Why is the antenna the most critical component of my design ?
Looking at the different elements that impact the quality of Sigfox connectivity, the device antenna is actually the only parameter that can drastically reduce the link budget (and therefore device connectivity) and that you can have an impact on as a device maker.
Sigfox base stations are installed in such a way that in normal conditions, the Sigfox Network ensures excellent coverage. Coverage is continuously being optimized and improved. Between the device and the different base station, some propagation effects may impact the budget link and in most cases, there is nothing much that can be done about this: for example. If your device is installed on a shop door and a big truck parks right in front of the door, this will automatically change the propagation conditions.
This kind of situation is taken into consideration in Sigfox's network deployment and supported in most cases. From a device perspective, most RF transceivers provide the recommended power level (14 dBm or 22 dBm). Therefore, the only parameter which can decrease device connectivity and on which you can have an impact is the device antenna quality.
This is why it is important that the radiated performance of your device be optimal and thus that the Sigfox antenna for your device be well designed and implemented.
An antenna is not a standalone component but uses and interact with all other components/physical parts of your device. Therefore, to succeed in your device antenna integration, you should consider it from the beginning of your device development. The earlier you start considering the antenna in your device development the more chance you have to end up with a high-quality product.
Because an antenna is impacted by its close surrounding, it is important to select the right antenna solution according to not only your device architecture but also your device use case and the way the device will be installed and used.
Once your device is designed and certified, it is also important to make sure that the way the device is installed does not decrease its radiated performance.
In short, optimizing the antenna design for your device and its use case as well as making sure that your device installation does not reduce its radiated performance, will have a huge impact on the Sigfox connectivity quality.