Design by Finding RF Interference Analysis with Altium

Radio frequency interference analysis is one important task in high frequency and high-speed PCB design. Interference at radio frequencies can arise due to many simple design errors, but these problems can be easy to spot with the right PCB design tools. When you need to identify areas of a design that can create RFI problems, an automated rules-driven toolset can help.

If you’re unclear on what RFI is or how you can spot areas in a design that can create RFI problems, then keep reading. RFI is not limited to analog systems, it happens in digital systems and produces the same types of problems seen in analog systems. However, you don’t need special design software to solve RFI problems, you can implement any design changes you need with the complete set of PCB routing and layout features in Altium Designer.

ALTIUM DESIGNER

A unified PCB design application with a full suite of RF circuit board design tools and a complete set of routing features for professional designers.

So much of the world runs on wireless technology, which is supported by RF PCBs with complex layouts. Getting these systems to work properly and identify RFI problems in a design radio frequency interference analysis, RF interference detection, and some basic field solver calculations to implement design changes. What can designers do to stay ahead of the curve and produce the best PCBs for their designs?

Professional designs that operate at high speed or high frequency should be analyzed thoroughly. This means performing radio frequency interference analysis using some basic equations, simple electromagnetic interference programs with field solver features, and even some tests for measuring an RF interference spectrum and performing spectral analysis. If you want to know what areas of a design you should check for possible EMI problems, then keep reading to learn more.

What is RFI Analysis?

Radio frequency interference analysis is a set of tests and procedures where emission from a design is determined, and any required design changes are used to ensure circuits do not interfere with each other when running at high frequencies. Some tasks in RFI analysis and applications of RF interference analysis involve testing and measurement, while others require calculations, often with an electromagnetic field solver.

Although you’ll often need a field solver for highly accurate RFI analysis, modern design tools will include some type of field solver utility. This allows your design to check basic signal integrity and RFI problems at a range of frequencies, including high GHz frequencies. Some points that should be examined include:

• Location of return paths around a circuit board layout
• Distance between reference plane discontinuities and interconnects
• Impedance controlled routing
• Strength of interference
• Large current loops involving discharging through capacitance or plane layers

If you can perform RFI detection through calculations in the above areas, you can take steps to ensure your design functions as intended and passes EMC checks.

Identify RFI Problems in an Intuitive Interface

Calculating an RFI spectrum and emitted power is a serious mathematical problem that requires a field solver to ensure wave characteristics are accounted for in the design. Although RFI detection and calculation may seem esoteric, most problems with RFI and noise in high-frequency analog systems can be traced to a grounding problem or incorrect routing. Impedance control up to GHz frequencies is just the start, you’ll need to design the stackup correctly with uniform reference planes and proper routing to maintain a well-defined return path.

The next time you need to design a PCB stackup that ensures RFI immunity and allows routing with low loop inductance, don’t settle for manual calculations. Altium Designer’s PCB stackup design and trace routing tools include an integrated field solver that runs basic electromagnetic interference calculations in a design. You can spot and eliminate RF noise sources and design rule violations instantly as you create your PCB.

• Changing layers during routing in a multilayer PCB is a common way to create a high loop inductance path that emits significant RFI.

  Learn more about routing your interconnects through vias while changing reference planes.

• Some basic structures on the surface of a PCB can be used to provide shielding and suppress reception of RFI in an interconnect.

  Learn more about designing shielding for RFI prevention in a circuit board.

• Preventing RFI problems in a design and solving them with creative routing requires a PCB stackup creator to place plane layers and plan layer transitions in your PCB.

  Learn more about designing a PCB stackup for low noise in Altium Designer.

Design your PCB stackup with accurate material property values and standard interconnect designs to ensure impedance control and RFI immunity.

The Best CAD Tools and Routing Features for Your RF Circuit Board

Whether you’re designing simple RF devices like hand-held radios or cordless phones, your design features should help you identify common areas where RFI can arise and show how to correct them. Once you’ve identified what needs to change in your design, circuit board CAD tools with an integrated design engine will give you the ability to easily change your design and check that it follows basic industry standards.

