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Anteverta Microwave Develops and Exploits Mixed-Signal Load Pull Open Loop Concept

January 16, 2013
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Mauro Marchetti received his B.S. and M.Sc. degrees in electrical engineering from the University of Naples, Italy, in 2004 and 2006 respectively. In 2006 he joined the Electronic Laboratory of Delft University of Technology, The Netherlands, where he carried out his Ph.D. research on the development and implementation of mixed-signal instrumentation for large signal device characterization and modelling. In 2010 he co-founded and was appointed CEO of Anteverta-mw B.V.

MWJ In 2010 Anteverta Microwave was born out of research carried out at the Delft University of Technology in The Netherlands. Please explain the nature of the university’s work.

MM – The TU Delft group from which Anteverta Microwave was born was, and is still headed by Dr Leo de Vreede. This group concentrates primarily on topics related to power amplifier design and modelling with specific regards to advanced measurement and characterization tools. Recent topics have included improving efficiency and linearity in amplifiers, Doherty amplifiers, outphasing amplifiers, and the measurement systems and techniques required to develop such amplifier technology.

MWJ From when you joined the Electronic Laboratory at the University in 2006 until the spin-off, what was your field of research?

MM My research was concentrated on the development and implementation of mixed-signal instrumentation for large signal device characterization and modelling. Specifically, I worked on projects including pulsed IV/RF isothermal device characterization, and mixed-signal active harmonic load pull, which evolved into Anteverta’s first commercialized product, the MT2000.

MWJ What was the specific research that led to the commercial spin-off of Anteverta Microwave in March 2010?

MM – All of the research performed by Dr. de Vreede’s group is state-of-the-art; however it was the mixed-signal active load pull technique that offered the potential to fill an existing need in the industry. The mixed-signal approach was the first (and only) load pull system capable of wideband impedance control for realistic modulated signals, removing the constraints of traditional passive and active load pull solutions. The approach was quickly patented, and Anteverta came into existence.

MWJ What persuaded you and your cofounder(s) that the timing was right and that the spin-off was viable?

MM – At the same time that we were working on the development of our technology at TU Delft, the spreading adoption of new WLAN, 4G and 4G LTE standards across the globe was heralding in an era of unprecedented bandwidth requirements. We were in a unique position to offer a customized solution to this growing market space of handset and base station transistor and power amplifier developers.

It also didn’t hurt that our industry partners and supporters were already pressuring us for a solution.

MWJ Very quickly, in May 2010, the decision was taken to license Anteverta Microwave’s products to Maury Microwave Corporation. What was the reasoning for going down the licensing route so soon?

MM – Around the time we created Anteverta, there were several start-ups and fledgling companies entering the active load pull market and creating confusion. In fact, some were giving active load pull a bad name by over-promising and under-delivering. We realized that customers (rightfully) analyzed the worthiness of suppliers as much as the solutions themselves. It seemed clear that the quickest path to market acceptance was to partner with a leader in device characterization, someone with an established brand and customer trust.

MWJ Why was Maury Microwave chosen and has the relationship developed as hoped?

MM – Maury Microwave was the first company to understand the true potential of our product and the value of our team and to believe in it like we do. Maury immediately understood that our mixed-signal active load-pull system would be complementary to their existing products and fit perfectly within their product portfolio. Our relationship has grown stronger since the beginning and has certainly developed to be a very fruitful and successful partnership.

MWJ Do you think that the decision to take the commercial spin-off route has accelerated the research quicker than would have been the case if it had remained within Delft University?

MM – I believe that our continuous effort to meet our customer demands has certainly helped to better direct our research efforts.

MWJ – As has been mentioned,Anteverta Microwave’s technology is based on a Mixed-Signal Load Pull Open Loop concept, can you explain this concept briefly.

MM – Mixed-signal active load pull is a unique form of open-loop active load pull. Instead of direct-frequency signal synthesis and analysis, it makes use of RF upconverters and downconverters along with wideband A/D and D/A converters to create and analyze waveforms in baseband.

Because of the wideband nature of the arbitrary waveform generators (D/A cards), wideband modulated signals (typically up to 120 MHz) can be created and after upconversion presented to our device under test. That means the a and b waves can now be synthesized with a near-infinite number of frequency components within the controllable bandwidth.

The distortion of wideband modulated signals caused by impedance-shift over bandwith (as caused by passive mechanical tuners) as well as phase delays (as caused by passive interconnects) can be eliminated, since the impedances presented to the DUT can be synthesized without restriction over the entire signal bandwidth.

Such a system has the capability to put every frequency component within the signal to a single impedance point, or to any arbitrary pattern, or even to the realistic frequency-response of a typical matching network. We can even compare various matching topologies with varying wideband response and see which gives better results.

MWJ What would you say were the advantages of this approach?

MM – One of the unique features of our mixed-signal approach is that it enables designers to successfully perform load pull with wideband modulated signals, removing the errors caused by impedance-shift and phase-delay over bandwidth. It cannot be stressed enough that this is the first time since the invention of advanced modulated signals that these errors can be completely eliminated. In the past, the modulation bandwidths were small enough that the errors were small and overlooked. With WLAN, WCDMA, 4G and 4G LTE, the modulation bandwidths are large; the errors are large and can no longer be ignored 

Another significant advantage of this new technique is the blinding speed at which it can take CW and pulsed-CW load pull measurements. Those familiar with traditional passive mechanical load pull systems know it can take hours to perform measurements over a range of impedances and power levels. Our solution enables the same number of measurements to be taken in seconds or minutes, a time-saving of 20 times to 100 times or more. In fact, some users are measuring up to 1,000 impedance/power states per minute!

And as an active load pull system, compared with traditional load pull systems, we are able to cover more of the Smith Chart, giving designers and engineers more details about their transistors and amplifiers.

MWJ The technique is scalable in frequency. Does this mean that there are no frequency limits and do you see higher frequency applications becoming a significant area of activity in the future?

MM – Yes, in principle there are no frequency limitations. The system can be scaled in frequency based on the availability of components used in our RF test set. Our current commercial product portfolio covers models up to 6 GHz, 18 GHz, 26 GHz and 40 GHz; and work in the 60 GHz range is looking promising.

MWJ Anteverta Microwave was built on research. Is that still a key driver for the company and an area where you invest significantly?

MM – Research is an extremely important part of our company. As a spin-off from TU Delft, you can say that it is embedded in our company culture. In fact, since Maury handles the sales and marketing activities, we can concentrate the bulk of our efforts on R&D and improving our current and future technology offerings. We continue to maintain close relationships with our colleagues at TU Delft and share many of the same research interests and goals.

MWJ Does the company have a worldwide presence and are their specific regions where it is particularly strong or where it plans to expand?

MM – Anteverta is based in the Netherlands and has historical relationships with various industry and research partners via the university; this gives us a major European presence. Maury is based in California, has over 57 years of history, and a global sales force of dozens of representatives and international distributors. Together, we are truly a global company with a dedicated sales and support network that spans all established and emerging territories.

MWJ What are Anteverta Microwave’s short term and long term goals?

MM – Our goal is to provide the customer with a comprehensive solution for large signal measurements and for power amplifier design.

Our short-term goal is to continue expanding on the capabilities of the MT2000 mixed-signal active load pull solution: cost, frequency-range, measurement parameters... Longer-term goals include developing new solutions for large signal measurement and modelling device characterization as well as advanced power amplifier design.

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