PCB antenna design

The PCB antenna can be either a small piece or a small ring, and can be spiral or linear. Their BOM cost is negligible and only takes up PCB space. It is worth noting that some PCB antennas are not part of the main board, but are separate devices that are usually attached to the product housing. Its performance also depends on the layout, geometry and its relative position to nearby components. In addition, the user's hand, body or head often adversely affects antenna performance. Any changes in the component or PCB layout in the product will affect the antenna performance. Therefore, this design is limited, and the modification of the final product before the finalization is not significant.

On the other hand, modifications to the antenna—whether to accommodate changes in the specification or to overcome design flaws—can be performed quickly once determined and do not affect the BOM. Modifications also affect the antenna impedance. So, you may also need to change the designed matching circuit.

In contrast, discrete antennas involve BOM cost and are typically designed by the vendor based on specific frequency bands, bandwidth, and other performance parameters. In return, this antenna occupies less PCB space than the PCB antenna, and if not completely unaffected, the PCB layout, adjacent devices, or the user's impact on it is much smaller. The antenna impedance is fixed by the physical design, so the matching network is also fixed and independent of the layout and device placement. These factors prevent designers from facing certain challenging constraints and eliminating the need to redesign PCB layouts and calculate BOMs.

There are many possible design approaches for small antennas that are typically based on PCBs. The most common are bright line (also known as open) structures (such as bipolar and monopole antennas), loop designs (such as loop antennas), and solid block designs.

The open antenna is actually a miniature version of the large antenna that has existed since the beginning of the radio technology. In fact, because Heinrich Hertz used a dipole antenna in his 1888 experiment, it is sometimes called a Hertz antenna. It is balanced with the ground plane, and it has faithfully fulfilled the duties of the VHF TV rabbit ear antenna before the advent of cable and satellite television.