Flexible PCB antennas (FCB antennas) are flexible, flat antennas that can be easily glued to the inside of a plastic enclosure.

An FCB antenna often consists of a flexible, thin printed circuit board made of polyamide with a structured conductive material. It can be used to develop different types of antennas. The antennas usually have a coaxial cable with a coaxial connector.

Features of FPC (Flexible Printed Circuit) antennas

• can be bent to be embedded in a small device such as an IoT module;
• can be placed vertically, horizontally or coplanar with the host PCB;
• can be bent flat or curved;
• can be supplied with different cable lengths;
• offer an omnidirectional radiation pattern;
• are cheaper than externally mounted antennas. High power levels can be achieved without the cost of an external antenna;
• can be manufactured using standard PCB fabrication processes, making them highly reliable and reproducible antennas.

As already documented in the study on DIY antennas, the size of a PCB together with the mass surface used directly influences the performance of an antenna. The FPC antennas also require a sufficiently large ground plane.

To avoid unpleasant surprises, a test setup with the flexible antenna in the plastic enclosure of the planned IoT device with a test board is recommended. This test board only requires two coaxial connectors. the antenna is connected with the one coaxial connector. The second coaxial connector is used to generate a test signal with the Vector Network Analyser and measure the return loss. More about this test setup here.