Overcoming noise challenges in analog and RF circuit design with Calibre PERC net shielding

By Hossam Sarhan

Communication has become the backbone of everything from personal routines to industry, and the demand for analog and radio frequency (RF) designs has increased significantly over the past decades. Designing these circuits can be quite challenging due to their sensitivity to various factors. Changes in layout design, operating conditions and manufacturing processes can significantly impact the performance of analog and RF circuits. One of the major hurdles faced in analog design is the issue of noise coupling between interconnects. The proximity and interactions between different circuit elements can lead to signal noise, which can degrade the overall circuit performance. Mitigating the impact of noise is a critical aspect of successful analog and RF circuit design. Fortunately, there’s a good solution.

Mitigating noise coupling with net shielding

One widely used technique to protect critical nets is net shielding. This approach involves surrounding the sensitive signal nets with power or ground nets, which serve as a shielding layer to isolate the critical signals from noise sources. The power and ground nets, with their stable and low-noise characteristics, create a shielding effect that helps maintain the integrity of the critical signals, preventing unwanted noise and disturbances (figure 1). Additionally, the geometries belonging to the same net, when placed in close proximity to each other, can also act as a form of self-shielding. The proximity of the same-net traces creates a shielding effect, further protecting the critical signals from external interference. By employing net shielding techniques, circuit designers can effectively safeguard the performance and reliability of analog and RF circuits.

Verifying net shielding effectiveness

Verifying the effectiveness of net shielding is not a straightforward task, as it requires tracing the critical net segments and checking the surrounding nets to confirm how much of the victim net is shielded. This process can be time-consuming and error-prone if done manually.

The Calibre® PERC™ reliability platform provides comprehensive reliability checking capabilities, allowing designers to quickly and easily combine multiple reliability checks into a single run for validating the reliability of a design. Calibre PERC packaged checks offer a dedicated check for net shielding, where designers can specify the critical nets and the minimum shielding percentage threshold, and the check will automatically trace each net, check the surrounding nets, calculate the shielding length, and determine if the net passes the user-defined minimum shielding percentage requirement, providing a streamlined and efficient way to ensure the reliability of analog circuits.

Conclusion

Protecting critical signals from noise coupling is a crucial aspect of successful analog and RF circuit design. Net shielding is a widely used technique that involves surrounding sensitive signal nets with power or ground nets to create a shielding effect, mitigating the impact of electromagnetic interference and crosstalk.

However, verifying the effectiveness of net shielding can be a challenging task. The Calibre PERC reliability platform from Siemens EDA provides an automated and streamlined solution for net shielding verification, helping designers to quickly identify and address noise issues, ultimately enhancing the reliability and performance of their analog and RF designs.

We have even more available on this topic in a recently published technical paper, Bulletproof signals: net shielding verification for RF and analog designs using Calibre PERC