Solid-state pulse Doppler radar tracks small targets in high clutter environments
Militaries worldwide are increasing funding for radar systems that can track small targets such as rubber boats in high clutter, littoral environments as well as in the high seas. In this Q&A with Spike Hughes, Sales and Marketing Director for Kelvin Hughes, he discusses how solid-state, pulse Doppler radar technology enables those capabilities and also is being developed to counter the threat of small unmanned aircraft. Edited excerpts follow.
MCHALE REPORT: Please provide a brief description of Kelvin Hughes such as the markets it serves, key technology areas, etc., and your role within the company.
HUGHES: Kelvin Hughes effectively has two main divisions. One focuses on charts – nautical charts and publications for the commercial shipping industry. The second is the radar equipment division, which serves two main markets – commercial shipping and the military. I am Sales and Marketing Director for this division.
This division compliments the activities of the charts division by providing type-approved X- and S-band radars to commercial shipping customers. On our military side we provide naval navigation radar and have more recently added a security division, which targets border security, drone detection, and critical infrastructure applications with smaller versions of our naval radar solutions.
MCHALE REPORT: For military radar programs where do you see the most investment from militaries around the world – maritime, airborne, ground, etc.? Is the military radar growing globally or is it more flat?
HUGHES: We have taken the view that it is a growing market for what we specialize in, which is maritime surface search, tracking small objects, and littoral applications. As threats in these areas increase – such as terrorists in small rubber boats or the proliferation of small drones – militaries worldwide are looking for ways to counter them and the radar technology best suited for that is X-band solid-state pulse Doppler radar.
There has also been an increased requirement for stealth in radar systems. Ship designs that have traditional aluminum casting antenna turning unit have degraded stealth capabilities. But by using a carbon composite housing formed with a stealth profile for the stealth structure, the radar cross section can be reduced by 90 percent. Notably the SharpEye transceiver is also located inside the turning unit housing making the system an upmast radar transceiver system unlike typical magnetron and other radar systems being downmast.
MCHALE REPORT: What are a couple key military platforms that use your radar technology?
HUGHES: Our systems are on the Trinidad and Tabago Coast Guard Damen Stan Patrol 5009 ships and our bridge systems and SharpEye Doppler radar systems are on the United Kingdom Royal Navy Tide Class also known as the MARS Tanker. The SharpEye systems will also be on the UK Royal Navy’s three new River class Batch 2 Offshore Patrol Vessels (OPV) to be named HMS Forth, HMS Medway, and HMS Trent. In the Far East our SharpEyes are used on the Republic of Singapore navy’s new Littoral Mission Vessels (LMVs).
MCHALE REPORT: Could you please explain solid-state pulse Doppler radar and how it differs from other radar technology in use today?
HUGHES: Basically about five years ago Kelvin Hughes transitioned from a magnetron radar-based product company to a solid-state transceiver, pulse Doppler radar. We didn’t invent them, but they’ve been around a long time, since the late 1980s.
Pulse Doppler radar can differentiate between moving and non-moving targets essentially via zero Doppler filters. The radar determines the range to target by timing pulses. Doppler processing enables clutter removal without picture degradation and by using solid-state transceivers you have less wear parts, which reduces maintenance costs and improves reliability.
The big difference between it and magnetron systems is in the operational benefit. The ability to detect range of Doppler radar transmissions is a fraction of what it would be with magnetron radar. A ship or submarine that uses pulse Doppler radars is far less likely to be heard than those using magnetron radars.
Having then adopted pulse Doppler technology we designed radar systems for marine applications. The radar systems can look at small, slow-moving targets – those moving at less than a 100 knots. It is also efficient at tracking helicopters. We are able to add flexibility in that we can change the radar systems transmission to optimize it for particular type of target. For example we could set it up in a mode that enhances the detection of helicopters, while decreasing its ability to see other things. We can also do the same with submarine periscopes. (See figure 1)
HUGHES: We don’t use VPX, but where possible we do use commercial standards. The digital output coming from the SharpEye radar system transceiver is ASTERIX, an open source air traffic management (ATM) protocol. Using this standard makes integration with legacy and other systems in various platforms much more cost effective for the customer. [Editor’s note: ASTERIX, or All Purpose STructured Eurocontrol SuRveillance Information Exchange, is an ATM Surveillance Data Binary Messaging Format which enables transmission of harmonized information between any surveillance and automation system, according to the Eurocontrol website.]
MCHALE REPORT: It seems every piece of electronic equipment today is getting smaller – GPS systems, radios, etc. How have reduced size, weight, and power requirements affected your radar designs? What are the tradeoffs with smaller tech?
