A high directive Koch fractal Vivaldi antenna design for medical near‐field microwave imaging applications

Abstract

We present a new fractal slot edge antipodal Vivaldi antenna (AVA). When compared to a conventional AVA, it simultaneously extends the low‐end bandwidth limitation, mitigates the side lobe level, and increases the main lobe gain. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:337–346, 2017

Design of an antipodal Vivaldi antenna with fractal‐shaped dielectric slab for enhanced radiation characteristics

“…Dielectric slabs of different shapes show little effect on the performance of the CAVA at high frequency. To achieve better performance, the fractal shape is used on the dielectric slabs because due to space‐filling properties of the fractal, it enlarges the electrical length of the dielectric slab without involving additional physical area . The presence of the fractal structure on the slabs beneficially couple more amount of energy from the transmission line side to the free space.…”

“…Basically, a fractal geometry includes multiple self‐copies at various scales. Helge von Koch in 1904 was the person who introduced Koch fractal, which is one of the most famous fractal shapes . It begins with a straight line known as initiator.…”

“…To improve the gain of the antenna, a novel method is used in Reference where two elliptical‐shaped dielectric sheets are placed parallel to the antenna. In Reference , a Vivaldi antenna for medical imaging application is presented where the Koch fractal structure etched on the radiator and ground edge makes the antenna more directive, which is appropriate for imaging applications. In Reference , to boost the gain and front‐to‐back ratio of the antenna at a higher frequency, comb‐shaped slits inscribed on the boundary of the radiator and ground plane.…”

Ultra‐directive palm tree Vivaldi antenna with 3D substrate lens for μ‐biological near‐field microwave reduction applications

“…In this antenna, the Exponential Slot Edge (ESE) shapes oftens the interface between metal (the edges) and air, playing a role similar to a small “parasitic” antenna and guiding energy from the side lobes, which is potentially collimated by 3DSL, to the ML. Another antenna that uses this technique of resonant cavities is FSE‐AVA …”

Low Side Lobe Tapered Slot Antenna with High Gain Using Gradient Refractive Index Metamaterial for Ultra Wideband Application

“…The gain of the ATSA is increased, but the side lobes of the antenna pattern are also increased. To reduce the side lobe, an exponential slot edge with kotch fractal antipodal Vivaldi antenna (ESE-AVA) are designed [10], [11]. But the reflection coefficient of the antennas are fluctuating and goes above -10 dB at some frequency, indicting a poor impedance matching.…”