Category Archives: fft

Fourier Explained: [3Blue1Brown] Style!

If you ask most people to explain the Fourier series they will tell you how you can decompose any particular wave into a sum of sine waves. We’ve used that explanation before ourselves, and it is not incorrect. In fact, it is how Fourier first worked out his famous series. …read more

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Posted in fft, Fourier, math, misc hacks | Leave a comment

A DIY EMC Probe From Semi-Rigid Coax And An SDR

Do you have an EMC probe in your toolkit? Probably not, unless you’re in the business of electromagnetic compatibility testing or getting a product ready for the regulatory compliance process. Usually such probes are used in anechoic chambers and connected to sophisticated gear like spectrum analyzers – expensive stuff. But …read more

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Posted in electromagnetic compatibility, emc, fft, ocxo, probe, radio hacks, RTL-SDR, sdr, spectrum analyzer, testing, wireless hacks | Leave a comment

Peering Into a Running Brain: SDRAM Refresh Analyzed from Userspace

Over on the Cloudflare blog, [Marek] found himself wondering about computer memory, as we all sometimes do. Specifically, he pondered if he could detect the refresh of his SDRAM from within a running program. We’re probably not ruining the surprise by telling you that the answer is yes — with a little more than 100 lines of C and help from our old friend the Fast Fourier Transform (FFT), [Marek] was able to detect SDRAM refresh cycles every 7818.6 ns, lining right up with the expected result.

The “D” in SDRAM stands for dynamic, meaning that unless periodically refreshed by …read more

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Posted in computer hacks, fft, Meltdown, refresh, Rowhammer, sdram, security hacks, Spectre | Leave a comment