Issue link: https://iconnect007.uberflip.com/i/1496727
26 DESIGN007 MAGAZINE I APRIL 2023 e challenge in grid- ding is to ensure your return paths in different sections do not inter- fere with each other, as this leads to noise coupling and cross- talk. Field solvers inte- grated into advanced PCB design tools can help you spot devia- tions from return paths as you create your lay- out. For high frequency designs, use a continu- ous ground plane struc- ture to ensure consistent return paths. 2. Isolate Antenna Sections Modern cell phones and cellular equip- ment have become the gold standard for RF isolation techniques through the use of cre- ative isolation structures. Very simply, isola- tion involves placing some shielding around an RF-sensitive element in the board to block propagation of waves between an emitter and receiver. Here are some options you can use in your RF antenna section to isolate compo- nents, feedlines, and the antenna from each other or external noise sources. Isolation structures are generally placed between RF elements to block noise coupling and power exchange between them. Determin- ing which isolation structure you should use to ensure RF antenna signal integrity is a com- plex design problem that has been thoroughly researched. If you're not an expert at elliptical integrals, you'll need to rely on an electromag- netic (EM) field solver to determine how these structures affect feedline/RF antenna imped- ance, as well as the level of isolation these structures provide. If you have access to an EM field solver, you can use near-field and far-field simulations to identify areas where strong radiation occurs in your PCB layout. Once you identify these areas and which frequencies are being emitted, it's easier to see which type of isolation strategy you should use. It's best to work directly using a finite element method (FEM) solver rather than using Fourier transforms to convert from FDTD results. While RF antenna design and layout requires careful attention to detail, this extra caution pays off, as you ensure isolation and signal integrity for your RF design. Key Takeaways • RF antennas come in many form factors, ranging from flat chip antennas integrated into ICs to copper antennas printed directly on a PCB. • Creating a layout with one or more anten- nas requires ensuring isolation between different circuit blocks in your PCB. • When you need to design an RF antenna, you should use CAD tools that help you design isolation structures, transition structures, and even printed antennas for your PCB. DESIGN007 Cody Stetzel is lead technical marketing engineer for Cadence Design Systems. This article appeared as a Cadence Design Systems blog post.