To change your PCB layout so that RFI and noise can be reduced, you’ll need to do some of the following tasks:

• Redesign the PCB stackup and layer selection to ensure consistent system impedance.
• Use uniform copper as reference planes for high-speed/high-frequency signals.
• Match impedances to the intended system value (usually 50 Ohm).
• Group components into clusters with similar functions and frequency.

CAD tools that include electrical rule specifications are exactly what you need for these tasks, and you can find the best set of PCB layout tools you need in Altium Designer.

Complete Your RF Circuit Board Design in a Single Program

Designing to low PDN impedance requires placing ground and power layers close together on adjacent layers to ensure high plane capacitance. It also helps to select the right set of PCB materials to ensure the design has low loss and low PDN impedance. The integrated Layer Stack Manager in Altium Designer is the first tool you’ll use to ensure you’re designing to your target PDN impedance as you create your design.

• The best CAD tools can help you visualize your return path. Altium Designer makes this easy and helps you spot return path violations without a separate program.

  Learn more about tracking the return current path in your PCB layout.

• If you accidentally route over a split in a ground plane, your CAD tools should help you locate and solve this problem to prevent RFI and noise.

  Learn more about problems that arise with split ground planes in a PCB layout.

• Altium Designer users can export their design into Ansys SIwave to help them identify and solve electromagnetic interference problems, signal integrity problems, and power integrity problems with a powerful simulation interface.

  Learn more about using field solvers for radio frequency interference analysis.

Altium Designer contains a complete set of PCB design features.

High-Performance RF PCB Layout in Altium Designer

Getting the layer stack correct, routing with controlled impedance, identifying parasitics, and grouping components are simple to implement if you have Altium Designer. All of these tasks are fundamental for high-performance RF circuit boards that run at multi GHz frequencies and have mixed-signal functionality. In addition, you’ll need to evaluate all aspects of your circuit board layout and routing to ensure manufacturability and compliance with industry standards.

Altium Designer takes all of these design tools and includes them in a single application with manufacturing features, schematic design and simulation utilities, and a comprehensive rules-checking engine. Layout problems that can cause RFI problems and noise between different circuit blocks can be easily identified and corrected before a board spin. When you’ve finished your design, and it’s time to prepare it for fabrication and assembly, Altium Designer will be there to help you finish the job.

Ensure Successful Fabrication and Assembly

Altium Designer helps you complete your design projects successfully by instantly preparing your board for manufacturing directly from your design data. You can quickly export standard fabrication files without using any external application. You’ll also have an integrated toolset for managing your PCB design and manufacturing data with the Altium 365 platform. Everything you need for high-speed/high-frequency design is accessible in a single program with Altium Designer.

• Everything you need for design, manufacturing, layout, routing, and simulation is included in Altium Designer.

  Learn more about unified design in Altium Designer.

• The integrated field solver utility in Altium Designer lets you calculate impedance and propagation delay on your interconnects within the Layer Stack Manager.

  Learn more about the integrated field solver from Simberian in Altium Designer.

• When you’re ready to share your project with other PCB designers or your manufacturer, Altium 365 lets you instantly share your circuit board design and production data through Altium Designer or on the web.

  Learn more about sharing your PCB project data with Altium 365.

Layout your impedance controlled high-speed PCB design with ease in Altium Designer.

Don’t settle for a budget RFI analysis calculator or budget design software. Instead, use the only application with the industry’s best PCB layout and routing utilities, integrated simulation features, and a comprehensive rules-driven evaluation engine. Only Altium Designer includes all these features and many more.

Altium Designer on Altium 365 delivers unprecedented integration to the electronics industry until now relegated to the world of software development, allowing designers to work from home and reach unprecedented levels of efficiency.

We have only scratched the surface of what is possible to do with Altium Designer on Altium 365. You can check the product page for a more in-depth feature description or one of the On-Demand Webinars.