Mitigating the effects of wind farms on air traffic control and military surveillance radar
Contributor: Defence IQ Press
Posted: 08/03/2015 12:00:00 AM EDT
Mitigating the effects of wind farms on air traffic control and military surveillance radar
Ahead of the 13th annual Military Radar conference (25-27 August, London, UK), Defence IQ caught up with Dr Krishna Venkataraman, a Radar Scientist in the Department of Defence in Australia. Dr Venkataraman provides specialist science and technology advice to the DoD for the acquisition of major radar capabilities.
He is also involved in research tasks related to small target detection, netted radars, and RF interferences to radar systems.
Thank you for joining us today, Dr Venkataraman. To begin in relation to your research, could you give an overview of the impact and mitigation of wind farm returns on radar systems? What are the challenges?
The surveillance radar detects aircraft returns amidst all other strong unwanted (clutter) returns by Doppler processing the radar returns. In a wind mill, the tip of the wind blade rotates at the angular velocity of about 150 m/sec (550 KM/hour) thus getting detected by the radar due to its similarity in Doppler frequency spectrum, as that of the aircraft. Hence, while the aircraft flies over in the proximity of the windfarm, both aircraft and the wind farm echoes are detected, processed and displayed, which can result in an ambiguity. It is a high risk for the tracker that the wind farm returns will be tracked instead of aircraft returns.
This poses a serious threat and a major safety concern to the Air Traffic Control radars. Various means of mitigating this risk are being researched either to avoid radiating in the direction of the wind farms or processing the signals to effectively filter out the windfarm returns.
But the challenge is how to mitigate this risk without compromising on the genuine aircraft detectability.
What sort of techniques are being used – or will be used – to mitigate the effects of wind farms on air traffic control and surveillance radar?
The techniques currently used and those evolving are, in general, designed to mitigate the windfarm interference of two kinds; one is to avoid transmitting in the direction of the wind farms and avoiding the returns; the second is to filter out the windfarm returns using suitable signal processing methods.
It is easy to blank a specific azimuth sector especially in a phased array radar by switching the transmit beams up and down in elevation in the desired sector. However, we face the risk of not detecting any genuine targets falling in the shadow of the wind farms as well.
The second technique employs, in general, a notch filter where the notch frequency is adaptive to that of the wind farm returns. There are many algorithms being developed to address the radar requirements and wind farm operational conditions.
Another way to mitigate the wind farm interference may be to use low cost navigational radars in and around the wind farms to provide improved elevation coverage by suitable data fusion methods.
What do you think will be the biggest technological advances in the surveillance radar field over the coming years? How might this impact the use and effectiveness of radar for the military in the future?
We can quote a few, but as of now, I would think the biggest technological advances in the surveillance radars would be:
1. development of cost effective phased array radars;
2. capable of optimal operation in the presence of intentional and un-intentional interferences;
3. optimal signal processing algorithms to detect very small targets of even 0.1 Sq mtr (micro UAVs etc)
Well, the motto of military radar users would be to see even an ‘invisible’ and also not to be seen by others at all on the same token. Hence, I would expect the present combat environment using radars may swivel around in the above direction in the coming years.
What will be the most important factor in driving radar technology?
I would think it is more a case of ever changing ‘user needs’ and ‘joint ventures’ with interested agencies that drive the radar technology these days.
Needs of various military agencies vary depending on the threats, environment, operational and political conditions. This encourages the rapid ongoing development of the radar technology worldwide further, with suitable collaboration or exchange of knowledge base.
What will your presentation focus on at the Military Radar conference? What are you hoping to achieve at the event and why do you feel it’s important for you to attend?
My tutorial on “Small target detection –techniques and applications” is aimed at providing an overview of the importance of detecting small targets like UAVs, small boats, periscopes etc and the various techniques that are being developed to detect and track the almost “invisible” targets. At the end of the day, the audience should be in a position to initiate a high level design on small target detection.
I will also present a talk on the “Impact of wind farm interference on surveillance radars”, which again provides an overview of the ever-increasing threat of the windfarms that reduces the radar sensitivity especially that of the ATC radars. I aim to introduce this new ‘risk’ element that needs to be mitigated to achieve reasonable radar detection performance.
I believe that the above two areas are of utmost importance for current military radar development and I’m looking forward to speaking at the conference.
