Patent ID: 7659849

Claim:
A frequency scanning antenna structure for a radar system, the antenna structure being capable of steering a radio frequency beam to a plurality of different angles about the antenna structure across a substantially contiguous angular region, the antenna structure comprising first and second travelling wave antennas and a controller for controlling input of radio frequency energy to the two travelling wave antennas and for controlling a frequency of the radio frequency energy, wherein the controller is arranged to: input the radio frequency energy to the first travelling wave antenna and to control the frequency of said radio frequency energy such that the antenna structure is capable of steering the beam across a first part of the angular region, and input the radio frequency energy to the second travelling wave antenna and to control the frequency of said radio frequency energy such that the antenna structure is capable of steering the beam across a second part of the angular region, and input the radio frequency energy to the first travelling wave antenna and to control the frequency of said radio frequency energy such that the antenna structure is capable of steering the beam across a third part of the angular region, wherein the first and second travelling wave antennas are disposed within the antenna structure such that, in use, the second part of the angular region is positioned between the first and third parts of the angular region.