29
votes
Accepted
What sampling frequency should I use if Nyquist is not available?
HINT
When you sample at below the Nyquist rate, aliasing happens. That means frequencies higher than half the sampling rate get folded back down to below half the sampling rate.
Have a read about ...
- 26k
21
votes
What sampling frequency should I use if Nyquist is not available?
As correctly stated in Peter K.'s answer, this question is about aliasing. Since you can't sample at a rate that is sufficiently high to avoid aliasing - i.e., $f_s>50\textrm{ kHz}$ - you have to ...
- 92.4k
10
votes
Accepted
What is the difference between continuous, discrete, analog and digital signal?
A signal is indeed a function. Given a signal $f(x)$, according to whether continuous or discrete for both the variable $x$ and the function $f(x)$, there are four types of combinations:
(1) $\mathbf{...
- 475
9
votes
How do I calculate the bandwidth from a waveform?
A sinusoidal signal is represented as
$$x(t) = \mathrm{cos}(\omega t) = \mathrm{cos}(2\pi f t)$$
$\omega$ is the angular frequency and $f$ is the frequency. See Frequency definition.
Your signal \...
- 6,725
9
votes
Accepted
what's the pass band ripple and stop band attenuation of a digital filter?
I hope the plot below helps answer your question. Typically I have seen the "passband ripple" and "stopband attenuation" expressed in dB as shown in the picture translating the ...
- 55k
7
votes
Accepted
Trying to understand the general scheme of how real-time audio signal processing works on embedded system
System acquires sound data through a microphone(Digital Mic, 16bit, 16khz)
Audio can come from all kind of sources. Could be a digital microphone with a PDM interface, could be an A/D converter (...
- 48.2k
6
votes
Average bit error and symbol energy
As explained in Maximilian Matthé's answer, the exact computation of the symbol error probability of this constellation (ITU-T V.29 modem standard) is quite complex. However, you can quite easily ...
- 92.4k
6
votes
Average bit error and symbol energy
The optimal decision regions are the Voronoi Regions. I dont know, if this is what you are looking after.
...
- 6,238
6
votes
Why is CDMA not enough for wireless communication?
From an abstract viewpoint, the space $\Omega$ of all signals that are essentially band-limited to a bandwidth of $W$ Hz (say from $f_0$ Hz to
$f_0+W$ Hz) and essentially time-limited to duration $T$ (...
- 20.9k
5
votes
What is IQ Data?
I and Q signal concept is relatively complex topic to explain without signal background, you first need a basic knowledge about Passband and Baseband real and complex signals. if you are familiar ...
- 184
5
votes
Why is CDMA not enough for wireless communication?
You're misunderstanding what CDMA, TDMA and FDMA do:
CDMA doesn't increase the channel capacity in any way. It's a MA, MA = Multiple Access mechanism.
In other words, it's just a way of dividing the ...
- 32.5k
5
votes
Accepted
Are there analog re-configurable filters?
can we have re-configurable analog filters?
Yes. The knob you turn on your grandma's kitchen or living room radio changes the tuning of an oscillator by changing the capacitance of a component. Any ...
- 32.5k
5
votes
Why is phase range between $-\pi$ and $+\pi$ (instead of $0$ and $2\pi$)?
It is just a convention, but it is useful in some cases. For example, the phase of the DFT of a real discrete-time signal is odd only if the angles are expressed in the range $[-\pi, \pi)$. Sometimes ...
- 15.4k
5
votes
Why is phase range between $-\pi$ and $+\pi$ (instead of $0$ and $2\pi$)?
First, when you're talking angles, in DSP pretty much all angles are $\mod 2\pi$. So $2\pi \equiv 0$. Usually it's more convenient to keep angles on the interval $\left [-\pi, \pi \right )$, because ...
- 13.3k
4
votes
Differentiating between zero and not sending for OOK
A simple way to do it would be using a start bit like UART. When idle, don't transmit anything. When you want to transmit something, first transmit a start bit which is a '1' (ON). Then transmit a ...
- 121
4
votes
Do integration/differentiation processes work as simple filters?
