Mission Impossible? If an Embedded Antenna Needs a Ground Plane of 100mm, ...

Do the laws of antenna physics prevent us from designing even smaller connected devices for the IoT? NB-IoT products are a hot topic with new applications in lighting, sensors, smart meters, tracking, and wearables. The demand is for smaller products using shorter ground planes, often battery operated, and not too power hungry. It is a dilemma for the designer because, for antennas to operate at sub 1GHz frequencies, they ideally need ground plane lengths of 100mm to achieve good efficiency. If the antenna efficiency should drop, this will cause issues with power consumption and achieving network approval for the finished product. So, the challenge is to create a physical design that meets the limitations of size and space, and still performs well in operation. How do you balance the two conflicting requirements – to make the PCB smaller and still enable the antenna to perform? The designer must consider the position of the antenna and its placement in the overall architecture and the area immediately around the antenna. Getting these factors right first time will be the first step in helping to improve the performance of the antenna in the finished design. Then the designer must select the correct antenna technology that will enable the product to operate in real life. We will discuss this and introduce an interesting technical solution for this problem – an Active Tuning feature for the antenna. This will enable it to perform well in a smaller device with a reduced ground plane.