Tagged: beam forming

KerberosSDR: Tracking Aircraft on a Map via Passive Radar and Beamforming Only (Future Code Demonstration)

If you've been following KerberosSDR development (our US$149 4 channel coherent RTL-SDR), then you'll know that one interesting experiment that you can set up with it is a passive radar. Passive radar makes use of already exiting strong transmitters that broadcast signals such as FM, DAB and HDTV.

With one directional antenna pointing towards the transmitter, and one pointing in the general direction of moving objects like aircraft, it's possible to detect the transmitted signal being reflected off the aircraft's body.From the time delay and doppler shift detected in the reflected signal, a simple distance/speed plot showing the aircraft in motion can be created. This previous post shows an example of what information you could potentially collect in a range/speed graph over time. In the past we've also used passive radar to detect vehicles and measure how much traffic is in a neighbourhood.

However, with two antennas we can only get the detected object's range and distance information. If we use four antennas (one pointing towards the transmitter, and three pointing in the direction of objects), it is possible to use beam forming techniques combined to obtain an estimated map coordinate of the object. This is possible as we then we have distance information available from the passive radar algorithm, and bearing information available from the beam forming algorithm.

Tamas Peto who wrote our open source KerberosSDR code has been working on some new upcoming features for the KerberosSDR software, and beamformed direction finding of passive radar is one of them.  We note that to be clear this software is not yet released, and we still expect there to be several months before it is ready. At the moment all data was processed manually offline after collecting data with a KerberosSDR as part of this early test.

The image below shows an example of a recent measurement made from an aircraft. The red tracks show the actual ADS-B GPS coordinates of the aircraft, and the black line indicates the positional data measured from a DAB signal reflecting off the aircraft body. The orange line to the east indicates the main lobe of the three beam formed directional antennas, and the lines to the west indicate transmit towers.

The measured trajectory is only about 1-2 km off the actual one. Tamas notes that the position offset may be because at the moment altitude is not measured yet.

If you're interested in more information, Tamas created a PowerPoint presentation which can be downloaded from our Google Drive.

Passive Radar with Beamforming and Direction Finding
Passive Radar with Beamforming and Direction Finding

Other upcoming features that are planned for the KebrerosSDR code include being able to use direction finding on short bursty signals, improvements to networked direction finding and beamforming which may be useful for applications like radio astronomy and performance improvements.

KerberosSDR can be purchased from the Othernet store or Hacker Warehouse, and every purchase helps us fund development of more interesting features like passive radar beamforming!

KerberosSDR Batch 2 Ships Soon! Pricing will Rise on Monday

KerberosSDR Batch 2 will begin shipping very soon! Thank you to all who have supported this project so far. If you didn't already know KerberosSDR is our experimental 4x Coherent RTL-SDR product made in partnership with Othernet. With it, coherent applications like radio direction finding (RDF), passive radar and beam forming are possible.

We just wanted to note that this Monday the reduced preorder pricing of US$130 + shipping will end, and the price will rise to the retail price of $149.95 + shipping. So if you have been thinking about ordering a unit, now would be a good time. Ordering is currently possible through Indiegogo. On Monday we will change to our own store. EDIT: Now available to purchase on the Othernet Store.

For shipping, US orders will be sent domestically from Othernet's office in Chicago. They are still waiting on the US shipment to arrive, but it is expected to arrive by the end of next week. Once shipped locally you will receive a shipment notification.

For international orders, the packages are being labelled now, and should be going out early next week, or sooner.

KerberosSDR Inside and Outside the Enclosure
KerberosSDR Inside and Outside the Enclosure

Future Updates to KerberosSDR

With the profits raised from KerberosSDR sales we are looking to continue funding development on the open source server software and visualization software being created (as well as applying updates ourselves). In future updates we will be looking at features such as:

  • Streamlining the sample and phase sync calibration process.
  • Experimenting with software notch filters for calibration (may reduce the need to disconnect the antennas during calibration).
  • Reworking the buffering code for improved sample ingestion performance and increased averaging.
  • Direction finding and passive radar algorithm improvements.
  • Creating a networked web application for combining data from two or more physically distributed KerberosSDRs over the internet for immediate TX localization.
  • Updates and bug fixes for the Android mobile direction finding app for use in vehicles.
  • Improving passive radar to be able to use all four RX ports for surveillance so that larger areas can be covered.
  • Plotting passive radar pings on a map.
  • Beginning experimentation with beam forming.
  • In the farther future we hope to eventually have even more clever software that can do things like locate multiple signals in the bandwidth at once, automatically plot them on a map, and track them via their unique RF fingerprint, or other identifiers.
  • Future hardware updates may see more streamlined calibration and smaller sizes.
KerberosSDR Android App for Direction Finding
KerberosSDR Android App for Direction Finding