The Importance of Antennas in Microwave Imaging

The goal of every microwave image-based system is to balance proper resolution and penetration as well as a means to illuminate the target in small areas. That is, we can have a better permittivity changes resolution in biological tissues if the sensors are more directive and use ultra-wideband (UWB) signals. However, most of the elements that make up such systems are wideband antennas of, around, 70% to 140% fractional bandwidth. To increase the bandwidth, in most antennas, it is necessary to modify its geometry, involving the modification of feeding structures and the use of coupling techniques. An element that meets such requirements as a planar structure, low profile, light weight, and wide-band applications is the Vivaldi antenna. In addition, it is a co-planar structure with moderate directivity, radiation end-fire, and radiation patterns symmetrical in the E-H planes, easy to manufacture, and economical.

For additional evidence, there was a study that conducted microwave tomography (MWT) experiments using four different antennas: a microstrip patch antenna with cut out sides, a microstrip folded patch antenna, a waveguide antenna, and a coaxial monopole wire antenna.

For our system, we are using “palm-tree” Vivaldi antennas. The shape of the "lobes" makes the antenna look a bit like a palm tree and the creators coined the term “Palm Tree Vivaldi Antenna”. More information about this antenna can be found here.

Why this Design?

• Extends the low-end bandwidth limitation
• Mitigates the side and back lobe levels
• Corrects squint effect
• Increases main lobe gain
• Decrease (in a controlled manner) surface current intensities on the antenna edges