Question

How can I make the frequency bandwidth of PCB antennas wider?

Answer

In some cases/applications the BW of printed antennas might not be sufficient. This article summarizes some design tricks on how to make a printed antenna wider bandwidth.

- Increase the board size (e.g. GND plane in the case of monopole-type antennas). Avoid using RF modules that have smaller size than quater-wavelength. Small modules generally have poor antenna gain and narrow bandwidth (due to the high Q factor).

- Increase the board thickness. Of course, it's typically limited by design.

- Decrease the dielectric constant of the PCB. Select PCB material with low epsilon value. 

- Use wider and/or tapered traces in the PCB antenna structure.

- Use coupled traces in the PCB antenna structure. Coupled structures typically have wider frequency bandwidth. 

- Do some tricks in the external antenna matching network. I.e. use more components to do the match (to stay within a given constant Q ellipse on the Smith Chart); create resonators in the matching network. Also, see Bode-Fano, Youla matching techniques.