How do I design a shielded compartment on a PCB to isolate sensitive RF stages?

A shielded compartment on a PCB (board-level shield or shield can) isolates sensitive RF stages from interference generated by adjacent digital or high-power circuits. Design approach: (1) Shield can: a stamped or drawn metal cover (typically tin-plated steel or nickel-silver alloy, 0.2-0.3 mm thick) that encloses a section of the PCB. The can makes contact with a ground pad perimeter on the PCB surface, creating a miniature Faraday cage. SE: 40-60 dB from 100 MHz to 10+ GHz (limited by the apertures at the PCB edge and any gaps in the ground pad contact). Dimensions: 5-50 mm per side, 2-5 mm height. The can is soldered or clipped to the PCB ground pads. (2) Ground pad perimeter: a continuous copper ring on the top layer of the PCB, connected to the internal ground plane by a dense array of ground vias. The via spacing determines the high-frequency SE: for effective shielding at frequency f, the via spacing must be < lambda/20 at f. At 10 GHz (lambda = 30 mm): via spacing < 1.5 mm. At 2.4 GHz (lambda = 125 mm): via spacing < 6 mm. (3) Via fence: a row of ground vias around the perimeter of the shielded area, connecting the top ground pad to the internal ground planes and the bottom ground plane. This creates a "via cage" that prevents signals from coupling through the PCB dielectric between layers. Via diameter: 0.2-0.3 mm. Via-to-via pitch: 0.5-2 mm depending on frequency. (4) Internal layout: within the shielded compartment: route all RF traces on inner layers (between ground planes) to prevent radiation from the traces. Keep the sensitive components (LNA, VCO, mixer) inside the shield. Route DC bias and control lines through the shield wall using feedthrough capacitors or filtered pins on the shield can.