RF Design in IoT Hardware
The Global IoT market is expected to grow from $157B in 2016 to $457B by 2020 (a 28.5% annual growth) according to forecasts published by Forbes. With billions of internet connected devices expected to be deployed in the next few years — including smart homes, smart cars, and a vast range of industrial uses–it isn’t complete hyperbole to view this innovative period as the fourth industrial revolution. In this post we’ll take a closer look at a key technical problem that many developers don’t discover until their thick in the mud: miniature RF design.
We often see IoT startups and developers run into problems when using off-the-shelf hardware like the Raspberry Pi, undermining the importance of RF-centric designs for performance, power, and certification.
Figure 1 below, shows the basic architecture of the RF Radio. Intel and Qualcomm are one of few companies in the world which designs the whole RF radio. Many other companies buy the baseband processors from the manufacturers and design the RF front-end themselves. This kind of design is called as discrete design. Companies such as Samsung, SIMCom and Quectel are doing discrete design with baseband processors from Intel and Qualcomm. Based on the market research firm Yole Développement, the RF front-end industry is set to grow at a CAGR of 14 percent to reach $22.7 billion in 2022.
These RF radios can be 5G, NB-IoT, LTE cat-M, LORAWAN, SigFox, Bleutooth, Wi-Fi, Zigbee, Satellite and so forth. The range of the IoT devices is subjective to the field of application. Short range IoT devices uses Bluetooth and Zigbee radios. Medium range IoT devices uses LoRa, SigFox, Wi-Fi and so forth. Long range IoT devices could use LTE cat-M, NB-IoT, 5G or Satellite. Regardless of the type of RF technology, the RF radio architecture will be almost the same, as given in the Figure 1.
Efficient RF for Low Power IoT
Deploying battery-powered internet connected devices in remote, autonomous contexts requires numerous optimizations. In addition to architectural improvements, careful design and optimization of the RF radio front end is required to maintain overall efficiency and RF performance requirements. Without this, additional components to compensate for RF performance inadequacies will be needed and will compromise the efficiency or low power consumption profile of the system.
Discrete Radio Design Process
Radio design for IoT solutions begins with a link budget calculation. Then, a radio system architecture is designed according to the link budget and the desired RF performance. The design of individual radio sections (LNA, PA, filter and etc) are accomplished with a theory, mathematical calculation followed by simulation.
- Individual radio components are designed with 50Ω input and output impedance so that the performance will be the same when connected to the system.
- Circuit and EM simulations are done to ensure the design meets all the test parameters for individual radio sections.
Upon meeting the desired performance in simulation, PCB layout design and fabrication are performed. Subsequently, the PCB assembly with the associated components are done. Finally, measurement and optimization is necessary because of the parasitics introduced by the PCB traces and the total interaction of the PCB, components and soldering.
Upon testing each individual radio sections, layout for the complete radio will be done. Finally complete radio design will be tested and optimized to meet system parameters.
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