Tagged: synthetic aperture radar

WHY2025 Conference: Passive and Active RADAR using Software Defined Radio

Videos from the WHY2025 (What Hackers Yearn) have recently been uploaded to YouTube, and there is one interesting talk by Jean-Michel Friedt titled "Passive and active RADAR using Software Defined Radio". 

RAdio-frequency Detection And Ranging (RADAR) aims at using electromagnetic signals for detecting target location and motion. We demonstrate in this talk various RADAR architectures using dual-channel coherent Software Defined Radio (SDR) receivers and the associated signal processing techniques relying heavily on cross-correlations. Embedded systems are tackled, with a Raspberry Pi providing enough computational power for recording and post-processing.

RAdio-frequency Detection And Ranging (RADAR) aims at using electromagnetic signals for detecting target location and motion. Being constantly illuminated with electromagnetic smog, we can benefit from existing radiofrequency emitters meeting RADAR requirements -- strong power and wide bandwidth -- for passive RADAR measurements where no active emitter is needed, using only coherent passive dual-channel Software Defined Radio (SDR) receivers for passive recording of existing signals. If existing signals are unsuitable, we can use the same principle with non-cooperative emitters such as a Wi-Fi dongle in an active RADAR setup.

All processing flowcharts are implemented using GNU Radio for real time acquisition, and GNU/Octave or Python for post-processing: generic principles will be demonstrated, applicable to all sorts of receiver hardware. We will conclude with Synthetic Aperture RADAR (SAR) where antenna motion is used to simulate wide aperture receiving antennas, adding azimuth resolution to range resolution.

Supporting documents are found a https://github.com/jmfriedt/SDR-GB-SAR or https://github.com/jmfriedt/passive_radar orhttps://github.com/jmfriedt/sentinel1_pbr

WHY 2025 - Passive and active RADAR using Software Defined Radio

Creating a Drone Based Synthetic Aperture Radar

Synthetic Aperture Radar (SAR) is a technique that can generate high-resolution imagery through the use of radar microwaves on a moving platform. Placing the radar system on a moving platform allows the system to simulate a very large aperture. Combined with some clever algorithms, the result is very high resolution imagery available in all weather conditions.

Typically, SAR implementation is the domain of high-level military spy and commercial satellites such as ICEYE and Sentinel-1. However, on his blog, Henrik Forstén has shown that it's possible to create a homemade SAR system using an FPGA, ADC, and custom 6 GHz radar antennas mounted on an FPV drone. Henrik's blog explains his setup in detail, discussing the radar and RF design, link budget, FPGA, his custom PCB, focusing, and more.

The results are rather stunning images that look almost like a photograph. And not only was Henrik able to take images, but a video too, which can be seen on his blog post.

A Synthetic Aperture Image from Henrik's Drone

FOSDEM 2024 Videos now Available: Synthetic Aperture WiFi RADAR, GPU DSP Acceleration and more

FOSDEM (Free and Open Source Developer’s Meeting) is a yearly conference that took place in Brussels, Belgium on 3 - 4 February 2024. This conference featured a room on Software Defined Radio and Amateur Radio.

Recently the videos of most the talks have been uploaded to their website. Some interesting talks include:

Covert Ground Based Synthetic Aperture RADAR using a WiFi emitter and SDR receiver

Link to Talk Page

Using a WiFi emitter as radiofrequency source illuminating a scene under investigation for slow movement (e.g. landslides), a Ground-Based Synthetic Aperture RADAR (GB-SAR) is assembled using commercial, off the shelf hardware. The dual-channel coherent Software Defined Radio (SDR) receiver records the non-cooperative emitter signal as well as the signal received by a surveillance antenna facing the scene. Spatial diversity for azimuth mapping using direction of arrival measurement is achieved by moving the transmitter and receiver setup on a rail along a meter-long path -- the longer the better the azimuth resolution -- with quarter wavelength steps. The fully embedded application runs on a Raspberry Pi 4 single board computer executing GNU Radio on a Buildroot-generated GNU/Linux operating system. All development files are available at https://github.com/jmfriedt/SDR-GB-SAR/

Synthetic Aperture RADAR with WiFi and USRP SDR

Using GPU for real-time SDR Signal processing

Link to Talk Page

GPU processors have become essential for image or AI processing. Can they bring anything to real-time signal processing for SDR applications? The answer is yes, of course, but not all classic algorithms (FIR, DDC, etc.) can be used "as is", sometimes a different approach must be taken. In this presentation, I will share the solutions that I implemented to achieve multi-channel DDC on NVIDIA Jetson GPU and will make a comparison with "classic CPU" approaches.

