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2. Measurements and Simulation in the Design Flow
Shortening the product development cycle has long been a key objective of today’s R&D organizations. Especially in the automotive and aerospace industries, one method to reduce development time is concurrent design and test, which is often represented with the V-diagram product development model. In these industries, for which the end product is a highly complex “system of systems,” the left side of the V-diagram is considered “design” and the right side represents “test.” The idea behind the V-diagram is that greater efficiency can be achieved by beginning the test and validation of subsystems before the development of an entire system is complete. While the use of concurrent design and test approaches such as the V-diagram is common in industries with highly regulated environments, adoption of these practices is growing in other industries and for other types of devices. For example, in the semiconductor and consumer electronics industries, shorter product life spans and increasing product complexity continually fuel the pressure to reduce product development time.
According to a 2009 McKinsey survey on fabless semiconductor design processes, the ratio of product life cycle to product development type in the semiconductor industry is approximately one-third of what it is in the automotive industry.1 The same McKinsey survey estimates that the average development time of a new semiconductor design is approximately 19 months. For this reason, the authors claim that “R&D Excellence” is a key differentiating factor.
Given the business imperative for improving R&D excellence in the product development process, the goal of concurrent design and test has become widespread throughout the electronics industry. A key method to empower this practice is increasing the connectivity between electronic design automation (EDA) simulation software and test software all the way to the component level.
Software in the Design Process
To understand the role of simulation software in the product design flow, engineers must understand the role of software in both the design and test phases of product development. During initial design and simulation, EDA software is used to model either the physical or electrical behaviors of a simulated product. Essentially, the EDA software is a utility that uses mathematical models to represent the output of a device under test (DUT) based on a series of inputs and then presents these metrics to the designer.
During the validation and verification stage of product development, engineers use software in a slightly different context—namely to automate measurements on a real prototype. However, similar to the design and simulation phase, the validation and verification process requires the same measurement algorithms as those used by EDA software tools.
The Role of Software in Product Development
One emerging feature in today’s EDA software is the ability to provide increasing levels of software connectivity between the EDA environment and test software. More specifically, this connectivity enables (1) modern EDA software environments to drive measurement software and (2) measurement automation environments to automate the EDA design environment.
One benefit of the connectivity between design and test software environments is that it allows design engineers to use significantly richer measurement algorithms earlier in the design process. They gain not only more valuable knowledge of their designs earlier in the design process but also the opportunity to correlate simulations with measured data from the validation and verification process. A second benefit of increased connectivity between EDA and test environments is that it allows test engineers to develop working test code much sooner in the design process, which ultimately reduces time to market for complex products.
Using EDA Software to Produce Richer Measurements
One way that EDA and test software connectivity improves the design process is through richer measurements. Fundamentally, EDA tools use behavioral models to predict the behavior of a new design. Unfortunately, the modeled design is often verified using measurement criteria that are ultimately different than those used to verify the final product, making it difficult to correlate simulated and measured data. One growing trend is to use a common toolchain for design through test—a trend that ultimately enables engineers to introduce measurements into the design flow earlier.
"Connectivity between our EDA tools and NI's test software allows engineers to develop a test bench simultaneously with product development, providing earlier test feedback in the design process, and greatly shortening design cycles by making development and test parallel rather than serial."
- Serge Leef, Vice President and General Manager of System Level Engineering Division, Mentor Graphics
For example, consider the design of a cellular multimode RF power amplifier. Traditionally, this type of component is designed and modeled using RF EDA tools such as AWR Microwave Office. With the EDA environment, engineers typically “measure” RF characteristics such as efficiency, 1 dB compression point, and gain through simulation. However, the end product must meet additional RF measurement criteria explicitly established for cellular standards such as GSM/EDGE, WCDMA, and LTE.
Historically, “standard specific” measurement data from metrics such as LTE error vector magnitude (EVM) and adjacent channel leakage ratio (ACLR) measurements required instrumentation on a physical DUT largely because of measurement complexity. Going forward, new connectivity between EDA software and automation software enables engineers to use these sophisticated measurement algorithms within the EDA environment on a simulated device. As a result, they will be able to identify system-related or complex product issues much earlier in the design cycle and, therefore, shorten design times.
Using Models to Parallelize the Test Development Process
A second trend toward integrating design and test practices is to use EDA-generated behavioral models to accelerate the development of product verification/validation and manufacturing test software. Traditionally, one source of inefficiency in the product design process is the delay of test code development for a particular product until after the first physical prototypes are available for testing. One way to accelerate this process is to use the software prototype of a given design as the DUT when writing either characterization or production test code. Using this approach, engineers can parallelize development time for both characterization and production test software with product design, which results in an overall improvement in time to market.
For example, consider the development approach Medtronic engineers chose for a recent pacemaker design. They were able to use a new software package specifically designed to connect the Mentor Graphics EDA environment to NI LabVIEW software. By connecting these environments, the engineers could begin developing a test bench well before physical hardware was ever produced. The inherent parallelism achieved by this design approach fundamentally enables engineers to deliver products to market more quickly than before.
Going forward, integrated design and test practices will be a major factor in improving engineering design excellence. Because of greater connectivity between EDA and test software, engineers in the next several years will more effectively use EDA software to provide richer simulations and more effectively use EDA simulations to improve their validation and production test processes.
1Bauer, Harold, Felix Grawert, Nadine Kammerlander, Ulrich Naeher, and Florian Weig. Autumn 2011. “Getting Mo(o)re out of semiconductor R&D,” McKinsey & Company, http://www.mckinsey.com/Client_Service/Semiconductors/Latest_thinking/Getting_More_out_of_semiconductor_RD.