Robulets P. Usage of single-negative metamaterials for transfer, modulation and filtering of signals

The thesis submitted in fulfillment of the Ph.D. degree in technical sciences on specialty 172 – “Telecommunication and Radio Engineering” – Department of Radio Engineering and Information Security at Yuriy Fedkovych Chernivtsi National University, Chernivtsi, Ukraine, 2021. Metamaterials are an object of research for many scientists because they make possible a lot of applications due to their unnatural properties at a width frequency range from microwave up to optics and higher. A number of the existing radio devices can be improved or completely changed by metamaterials or metaatoms. It is possible due to their sizes are more less than their operational wavelength. Therefore, the aim of the thesis is expansion of functional possibilities of components of communication means based on split-ring resonators for filtering, modulation/demodulation of harmonic and deterministic chaotic signals in order to their transfer through wire media at wide sub-GHz and GHz frequency ranges. A number of tasks were defined to achieve the aim. Those include a development and investigation of approaches and methods of modulation and demodulation of analog and digital signals as well as the transfer of harmonic oscillations through a wire media. The solutions of such tasks were found by using μ- and ε-negative metamaterials which are artificial materials with unusual properties (negative values of permittivity and permeability). The approach and methodology of the picking up of the operation frequency range and carrier signal are shown in the work through S-parameters as a response of SRR. The carrier signal feeds SRR via an additional loop antenna due to strong magnetic near-field coupling. The oscillations that appear in the SRR are amplitude modulated at the previously defined carrier signal. Thus, the frequency range where the interaction between SRR and additional loop antenna is much possible can be found by feeding the loop antenna by HF signals step-by-step in a wide frequency range and detecting SRR’s response. It was defined that such frequency range is Δf = fmin…fmax = 0,95…1,11 GHz for the bias voltage variation ΔU = Umin…Umax = ₋4,0…3,0 V. The realization of digital signals modulation is carried out based on the HF signal (carrier one) transmission line modification by SRR. SRR is placed as close as possible to the transmission line in order to provide strong near-field coupling. In the case of the same values of resonance state of SRR and the carrier signal, the last one is filtered by SRR and the output signal cannot be detected. However, it can be detected for the case when resonance frequency of SRR and carrier signal frequency are not the same. The obtained amplitude-frequency characteristics is the same to pass-band filter’s one. The device 30 by 22 mm dimensions was suggested and investigated in the work. The switching between different values of capacitance was shown by simulations. The interaction of transmission line and SRR was demonstrated by distributions of magnetic field at the resonance frequency – 635 MHz and non-resonance one – 800 MHz. One can see that the SRR oscillations appear for the resonance frequency and filtration happens. The HF signal from the input port is blocked and the signal at the output port is absent which corresponds the information bit “0” and vice versa. Two principles of on/off-switching circuits realizations were presented by experimental investigations. There are the circuit based on bipolar transistor which can switch two capacitors and optical control for changing of a varactor diode capacitance. In the paper WM was proposed to use for the transfer of a few signal simultaneously via parallel nodes (the area between four adjacent wires). Nevertheless, such signals can be broadband. The investigations shown the possibility of such device realization that can operate at the sub-GHz (from 0.45 to 0.8 GHz) and GHz (from 1 to 2 GHz) frequency ranges. In the thesis the principles of modulation of analog and digital signals were suggested and investigated as well as the structure was studied which makes possible to transfer of a few broadband signals of different types simultaneously. Key words Metamaterials, split-ring resonator, wire medium, amplitude modulation, digital modulation, filtering, analog and digital signals, broadband frequency range.