company profile mesuro
Although customers tend to want to keep the details of their improvements under wraps, Mesuro is able to share the results of its efforts at increasing the efficiency of a low-power 900 MHz amplifier made by TriQuint. This device, which was built with a GaAs technology that the US outfit knew very well, initially delivered an efficiency of around 65-70 percent. Following harmonic tuning by Mesuro, efficiency rocketed to over 90 percent.
“I think that’s still an industry record,” says Emsley, who adds that the engineers at TriQuint were also pleased with the characteristics of the waveforms producing this far higher efficiency, and the mode of operation of the device.
Dynmaic load line measuremnets with Mesro’s system
The amplifier required modifications before it could be used in the end application, so the team at Mesuro, in partnership with researchers in Cardiff’s Centre for High Frequency Engineering, built a MMIC around this device. It took just one go to build that circuit, which delivered a highly creditable efficiency of 82 to 83 percent.
“Bear in mind that it was a student designing the MMIC, and most commercial customers will take two to three goes to get a design correct,” says Simon Mathias, Mesuro’s Vice President of Sales. “This was a very simple design, but it proved a point: You can get device data, translate it to a usable circuit design, and achieve very good performance.”
A different approach The key to this fast, successful approach for understanding and optimising device performance is that it is the device that is the model. Engineers adopting the Mesuro method run the device under its standard operating conditions and then optimise its performance by adjusting current and voltage waveforms, taking in account the impact of harmonics. “You are not mathematically modelling,” explains Emsley. “You are obtaining a complete emulation of the environment in which the device is going to be used.”
A more technical description for the measurement technology employed by Mesuro is open-loop, active- harmonic load pull.
The term open loop refers to the architecture of the system: It defines how the load is presented to the
device, and how this device is driven. A more stable testing environment results from using an open loop rather than a closed one, according to Emsley: “The device reacts, but only to the instructions that you put in; and because of the open loop architecture, the tendency for the device to oscillate is significantly reduced.”
To realise active load pull, the device is driven by an amplifier so it overcomes the losses in the system. In Mesuro’s case the approach is also described as ‘harmonic’, because the first, second and sometimes the third harmonics are controlled in this type of measurement.
Benefits associated with measuring the device in this manner extend beyond uncovering pathways to higher efficiency, and include the possibility of improving device reliability. That’s because insights provided by the Mesuro’s technology can expose overdriving of the device, which can be to blame for its modest efficiency. There are occasions when devices driven at their peak voltages produce current when they should shut it off, and this destroys the device.
This understanding of the relationship between current waveforms, voltage waveforms and reliability comes from the research group led by Paul Tasker, head of the Institute of High Frequency and Communications Engineering at the University of Cardiff. Tasker founded this group when he took up a chair in the department in 1997, motivated by a belief that there was tremendous
The term open loop refers to the architecture of the system: It defines how the load is presented to the device,and how this device is driven.A more stable testing environment results from using an open loop rather than a closed one
March 2012
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