What isolation is required between adjacent jammer transmitter modules operating on 2.4 GHz and 5.8 GHz?

Minimum 70 dB module-to-module isolation is required to prevent intermodulation products from desensitizing the GNSS L1 (1575.42 MHz) downlink jamming chain. This is achieved with a two-piece shield can with continuous solder fence and a lid contact resistance below 20 mΩ at every closure point.

How do I prevent cavity resonance inside a shield can covering a 100 mm × 60 mm PA stage operating from 400 MHz to 6 GHz?

Insert internal ground partitions to keep the longest unbroken internal dimension below λ/4 of the highest operating frequency. For 6 GHz, that is 12.5 mm. Combine with RF absorber pads (3 mm BIIR-loaded foam, 10–15 dB return loss from 1–6 GHz) bonded to the lid interior.

What is the minimum order quantity for custom two-piece shield cans with non-standard footprints?

POCONS USA tools custom two-piece shield cans starting at 5,000 units per SKU for nickel silver or tin-plated cold-rolled steel. Prototype runs of 100–500 units are available with 3–4 week lead time using soft tooling. Spring contacts and SMD pan nuts ship from stock for verification builds.

Counter-UAS Jammer EMI Shielding: Multi-Band Transmitter Isolation Design Guide

Executive Summary

Counter-UAS jammer payloads — whether trolley-case, vehicle-mount, or man-portable — concentrate four to six high-power transmitters within a single chassis, simultaneously radiating across GNSS L1/L2, 433 MHz, 915 MHz, 2.4 GHz, and 5.8 GHz ISM bands. The dominant failure mode is not radiated emissions to the outside world; it is internal coupling that drives the front-end LNAs of adjacent bands into compression, collapses jamming-to-signal ratio at the antenna port, and produces spurious intermodulation tones that violate ITU-R SM.329 and MIL-STD-461G CE102/RE102 limits. This application note specifies two-piece shield can geometry, partition design, and lid contact strategy using POCONS USA SMD pan nuts, custom-tooled shield cans, and gold-plated spring contacts to achieve ≥70 dB inter-module isolation from 100 MHz to 6 GHz.

Technical Specifications & Attenuation Data

Shield effectiveness for a counter-UAS jammer is dominated by aperture leakage and seam impedance, not by bulk material attenuation. A 0.20 mm cold-rolled steel wall already delivers >100 dB of plane-wave attenuation through the metal itself; the engineering problem is keeping the seam, lid, and via fence below the same threshold. The following parameters are the minimum POCONS USA specifies for jammer-grade enclosures.

| Parameter | Specification | Standard | |-----------|--------------|----------| | Shielding effectiveness, two-piece can with seated lid | ≥80 dB, 30 MHz–1 GHz; ≥70 dB, 1–6 GHz; ≥60 dB, 6–10 GHz | IEEE 299 / MIL-STD-285 | | Wall material — nickel silver C7521 | 0.20 mm, σ = 4.0 × 10⁶ S/m, μr ≈ 1 | ASTM B122 | | Wall material — tin-plated CRS | 0.25 mm, σ = 1.0 × 10⁷ S/m, μr ≈ 200 (low-freq H-field) | ASTM A623 | | Lid-to-frame contact resistance (spring beam) | ≤20 mΩ initial, ≤50 mΩ after 500 mating cycles | IEC 60512-2-1 | | Spring contact (pogo pin) compression force | 0.5–1.2 N at mid-stroke | POCONS PC-Series | | SMD pan nut pull-out force, M2.5 | ≥45 N axial | IPC-7711 | | Reflow compatibility | Pb-free, 260 °C peak, 3 cycles | J-STD-020E | | Operating temperature | −40 °C to +105 °C | AEC-Q200 (for vehicle-mount jammers) | | Conducted emissions compliance | CE102, 10 kHz–10 MHz | MIL-STD-461G | | Radiated emissions compliance | RE102, 10 kHz–18 GHz | MIL-STD-461G | | Radiated susceptibility | RS103, 10 kHz–40 GHz, 200 V/m | MIL-STD-461G |

For man-portable units that fall under civilian authorization frameworks, CISPR 32 Class B and FCC Part 15 Subpart B apply to the non-transmitting auxiliary electronics (battery management, control MCU, telemetry). The shield can system must isolate those subsystems from the transmitter chain by an additional 40 dB to keep self-emissions below the 30 dBμV/m quasi-peak limit at 3 m.

