Hardware Engineer — Schematic + PCB Layout for a Wearable Android LTE Camera Device

## The product A small, screenless, body-worn safety camera. It runs Android, records and live-streams video over LTE, and has an LED ring on the front face. Target enclosure is roughly the size of a name badge. We have industrial design, mechanical CAD, a working functional prototype of the LED subsystem, and a full product specification. We need an experienced engineer to take the main board from requirements to manufacturable design. ## Scope of work - Architecture and block diagram sign-off - Schematic capture for the main PCB and the associated flex boards - Component selection and BOM (with second sources where sensible) - PCB layout, including RF and high-speed routing - Stack-up definition and impedance control - DFM/DFT review, panelisation input, test point strategy - Gerbers, assembly drawings, pick-and-place, fabrication notes - Support through bring-up and design review with the contract manufacturer Altium preferred. KiCad acceptable if the output is clean and portable. --- ## Requirements ### Compute and OS - Android 10 or later, target SDK 33+, GMS-certifiable - Hardware H.265 (HEVC) encode, software encode is not acceptable - MIPI CSI-2 ISP adequate for a 2 MP low-light sensor with HDR and gyro-assisted EIS - Integrated LTE modem, Cat-4 minimum - GPU / NPU / TPU block required - 4 GB LPDDR4X + 32-64 GB eMMC 5.1, eMCP strongly preferred for area **We have not fixed the SoC.** Telling us which one you would use, and why, is part of the application (see below). ### Camera - Sensor: SC235AI or equivalent, 2 MP, 1/2.8", ~8680 mV/Lux-s, MIPI CSI-2, HDR - Lens: 105-150° diagonal FOV, focal distance 30–500 cm, f/1.8–f/2.0 - IR LEDs plus drive circuit; IR-cut filter preferred - 720p H.265 at 15 fps sustained, streamed live while recording ### Cellular and eSIM - eSIM only in production: MFF2 eUICC, GSMA SGP.22 / SGP.32 - LTE Cat-4 minimum, uplink larger than 5 Mbps sustained - Bands: B1/3/7/8/20/28 plus B2/4/5/12/13/25/26/66/71 - Certification samples need physical SIM access for conducted conformance testing at the lab. Our current approach is a ZIF connector to a small SIM flex carrying a 2FF socket, populated on cert samples only, with no change to production board outline or thickness. We are open to better ideas. ### Other radios - GNSS - BLE, 10 m range - Three antennas to place and tune: LTE, GNSS, BT ### Audio - Digital MEMS microphone: SNR larger than 64 dB, AOP larger than 120 dB SPL, tuned for 100 Hz–10 kHz speech - Speaker: larger than 100 dB(A) SPL @ 0.5 m peak, larger than 95 dB(A) sustained, 300–3400 Hz ±6 dB, lower than 10% THD @ 90 dB(A). This needs a class-D amplifier with boost, a PMIC codec output will not get there. - AAC encode ### Sensors and controls - 6-axis IMU (accelerometer + gyroscope) on I²C or SPI, exposed to the application layer; gyro feeds EIS - Right-angle power button, PCB or flex mounted - Vertical SMD momentary button for an alert function, routed to a spare external interrupt - Vibration motor with PWM-capable driver - variable frequency is required, a GPIO and a MOSFET is not enough ### Power and charging - 1S1P LiPo, 1000 mAh, 0.5C charge - USB-C, 5 V, must charge from a USB-C-to-USB-C cable (correct CC resistor implementation) - Fuel gauge with 1% SOC granularity, readable from the application layer - All hardware buttons, LEDs, motor, camera, speaker, thermal and battery diagnostics must be readable and controllable from the application layer - Kernel watchdog with auto-reboot on hang; ADB and logcat enabled on engineering builds --- ## Constraints ### Space - PCB's edge cuts are approximately LxW (60 × 30mm) including the clip. Thickness-wise - up to 4mm - The main PCB shares that volume with a 1000 mAh cell, the camera module, the speaker, and a magnet assembly. Board outline will be provided from mechanical CAD. - Area is the hardest constraint on this project. We expect deliberate partitioning across the main board and two or three flex boards, and we would rather move parts off the main PCB than grow it. ### Power budget Target is 3 hours of continuous 15 fps video and audio streaming from 1000 mAh. That is roughly **333 mA average**. Rough allocation from a comparable platform: | Load | Approx. current | |---|---| | SoC + modem, streaming over LTE | 120 mA | | Camera sensor | 35–50 mA | | LED ring, breathing at 8 mA per LED | 147 mA | | GNSS, audio, IMU | 40–60 mA | | **Total** | **340–380 mA** | This is already marginal before margin. Managing it is a core part of the work, not an afterthought. ### Thermal Surface temperature must stay below 47 °C after 5 minutes of streaming, in a sealed plastic enclosure with passive cooling only. Expect to work with DVFS caps, core gating, and copper/thermal-path planning in layout. ### RF A neodymium magnet and a metal plate sit in the assembly near the antenna region and are measurably degrading antenna efficiency on low LTE bands. Antenna keep-out, ground plane strategy, and mitigation (ferrite/absorber, magnet geometry) need to be handled in the design rather than patched afterwards. ### Certification targets FCC (US), UKCA and CE (UK/EU), GCF, PTCRB. The design needs to be certifiable, and we need test access designed in before layout freeze. previous experience with designing the boards with esim modules that passed any/all of the above mentioned certifications is an asset. --- ## Deliverables Schematics, BOM, layout database, Gerbers, drill files, assembly drawings, pick-and-place, stack-up and impedance spec, DFM report, test point map, and bring-up notes. --- ## How to apply Please write to us **in your own words**. A short paragraph on each point below is enough. If you would rather attach a document or a sketch, fine but we want your thinking, not a formatted brochure. 1. **How would you approach this design?** Where would you start, what worries you most, and what would you want to resolve first. 2. **How many layers, what stack-up, and why?** Tell us how you arrived at that, given the area constraint, the SoC and eMCP you would use, and the RF requirements. 3. **How soon could you finish?** Give us separate estimates for schematic complete and layout complete, and tell us your current availability. 4. **Similar projects.** What have you built that is comparable wearables, body cameras, LTE devices, anything dense and battery-powered. Links, photos, or a description are all fine. 5. **eSIM experience.** Design and validation experience with eUICC is a strong asset. Tell us what you have done, including anything on the certification side. 6. **Which exact SoC would you choose, and why?** Name the part. Tell us how it meets the H.265, ISP, modem, GMS, and thermal requirements, and what NPU or accelerator it brings. If you have worked with MediaTek, Rockchip, Allwinner, UNISOC or similar Chinese silicon, say so that is a significant asset here. Applications that read as AI-generated will be discarded without reply! We are hiring for judgement, and we can tell the difference. A short, blunt, specific answer as a short paragraph (with specific arguments towards why certain solution been selected) will be preferred to generic polished document or ai slop. We will share full specifications, mechanical CAD, and the existing prototype documentation under NDA with shortlisted candidates. Budget will be milestone based and discussed separately with the final candidate(s).