The current work presents a study of the implementation of a quadrature chaos phase-shift keying communication system (QCPSK) based on the employment of different chaos oscillators. The research takes two directions, with one being the study of the chaos synchronization’s noise immunity for several chaos oscillators that are the potential core blocks of the QCPSK system. The correlation coefficient over time is used to estimate the synchronization noise immunity. The second direction is the estimation of the QCPSK system’s baseband model performance in the AWGN propagation channel using the bit error ratio (BER) as the estimation method for several chaos oscillators employed as the core of the QCPSK system’s model.

The current work presents a novel digital chaotic communication system with antipodal chaotic shift keying modulation, implemented in a field-programmable gate array (FPGA). Such systems provide high security on the physical communication level and can be used in wireless sensor network systems. A modified Chua circuit chaos generator and error linear feedback chaotic synchronization are implemented in FPGA and used to develop a chaotic communication system with digital transmitter and receiver an analog in-between signal transmission. Additionally, a validated mathematical model of the communication system prototype is created in the Simulink environment, which is used to compare the performance of the prototype and its nodes with the simulation and simplify its development. The performance is evaluated using simulation with the additive white Gaussian noise channel and analyzing the bit error ratio.

Possibilities of far field wireless power transfer (WPT) for creation of energy autonomous sensor nodes employing LoRaWAN technology for radio communications are explored in this study. WPT experiments were performed using continuous wave signal generator followed by amplifier at the transmitter side and RF-DC converters with different parameters at the receiver side. Two pairs of antennas with different gain and directivity were used. According to the experimental results it is possible to accumulate sufficient electrical energy to perform data transmissions at regular time intervals of several seconds. However, the energy requirements of sensor node depend strongly on operation mode of LoRa communication module together with supplementary circuit. Therefore, careful configuration of sensor nodes is required to achieve acceptable performance of wireless sensor network (WSN). Because of specific propagation of electromagnetic radiation in indoor environment there are locations with minimum available power even close to the transmitter. Consequently, installation of sensor nodes in closed areas requires knowledge of electromagnetic field distribution around transmitter.

This paper is dedicated to the experimental study of the impact of multi-tone signal with a high peak-to-average power ratio (PAPR) on the performance of wireless power transfer (WPT) using a single stage Cockcroft-Walton voltage multiplier with HSMS-285C diodes. The study is done using unlicensed sub-GHz frequencies 863 - 868 MHz in a laboratory under real-life conditions. Two types of design of radio frequency (RF) energy harvesting device (with and without matching network) are used to demonstrate PAPR impact on WPT performance. Eight sub-carriers summed in-phase are used to produce a multi-tone signal with a high PAPR level. For WPT results comparison, a single-tone signal with the same average power is exploited. For the experimental implementation of WPT, pairs of directional (LP0410 Log Periodic PCB) and omnidirectional (VERT900) antennas are used. Moreover, during the experiments the distance between transmitting and receiving antennas is being changed up to 3.2m. The main objective of the experiment is to find conditions when multi-tone signal with a high PAPR provides substantially higher output power compared to single-tone signal. The experimental measurement process includes evaluating the average power at the RF rectifier circuit output for different signals, distances, antennas, and RF-DC converter circuit designs. Furthermore, an additional WPT experiment is performed and the analysis of channel characteristics in the frequency range of interest is done to investigate the reason of the difference between the harvested power using single-tone and multi-tone signals.

The current paper presents the experimental study of the frequency-modulated chaos shift keying (FM-CSK) communication system. The proposed system has the potential to enhance the security aspects of the physical layer to meet the needs for safe data transmission in wireless sensor networks (WSN). Compared to common digital FM-DCSK, the studied analog FM-CSK communication system provides a more straightforward design. As chaos oscillators are the core elements of the FM-CSK communication system, the paper investigates the selected oscillators’ properties, including the implementation aspects—the impact of reactive element value deviations on dynamics and synchronization stability. Chaotic dynamics are evaluated with the mean-square-displacement-based 0–1 test, while correlation analysis is used to evaluate synchronization. The impact of the different chaos oscillators’ employment on FM-CSK communication system performance is examined, and the bit error ratio is used for noise immunity evaluation.

This paper presents a chaotic communication system based on a modified Chua’s circuit. The proposed system can be classified as chaos shift keying (CSK) based on chaotic synchronization phenomena. The mathematical model of the modified Chua’s circuit is based on a system of four differential equations. A linear feedback is used for chaotic synchronization implementation. One driving chaotic oscillator in the transmitter and two responding oscillators in the receiver are employed for data transmission. The paper presents not only the concept of a new chaotic communication system but also addresses the stability of the chaotic synchronization with different initial conditions in responding and driving chaotic oscillators. To validate the proposed concept of the advanced CSK system, simulation in MATLAB/Simulink environment is employed.