The Self-Grounded Bat Bow-tie Antenna Hinal Patel (1386219) School of Electrical and Information Engineering, University of the Witwatersrand, Johannesburg 2050, South Africa Abstract—An investigation is carried out into the design, modelling, construction and testing of a new, unique, bat bow-tie self grounded antenna. The purpose is to use it for the application of a dual band WiFi modem operating between the frequency ranges of 2.4-2.5Ghz and 5-6GHz. The antenna was a success and theoretically had a VSWR less than 2:1 and increased signal strength by 3db which corresponded to double the power. The existing model was analyzed and the results of the measurements and testing led to an upgraded MIMO model. 1. I NTRODUCTION S INCE Heinrich Hertz and Guglielmo Marconi, antennas have become subtly prevalent in society and are indis- pensable throughout history and in particular the migration from the 3 rd to the 4 th industrial revolution. These devices are present everywhere in the modern world today: cellphones, WiFi, aviation, satellites and have a plethora of various appli- cations. These interfaces have infinite geometries and configu- rations, however the all operate according to the fundamental principles of electromagnetics. The first bi-conical antenna was constructed in 1897 by Sir Oliver Lodge and prior to this a single cone antenna was favoured by Marconi and others. These were useful for various applications due to their ultra-wide band characteristics [1]. Brown and Woodward conducted a set extensive set of measurements on cone and triangles on a ground plane along with the biconical and triangular bow-tie dipoles to characterize their impedance in 1945. The bow-tie and self-grounded bow-tie antennas are types of biconical antennas and can be derived from them. However, they are unfavourable due to their large, heavy and bulky structure although they have attractive radiation characteristics compared to triangular monopole singular antennas. Hence, mechanical variations are made to the base structure to retain their electromagnetic features. Modern constructions have led to the development of designs of flat planar bow-tie antennas. They are the simpler alternative because it is compact, weighs less and costs less to build. The geometry of these designs have been transformed into the 3D self grounding bow-tie antenna presented in [2] and [3]. Further and advanced designs have led to the development of dual-polarized MIMO self-grounding antenna which is evident in [4],[5],[6],[7],[8],[9] and [10]. The progressive development of man is vitally dependent on invention [11].This report advocates for the design and construction of a unique geometrical configuration of an ultra- wide-band, linearly polarized, compact self-grounding bow-tie antenna. The progression of this design has ultimately led to further developments on the existing geometrical configura- tion to allow for the design and construction of a MIMO, TABLE I BANDWIDTH SPECIFICATIONS Designated Band F1 [GHz] F2 [GHz] F0 [Ghz] Bandwidth [MHz] [%] Ratio [F1/F2] 1(S) 2.417 2.437 2.427 20 0.82 1.06:1 2(C) 5.170 5.190 5.180 20 0.39 1:00:1 Designed Bat Band 2.5 6 4.2 3500 85.71 2.4:1 ultra-wide-band, dual polarized, large self-grounding bow-tie antenna. The antenna is designed for the application of a dual band WiFi modem operating in two bands (2.4– 2.5GHz) and (5–6 GHz). The report contains section 2 which details the de- sign considerations and characteristics, section 3 which briefly overviews the simulation, section 4 details the construction process, section 5 describe the testing environment, section 6 the results obtained followed by section 7 which provides an analysis on the results achieved. 2. ENGINEERING DESIGN The two designated bands of operation requires the antenna to radiate at 2.4Ghz and 5.4Ghz efficiently and effectively. f = c λ = c 2L (1) Equation 1 was solved and evaluated a length L = 62.5mm for a half wavelength dipole bow-tie antenna which meant that the antenna would radiate well at exactly 2.4Ghz for a length L = 62.5mm. However, this length is too long for the antenna to also radiate in the other designated band at 5Ghz which would require a length of 30mm. Thus the design specification for the length was chosen such that L>λ at the lowest frequency. 2.1 Bandwidth Equation 2 was used to calculate the bandwidth from the specifications for the required application in table 1. The frequencies were specified according to the WiFi modem that the design will be tested on. This antenna parameter was considered for the choice of antenna that was designed to radiate efficiently. Bandwidth(%) = F 1 - F 2 F 0 × 100 (2) where F 0 represents the center and designed frequency. Designated bands 1 and 2 revealed that a narrow bandwidth antenna such as the 2D bow-tie antenna which generally exhibits narrow bandwidth behaviour and would be apt how- ever, the choice of designing an ultra-wide band antenna was 1