47
votes
Accepted
Difference between bit rate and baud rate and its origins?
Baud rate is the rate of individual bit times or slots for symbols. Not all slots necessarily carry data bits, and in some protocols, a slot can carry multiple bits. Imagine, for example, four ...
- 311k
30
votes
Difference between bit rate and baud rate and its origins?
The line bit rate is the number of bits per second being moved.
The data bit rate is the number of information bits being moved per second.
The baud rate is the number of symbols per second (Baud is ...
- 22k
25
votes
Accepted
Can I use the FFT to recognize musical notes on a piano?
The concept is good, but you will find it is not so simple in practice.
Pitch is not simply the predominant tone, so there's problem number 1.
The FFT frequency bins can't hit all (or even multiple)...
- 67.8k
25
votes
How is it that two electric currents can travel in opposite directions on the same wire, at the same time, without interfering with each other?
in the sense that two telegraph signals (in other words, two electric currents) can travel in opposite directions on the same wire, at the same time, without interfering with each other
This is the ...
- 901
25
votes
Accepted
Why would you put your input amplifier in front of your filtering for an ECG signal?
Am I missing some important reason why you would do the signal
conditioning in this order?
Yes you are...
The front-end differential amplifier will be chosen such that it has a common-mode ...
- 437k
23
votes
Writing DSP algorithms directly in C or assembly?
If the compiler writers put some effort into optimizing it for that target, it will at least make some use of the special DSP instructions / architecture. But for ultimate performance it will never ...
- 6,164
23
votes
Accepted
Can sampling rate be a floating point number?
Forget sampling rate for a few seconds... Think about sampling period for a second, which is the time interval between two consecutive samples. This time can be an integer or any real number (as long ...
- 2,197
21
votes
Writing DSP algorithms directly in C or assembly?
Premature optimization is the root of all evil. - Donald Knuth
When you find that you don't get enough performance from your code, profile your program first, find the bottlenecks, analyze your ...
- 37.8k
21
votes
Accepted
Writing DSP algorithms directly in C or assembly?
It's always better to have your algorithm implemented in a higher-level language (which C is compared to assembly), even if you plan to implement everything in assembly in the end.
chances are, you ...
- 25.7k
21
votes
Detection of signals buried in noise
The only way that a signal that is "buried in the noise" can be detected is if you can run the signal + noise through some filter that attenuates the noise more than it attenuates the signal. At ...
- 45.1k
21
votes
Accepted
Does "a signal is buried in noise" mean that the noise amplitude is still smaller than the signal amplitude? (Special case: Lock-in amplification)
What you're missing is the bandwidth, both of signal and noise.
If you look at, let's say, a 1 V rms sinewave signal, together with 10 V rms noise on an oscilloscope, you'll see only noise.
However, ...
- 159k
21
votes
Accepted
How do receivers decode multiple GPS signals on the same carrier frequency?
The system takes advantage of a couple of mathematical properties of the PRNs:
First, the cross-correlation of a PRN with itself (i.e. the auto-correlation) looks somewhat like a single impulse with ...
- 18.1k
21
votes
How much data could be stored on a standard compact cassette using modern encoding?
Have there been any projects trying to explore that?
Ben North attempted to play video from a standard audio cassette tape using QAM modulation. First he tested the signal through a loopback cable. ...
- 55.6k
19
votes
Accepted
Lossless compression technique for digital signals in an embedded system
Compression is all about finding the redundancies in the data and removing them. Since you don't seem to be able to tell us much about your actual data sets, this answer will have to be very generic.
...
- 169k
18
votes
Accepted
Why is one return conductor for each forward conductor in a ribbon cable better than a shared return conductor?
Ask yourself which cable is likely to have the lowest loop area:
A large loop area has greater inductance and can emit more EM interference. It can also receive more EM interference.
If each forward ...
- 437k
18
votes
Writing DSP algorithms directly in C or assembly?
Your DSP will be advertised with a maximum sustained MACs, assuming all the pipes are filled. That is obviously an upper limit to what can be achieved. You know how many MACs your filters and other ...
- 159k
17
votes
Accepted
Why can the effective number of bits be a non-integer? What does this physically represent?
It is a result of calculating the number of bits after the imperfections such as noise and distortion are taken into account.
An ENOB of 6.8 basically tells you that for example an 8-bit ADC has real ...
- 131k
16
votes
Is the so called kTC noise, that is inherent in an RC filter, dependent on bandwidth?
The KTC noise is actually the total RMS noise power at the output of the low pass RC filter. The noise power is the product of the noise power spectral density (PSD) and the bandwidth (more accurately ...
- 3,686
16
votes
Accepted
Sampled 100 Hz sinusoidal signal from Hall sensor shows 10 Hz sidelobes when sampled at 500 Hz
If the sensor is set to 500 Hz sampling, and you have a MCU timer also set to 500 Hz to read the results, this is never going to work, because nothing is ever exact, especially devices with internal ...
- 131k
14
votes
Accepted
How does a car with keyless entry know where the key is?
They either use multiple antennas for each exterior zone of the car and/or use RF in combination with other sensors, for instance detecting that the user has touched the front driver's side door ...
- 3,379
14
votes
Can sampling rate be a floating point number?
Yes, the sampling rate can be any number you want.
But you obviously would not get partial samples in the end, you just have to round down.
In your example the first sample is taken at \$ \frac{1}{15....
- 9,354
14
votes
Why is a signal that is finite in time domain, infinite in its frequency domain?
Many texts prove that a signal cannot be both time limited and bandlimited. It is quite a deep result and depends on complex analysis, but the shortest proof I know starts with a bandlimited signal \$...
- 3,083
14
votes
Accepted
Does the DC component of any signal also carry information?
A fixed DC signal has information - the DC offset - that would be lost if it were blocked (that is, reset to 0V potential.) The bandwidth of that information is nevertheless 0Hz.
This idea comes up in ...
- 50.1k
13
votes
Performing FFT at low frequencies but high resolution?
I assume for "high speed" you mean a small delay from data collection to the resultant FFT. With a low sample rate, your computational ability isn't the limiting factor, given modern computers. The ...
- 2,878
13
votes
What does "shift keying" mean in the context of digital modulation?
It's not (phase) (shift keying), for example. It's (phase shift) (keying).
Another answer has explained why the word keying is used --- it dates to the days when modulation was controlled by a human ...
- 127k
13
votes
Accepted
How is it that two electric currents can travel in opposite directions on the same wire, at the same time, without interfering with each other?
The physics explanation is that waveguides (including the free space) have orthogonal modes for the two propagation directions. This means that the two signals traveling in opposite directions will ...
- 882
13
votes
Can sampling rate be a floating point number?
Some things are always an integer. Samples are always integer. You can take 108 or 109 samples.
Sample rate can be a floating point number, or more generally a rational, or even a real.
You ...
- 159k
12
votes
Accepted
Does USB cable quality matters (affects in someway the signal) on audio interface (or DAC)?
It's worth having a USB cable with ferrite 'stoppers' on it, to attenuate conducted emissions along the cable. This will reduce the chance of hash from the switch mode power supply and other PC ...
- 159k
12
votes
Accepted
Circuit to "zoom in" on mV fluctuations of a DC signal?
Capacitors block DC and pass AC.
You can use a series capacitor into an opamp with whatever gain you need.
Even better might be a simple RC high-pass filter...One capacitor (series) and one resistor ...
- 8,793
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