Antenna Choice, Design, and Integration in Connected Devices
Antenna performance in connected devices affects the total system performance and drives many system and subtle design choices. Correct antennae choice, design, and integration are critical to achieving optimal data rates and link reliability in varying environments and time-varying use cases.
The antenna and its implementation are critical elements in wireless applications for any physical link i.e. BLE, LORA, NbIOT, Sigfox, WiFI, etc.
There are many antenna system factors to consider when designing a connected device, particularly for a device that may be placed into highly varying use case environments, such as IOT remote sensors, body-worn sensors, or sensors that require wide area connectivity and long range at challenging signal to noise ratios for outgoing and incoming signals.
IoT devices must operate in the presence of highly varying reflective and absorptive materials as well as other nearby wireless systems that have the potential to cause interference and performance degradation.
As devices and antennae decrease in size and form factors vary, the radiation pattern around the antenna is no longer spherical and may contain nulls and voids that are difficult to predict, or control in the field.
Simulation of wireless systems and the construction of evaluation prototypes to predict performance in complex environments must begin very early in the design process.
The size of the antenna and its placement in the system, and its location relative to other conductors are the primary factors in determining the radiation pattern of the device. In most modern devices the designer often does not have the choice of mounting a whip or external antenna, but must integrate a PCB trace antenna into the design. Often this antenna is on the edge of a PCB, and surrounded by ground planes, and other conductors such as wiring and batteries.
While it is often not possible to achieve a spherical antenna pattern, it is possible to achieve a more consistent pattern along the axis that the devices operate in. For example, an IOT device that must reach a cell tower does not need to be optimized for radiation above and below the device but horizontally.
The use of computational models and early prototypes, as well as measurements in the field and/or in a calibrated environment, can provide valuable information to predict the performance of the device in the field and ensure that the device can reliably transmit and receive information in its intended use case. In addition, understanding how the antenna and its matching network perform in the presence of other internal components and nearby components, mounting plates, surrounding tissue, hand etc. is key to maximizing the performance of the system.
Also, building into the system mechanisms of monitoring radio system performance early in the system design, such as received message signal strength, is key to making sure that the design is effective and the device performs as expected when placed in the field.
