Radioelectronics and Communications Systems

Combined sensor-converter of light based on oscillator with unijunction transistor

I. M. Vikulin — 2024-10-26

A sensor-converter of light radiation has been developed based on an oscillator with a unijunction photo-transistor. To enhance photo-sensitivity, the oscillator circuit incorporates a field-effect transistor with a semiconductor gate in the form of a longitudinal structure from parts of opposite conductivity types.

Search method for identifying permutation sequence groups of maximum size with specified cross-correlation level for IC-FSCM modulation

Oleksandr Honcharov — 2024-10-26

The paper considers methods for modulating signals with a spread spectrum based on signals with linear frequency modulation CSS (Chirp Spread Spectrum). One of the methods of data coding based on CSS signals is the cyclic frequency shift of the LFM pulse known as Frequency Shift Chirp Modulation (FSCM). The Interleaved Chirp FSCM (IC-FSCM) modulation method uses a set of permutation sequences of the LFM pulse segments to encode additional information bits. It has a higher spectral efficiency compared to the FSCM method. The minimum level of cross-correlation between the signals obtained by using different permutation sequences is essential. We propose a search method for identifying groups of permutation sequences with a specified maximum level of cross-correlation, which involves representing the matrix of cross-correlation between sequences as a graph and searching for complete subgraphs of maximum size within this graph using the Bron-Kerbosch algorithm. As a result of applying the algorithm, groups of sequences have been identified that enable us to increase the number of additional bits in a symbol to 5 without increasing the level of cross-correlation between symbols. Additionally, we have reduced the level of cross-correlation between symbols when the number of additional bits is set to 3 and 4. The characteristics of the found sequences and the distribution of error probability among the main and additional bits of the symbol have been analyzed.

Hartley angular modulation

A. B. Kokhanov — 2024-10-26

Hartley angular modulation (HAM) differs from the known angular modulation (AM) by the presence of an additional orthogonal (quadrature) component, which allows us to form the HAM signal as a sum of sine and cosine signals of the same frequency with the same current phase of the signal. It is possible to use a variant of both Hartley phase modulation (HPM) and Hartley frequency modulation (HFM). This allows us to form a signal that corresponds to the sum of two signals with angular modulation on orthogonal carriers, which in turn corresponds to the known sum of the sine and cosine, i.e., the Hartley signal. Signal HAM has increased resistance to noise in the communication channel compared to AM. The power gain of Hartley angular modulation as compared to the known angular modulation is 6 dB. Provided other things are equal, for signals with the Hartley angular modulation and the known angular modulation, the signal with HAM offers the possibility of increasing the communication range by a factor of two. Suppose a fixed communication range is used (e.g., on VHF). In that case, the transmitter power can be reduced by a factor of four, providing a significant reduction in power consumption by the transmitting device. The HAM signal can also be detected by a conventional frequency or phase detector, which enables the reception of a signal with Hartley angular modulation using a traditional receiver for AM signals (e.g., with frequency modulation). However, there will be no power gain in this case.

PDEPE: CMOS implementation of power and delay efficient polar encoder for modern communication systems

Sourav Kumar Das — 2024-10-26

Polar codes are straightforward and effective channel codes for discrete memoryless channels with binary input. Due to its low encoding and decoding complexity, polar code has been embraced by the 5th Generation (5G) wireless communication systems as a channel coding scheme for control channels. In this paper, a low-power and fast polar encoder, namely, Power and Delay Efficient Polar Encoder (PDEPE), has been designed and implemented using 22nm CMOS technology. In this work, three fundamental parameters are considered to analyze the suggested design: supply voltage V_DD, aspect ratio of NMOS transistor W/L, and the transconductance K_PN. The suggested PDEPE design has been enhanced using a proposed optimization approach based on common sub-expression elimination methods. According to the synthesis results, the power delay product (PDP) of the proposed design is improved by 54, 40, and 44% respectively, with respect to V_DD, W/L, and K_PN compared to related designs. The proposed design consumes less power and is faster than the conventional polar (8, 4) encoder. The proposed design is more suitable for modern communication systems like 5G.

Combined frequency tuning of resonators from TL segments

Sergii Litvintsev — 2024-10-26

The tunability limitations of distributed resonators with variable lumped capacitances C_i and inductances L_j are established. They significantly exceed the similar limitations of distributed resonators with variable C_i or L_j. This suggests the potential for utilizing resonators with combined frequency tuning. Such frequency tuning is provided by a smooth change in C_i and a step change in L_j by switching. It has been proven that the use of step-impedance resonators (SIR) with combined frequency tuning enables a further increase in the tuning range. The intersection effect of neighboring resonant regions is observed in SIR. Experimental data for a second-order microstrip bandpass filter with combined frequency tuning are presented.

Frequency symbolic analysis of high complexity LPTV circuits

Yuriy Shapovalov — 2024-10-26

This paper extends the frequency symbolic method (FS method) for analyzing linear periodically time-varying (LPTV) circuits to highly complex circuits. It has been demonstrated that this extension is achieved by applying the d-tree method to the FS method developed by the authors. At the same time, the d-tree method, based on the nodal voltage method and extended to LPTV circuits, has demonstrated high efficiency, making it possible to analyze circuits of high complexity. The paper considers the problem of transforming a system of linear integro-differential equations describing a circuit into a system of linear differential equations, which requires the application of L.A. Zadeh’s equation in the FS method. Two methods for eliminating integral expressions from a system of differential equations are proposed, one of which (the variable substitution method) is implemented in the UDF MAOPCs program. The reverse transformation to the original variables in the form of nodal voltages is proposed to be performed by differentiating transfer functions or multiplying them by the corresponding values of complex variables associated with individual harmonic components present in the transfer function. The results of analyzing a highly complex LPTV circuit, containing 33 nodes and 32 parametric elements, have been presented.