For an application operating both in the 868-870MHz and 902-928MHz bands, the antenna
can be tuned to a frequency in between the two bands. Because of the very wide gain
bandwidth of the antenna, the antenna will show good overall performance in the whole
frequency range 868-928MHz when tuned to 900MHz.
The antenna is fabricated on a standard 1.6mm FR4 substrate material with a typical dielectric
constant er of 4.4 at 900MHz.
The width of the monopole trace is W = 1.5mm. The wavelength in free air is l0 = 333mm. It
may be approximated that the guided wavelength lg on the FR4 substrate is about
lg ˜ 0.75 · l0 = 0.75 · 333mm ˜ 250mm