IoT Environmental Sensor PCB Review – ESP32-S3 + Sequans GM02S 4G/LTE-M/NB-IoT + WiFi/BT Ended

Project Description:
I need a senior hardware/PCB engineer with direct experience in LTE-M/NB-IoT designs to perform a thorough pre-production review of my battery-powered IoT environmental sensor board before approval is provided for prototyping.

Key components

MCU: Espressif ESP32-S3
Cellular module: Sequans GM02S (LTE-M / NB-IoT) + PCB antenna / U.FL
Wireless: Wi-Fi + Bluetooth from ESP32-S3
Main sensor: SPEC Sensors Ethylene (C2H4) 110-65x series (analog output) + additional digital environmental sensors (I2C/SPI)
Power: Single-cell LiPo battery, charging via dedicated charger IC, ultra-low power sleep modes
Design files: Altium Designer project + Gerbers
Target markets & certification Primary: Australia (RCM mandatory) Future: Europe (CE RED), North America (FCC/IC), global roaming

Scope of work

Full schematic review
ESP32-S3 ↔ Sequans GM02S interface (UART, control signals, power-on sequencing, SIM interface)
Ethylene sensor 110-65x analog front-end, op-amp / ADC configuration, noise filtering
Power management: battery charging, LDOs, sleep current optimisation
Pin conflicts, ESD/EMC protection, decoupling
PCB layout review (Altium + Gerbers provided)
RF layout for GM02S (antenna placement, matching network, ground plane, keep-out)
2.4 GHz antenna for ESP32-S3 Wi-Fi/BT
High-impedance analog traces for the ethylene sensor
Battery safety and thermal considerations
RF & regulatory verification
Confirm antenna design (PCB trace or external) meets Sequans GM02S recommendations
Verify supported bands cover Australian networks (Telstra, Optus, Vodafone LTE-M/NB-IoT) and major global bands (especially B1, B3, B5, B8, B20, B28)
Check pre-compliance with Australian RCM, CE RED, FCC, and RoHS
Flag any obvious show-stoppers for modular vs. full-device certification
Deliver a detailed report (PDF) with
Critical issues that must be fixed before prototyping
Recommended changes with priority
Optional improvements
Annotated schematics and layout screenshots
Deliverables

Comprehensive review report (~10 pages)
Marked-up schematics & PCB layout PDFs
Optional 30–60 min call to discuss findings
Files you will receive

Altium Designer project (.PrjPcb, schematics, PCB)
Gerbers & NC drill
BOM (Excel)
Datasheets & application notes for GM02S and 110-65x
Required experience

5+ years commercial IoT hardware design
Shipped products using ESP32-S3 and LTE-M/NB-IoT modules (Sequans GM02S or Monarch highly preferred; Quectel BG96/BG95 also relevant)
Direct experience with SPEC Sensors analog gas sensors (or similar electrochemical sensors)
Taken at least one device through Australian RCM certification and preferably CE RED/FCC
Expert in RF layout for cellular + 2.4 GHz, antenna tuning, and matching networks
Altium Designer expert
Battery-powered low-power design (deep sleep < 10 µA ideal)
Please start your proposal with “ESP32-S3 GM02S Review” so I know you read the full brief. Include:

A short description of a previous project that used Sequans GM02S (or Monarch/Calliope) or another LTE-M/NB-IoT module + ESP32
Whether you have taken a device through Australian RCM (or worked with an Australian test house)
Your fixed-price quote and estimated turnaround time
Timeline Review to be completed within 5–8 days of project award and file handover.

Budget Fixed price quote expected (experienced freelancers with Sequans/SPEC experience typically charge $600–$1,200 for this depth of review). read less