What is the recommended design review checklist for an RF circuit board before fabrication?
RF PCB Pre-Fabrication Review
A thorough design review before PCB fabrication prevents costly respins and schedule delays. RF boards are particularly sensitive to layout errors because electromagnetic effects (coupling, radiation, impedance discontinuities) are not always visible in schematic-level simulation.
Frequently Asked Questions
How many review iterations are typical before RF PCB fabrication?
For a new RF design: 2-3 formal review iterations are standard. First review: schematic and component selection (before layout begins). Second review: layout review (after placement, before routing is complete). Third review: final review with completed routing, DRC clean, and all fab notes. Each review should involve at least one reviewer besides the designer (peer review catches errors the designer is blind to). For experienced teams doing incremental updates to existing designs: 1 review may suffice. Quick-turn prototype fabrication (3-5 day turn) often justifies a slightly less thorough review compared to production boards with 6-8 week lead times.
What are the most common RF PCB design mistakes?
The top 5 errors that cause board respins: (1) Ground plane discontinuity under an RF trace (slot from a signal route on an adjacent layer). (2) Incorrect transmission line width due to wrong stackup assumptions (designer used nominal dielectric thickness instead of the fabricator actual stackup). (3) Missing DC blocking capacitor on an RF path (causes DC offset that damages downstream components or biases amplifiers incorrectly). (4) Via transition not designed for the operating frequency (acceptable at 1 GHz but creates 3 dB loss at 10 GHz). (5) Connector footprint mismatch (the land pattern does not match the actual connector dimensions, causing impedance bump and poor soldering). All of these are catchable in a thorough design review.
Should I simulate the full PCB layout before fabrication?
For operating frequencies above 6 GHz: yes, simulate critical RF paths using 3D EM tools (Ansys HFSS, CST Studio, Keysight ADS Momentum). Focus on: connector launches, via transitions, filter and coupler structures, and any custom impedance matching networks. Simulation time is well spent: finding a 2 dB loss in a via transition in simulation costs 2 hours; finding it after fabrication costs 2 weeks and $5,000+ for a respin. For frequencies below 3 GHz: 3D simulation is typically unnecessary if standard RF layout practices are followed. 2D cross-section tools (for impedance) and circuit simulation (for matching networks) are sufficient.