232506 - EverTag Connectivity Module Enclosure¶
| Article Number | 232506 |
| Name | EverTag Connectivity Module - Plastic Enclosure white matte |
| Material | PC+ABS matte, UL94 V0 |
| Scope | Shared across all Station connectivity module variants |
Enclosure Design Input
PCB designer receives enclosure drawings separately. This document specifies mechanical and electromagnetic requirements, especially for the A121 radar (232204 Bat+Radar variant). PCB placement constraints are in the 232204 PCB doc.
1. General Enclosure¶
The enclosure houses the Connectivity Module PCB (232200–232204) and, when populated, the LTE extension PCB (232210/232211). It is prepared for:
- PIR/Radar window region — Front face area for occupancy sensor (232204)
- LTE antenna routing path — Internal volume for extension board and on-board chip antenna
- LED light guides — LED1 (system) and LED2 (gateway) alignment
- Service button pinhole — Side access for recessed tactile switch (P2.06)
PCB Not Centered
The PCB is not centered inside the enclosure. LED and button placement on the PCB must account for the off-center position to align with enclosure windows and access points.
2. Radar Radome Design (232204 / Acconeer A121)¶
When the 232204 Base Bat+Radar variant is populated with the Acconeer A121 (60 GHz SPI radar), the front wall of the enclosure acts as a radome — a dielectric cover in front of the radar that protects it while remaining transparent to the 60 GHz signal.
No IR Window Required
Unlike PIR sensors, the A121 radar does not require an IR-transparent aperture. 60 GHz penetrates plastic; the full enclosure wall acts as the radome.
2.1 Radome Thickness¶
At 60 GHz, the free-space wavelength λ₀ ≈ 5 mm. Optimum radome thickness minimizes reflection when the plastic thickness is a multiple of half a wavelength inside the material:
| Material | εᵣ @ 60 GHz | Optimum thickness (m=1) |
|---|---|---|
| Polycarbonate (PC) | 2.75 | ≈ 1.5 mm |
| PMMA (acrylic) | 2.6 | ≈ 1.55 mm |
| Polypropylene (PP) | 2.2 | ≈ 1.7 mm |
| Polyethylene (PE) | 2.3 | ≈ 1.65 mm |
| PTFE (Teflon) | 2.05 | ≈ 1.75 mm |
Avoid λ/4 Multiples
Do not use thicknesses that are odd multiples of λ/4 (e.g. ≈0.75 mm, ≈2.25 mm for PC). These maximize reflection and degrade radar performance.
Recommended: For PC+ABS (εᵣ ≈ 2.75 typical), target 1.5 mm or 3 mm wall thickness in the radar window region.
2.2 Radome Distance (Sensor to Enclosure Wall)¶
Radome distance is the air gap between the radar antenna face and the inner surface of the plastic enclosure wall. It is not the wall thickness. The radar "sees" this gap before the signal reaches the plastic; reflections between the antenna, PCB ground plane, and the plastic–air interface create standing waves that affect gain. Choosing the right distance minimizes these effects.
The distance between the A121 sensor and the radome affects performance. Multiple reflections between sensor, PCB, and radome create standing waves. Optimum distance:
Recommended: Target 2.5 mm, 5 mm, or 7.5 mm air gap between the A121 antenna face and the inner surface of the enclosure wall in the radar region.
Distance Offset for Absolute Measurements
If the application requires absolute distance measurements, add an offset in firmware to compensate for propagation delay through the radome. Determine via reference measurements; reference plane can be positioned at the desired product boundary.
2.3 Material Permittivity Reference¶
Relative permittivity of common polymers at 60 GHz (from Acconeer):
| Material | Re(ε) @ 60 GHz |
|---|---|
| PTFE (Teflon) | 2.05 |
| Polypropylene | 2.2 |
| Polyethylene | 2.3 |
| Acrylic / PMMA | 2.6 |
| Polycarbonate | 2.75 |
| PEEK | 3.12 |
2.4 Typical Recommendations (60 GHz)¶
Many 60 GHz radar suppliers recommend:
| Parameter | Typical range | Notes |
|---|---|---|
| Radome distance (air gap) | 1–5 mm | Gap between antenna face and inner wall surface |
| Wall thickness | 0.8–2 mm | Plastic in radar window region; avoid λ/4 multiples |
| Surface | Smooth, no ribs | No ribs or ridges in front of the antenna; flat or gently curved only |
Radar Window Size
As a rule of thumb, the radar window opening should be larger than the sensor plus margin on all sides. The entire radar field of view (FoV) must pass through the plastic without being clipped at the edges.
3. Validation¶
- PCB placement: Validate A121 sensor position in the radar window region against enclosure CAD. Ensure radome distance (d₁) and wall thickness (d₂) meet the criteria above.
- STEP files: PCB project (WP2) delivers STEP files for enclosure fit validation. Available at PCB STEP Files. CargoBeacon validates against enclosure 3D model.
4. References¶
| Document | Description |
|---|---|
| Acconeer Radome and Mechanical Design | Transmission, reflection, thickness, distance |
| Acconeer PCB Guidelines | Ground plane, conformal coating |
| Acconeer A121 Datasheet | Sensor specification |
| 232204 Base Bat+Radar PCB | PCB placement, ground plane, cross-reference |
5. Revision History¶
| Revision | Date | Author | Changes |
|---|---|---|---|
| Rev A | TBD | TBD | Initial enclosure design spec. A121 radome requirements from Acconeer integration guidelines. |