Using GPU's for Real Time Signal Processing

Maia SDR: an open-source FPGA-based project for AD936x+Zynq radios

Link to Talk Page

Maia SDR is an open-source project with the main goal of promoting FPGA development for SDR and increasing the collaboration between the open-source SDR and FPGA communities. Currently it provides a firmware image for the ADALM Pluto and other radios based on the AD936x and Zynq. This firmware can display a real-time waterfall at up to 61.44 Msps in a WebSDR-like interface using WebGL2 rendering, and record IQ data in SigMF format in the SDR DDR. The FPGA design is implemented in Amaranth, an Python-based HDL, and the software stack is implemented in Rust, targetting the embedded ARM CPU and WebAssembly.

The first firmware version was released in February 2023, and the project was presented in June in the Software Defined Radio Academy. In this talk we cover the progress since the summer, including the addition of support for devices such as the Pluto+ and AntSDR. We focus on the technical details of the project and the possibilities for re-using some of the components in other projects.

Maia SDR

DAPNET: Bringing pagers back to the 21st Century

Link to Talk Page

When talking about pagers, most of us will think about an object of the past, often seen in TV shows from the 90s, used by medical staff and businessmen. However, they're an interesting way to get simple data broadcast over amateur radio frequencies, with receivers that can be built for less than 20€. We'll explore this and understand how an extensive network can be deployed with simple equipment and using open source hardware and software.

DAPNET Talk

Passive Radar Sensing via Ambient Radio Noise from the Sun and Jupiter

Recently Dr. Sean Peters from the Naval Postgraduate School, in Monterey, CA presented an interesting webinar titled "Leveraging Ambient Radio Noise for Passive Radar Sensing of the Terrestrial and Space Environment".

In passive radar, the radio source is typically an existing powerful terrestrial broadcast station, such as FM, DAB, TV or cellular. However, Dr. Peters makes use of more ambient radio noise sources, such as sun noise, and even noise from Jupiter.

By using Sun noise as the source and an Ettus USRP SDR as the receiver, he's been able to measure the ice sheet thickness at the Store glacier in Greenland. Furthermore he's also been able to utilize sun radio noise and radio noise from Jupiter for passive synthetic aperture radar, with the application being planetary remote sensing.

Traditional active radars transmit a powerful electromagnetic pulse and record the echo’s delay time and power to measure target properties of interest, such as range, velocity, and reflectivity. Such observations are critical for investigating current and evolving conditions in extreme environments (i.e., polar regions and planetary missions); however, existing radar systems are resource-intensive in terms of cost, power, mass, and spectrum usage when continuously monitoring large areas of interest. I address this challenge by presenting a novel implementation of passive radar that leverages ambient radio noise sources (instead of transmitting a powerful radio signal) as a low-resource approach for echo detection, ranging, and imaging. Starting from theory, simulation, and lab-bench testing, I first present the results of our passive radar sounding demonstration using the Sun to measure ice sheet thickness at Store Glacier, Greenland. I then project the passive radar’s performance and ability to provide valuable glaciological observations (such as melt rates, bed reflectivity changes, and englacial water storage) across Greenland and Antarctica.

In the second part of my presentation, I then extend this technique to enable passive synthetic aperture radar (SAR) imaging using radio-astronomical noise sources (e.g., the Sun and Jupiter’s radio emissions). I conclude by highlighting applications of this technique to planetary remote sensing, such as (1) using Jupiter’s HF radio emissions alongside an active VHF radar to characterize and correct for Europa’s ionospheric dispersion during a flyby mission and (2) using the Mars Reconnaissance Orbiter (MRO) Shallow Radar (SHARAD) to analyze solar radio burst candidates for Martian passive sounding.

Leveraging Ambient Radio Noise for Passive Radar Sensing of the Terrestrial and Space Environment