Digital Twins: Is it real or is it EDA?

Some of you may remember the very successful marketing campaign, "Is it real or is it Memorex". Memorex was a brand of audio recording tape. The company claimed such a high recording fidelity that the ad challenged the listeners to tell the difference between live music and music recorded on Memorex tape. How is this relevant to digital twins and EDA (electronic design automation)? For that, we must look at the early history of EDA, and the convergence of software integration, parallel computing, and simulation software.

What are digital twins?

Before we dive deeper into EDA, let's briefly review digital twins as a technology. A digital twin is a dynamic virtual copy of a physical system. This can be mechanical, electrical, or any other system that can accurately be described mathematically. The purpose of a digital twin is to mimic the real-world counterpart. Essentially, it's simulation software with a twist. Real-world measurements are fed to the simulation software, which then computes the output algorithmically or through ML (machine learning). The predicted output is compared with the real-world output, to determine whether the system is operating properly. This allows you to anticipate failures and experiment with what-if scenarios by virtually changing the operating environment. As a nascent technology, the methodology may vary depending on the application.

Figure 1. PathWave RF Synthesis (Genesys)

History of EDA

The origin of EDA goes back to the 1970s when text-based circuit simulation called SPICE (Simulation Program with Integrated Circuit Emphasis) was developed at UC Berkeley. Its use was initially limited to simulating analog circuits. It wasn't until the 1980s, when graphical displays became available on computers, that schematic capture and PCB (printed circuit board) layout tools became possible. These early tools were essentially drawing tools, albeit with DRC (digital rule check) and auto-routing capability. The tools didn't understand what a transistor was or how the traces on the PCB could affect the impedance and propagation delays. The lack of computing power and high-speed storage kept these tools from becoming integrated. In the last decade, schematic entry, layout tools, circuit simulation, thermal simulation, and EM (electromagnetic) simulation have converged to create a comprehensive design environment that is virtual end-to-end. Figure 1 shows PathWave RF Synthesis in action, where it integrates the workflow of a complex RF design.

Figure 2. PathWave EM Design (EMPro)

EDA Integration

The power of an integrated EDA ecosystem can be demonstrated with a simple design example. When a transistor is selected for the final stages of an RF power amplifier, the EDA tool not only understands the pinout of the transistor but has a complete model of its electrical characteristics, thermal properties, and physical dimensions. This information is passed off to the circuit simulator to verify the design for signal analysis. The board layout can then be done using a front-end PCB simulation tool to ensure that the traces meet the impedance and timing requirements. Finally, EM simulation considers all the physical and electrical properties of the design to model whether the product will pass regulatory standards, such as EMI (electromagnetic interference).

An EM simulation is illustrated in figure 2, where the radar profile of an airplane is modeled, taking into account the aircraft's intricate geometry as well as the RF signal's radiation profile. This type of simulation is not unlike a wind tunnel simulation in that it requires massive amounts of data storage and computational power. What was once the reserve of government-funded research using supercomputers has become more widely accessible because of cloud computing.

Figure 3. A digital twin test instrument of the future

Future of EDA

As you can see, EDA tools allow you to virtually create, test, and operate a design without leaving the workstation. What is partly missing in the EDA toolchain is the ability to close the loop by interfacing test instruments with the simulation software. This is the exciting part that will make digital twins a standard tool for the industry. Allowing test instruments to feed live data into the simulation software will allow you to verify the operational integrity of the device and determine whether any service or calibration is required. Today, when you are troubleshooting a circuit, you are burdened with knowing what a good signal should look like since that knowledge is buried deep in the schematics and datasheets. By integrating the instruments with the knowledge stored in the EDA system, the designer will one day use EDA as a digital twin. Figure 3 shows a test instrument from the future that will become "awareā€¯ of which part of the circuit is being probed. It will obtain the go/no-go parameters from the circuit simulation software to automatically validate the signal integrity and display pass/fail.

Conclusion

The blurring of reality with digital simulation will have us asking whether it's real or Memorex all over again, but this time, it won't be just a marketing slogan. High-fidelity test instruments and simulation software running on massively paralleled computing platforms will play a pivotal role in actualizing digital twins as a powerful solution for design automation and maintenance management. If you'd like to learn more about the state-of-the-art in EDA and simulation software, check out the links below.

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