Electronic – How does square metal plate antenna work

antenna

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

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?

Best Answer

Andy's comment is correct- this is a microstrip patch antenna, which has a hemispherical radiation pattern.

enter image description here

The construction is similar to a capacitor with a ground plane on the back, a dielectric (possibly ceramic in this case), and a rectangular patch on the top. It's designed to resonate at the desired frequency (1.575 GHz in this case).

The round bit is the inner feed to the patch, which is impedance matched to the receiver input through a network (a network which in microwave-world is just a pattern on the substrate).

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.