# How does square metal plate antenna work?

I have a GPS receiver(works at 1575.42 MHz) with chip-antenna:

As I understand, this metal square plate is an antenna which is connected to PCB with short 5-6mm metal rod. This metal rod is hidden iside the black ceramic enclosure seen on the image. However, if I read abount antenna basics, then antenna lenght should be 1/2 or 1/4 of the signal wavelenght, i.e. 9.5cm or 5cm respectively because wavelenght in case of 1.5GHz is 0.19m. How does this square metal plate work as an antenna?

• It could be that the ceramic material affects the velocity factor of the antenna, which results in a change of wavelength of electromagnetic waves, which can result in an antenna of appropriate size. – AndrejaKo Jun 21 '14 at 13:57
• You're thinking 1/2 or 1/4 wavelength for dipole aerials. – Majenko Jun 21 '14 at 13:58
• @Majenko This 1/2 or 1/4 of wavelenght rule does not apply to square(I don't know the tecnical term for this type) antennas? – Martin Jun 21 '14 at 14:46
• It looks like a patch antenna to me. – Andy aka Jun 21 '14 at 14:49
• If it is, the "ceramic" will be a solid layer with a dialecric constant $\epsilon_r$ that affects the resonant frequency of the patch antenna. The higher the $\epsilon_r$ the smaller the antenna for the same frequency. – Majenko Jun 21 '14 at 15:00

Here is a calculator to find the dimensions, given $\epsilon_r$, dielectric thickness, and desired resonant frequency, and here is some info from Rogers (laminate maker) on designing your own.