Radioelectronics and Communications Systems

Low-energy 3:2 compressor using XOR-XNOR gate combined with 2:1 multiplexer in QCA technology

Sankit Kassa — 2024-01-26

In the field of circuit design, there is a growing trend toward the design of high-speed circuits with a minimum amount of faults on a nanoscale level. In this way, quantum-dot cellular automata (QCA) is a nanoscale-based paradigm that uses a quantum cell with four dots and two electrons to compute logic bits, comparable to transistor-based CMOS architecture. This article focuses on the low-energy compressor design employing an XOR-XNOR gate and a 2:1 multiplexer. Furthermore, a compressor design provides 152 cells employing a coplanar arrangement in QCA with eight majority gates (MG). The compressor energy dissipation is examined using the QCAPro tool, which has various tunneling energy values. Furthermore, the compressor thermal and polarisation layouts are presented. The novel circuit performance is compared with the best existing circuits on QCA regarding cell count, entire area, MG, and latency to assess the newly designed compressor performance. The proposed compressor is tested using the missing cells in the QCADesigner tool. This design has only 5 test vectors, 100% fault coverage, and is best suited for design for testability (DFT). The proposed compressor can be used with various multipliers, including the Wallace tree multiplier, DADDA multiplier, and higher order 7:3 compressor.

Simple technique for determining length of biconical cavity’s evanescent zones

Mikhail Andreev — 2024-01-26

This paper presents a simple technique for finding the length of evanescent zones near the ends of the biconical cavity, where sample insertion openings can be made without significantly affecting the resonance frequencies or the field structure. The technique combines the overlapping domain decomposition method with the collocation method. The interior of the cavity is divided into two overlapping regions, on the boundaries of which collocation points are specified. In each region, the electric field is represented as an eigenfunction expansion. A homogeneous system of linear equations in the expansion coefficients is derived from the equality of the electric fields in both regions at the collocation points. The expansion coefficients are determined as an eigenvector of the system matrix associated with its zero eigenvalue. Using the found expansion coefficients, the distribution of the electric field normalized to the maximum electric field in the cavity is calculated to give the length of evanescent zones, which are defined as regions where the electric field does not exceed a specified small fraction of the maximum electric field in the cavity. Because as few as four pairs of collocation points were proved to be sufficient, the computational effort of the proposed technique is relatively moderate, thus allowing it to be used in the development of instruments based on open-ended biconical cavities.

Directional and band properties of dipole antennas with square-shaped screens

Nadezhda Yeliseyeva — 2024-01-26

The paper presents a quantitative analysis of the directivity characteristics and the operating frequency band of a resonant dipole antenna parallel to a perfectly conducting square-shaped screen. This analysis considers the effect of in-phase diffracted fields at all four edges of the screen with a geometrooptical field in the direction normal to the screen, the dimensions of which ensure the in-phase operation of these fields. The paper uses the solution of the three-dimensional vector problem of diffraction of dipole radiation on a rectangular screen obtained within the framework of the method of uniform geometric theory of diffraction (UGTD). The programs developed in the FORTRAN environment were used to calculate radiation patterns (RP), directed action coefficient (DAC) in the direction normal to the screen and the direction of the main maximum of RP, radiation resistance of the resonant half-wave dipole, and optimal dimensions of a square screen in terms of the DAC maximum for varying the operating wavelengths and screen dimensions in a wide range. It is shown that the optimal dimensions of the square screen amount to 0.7–1.3 of dipole resonant wavelength, and the resonance of the antenna radiation resistance occurs at the electrical dimensions of the square screen in the range of 0.7–0.9. The width of the main lobe of antenna RP in the plane of the electric field vector is about 60° and about 100° in the plane of the magnetic field vector, and it is slightly dependent on the screen size. The band of operating wavelengths is limited by the radiation resistance and the identity of the main lobe of antenna RP; this band varies from 0.75 to 1.5 of the resonant wavelength depending on the screen size. The bandwidth index of the dipole antenna with a square screen can reach unity.

Refinement of expression for calculating losses of single-layer winding of inductive element

Andrii Seredin — 2024-01-26

The paper briefly presents the results of preliminary studies, during which it was determined that the probable reason for the appearance of a significant error in calculating the losses of a single-layer winding of inductive element without a core by using the Ferreira analytical technique in the ultrasonic frequency range is the neglect of the influence of some geometric parameters of the winding, such as its diameter and the number of turns, on the current distribution in the turns. Thus, the calculation expression of this technique needs to be refined by including the neglected geometric parameters in this expression. It has been determined that solving the refinement problem analytically is difficult. Therefore, we propose to solve it empirically. Using computer simulation, the losses of a single-layer winding without a core were determined for the most common in-practice values of winding diameters, conductor diameters, the number of turns, and the operating frequencies. Several graphs of relationships are presented, based on which the types of refining expressions and the method of their introduction into the calculation expression as complementary factors are determined; in addition, the corresponding correction factors are calculated. The results of calculating the values of losses by the refined expression and the initial one are compared. It has been established that the discrepancy between the theoretical and experimental results changed from 59.5 to 11% when the number of turns was changed and from 63 to 4% when the influence of the winding diameter was considered.

An alternative method for calculating the value of losses of single-layer windings for most common specific practical cases was proposed. Based on the simulated data, curves of the relationships of the winding losses as a function of the specified geometric parameters were built. The optimal type of approximating function was selected, the approximation was performed, and the approximating coefficients for the conductor diameter, frame diameter, and the number of turns in the winding for different operating frequencies were calculated.

Low complexity subcarrier activation scheme for OFDM with index modulation

Hussein N. Fadhel — 2024-01-26

In orthogonal frequency division multiplexing with index modulation (OFDM-IM), data is mapped to subcarrier activation patterns (SAP) using look-up tables or combinatorial schemes. The complexity of these mapping schemes increases with the number of subcarriers. Therefore, they are applied to subgroups of subcarriers, but unfortunately, at the expense of reducing the amount of data loaded to an OFDM block. In this paper, low-complexity direct data to SAP mapping is proposed, the necessary analysis to determine the analytical bit error rate (BER) is presented, and the computer simulations are performed to find and compare theoretical and simulated BER results under conditions of the frequency selective Rayleigh fading channel. The proposed scheme can load more data bits to an OFDM block than conventional schemes. The results from computer simulations demonstrate the superiority of the OFDM-IM system using the proposed scheme over conventional OFDM-IM in terms of BER performance.