Common Design Pitfalls

Lid-only shielding without a soldered fence. A snap-on one-piece can relies on intermittent spring fingers around the perimeter. At 5.8 GHz the contact-to-contact spacing must be below λ/20 (≈2.6 mm) to prevent slot radiation. Most one-piece designs ship at 5–8 mm pitch and leak 25–35 dB at the upper ISM band. Mitigation: specify a two-piece can — a soldered frame creates a continuous 360° RF seal; the removable lid only needs to seal the top aperture, where spring beam pitch can be relaxed to 4 mm without penalty.
Insufficient ground stitching beneath the fence. Designers route the can-fence pads as a single net but stitch to the inner ground plane with vias spaced at 5 mm or greater. This creates a slot antenna at the can-PCB interface; cavity resonance at λ/2 of the longest internal dimension couples directly out through the under-can slot. Mitigation: via stitching at 1.5 mm pitch (λ/20 at 6 GHz) along the entire fence perimeter, with 0.3 mm finished hole and 0.6 mm pad. Connect to all internal ground layers, not only L2.
Shared ground return between PA and LO. A 5 W PA at 2.4 GHz drawing 2 A pulse current shares a return path with the synthesizer reference; ground-bounce modulates the LO and produces close-in phase noise sidebands that re-radiate as broadband emissions outside the intended jamming mask. Mitigation: internal partition wall inside the shield can with its own solder fence and via stitch, splitting PA and LO into separate shielded compartments. POCONS custom two-piece cans accept welded-in partition walls at any orientation.
Unfiltered DC and control feedthroughs. Every wire that crosses the shield boundary is an antenna unless it is decoupled at the wall. A 12 V supply line carrying the 100 kHz switching ripple of the upstream buck regulator radiates through the can if it enters as bare copper. Mitigation: feedthrough capacitors or three-terminal pi-filters at the wall; for low-current control lines, a ferrite bead plus 100 pF MLCC immediately at the entry pad. Ground the filter return to the can fence pad, not to a remote ground island.
Cavity resonance in large enclosures. A 100 × 60 × 8 mm shield can resonates at the TE₁₀₁ mode near 2.9 GHz; Q-factors above 200 are common with bare metal interiors. The resonance amplifies any internal field and can desense an LNA in the same can by 15–20 dB. Mitigation: bond a 2–3 mm BIIR or carbon-loaded urethane absorber pad to the lid interior; expect 8–15 dB of cavity Q reduction across 1–10 GHz. Combined with internal partitioning, target longest unbroken cavity dimension below λ/4 at the highest band.

PCB Footprint & Soldering Profile Guidelines

Shield can frame footprint: outline pad width 1.0 mm, courtyard clearance 0.5 mm to nearest non-ground feature, soldermask opening matching pad dimensions with 0.05 mm expansion. Stencil aperture ratio 0.85 (pad area : aperture area) using 0.12 mm laser-cut stainless stencil; a 1:1 aperture causes solder bead overflow into the can interior. For 0.20 mm wall thickness frames, paste deposit volume should land between 0.085 and 0.105 mm³ per linear millimeter of fence.

SMD pan nut footprint: copper pad 0.4 mm larger than the nut flange diameter on all sides, thermal relief with four 0.3 mm spokes to local ground pour. For M2.5 pan nuts, pad outer diameter 6.4 mm, soldermask defined, with no via-in-pad. Place pan nuts at lid corners and at the midpoint of any edge longer than 40 mm to keep lid deflection under 0.1 mm during operation.

Spring contact (pogo pin) footprint: pad diameter 1.6 × pin barrel OD; for 1.5 mm OD contacts, use 2.4 mm round pads, soldermask defined, with the pad on the same layer as the can fence ground. Verify clearance from adjacent traces equal to 2× dielectric thickness to prevent capacitive crosstalk into the contact body.

Reflow profile per J-STD-020E for SAC305 with shield can frames present: preheat ramp 1.0–2.5 °C/s from 25 °C to 150 °C; soak 60–120 s between 150 °C and 200 °C; ramp 1.0–3.0 °C/s above 217 °C liquidus; peak 245–250 °C (not 260 °C — large can frames act as heat sinks and drag adjacent 0402 components into spalling territory if peak is pushed); time above liquidus 60–90 s; cooling ramp ≤6 °C/s. Inspect fence solder joints with X-ray for voiding; reject any joint above 25% void area per IPC-7711/7721 acceptance criteria.

Recommended POCONS Components

Custom Two-Piece Shield Cans (/products/shield-cans/two-piece/) — Tooled to your exact PCB footprint with internal partition walls, integrated absorber bond areas, and lid spring-beam pitch optimized for your highest operating frequency. Standard wall material: 0.20 mm nickel silver C7521 or 0.25 mm tin-plated CRS for high-power thermal sink applications. Soft-tool prototypes at 100-piece minimum; production tooling amortized at 5,000 units. Specify partition placement on submission to lock PA, LO, and LNA into independently shielded compartments.

SMD Pan Nuts (/products/smd-hardware/pan-nuts/) — Reflow-compatible M2 and M2.5 captive nuts for shield can lid retention, chassis grounding, and antenna pigtail strain relief. 45 N pull-out, AEC-Q200 qualified for vehicle-mount counter-UAS platforms. Use at every lid corner plus mid-edge for spans >40 mm to maintain consistent lid contact pressure and the 20 mΩ contact resistance target.

Spring Contacts / Pogo Pins (/products/spring-contacts/) — Gold-plated beryllium-copper spring probes for lid-to-frame RF contact, board-to-board ground continuity, and removable RF module interfaces. PC-Series rated 0.5–1.2 N at mid-stroke, 500-cycle endurance, contact resistance ≤20 mΩ initial. Specify Au plating ≥0.76 µm over 1.27 µm Ni for jammer applications where lid removal in field service is expected weekly.

Application note produced by POCONS USA engineering team. Contact applications@poconsusa.com for design review.