IDB Design Series - Radio Chipset Selection

Selecting suitable radio ICs or modules is not a simple task. Once selected and designed in then changing can be difficult, consuming costly time and resource. For this reason many organisations use a preferred chipset, but is this the best choice for your immediate project or long term goals?

0ur Approach :

Whilst there are some components and prior designs that are available to us, we prefer to evaluate the best solution for our clients. We keep a keen eye on the critical components and speak with distributors and manufacturers to understand their product roadmaps. We review the roadmaps for the radio products, providing data and analysis in a comparison matrix, evaluating the key performance parameters identified as most important for our clients and making recommendations for the most suitable components.

In this blog we provide some of the parameters you may find it helpful to consider when selecting radio components:

Power consumption

It is critical in battery powered equipment to optimise the solution for specific run times from a small battery. It is likely a systems approach will be required here as battery choice, antenna design, PSU efficiency and system resources can all be significant in optimising the final solution.

For the radio solution then shutdown and sleep modes are important, but generally more important is the power consumption when the radio and tx amplifier are active.

The antenna choice, location, matching and gain can also significantly reduce the required transmit power and may be critical when choosing between modules with integrated antenna and discrete solutions.

Transmit power

The transmit power is normally directly proportional to the range over which data can be transmitted. It is important to understand the power profile of the transmit bursts including peak and average current consumption. Care is required in the power supply design to avoid high impedances causing excessive voltage drops due to peak currents during the radio transmit bursts.

Receive sensitivity

The sensitivity of the receiver is particularly important for data reception. Filtering may be employed to prevent out of band noise, however care must be taken in design as filtering also creates insertion losses. Mounting position and proximity of other structures will need consideration and may necessitate alternate antenna solutions.

Size

The surface area required to layout the manufacturer recommended solution including filters, matching components and antenna should be considered. The population density and complexity of the board design is a strategic decision. If size is fundamental to additional value then additional investment in a high population density layout may be worth while, otherwise we recommend to keep it simple. It is important to review and follow manufacturers guidelines around impedance matching and clearances. Of particular importance will be the location and isolation of antenna, this may require some simulation or experimental evaluation to optimise performance.

Cost

Always a critical factor the total bill of materials cost including all external components required should be calculated and used for comparison. We recommend early engagement with the supply chain and where possible direct negotiations with device manufacturers to arrive at detailed cost for launch through to high volume manufacture. Often there is a choice between SoC or discrete serial radio solutions, hence one must always compare the total solution costs and the trade-offs in approaches must be examined.

Time To Market

A module with integrated antenna and associated rf circuit is likely to offer the fastest route to market as design optimisation and approvals times are minimised, the trade-offs generally being unit cost and inability to optimise radio performance. When considering a module then ensuring a standard interface accommodating multiple manufacturers may be possible. This allows future flexibility in adopting alternate / improved radio solutions.

Product Life

The manufacturer will guarantee a specific product lifetime for the supplied components. It is important to understand this in order to avoid obsolescence during your planned product life cycle. It is also important to understand their road map for the chosen radio components and plan any future product improvement activities. Changes to manufacturers SDK can force unplanned firmware effort.

Design Support

Distributors and Component manufactures may offer value through design support. This may include training, design reviews of schematic and pcb layout, pre-compliance rf testing, software development kits (SDKs) and online technical support forums. The level of support and responsiveness of the supply chain is worth understanding during the selection process.

Approvals Documentation

The approvals documentation should be easily accessible including Declaration of Conformity and associated test reports. These require evaluation to ensure standards are active and align with those planned for the final product. It is possible some updates will be required based upon changes to standards, so it may be important to understand the plans for implementation to upcoming changes in legislative requirements.

Industrial Certifications

Radio Protocols may require approval by a governing body. In some cases this may be simplified if the component is certified. For example some Wi-Fi components carry certification from the Wi-Fi Alliance.

Proof of concept Evaluation

Having shortlisted one or more radio components then we would recommend a rapid evaluation of the critical performance criteria. Generally this can be done with evaluation Kit and allows an early evaluation of hardware, firmware (SDKs), the associated development environment/tools and support from the supply chain. We find it useful here to explore and plan work for radio compliance test set-up and manufacturing test. There may be specific design criteria to provision test interfaces and/or develop test scripts to support radio testing. It can also be useful here to explore radio co-existence and interoperability, although this may require a more complete prototype in the desired physical form.

In Conclusion

This article has highlighted some of the key considerations when selecting and designing with radio components. At Invent Design Build we have learned that the most obvious component solution is not always the best choice and that allowing for a selection process and the ability to change if outcomes are not as anticipated is important to project success.