TomRoelandts.com

This article explains how to create a windowed-sinc filter with a Kaiser (or Kaiser-Bessel) window. The windowed-sinc filters in previous articles typically had two parameters, the cutoff frequency and the transition bandwidth (or rolloff). With a Kaiser window, there is a third input parameter, the ripple. For the specific case of the Kaiser window, the same… read more

This article contains more detailed information on setting the transition bandwidth (or roll-off) from How to Create a Simple Low-Pass Filter. That article suggest to use, as the filter length N, an odd number close to 4/b, where b is the required transition bandwidth. This is a good basic rule. However, in… read more

Mathematics is everywhere. In this article, I present some of the mathematics behind “Catching Them All”. Say that a rare Pokémon pops up in your Sightings, and that you walk in a straight line until it disappears again. What have you then learned about the position of that Pokémon? Well, since the… read more

This is part three of an article that describes the signal path of a radio meteor. The next step is sampling. At the point of sampling, there is a difference between a real-world BRAMS system and the simulation that produced the illustrations in this series of articles. In the real system… read more

This is part two of an article that describes the signal path of a radio meteor. At the antenna of the receiver, the reflected signal is combined with a (much smaller) directly received signal. At first sight this might seem unimportant, since the amplitude of the direct component is typically much less than… read more

If you’ve enjoyed, or simply read, my articles on the BRAMS network, you might be interested in the Radio Meteor Zoo. The Radio Meteor Zoo is a so-called citizen science project. In these kinds of projects, members of the public can help scientists with… read more

This is part one of a rather basic article that describes the complete signal path of a radio meteor, from the sinusoidal carrier wave that is initially transmitted, to the spectrogram that is typically used as the final result in the receiving chain. I have presented this material at… read more

In digital communications, the measure of the signal to noise ratio of a signal is Eb/N0. Why is that? To figure it out, let’s start from the classical SNR, which is the ratio of the average signal power S to the average noise power N, given by… read more

Not that I am going to try, but it is difficult to underestimate the importance of the first detection of gravitational waves for physics. Apart from the fact that it is another gloriously successful test for general relativity, it actually opens up a new observational window on the universe… read more

This article presents spectral reversal, a technique to turn a low-pass filter into a high-pass filter. Spectral reversal is an alternative for spectral inversion, as described in How to Create a Simple High-Pass Filter. Starting from the cutoff frequency… read more