A tx/rx antenna structure enabling accurate terrestrial positioning

An antenna, wherein that the antenna comprises:

• a cylinder-shaped housing;
• a ground plane within an upper half of the cylinder-shaped housing;
• a single choke ring locating coaxially on the cylinder-shaped housing on top of the ground plane, where the choke ring and the housing are integrally part of the same piece of material, where the diameter of the choke ring is less than the diameter of the cylinder-shaped housing;
• a single round-shaped patch element, which patch element is connected by four legs onto a feeding network through the ground plane, the patch element locating coaxially with the choke ring, within a cylindrical volume determined by the choke ring, obtaining an essentially rotationally symmetric structure;
• wherein a level difference of the patch element in relation to the ground plane is less than the height of the choke ring, and the ground plane forms a top surface of a circuit board locating on top of the housing, and a bottom surface of the circuit board comprises the feeding network of differential input signals, fed via each of the four legs onto the patch element, wherein the feeding network locates in an area determined to be inside the choke ring but on an opposite surface of the circuit board.