HUGHES: The biggest problem we face when we get smaller is dissipating the heat. It is a boring problem to have, but can be quite complex. It is a critical part of our designs, as we want to avoid using air conditioning (AC) systems that add size, weight, and power. Some radar designers in the coastal surveillance market put AC systems up the mast. Of course, then in a remote station, you have to double that AC system with a user that does not like to add extra weight.
So we made our solution smaller and dispensed with heat through power management and the design of the transceiver housing. When we did militarize on the smaller variant we reduced the power we were transmitting and thus reduced the transceiver size enabling it to be enclosed within a radome, which also houses the antenna. This made this smaller variant of SharpEye called SCV suitable for small watercraft.
MCHALE REPORT: Kelvin Hughes also designs radar systems for submarines. How does submarine radar differ from that used on surface ships?
HUGHES: There are two main types of submarine radar. One is with a transceiver sitting inside the pressure hold in the downmast system where you pass a waveguide through the pressure hold and have with the turning motor and antenna located upmast.
The second type puts the transceiver outside the pressure hold upmast as close as possible to the antenna and then going to pressure hold is a line cable.
From a submarine designer’s perspective the latter is more preferable, but you bring in new complications by having the transceiver outside of the pressure hold. Unlike sailors on surface ships, submariners hate using radar as it is like having a loud speaker. Aside from when they come in and out of harbor they shy away from it. However, by having a SharpEye solid-state transceiver results in a quieter operation in transmission terms that makes it more viable for uses outside of harbor entry/exit.
MCHALE REPORT: What are the next challenges/threats your military customers are looking to counter with radar technology and what innovation in radar systems will be necessary to counter those threats?
HUGHES: The proliferation of submarines around the world has increased, as has that of threats from adversaries using small boats. Seeing a submarine periscope with radar is a demanding type of task and requires a better type of radar. Seeing small targets in degraded conditions requires phased array radars with SharpEye Doppler processing technology.
Drones are also an increasing concern to ships at sea and to operations on land. Similar requirements also exist in border security and critical infrastructure applications where our customers are looking to spot people as far out as four or five kilometers.
Non-Doppler, typically magnetron radars cannot see through heavy clutter. During my service in the navy when we were on exercises and it was raining, we would drift with the rain cloud while being almost undetectable to adversaries. Today with solid-state Doppler radar you are not just able to track smaller targets, but you can track targets in conditions where you could not in the past. It is no surprise that many of our key customers are located close to the equator as that’s where you get heavy rain. Smugglers and pirates in heavy rain are difficult to see in their rubber boats when using a magnetron radar. Not so with solid-state Doppler systems.
MCHALE REPORT: Is Kelvin Hughes working on any solutions for unmanned aerial vehicle (UAV) detection from single aircraft to swarms?
HUGHES: We get about four to seven inquires a week just from drone detection. In the radar business that is a lot of inquiries and shows how important that particular application is to the market.
What we’ve been doing involves algorithms and waveforms for our portable SxV radar. Currently the range is just under a kilometer for picking up quadcopters and similar sized aircraft. We think can do better than that and are working to refine those algorithms. SxV is a low-powered, small radar. It will have more flexibility to be placed on top of a land rover, or a man portable mast. The system is very easy to operate. I’ve actually done it and to get it up and running takes ten minutes. The display and attached cameras can be cued from the radar.
We are participating in about 20 trials and at the moment testing the algorithms and refining the system in the field. (See figure 2)
MCHALE REPORT: You served in the Royal Navy more than 30 years ago. How would say radar technology has changed since your days in the service?
HUGHES: I was in the Navy from 75 to 88 and there is not a lot of difference from the radar we used then and the magnetron radar of today. The big difference is the development of solid-state Doppler transceivers for radar. It is a more recent technology as magnetron had been around since 1947. It was tweaked and played with and refined by the 70s and 80s, but was not able to go much farther in terms of performance and is why the switch has been made to solid-state pulse Doppler radar.
MCHALE REPORT: Looking forward, what disruptive technology/innovation will be a game changer for radar technology? Predict the future.
HUGHES: Adapting solid-state radar technology for general use in addition to specialist users such as the military. When you start removing all rotating parts in systems it becomes affordable for a wide user market. Phased array radars today are quite expensive beasts. As technology improves here the price will come down.
It will be similar to what happened with GPS devices. I remember when we were selling GPS products for pretty close to $50,000 a pop and now they are cheap and found in wristwatches. The same approach can be applied to solid-state radar. When we went down the solid-state route, we had no idea we’d be developing drone detection solutions. With developing phased array systems we cannot fully predict how the technology will be used as time goes on.