?
0 votes

There are 2 types of digital here. Think of OFDM using 16QAM. You have a bit stream that you are taking and correlating it to discrete amplitudes of 2 4PAM signals, one in phase and one in quadrature. ...

View answer
Why the RMS of a PSD curve is the root of the area below
-1 votes

Let's just visualise what we get from the fourier transform of a real signal consisting of real cos frequencies only, in this case $A_c\cos(ct)$, within a centred rect window of length $T$. $A_{\omega}...

View answer