Yes, integration and differentiation can be linear filters.
You can start from laplace properties that say:
$ \int_{0}^{t} {x(t)dt} \longrightarrow \frac{X(s)}{s} \...
4
votes
Accepted
Confusion implementing Quantization in MATLAB?
Why i am getting same quantized signal in xq2 and xq3,
Very poor choice of test signal.
A 10 Hz cosine wave sampled at 100 Hz has only 3 different values that keep repeating (in flipped in sign and ...
- 48.2k
4
votes
Trying to understand the general scheme of how real-time audio signal processing works on embedded system
Buffer Management:
In most embedded systems, buffer management is typically a
combination of hardware and software functionalities. For a
microcontroller like ARM Cortex, the Direct Memory Access (...
- 6,814
3
votes
Accepted
Bandwidth and Bit rate
Bandwidth is of course occupied by the signal itself. The modulation design of the signal determines the bandwidth. That's why pulse shaping techniques are adopted by many different kind of ...
- 195
3
votes
Accepted
Comparison using cross correlation
A stereo audio file will have 2 channels. You will need to select each channel separately and do cross-correlation. The Xcorr function understands only real or complex vectors as input but you are ...
- 139
3
votes
Accepted
Why must the angle contain $\pi$ for $\cos$ be periodic?
I will reuse a former answer of mine too: Proof of complex conjugate symmetry property of DFT. It relates to how sines and cosines can be defined. One answer is: from the exponential, and thus derives ...
- 32.3k
3
votes
difference between GMSK (Gaussian Minimum shift keying) and GFSK (Gaussain frequency shift keying)
With GMSK, the frequency modulation index is 0.5. With GFSK, the frequency modulation index is larger than 0.5 (the signaling tones are farther apart).
The receiving techniques used for GMSK as an FSK ...
- 2,710
3
votes
Why is cos(n/6) aperiodic?
The periodicity of a signal holds if we can show $x(n)=x(n+N)$, otherwise, the signal is nonperiodic. Simply start with
$$
\begin{align}
x(n+N) &= \cos( \frac{n}{6} + \frac{N}{6}) \\
&= \cos(\...
- 357
3
votes
Digital Derivative
Practically calculating the derivative of a digital signal is straightforward, just convolve the signal samples with the taps of a(n approximate) derivative filter. MatLab has the functions filter() ...
- 2,710
3
votes
Accepted
How does cascading low pass modules affect pass band ripples?
The passband region of an equi-ripple filter is the region where its magnitude is in the interval $[1-\delta,1+\delta]$, where $\delta$ is the maximum approximation error. At the passband edge the ...
- 92.4k
3
votes
Accepted
polyBLAMP anti-aliasing in C++
First of all, if your phasor oscillator has a step discontinuity (as opposed to a ramp one) at $\phi\bmod 1 = 0$, then you should use the four-point, fourth order polyBLEP residual, not the fifth-...
3
votes
Accepted
What are the definitions of symbols and samples related to PCM?
Quantization and encoding are largely independent. "Symbols" is another word for "pulses", and the line encoding can also play a role in how the information is transmitted.
Say you quantize one ...
- 15.4k
3
votes
Accepted
When calculating SNR, is noise included in signal?
The SNR is the ratio of $S$, the power in the signal $s(t)$, and $N$, the power in the noise $n(t)$. So, $$\text{SNR}_\text{dB} = 10\log_{10}\frac{S}{N}.$$
When using RMS values, we have $S = s_\text{...
- 15.4k
3
votes
Accepted
Discrete signal vs digital signal?
For most in signal processing, a digital signal (source: wikipedia)
is a representation of a physical signal that is a sampled and
quantized
So it represents data as a finite sequence of ...
- 32.3k
3
votes
Accepted
Why symbols have to be upsampling, if the symbol rate and sample rate is same what happen?
The baseband information-bearing signal $s(t)$ is a train of time-shifted orthogonal pulses: $$s(t) = \sum_k a_k p(t-kT),$$ where $a_k$ is the sequence of symbols and $T$ is the symbol rate. The ...
- 15.4k
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