Hot answers tagged

13 votes
Accepted

Is it possible to "boost" a WiFi signal using an aluminum soda can?

What you show is a crude reflector. Yes, you can use reflectors around a antenna to get more power in a particular direction at the expense of other directions. This can be useful when the other ...
  • 11.3k
8 votes

Can wifi signal reception be improved by opening a door?

This is engineering. Test it. It's not like it takes a lot of money or time to do experimentally. As far as what the theory says, it will always have a slight effect. The magnitude of this effect ...
7 votes
Accepted

Best way to send a signal in a very low frequency (250Hz)?

With a sample rate of 250 Hz, you could easily send 100 bits/second or more. In 0.5 second, that would be on the order of 50-60 bits. The question is, what bit patterns should you select that are ...
  • 6,759
6 votes

What are the meanings of the second argument to the convolution?

I think the diverse range of names for the second argument arises from the fact that the convolution operation is so useful in so many different fields. It is helpful to recall what the convolution ...
4 votes

Finding the sampling period to avoid loss of signal

The smallest feature that you need to capture is the dip between 3.5 and 4. If you use a sampling period which is greater than 0.5, then you may end up not capturing this feature. The sampling ...
4 votes

What is a "window of length N" in a signal processing algorithm?

"Window" is often used to mean a successive set of samples processed as a batch. In this case it appears that the algorithm works on batches of 500 samples at a time.
  • 11.3k
3 votes

Are there offsets in these accelerometers signals?

Alhtough this answer should be awarded to Pete, because he has spotted it first. The accelerometer has a sensitivity of 5%, which corresponds to 100[mV/g]. what you are measuring is 0.1[m/s^2], which ...
  • 22.9k
3 votes

Is it possible to "boost" a WiFi signal using an aluminum soda can?

This might work to boost the signal in one direction, but it will reduce it in other directions. Antennas are often built with elements (like your drink can) that couple to the primary radiator. These ...
3 votes

What is a "window of length N" in a signal processing algorithm?

The term time-window or often just window is used to mean a short period of time during which something is possible, or during which you observe something, or during which you look for something. ...
  • 5,960
3 votes

signal-to-interference-plus-noise ratio (SINR) and others calculation

First, you should link in a reference to the Hata and Ericsson models. I haven't heard of them, and a quick search on Google didn't give anything. Path loss and received signal strength are typically ...
2 votes
Accepted

What kind of signal is the signum function? A power signal or an energy signal?

First point is that signum is not continuous with the jump at $t=0$. Second because of the absolute value in the integral it has the same $E$ and $P$ as a constant signal $1$. This means that $E_{...
2 votes

Is it possible to "boost" a WiFi signal using an aluminum soda can?

All of these cans are made up of Aluminum. Aluminum is a good conductive material and a dense material. More dense material means more capability of conductance. They can be used as antennas to ...
2 votes

Finding the sampling period to avoid loss of signal

To prevent loss of signal you need to sample at twice the highest frequency presented in the signal. This is also known as Nyquist rate. Assuming that time t is in seconds, the smallest time period ...
2 votes

Can wifi signal reception be improved by opening a door?

I live in a big old 1920s built house. The bedroom is one floor above the router, and one room adjacent. The floors in my house are wooden, the walls are stone, the cielings are high and the doors ...
  • 121
1 vote

Finding a signal output $y(n)$ with input signal $x(n)$ and impulse response $h(n)$ with a DTFT

As seen here at Wikipedia, the DTFT of signals of the form $a^n u[n]$ is $$ a^n u[n] \leftrightarrow \frac{1}{1 - a e^{-i \omega}} $$ To perform convolution of two sequences, it is enough to use to ...
  • 638
1 vote

Active noise cancelling headphones - How fast does a digital signal processor have to be to perfectly cancel out noise with an inverted signal?

There's a "rule of thumb" for any phase-sensitive control loop that the processing phase lag has to be less than $\frac{\pi}{4}$ at the frequencies of interest to be stable. For decent noise-...
1 vote

How to add a Gaussian noise signal with zero-mean in a given data set?

You can use the following formula to produce the white noise for one cell. = 0.5*NORM.S.INV(RAND()) Where: 0.5 : can change to ...
  • 22.9k
1 vote

Is it possible that room noises could end up on the recording when recording audio from an analogue source?

Unless the room noise is loud enough to cause physical vibrations in the playback head, leading to misalignment of the head vs. tape track (which could cause crosstalk or amplitude dropoff), there's ...
1 vote

Are there offsets in these accelerometers signals?

You are using a piezo electric accelerometer. There are always always always offsets and low frequency noise on a piezoelectric accel. Depending on the charge amp, anything below about 3 hz is ...
  • 2,526
1 vote

Quickly stopping a phone from attaching to a network

The stereotypical tinfoil hat (or the equivalent) would allow you to create a faraday cage, preventing the signals being sent/received. Of course, it would have to have been done prior to turning it ...
  • 6,427
1 vote

Small wireless proximity device to alert me when my cat gets into my WiFi range

If your objective is only to determine device in range, and you've located a suitable wireless camera to meet your size requirements, such a device could be used without privacy concerns if you ...
  • 6,427
1 vote

How does free space path loss change with receiver's antenna's height

Your equation is correct for your definition of $d$. However, your definition of $d$ seems incorrect. $d$ is supposed to the be distance between the transmitter and the receiver, that is the ...
1 vote

How to read the block diagram for the 2nd order integrator feedback system?

The wavy symbols are integrators, which means that: $$\frac{dy}{dt} = x_1$$ $$\frac{dx_1}{dt} = x_2$$ Then the "+" sign gives you (the triangles are "gains", which means multiply): $$x_2 = x(t) - ...
  • 1,816
1 vote

Filtering Long-duration Signal

First, I'm assuming that by "moving window", you mean breaking the signal up into smaller chunks and filtering each chunk separately. In the signal processing word, "moving window" would often mean ...
  • 2,526
1 vote

Center line of cut-off periodic signal

The problem that you describe comes from the fact that you calculating the average of the vector with numerical values. In order to calculate the exact mean of $\sin(x)$ or other functions, you should ...
  • 1,046
1 vote

Hilbert transform LTI

A linear operator $\Theta$ is an operator acting on functions $F$ and $G$, with coefficients $a$ and $b$, such that the following equality holds: $$ \Theta(aF+bG) = a \Theta(F) + b \Theta(G) $$ Put ...
  • 3,981
1 vote

Is it possible to "boost" a WiFi signal using an aluminum soda can?

It is too small a surface area to be an effective microwave reflector. The shape is wrong too, it must be parabolic with respect to the transmitting fractal antenna of the router. Yours is ...

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