Difference between revisions of "Projects:2021s1-13010 Socially Distant Radar"
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== Objectives == | == Objectives == | ||
| − | + | This project aims to demonstrate an operational passive radar system using | |
| + | DAB illumination in the Adelaide region by designing a “passive radar in a box” | ||
| + | containing a 2-channel passive radar system to detect aircraft on an ellipsoid | ||
| + | and compute the intersections of these ellipsoids to resolve the aircraft in | ||
| + | angle. | ||
== Background == | == Background == | ||
| Line 37: | Line 41: | ||
=== Advantages of passive radar === | === Advantages of passive radar === | ||
| − | |||
There are many advantages of using passive radar, many of these are of significant interest to the defence industry, particularly for air defence systems because it provides situational awareness. The main benefits of passive radar are listed below: | There are many advantages of using passive radar, many of these are of significant interest to the defence industry, particularly for air defence systems because it provides situational awareness. The main benefits of passive radar are listed below: | ||
| − | + | *Since an existing transmitter is used, the passive radar receiver and its location is undetectable. | |
| − | + | *Relatively low cost because a passive radar system does not require a transmitter, rotating elements and has low power requirements. | |
| − | + | *Passive radar systems are inherently resistant to jamming due to its location being unknown. | |
| − | + | *Almost any emission can be used as the basis of a passive radar. | |
These advantages can all be attributed to the use of an existing transmitter as the reference signal for the passive radar system. Some examples of transmitters include FM radio, DAB radio, DVB-T or digital television signals, and GSM or cellular network. | These advantages can all be attributed to the use of an existing transmitter as the reference signal for the passive radar system. Some examples of transmitters include FM radio, DAB radio, DVB-T or digital television signals, and GSM or cellular network. | ||
| − | == | + | == Theory for Operation == |
| + | The 2-channel passive radar system contains a reference channel (directed | ||
| + | towards the Mount Lofty DAB Transmitter) and the surveillance channel | ||
| + | (directed towards the target), which are cross correlated. The output from | ||
| + | these channels allows for the detection of aircraft on an ellipsoid and | ||
| + | compute the intersections of these ellipsoids to resolve the aircraft in angle. | ||
| + | This data can then be displayed on a range delay-Doppler map for the user to | ||
| + | view. | ||
| − | + | [[File:Ellipsoids.jpg|thumb|center|Ellipsoids over Adelaide to detect aircraft]] | |
| − | == Conclusion == | + | === System Architecture === |
| + | A custom 2-channel RF passive radar box was developed which included an | ||
| + | amplifier and filter. Each signal is fed into a PC running GNU Radio software which | ||
| + | records the data to file. The recorded data then undergoes post-processing in | ||
| + | MATLAB to obtain results. | ||
| + | |||
| + | [[File:PassiveRadarBox.png|thumb|center|Passive Radar in a Box Hardware]] | ||
| + | |||
| + | == Conclusion and Results == | ||
| + | |||
| + | Through testing, validation and guidance from the literature review, a passive radar box was able to be assembled and utilised as part of a passive radar system to detect and record targets. This consisted of physically synchronising 2 RTL-SDRs, sourcing and assembling Mini-Circuits components and a Yagi antenna, as well as constructing the enclosure for the hardware. The passive radar box was then thoroughly tested, which led to data being able to be successfully recorded during two trials for several targets. | ||
| + | |||
| + | The recorded data was then able to be successfully processed to show the ambiguity plots for each recorded flight. To get to this stage in the software development, several simulated results were generated and tested to verify their functionality. These simulations included generating fake DAB, fake targets, multipath fading, and clutter removal. | ||
| + | [[File:AmbiguityPlots.jpg|frameless|right]] | ||
| + | The results included several ambiguity plots showing an abnormal clutter line at approximately 40-50Hz, which were concluded to be either interference, a function of DAB itself, or a hardware issue. Further analysis of the bistatic geometry for the trial showed that the targets are expected to appear extremely close to the zero-Doppler line, as the angle between the transmitter to target and the flight path of the target was almost exactly 90 ̊. This meant that it was almost guaranteed for the target to be masked by clutter around the zero-Doppler line. It is recommended that further trials be conducted at a different location and analysing the bistatic geometry prior to trials. | ||
| + | |||
| + | Overall, the project was successful in that is was able to address the major success criteria of providing Adelaide University the capability to record passive radar using the passive radar boxes, opening the opportunity for future students to collaborate with DSTG to extend and improve on the project. | ||
== References == | == References == | ||
Latest revision as of 16:23, 27 October 2021
Contents
Introduction
Radars use radio waves with the principle of echolocation to estimate the location and velocity of targets. A radar system consists of a transmitter producing radio waves, a receiver to collect any scattered waves and a series of processing steps to obtain useful information about any target(s) present. In recent times, passive radars have gained prominence as they use `transmitters of opportunity’, which greatly lowers cost and detectability. A modern radar system often uses a phased array antenna, capable of generating a number of beams to improve the ability to resolve targets with different directions of arrival. For this to work, the multiple channels need to be coherent or phase locked, which present a great technical challenge. An alternative is to use a multi-static system – one with multiple pairs of transmitters and receivers – to provide angle resolution. This project uses a number of 2-channel passive radar systems to detect targets on an ellipsoid and computes the intersections of these ellipsoids to resolve the target in angle. This project will develop skills and knowledge in a key technology of interest to defence. Many of the hardware and software know-how are easily transferable to other fields such as communications and RF engineering. It offers an opportunity to work with scientists and engineers in the defence sector, exposing you to professional practice in a major growth industry in South Australia.
