National Instruments

National Instruments Uses AWR Software with Confidence in the Design of High-Performance Vector Signal Analyzer

The Design Challenge

The design challenge was to optimize the performance of a 20Hz - 3.6GHz downconverter, a key element within NI's PXIe-5665 Vector Signal Analyzer (VSA), while adhering to specific space constraints. Typically, footprint limitations compromise performance parameters such as isolation and RF power; however, for the 5665 VSA, this was not an acceptable compromise. So, we got creative.

With AWR's software, we were able to explore various component selections (Modelithics library was a nice addition here), shielding schemes and of course RF layouts too. AWR was also extremely helpful in designing the high frequency filter that in the end helped us to meet both size and performance requirements, including spurious specs. We also relied on AWR's Microwave Office software to design efficient bias networks for our RF amplifiers -- making the bias networks broadband enough while providing sufficient RF isolation, not wasting DC power nor generating excessive heat.

The Solution

The system-level development of the downconverter was first modeled within AWR's Visual System Simulator. The RF system model then enabled us to further investigate component behavior such as noise level, distortion level and frequency response. Following from this, we drilled down into the circuit level design of key components within the downconverter itself like filters, RF amplifiers and bias networks.

Additionally, we used Modelithics lumped-element component library within Microwave Office for the design of critical components. For example, the design of a 4GHz interdigital filter was initially carried out using closed form models. It was then subsequently analyzed in an EM simulator. The observed offset was then used for space mapping to guide the re-design with actual circuit models.

This entire design flow process converged in a few quick steps and resulted in minimal EM simulation/time. Not only were we able to minimize the layout and number of design spins, but we got to market fast.

Our key reasons for choosing and continuing to use AWR software

1. AWR's intuitive user interface puts it in a class all its own among EDA tools. The learning curve is fast. We were productive in less than a week.
2. AWR's seamless link between system and circuit design. Drill up/down for a more macroscopic or microscopic view of design performance without user redundancy.
3. AWR support - whether it is the extensive AWR documentation and on-line context sensitive help or the models that are robust and accurate or the technical support... it all works very well and gets the information to the users quickly.

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