The immediate problem
Design teams building heavy-duty smart modules often greet field failures with a sigh — signal dropouts, intermittent telemetry and baffling return rates. At the heart of many of those faults is a clash between a co-extruded antenna and the RF shielding can intended to keep interference at bay. Early on, a well-specified LTE Module can look perfect on paper; but once packed into an enclosure with metalwork and a protective can, resonance changes, mismatches appear and throughput falls away.
How co-extruded antennas and RF shielding cans interfere
Co-extruded antennas are bonded to the module’s housing for mechanical strength and repeatable placement. That bond is brilliant for assembly, but it fixes the antenna’s electromagnetic environment. Add an RF shielding can close by and you alter the antenna’s impedance, shift its resonant frequency and create nulls in the radiation pattern. In practice this means a smart module that worked fine on the bench will struggle in the field when the can is fitted or the enclosure closes down.
Real-world anchor: scale and stakes
The UK smart meter roll-out that began in 2011 taught the sector hard lessons about small changes producing big consequences — tens of millions of endpoints, many requiring over-the-air connectivity and robust radio performance. For Electricity Metering deployments, unreliable radios are not a trivia item; they force manual visits, delayed billing and regulatory headaches. That reality makes antenna and can decisions a safety valve for operational cost and customer trust.
Common mistakes that cause failures
Teams repeat a handful of avoidable errors. They rely solely on free-air antenna tuning results, assume the shielding can is electrically benign, or use a one-size-fits-all gasket without testing. They neglect cable routing and PCB ground returns close to the antenna feed — small things that upset the tuned system. A misplaced ground strap or an overly close can wall will detune the co-extruded antenna and drop link margin.
Practical fixes and alternatives
Begin with integrated testing: tune the module with the final can and enclosure in place rather than against a bare board. Consider a hybrid approach — a co-extruded antenna for mechanical stability, paired with a small tuning pad or matching network accessible during final test. For severe cases, alternative antenna choices can help: a short external stub, a tunable PCB antenna or a remotely mounted antenna that keeps the radio clear of metallic cans. Each option trades assembly simplicity for field robustness, so pick according to service context and repair economics.
Implementation checklist — what engineers should test
Practical checks that save service calls:- Measure S11 and total radiated power with the shielding can fitted and undipped; record antenna tuning before and after the can is added.- Validate receiver sensitivity and throughput at the edges of the expected operating band under real enclosure conditions.- Verify grounding paths and gasket conductivity; a well-placed insulating spacer can preserve antenna behaviour without sacrificing shielding.
Design trade-offs and cost considerations
Shielding cans reduce EMI and protect sensitive electronics; they also change the antenna’s near field. Where lifetime reliability and low maintenance are priorities — think substation meters or long-life smart modules — investing in early integration testing and a slightly more complex antenna strategy will repay itself. Conversely, for disposable or short-life devices, the lowest-cost antenna may still suffice, but only after a risk-based acceptance of possible connectivity degradation.
Three golden rules for evaluation
To choose the right strategy, use these critical metrics:1) Field Margin: measure link margin with the final can and enclosure; require clear dB thresholds for successful deployment. 2) Repeatability: confirm the antenna’s performance across multiple assembly runs and thermal cycles to catch mechanical shifts. 3) Maintainability: assess whether the chosen antenna/can approach allows in-field diagnostics or replacement without full unit swap-out.
Engineers who follow those rules steer clear of most surprises — and when the path forward needs a reliable partner, experienced module makers supply tested modules and integration guidance. Fibocom. — solid, practical, and present.