###### Abstract  
In this paper, a planar, bow-tie antenna with an enhanced bandwidth and a bi-directional radiation pattern is proposed. The concept of multi-resonance is applied by implementing the superposition of three different bow-tie components with various radii and flare angles in an overlapped fashion into a single element, resulting in a significant increase in bandwidth. The antenna has an electrical size, \(kr\), of 1.10, calculated at the lowest frequency of operation. The proposed antenna is simulated, and a prototype is fabricated for verification by measurement. The result is a wide \(-10\) dB bandwidth of 80.3% (1.23-2.88 GHz) from the measurements. The antenna also maintains a bi-directional radiation pattern, with a negligible difference between the forward and backward realized gains, within the entire \(-10\) dB bandwidth. The measured realized gain values in the forward and backward directions are between 1.5 dBi and 3.7 dBi over the \(-10\) dB bandwidth. The comparison of the measurement and simulation results shows good agreement. bi-directional antennas; bow-tie antennas; electrically small antennas; planar antennas; printable antennas; wideband antennas +
Footnote †: journal: _Applied Sciences_  
the bow-tie antenna while maintaining its wide bandwidth in [7; 8; 9]. In [7], a half bow-tie antenna was miniaturized--an integrated balun was applied on a truncated ground plane for improved bandwidth and gain. In [8], the size of the bow-tie antenna was reduced by 40% through the use of double-layering a folded bow tie and meander lines beneath the bow tie. In [9], the tips of the triangular bow-tie patch were removed for a more compact antenna structure. In [10], a wide bandwidth was demonstrated through implementing a rounded edge on a double-sided, bow-tie antenna. In [11; 12; 13], various alterations were made to the shape of the bow-tie slots, which required a large ground plane. These alterations were implemented to enhance the bandwidth of the antennas. Previously, the multi-resonance principle has been used in a log-periodic dipole array (LPDA) antenna as a method for achieving a wide bandwidth. This method consists of scaled versions of the driver (fed) element combined into an array. Each individual element generates a resonance at a distinct frequency determined by its length. The summation of the resonances of each individual element results in a wide bandwidth. In [14; 15; 16], bow-tie antenna geometry was implemented for each element in the LPDA antenna to achieve an even wider bandwidth. However, the total sizes of these LPDA antennas were still large because the antennas required a large number of elements located next to each other with log-periodic distances in series. For example, in order to achieve more than 80% of \(-10\) dB bandwidth with LPDA antennas, at least six elements were required [17]. In this paper, an entirely planar (single layered), bandwidth-enhanced, single-element, bow-tie antenna is proposed. Contrary to previous designs using the multi-resonance principle, the antenna presented in this work is not an array. The single-element, shaped antenna design is realized through a combination of three different bow-tie components with various flare angles and radii, oriented to lay in the same plane, and centralized at the feed. Its enhanced bandwidth is achieved through the summation of the resonances of the individual components of the bow-tie elements. This configuration of overlapped bow ties occupies a much smaller area compared to the log-periodic array arrangement. The planarity and printability of the proposed antenna on 50 \(\upmu\)m PET film allows for easy and cost-efficient fabrication--ideal for mass production. In addition, the electrical size (a _kr_ of 1.10) of the proposed antenna is around 30% smaller than that of a full-sized, \(\uplambda/2\) dipole. A genetic algorithm (GA) is used to optimize the dimensions of the antenna to increase its bandwidth. All the simulations are performed in CST Microwave Studio.