Wide-band conversion of donut-shaped pattern to directive one by square-shaped pattern director antenna

Abstract

In this paper, an antenna with 8 GHz (7–15 GHz) bandwidth is designed, simulated, fabricated, and measured. Commonly, for the effective use of electromagnetic sources, mode converters are used to transform donut-shaped patterns to directive patterns. This paper introduces a novel antenna called the pattern director antenna (PDA) that solves most problems associated with the azimuthally symmetric output modes of high-power microwave sources. The PDA accepts directly (without the need for mode conversion) an azimuthally symmetric generated mode of an electromagnetic source and converts it to radiate a directive pattern. For the proof of concept and validation of the design by simulations, the 3D printing technology [using polylactic acid (PLA)] is used to fabricate the PDA and measure its radiation patterns and return loss. The selected material is cheap and also environmentally friendly. The antenna was coated with aluminum to become a conductor. The gain is from 16.8 to 21.8 dB in the frequency range. The S11, main lobe deviation (MLD), and sidelobe level (SLL) are less than −15 dB, 2°, and −7 dB, in all frequency range, respectively. The simulation results are in good agreement with the measurement.

A circularly polarized TEM to TE 11 mode converter antenna

“…Due to an input impedance of 50 Ω (to minimize return losses if experimented [30] and [31]), according to (2), the internal conductor radius can be calculated as (7).…”

“…The outer waveguide dimension is selected 50 mm, arbitrarily. Due to an input impedance of $$50\;{{\Omega}}$$ (to minimize return losses if experimented [30] and [31]), according to (2), the internal conductor radius can be calculated as (7). $$\begin{equation}a\; = \;b{e^{ - \left( {\frac{{{Z_0}}}{{60}}} \right)}}\end{equation}$$so $$a\; \cong \;21.7mm$$.…”

“…According to (5), and 𝜂 TEM = 𝜂 0 = 120𝜋 Ω, the maximum value of Z T E 11 can be calculated, which is 94.93 Ω. Now, according to (10) and Z T E 11 range, the range of the operating frequency must be f > 2.068 GHz. The working frequency is selected at 10 GHz.…”

“…Using some electromagnetic diodes, due to their non-applicable output field shape, is usually not very effective [1] and [2]. In some electromagnetic diodes such as coaxial-VCO [3][4][5][6] and MILO [7][8][9][10][11], the output fields are in the TM01 and TEM modes, respectively. Now, if these two types of diodes direct the free space with a conical horn antenna or an openending waveguide, the shape of the radiation pattern is donutshaped [6] and [8].…”

“…Also, the antenna has large sidelobes. The other common MCA is the sectorial mode converter [1,7,9,10,22,23]. The structure can convert TEM mode to TE 11 mode.…”