RF Shielding Approaches
| Method | Typical Isolation | Best For |
|---|---|---|
| Metal shielding can | 40–60 dB above 1 GHz | Complete circuit section isolation |
| Ground via fence | 10–20 dB | Between adjacent PCB sections |
| Ferrite sheet absorber | 15–30 dB (10 MHz–1 GHz) | Near-field coupling reduction |
| Multi-layer ground planes | 25–40 dB | Top-to-bottom layer isolation |
Metal Shielding Can Design
Shielding effectiveness (SE) of solid metal can: SE ≥ 40 dB above 1 GHz for copper/brass ≥0.3mm thick Key design rules: - Seam gaps < λ/20 (at 2.4 GHz: <3.4mm) - Finger contacts every 5–8mm for removable cans - Ground pad directly below can wall for soldered cans - Holes for components: diameter < λ/20 (resonance-safe) Cost vs performance: stamped brass cans (~$0.10) provide excellent shielding for cellular frequency designs
Via Fence as Internal Shielding
Via fence between RX and TX PCB areas: Row of ground vias spaced λg/20 at highest operating frequency Height = substrate thickness H Achieves ~15–20 dB isolation between areas For >40 dB: use full shielding can
RF View: Measure shielding effectiveness by loading S21 of two-port shielding structure (antenna-to-antenna measurement through shield). Single marker reads isolation at operating frequency. Free on Android.