Background and Introduction

Short Back-Fire antennas (SBFs) are compact antenna topologies that are used in applications requiring medium gain. The original design was reported over 50 years ago in a publication by Ehrenspeck. Since then, designs using variations of feeding mechanisms and optimizations have been reported in the literature. The antenna can be used as a directional antenna in point-to-point communications, as well as a sensor for remote sensing applications.

Many of the early designs were inherently narrowband and work has been conducted to extend the bandwidth of operation. The designs scale with frequency and can be adapted to a variety of applications. SBF designs have been reported in the low end of the microwave spectrum (e.g., S-band designs for communications), in the mid-range as Wi-Fi antennas, and extend into millimeter-wave designs.

In recent years, antennas have been mounted on a variety of unmanned aerial vehicles (UAVs) for remote sensing applications. Additionally, these UAV systems can be used as a flight “test of concept” for hardware that is planned for use on satellite systems. Therefore, antennas designed for these applications need to have characteristics such as being low-profile, low mass, and highly efficient. Furthermore, antennas with past space heritage are more likely to be selected for future space missions, based on the need for high reliability and well-known characteristics. The SBF is an excellent candidate, as it can be designed to meet these requirements.

Design Criteria and Goals

The final goal of this antenna design is to mount the designed antenna on a drone to conduct remote sensing of sea ice in the Arctic region. For this purpose, the designed antenna should be able to handle higher input power. Therefore, a waveguide-fed short back-fire antenna is a good candidate. This antenna is a robust structure and has a very small back lobe radiation. The majority of the radiation focuses on the antenna boresight, which makes it a good candidate for remote sensing. The design criteria for this project was as follows:

1. Realized gain > 14dBi

2. Bandwidth >500 MHz

3. Cross-polarization isolation > -25 dB

In this project, I designed a waveguide-fed SBF antenna with significant enhancement on the radiation characteristics, realized gain, and impedance bandwidth.

Final Otucome

The outcomes of this work were two papers:

One IEEE Journal Paper and one conference proceedings (IEEE ANTEM). These papers can be found in my google scholar profile.

I am still working on further publications based on the available results (both simulations and actual measurements) of my study. I will update this page as soon as the current paper that I am working on gets published. The next stage of the design is to reduce the cross-polarization of the antenna while maintaining the same radiation characteristics including the realized gain greater than 14dBi and the bandwidth greater than 500 MHz.