Vol 68, No 2 (2023)

A multibeam antenna based on a Morgan double-layer lens in the form of plane waveguides coupled via a frequency-periodic array is investigated. The lens synthesis problems are considered. The analytical model of coupled plane waveguides is constructed. The model uses the equivalent boundary conditions. It is verified using the electromagnetic modeling in the HFSS system. An approximate electromagnetic model of the antenna is proposed. The model is based on the representation of the structure electromagnetic field in
the form of radial waves of coupled plane waveguides of the fundamental type. It is shown that, in the doublelayer lens, the effect of its shading by irradiators is substantially attenuated. This fact makes it possible to form the system of rays with fan-shaped patterns, which provides for the space view in the azimuth angle sector of 360°. The possibility of formation of narrow rays with the low level of the side and back irradiation is demonstrated.

The frequency dependences of the effective permittivity of the structure in the form of an array consisting of ring resistive elements that are located in a dielectric layer are obtained. The calculations are based on the solution of the problem of diffraction of an electromagnetic wave normally incident on the structure. The possibility of variation of the dispersion dependences in wide limits by means of changing the structure
parameters is shown.

A single-position method of non-bearing passive location has been developed with allowance for the periodicity of a radiated pulsed radio signal during the motion of a radiation source along a curvilinear trajectory. The method does not require the current Doppler frequency to be estimated and the measured
parameter is the time discrepancy between the periods of the emitted and received signals caused by the motion of a source. The problems of the computational correctness and accuracy of the method are discussed and practical recommendations are made. A numerical example is given.

The sets of nonbinary pseudorandom sequences (NPSs) for periods N = p^S– 1 < 20 000 (p = 3, 5,7, and 11) generated in finite fields GF(pS) whose power is V = N + 1 and the maximum of the module of peaks of the periodic autocorrelation function (PACF) and periodic cross-correlation function (PCCF) satisfy the bounds obtained by Sidel’nikov. In addition to the minimal polynomials of elements α and α^2 , where α is a primitive element of field GF(p^S), the minimal polynomials of elements α and α^(i_d)(i_d is the decimation index) are determined on the basis of which the new sets of NPSs can be formed with the equivalent correlation properties. Sets of indices i_d > 2 are determined for various combinations of parameters p and S. The cases of even and odd values of parameter S are considered, for which the values of the PACF and PCCF with the maximum module are obtained and the number and values of different levels of correlation functions are determined.

Significant differences observed in the behavior of photoinduced permittivity ε of semiconductors in the gigahertz (GHz) and terahertz (THz) ranges are explained within the framework of the exciton mechanism by the different position of these ranges relative to the frequencies of exciton interlevel transitions. The measurements in the GHz range of the photoinduced changes of quantities Imε(P_λ) and Reε(P_λ) of CdS, CdSe and Si samples in a waveguide resonator (f = 4.7 GHz) and transmittance T of Si samples in free space (f = 8–36 GHz ) under fiber-optic irradiation (P_λ = 0–370 mW and λ = 0.97 μm) that exhibit non-Drude response prove the theoretical conclusions: an increase in Reε^(GHz)(P_λ) with increasing P_λ and an increase in transmittance T with decreasing frequency f at fixed power P_λ.

The practical feasibility of a wireless relative transmission scheme based on chaotic radio pulses is demonstrated. New components necessary for the implementation of this scheme have been developed. A prototype of a transmission system in the frequency range of 200–500 MHz was created on which experiments were carried out on the transmission of binary information. The measurement results correspond to the previously obtained theoretical and computational estimates on the main properties and characteristics of a new transmission scheme that uses dynamic chaos as  an information carrier.

Optically and mechanically controlled attenuators and an electrically controlled phase shifter are developed on the basis of a dielectric waveguide made of the high-resistance silicon. The characteristics of the waveguide and elements developed on its basis are theoretically and experimentally determined in the frequency band 26–37 GHz.

Within the balanced approximation of fiber lasers (FLs) considered as distributed systems, an improved mathematical model is constructed that describes the low-frequency dynamics of FLs with mirrors based on optomechanical micro-oscillators (MOs), taking into account the effect of spontaneous emission (SE) localized in the cladding modes of the active fiber (AF). The mechanisms of the effect of SE on the synchronous self-oscillations (SSOs) in the FL–MO laser system are revealed: additional inversion removal in the AF due to the finite path length of SE cladding mode photons in the FL active medium, violation of the condition  for the internal resonance in the laser system, and perturbation of MO oscillations by photoinduced force caused by SE. By means of numerical simulation of SSOs in an erbium–ytterbium FL with an MO and experimental studies, the dependence of the SSO frequency on the geometric-optical parameters of the AF and the reflectivity of the AF–environment interface has been established, which can be used to improve the frequency stability of laser pulses in fiber sources of pulsed radiation and create a new class of resonant fiberoptic sensors.

An experimental photonic analog-to-digital converter designed for X-band signal processing is presented. The functioning of the created device in laboratory and field conditions was studied.

Functioning of a prototype of a micropower system (energy storage device) consisting of a biofuel cell (BFC) and converter–capacitor is demonstrated. The system allows conversion of a low input voltage from an unstable energy source to a standard working voltage used in radio equipment. For the series connection of two biofuel cells, the voltage is summed up and amounts to ~500 mV, and the output storage capacitor of 100 μF is charged in 13 min to a working voltage of 3.1 V upon a cold start of the converter. It is shown that energy storage substantially depends on the capacitance of the final storage unit and on the type of energy consumption. The proposed system can be used for different unstable energy sources.