Electronics Update - Use SIP technology and ultra-small RF modules for IoT wireless communications
Nick Wood, VP Sales & Marketing, Insight SiP explains how design engineers can use SIP (System-in-Package) to squeeze ever more RF functionality into ever smaller spaces for high performance IoT wireless communications.
System-in-Package provides a complete system in a single component similar externally to a chip in a QFN package, but internally integrates increasingly sophisticated systems incorporating semiconductors, passives and RF components.
SIP & IOT ADVANTAGES
Compared to traditional PCB modules, a SIP component is smaller in all dimensions, without compromising performance or adding to cost. All the advantages of the module approach remain equally true for a SIP module and make the technology ideal for IOT product developers seeking to pack as much RF functionality into as small a version of their products as possible.
DISCREET VS. MODULE SOLUTION
To take a discreet component or module approach is one of the key IoT design decisions when including an RF function such as Bluetooth Low Energy in a solution.
With a discreet approach you can, at face value, end up with a lower cost, if you focus narrowly on the BOM price.
However, the advantages of the module approach are considerable. Firstly, the engineer can completely forget about the analogue/RF parts of the design, making only a digital connection to the module. This lowers the time and cost of the design cycle, and perhaps more importantly reduces risk, as RF is a complex area where it is easy to make mistakes.
Lastly, the final procurement and assembly of the end-product is simpler with a pre-tested module replacing many individual components.
It is also unlikely that the customer will be able to design a solution as small as specialist RF developers can, as achieving this level of miniaturisation takes significant R&D.
The final choice depends on the particular circumstances of a project. Unless the volumes for a product are going to be very high at several hundred thousand pieces per year, it is unlikely a discreet design will make sense when all factors are taken into account.
TYPICAL IOT APPLICATIONS
SIP Technology was previously limited to custom devices for high volume producers, principally mobile handset vendors. However Bluetooth SIP module devices are now available to all types of manufacturers in the IoT and general electronics design community using flexible off the shelf products. Bluetooth Smart modules can be found in many IoT applications including bionic arms for children (Limbitless Solutions), hydration measurement water bottles (My_SmartBottle), DNA-based healthier food selection app (DnaNudge), Security Bubble Covid-19 for social distancing (Insight SiP), wearables to measure sleep quality (SleepTuner), gas measurement (Microtronics H2S sensor), industrial control (TeepTrak), wearable fitness monitor (Arion), Vernier Caliper (Sylvac), car park barrier control (ComThings) plus many more.
The smallest modules on the market measure only 8 x 8 mm in x/y dimension, with a thickness less than 1mm and can include a single antenna and technology such as BLE, UWB or LoRa or in some cases, a combination of technologies and antennas embedded into the module.
RF DESIGN MATTERS FOR IOT DEVELOPERS
RF & ANTENNA CHALLENGES
When using Smart Bluetooth modules, there are very few special requirements apart from being careful to ensure that the antenna area is devoid of metal. The drawing below indicates the ideal antenna keep-out zone.
The range achieved by modules is an important factor. RF product specifications quote a range under ideal conditions, typically 1m above ground with no obstructions. Most real-life situations are not straightforward. For example, any solution close to the human body in a wearable or hand-held solution, significantly reduces the real range. So whilst RF developers confidently state that their modules can achieve a range of over 50m in ideal circumstances, it is important to test an application under realistic conditions.
A further aspect of any antenna is the directional performance. If the orientation of the IoT application device is not fixed, it is important that the antenna has an omnidirectional performance and the module a largely spherical radiation pattern. A more directional antenna is fine if the orientation of the solution is fixed. If not, the solution can stop working under certain conditions e.g. if the system radiates mainly into the human body.
Power consumption for BLE based IoT solutions is often a key design feature if the application runs for a long period – months or maybe even years – off a coin cell battery.
Vendors often focus on key performance numbers such as peak Rx/Tx current, but the issue of actual power consumption is more complex.
So the overall power consumption of a solution depends on several factors – the frequency of connection required; the chip’s wake up speed; the quantity of data transmitted and length of the transmission cycle; and the amount of processing required andspeed of the processor. By looking at the above figures, one can see that peak Rx/Tx current is only one factor in assessing the performance of different BLE solutions, and not necessarily the most important factor.
Optimising the power consumption is a question of designing the application software appropriately. Nonetheless it is useful to understand the underlying process to produce the best design.
A further element related to power consumption is the inclusion of a crystal in the solution. This crystal is not essential for the solution to function correctly, but it does improve power consumption, by improving the timing of the wake up cycle, and thus maximising the “sleep” time.
Whilst certification is not strictly speaking a “design” activity, it is a task typically expected of the engineering department
Requirements vary according to territory, but normally RF enabled IoT solutions require certification by the relevant national or supra-national body. This involves engaging a third-party accredited laboratory to carry out tests to ensure that the RF application is “well-behaved” e.g. it only radiates in the bands that it is meant to, and at the power levels expected. Failed tests require a re-design.
Each product must be individually certified even if it shares some design with a similar product.
Certification is an area where a module can save time and money, where modules are pre-certified for global markets by the FCC (USA), CE (Europe) and Telec (Japan).
To support product developers, most RF module vendors offer a complete development kit together with sample software that provides everything required out of the box to start developing a solution on day one. A complete breadboard can be built using the kit together with external sensor development kits so that software development can proceed in parallel with hardware design.