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Reposted by Daniel Estévez

hforsten @hforsten.com · 2d

New blog post: Synthetic aperture radar autofocus and calibration.

Synthetic aperture radar autofocus and calibration

3D trajectory position error estimation autofocus, antenna pattern normalization, and polarimetric calibration for drone mounted SAR radar.

hforsten.com

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Daniel Estévez @destevez.net · 1d

Would you like to work in RF signal processing at Muon Space
for SIGINT and RF science missions with a team of great engineers including myself? If you are eligible to work on ITAR/EAR and interested in helping us grow our cloud-based and onboard processing, my DMs are open.

RF Digital Signal Processing Specialist - Geospatial Intelligence

Mountain View, CA or Remote

job-boards.greenhouse.io

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Reposted by Daniel Estévez

hforsten @hforsten.com · 5d

Synthetic aperture radar vs Gopro.

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Daniel Estévez @destevez.net · 11d

When setup timing is violated, typically the output delay becomes much larger than the nominal one, increasingly more as the data transition approaches the clock edge. This goes somewhat against the usual idea that setup violations mainly cause metastability.

Read more: destevez.net/2025/09/flip...

A simulation of a setup timing violation. A data transition from zero to one is done increasingly close to the clock rising edge. We can see the corresponding outputs in traces of different colours. As the data transition approaches the clock edge, the output delay increases a lot, until the new data is no longer captured.

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Daniel Estévez @destevez.net · 11d

Using ngspice, the timing properties of the flip-flop can be measured. Here is an output delay simulation, where the output for different process corners is shown in different colours.

A simulation of output delay. Two clock cycles are simulated, and the data input first is one and then is zero, so we can see how the input data propagates to the output after the clock rising edge. Different process corners are shown with different colours in the flip-flop output voltage trace, so we can see the difference between the fastest and slowest corners.

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Daniel Estévez @destevez.net · 11d

New blog post: Flip-flop timing experiments. I design an ASIC flip-flop using Magic and play around with some ngspice timing simulations of output delay, setup and hold. I have made my flip-flop (top) as small as possible, so it is half the area as the standard cell (bottom).

Two ASIC cells. The one on the top, which is the flip-flop I have designed is half as tall as the one on the bottom, which is the equivalent cell from the standard library. My flip-flop is also slightly narrower. There is a large difference between the transistor size in both cells, and also the amount of room available to route all the signals. The standard cell can route everything in one metal layer, while my flip-flop needs three metal layers.

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Daniel Estévez @destevez.net · Sep 4

Everything is working fine, except that with sawtooth ramps the overshoot is too large (~100 MHz), which could be fixed by a loop filter redesign, and the fast lock mode seems to make the loop unstable (I don't know exactly why this happens).

Read more: destevez.net/2025/09/10-g...

10 GHz FMCW radar LO board – Daniel Estévez

destevez.net

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Daniel Estévez @destevez.net · Sep 4

New blog post: 10 GHz FMCW radar LO board. I've finished assembling and testing my ADF4158+HMC391 3.9-4.45 GHz LO board, for which I asked for reviews a few months ago. In the post I explain some aspects of the board design, and the software I've written and testing I've done.

A photo of an assembled PCB. It is a small board with an SMA connector, a few surface mount chips, a pin header, and tiny 0402 passives.

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Daniel Estévez @destevez.net · Aug 19

I study the Normalized Burn Ratio that measures burn severity, and three different vegetation indices that measure vegetation density and health. With these I obtain some conclusions about the damage caused by the fire.

Read more: destevez.net/2025/08/mult...

Multispectral analysis of the Tres Cantos wildfire with Sentinel-2 data – Daniel Estévez

destevez.net

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Daniel Estévez @destevez.net · Aug 19

In this post I dive into the 13 spectral bands captured by Sentinel-2 and explain how they can be used to measure vegetation health and fire affectance. This image shows SWIR in red, highlighting burnt areas, NIR in green, highlighting vegetation, and visible green in blue.

A false colour image that shows short wave infrared in red, near infrared in green and visible green in blue. Vegetation looks green or bright green, depending on density. The burnt area looks red, except for some surviving vegetation which can still be seen in green.

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Daniel Estévez @destevez.net · Aug 19

New blog post: Multispectral analysis of the Tres Cantos wildfire with Sentinel-2 data. This image shows vegetation surviving the fire in green, vegetation lost by the fire in magenta, and areas affected by the fire but with less vegetation loss (dry grass) in blue.