New Advances in Receiver Performance and Reliability
Editor’s Note: This article reproduces the acceptance speeches given by the winners of GPS World’s 2012 Leadership Awards, at the Leadership Dinner in Nashville in September. The Leadership Dinner was sponsored by Lockheed Martin and Deimos Space.
Remarks by Robert Lutwak, Symmetricom; Chief Scientist, winner in the Products category. His expertise is practical advances to overcome the intrinsic physical barriers to affordable chip-scale atomic clocks, enabling precision time and time transfer in mobile GNSS and communications systems.
Thank you to the awards committee and especially to the individual who nominated me.
I would be remiss if anyone left here with the impression that the development of the chip-scale atomic clock was in any way a solo effort. On the contrary, while I have had the privilege of being the front man, the success of this program can be attributed entirely to the fantastic collaboration between three highly disparate groups, from very different industries and cultures: our Research Group at Symmetricom’s Technology Realization Center, in Beverly, Massachusetts; the MEMS group at the Charles Stark Draper Laboratory, led by Mark Mescher and Matt Varghese; and the optoelectronics group at Sandia National Laboratories, led by Darwin Serkland. If any of these groups and people had been anything less than extraordinary, both technically and personally,I would not be standing here this evening.
With this introduction I can say, with little loss of humility, that the chip-scale atomic clock (CSAC) is a really cool device. Depending on where you’re coming from, it’s either 100 times lower size, weight, and power (SWAP) than traditional atomic clocks or it’s 100 times more accurate than quartz oscillators with comparable SWAP. Regardless of your perspective, it clearly represents a disruptive technology and a paradigm shift for portable battery-powered navigation, communication, and timing applications. For comparison, the CSAC can run for a day on a full cellphone battery charge, whereas the next lowest power clock of comparable performance will run down a car battery in an hour. The CSAC is not an evolutionary improvement in SWAP, it is revolutionary in that it enables previously untenable system architectures, mission scenarios, and network topologies.
Since Symmetricom introduced the first commercial CSAC, roughly two years ago, the market response has been overwhelming. Despite having done our due diligence to predict the market demand and despite having nearly doubled our manufacturing output every quarter, our shipment backlog remains strong, and I am frequently surprised by innovative customer applications that we had not envisioned at the product launch. We have to date shipped many thousands of CSACs to more than a hundred different customers, representing vastly different markets and applications. While many of the novel applications are still in the early stages of prototype development and evaluation, it is clear that CSACs will be ubiquitous across diverse applications within the decade.
I am fortunate, in my position, to interact directly with the technical integrators of the CSAC and learn the details of many of the applications. My general impression is that the timing and frequency stability performance of the CSAC is adequate for most of the emerging applications. The most common requests that I hear from customers are for reduced cost, power consumption, and size, in that order. It is not surprising that size is at the bottom of the list. In most applications, the batteries are still larger and heavier than the CSAC, so small improvements in power consumption are generally more valuable to reducing system SWAP than size reduction of the CSAC itself.
As in any new technology, the cost will come down naturally with increased volume and improved manufacturing efficiencies, both at Symmetricom and at our vendors. While it is unlikely that you will get a CSAC in your next free cellphone, I do expect that the cost will progressively decrease over the next several years, and the technology will become cost-viable to an exponentially increasing spectrum of applications. Similarly, we continue to evolve our electronics and algorithms for improved power consumption, aided by external advancements in microwave and microprocessor electronics driven by the smart-phone industry. It is my expectation that a factor of 2X improvement in power consumption is likely within the next three to five years.
To date, most of the commercial products that have emerged, based on CSAC technology, have been in the timing and frequency calibration space. It is not surprising to me that the time and frequency community was the first to adopt and exploit the technology, as many of them have been closely monitoring the development program and had the internal expertise and experience to rapidly exploit it.
I admit, though, that I am a bit disappointed to see that there are no papers with “CSAC” in their titles at the 2012 ION-GNSS, but I am confident that this will change in the years to come. Adoption of CSAC by the navigation community has lagged behind the timing community in large part, I believe, because the technology has caught the community somewhat off-guard, and the benefits of the CSAC to INS and GNSS are just now beginning to be realized.
The most obvious and straight-forward application of CSAC to GNSS is rapid P(Y) acquisition; we have demonstrated 15-second time-to-subsequent-fix (TTSF) after two hours of GPS denial. This was a fairly simple demonstration that consisted of jamming time into an unmodified GPS receiver, but I believe that this is just the tip of the iceberg. With access to the core navigation algorithms within the receiver, precise knowledge of time could improve the receiver performance and reliability on other levels, including (at least):
◾ Improved uncertainty of the navigation solution
◾ Navigation with less than four (or less than three) satellites
◾ Anti-spoof and anti-jam detection
◾ Seamless co-integration of GNSS and INS systems
Another navigation area that I believe is ripe to benefit from CSAC technology is in self-assembling navigation systems, such as a local ad hoc GNSS-like network which self-assembles from handheld timing beacons/receivers. Such a system would have value for safety-of-life applications in GPS-denied environments, such as indoor firefighting and mine safety.
Thank you again for the recognition and opportunity of this award.