Project team
Project students
- Angela Vanderklugt
- Michael Makris
Supervisors
- Dr. Brian Ng
- Nathan Misaghi (DST)
Objectives
This project aims to demonstrate an operational passive radar system using DAB illumination in the Adelaide region by designing a “passive radar in a box” containing a 2-channel passive radar system to detect aircraft on an ellipsoid and compute the intersections of these ellipsoids to resolve the aircraft in angle.
Background
What is passive radar?
Passive radar can be described as a set of radar techniques that utilise existing signals as their transmitting source. This is the significant distinction between passive and active radar, as the latter uses a dedicated transmitter and single antenna for both transmitting and receiving. Another further distinction is that the transmit sources used in passive radar systems are noncooperative sources as opposed to active radar where the form of the signal is optimised for the radar function.
Advantages of passive radar
There are many advantages of using passive radar, many of these are of significant interest to the defence industry, particularly for air defence systems because it provides situational awareness. The main benefits of passive radar are listed below:
- Since an existing transmitter is used, the passive radar receiver and its location is undetectable.
- Relatively low cost because a passive radar system does not require a transmitter, rotating elements and has low power requirements.
- Passive radar systems are inherently resistant to jamming due to its location being unknown.
- Almost any emission can be used as the basis of a passive radar.
These advantages can all be attributed to the use of an existing transmitter as the reference signal for the passive radar system. Some examples of transmitters include FM radio, DAB radio, DVB-T or digital television signals, and GSM or cellular network.
Theory for Operation
The 2-channel passive radar system contains a reference channel (directed towards the Mount Lofty DAB Transmitter) and the surveillance channel (directed towards the target), which are cross correlated. The output from these channels allows for the detection of aircraft on an ellipsoid and compute the intersections of these ellipsoids to resolve the aircraft in angle. This data can then be displayed on a range delay-Doppler map for the user to view.
System Architecture
A custom 2-channel RF passive radar box was developed which included an amplifier and filter. Each signal is fed into a PC running GNU Radio software which records the data to file. The recorded data then undergoes post-processing in MATLAB to obtain results.
Conclusion and Results
Through testing, validation and guidance from the literature review, a passive radar box was able to be assembled and utilised as part of a passive radar system to detect and record targets. This consisted of physically synchronising 2 RTL-SDRs, sourcing and assembling Mini-Circuits components and a Yagi antenna, as well as constructing the enclosure for the hardware. The passive radar box was then thoroughly tested, which led to data being able to be successfully recorded during two trials for several targets.
The recorded data was then able to be successfully processed to show the ambiguity plots for each recorded flight. To get to this stage in the software development, several simulated results were generated and tested to verify their functionality. These simulations included generating fake DAB, fake targets, multipath fading, and clutter removal.
The results included several ambiguity plots showing an abnormal clutter line at approximately 40-50Hz, which were concluded to be either interference, a function of DAB itself, or a hardware issue. Further analysis of the bistatic geometry for the trial showed that the targets are expected to appear extremely close to the zero-Doppler line, as the angle between the transmitter to target and the flight path of the target was almost exactly 90 ̊. This meant that it was almost guaranteed for the target to be masked by clutter around the zero-Doppler line. It is recommended that further trials be conducted at a different location and analysing the bistatic geometry prior to trials.
Overall, the project was successful in that is was able to address the major success criteria of providing Adelaide University the capability to record passive radar using the passive radar boxes, opening the opportunity for future students to collaborate with DSTG to extend and improve on the project.
References
[1] Australian Communications and Media Authority (2020). What is digital radio? | ACMA. [online] Acma.gov.au. Available at: https://www.acma.gov.au/what-digital-radio#digital-radio-versus-internet-radio [Accessed 9 Apr. 2021].
[2] Eleceng.adelaide.edu.au. 2021. Guide to technical writing - Derek. [online] Available at: <https://www.eleceng.adelaide.edu.au/personal/dabbott/wiki/index.php/Guide_to_technical_writing> [Accessed 15 April 2021].
[3] Griffiths, HD & Baker, CJ 2017, An introduction to passive radar , Artech House, Boston, [Massachusetts] ;
[4] Kaira.sgo.fi. 2021. $16 dual-channel coherent digital receiver. [online] Available at: <http://kaira.sgo.fi/2013/09/16-dual-channel-coherent-digital.html> [Accessed 17 March 2021].
[5] Mark A. Richards, Mark A. Richards, James A. Scheer & William A. Holm 2010, Principles of modern radar (Vol. I: basic principles)., vol. 1, SciTech Publishing.
[6] Vierinen, J., 2021. Building Your Own SDR-based Passive Radar On A Shoestring. [online] Hackaday. Available at: <https://hackaday.com/2015/06/05/building-your-own-sdr-based-passive-radar-on-a-shoestring/> [Accessed 20 March 2021]. Wiki.gnuradio.org. 2021. Tutorials - GNU Radio. [online] Available at: <https://wiki.gnuradio.org/index.php/Tutorials> [Accessed 11 March 2021].
