DEVELOPMENT OF CALIBRATION MODULES FOR A COMPLEX OF ASSESSING THE IMPACT OF ELECTROMAGNETIC INTERFERENCE ON ELECTRONIC DEVICES

В современном мире при стремлении человечества к миниатюризации электротехнической и радиоэлектронной продукции без потери технических характеристик устройств, наряду с их расширением одной из значимых проблем является влияние электромагнитных помех на стабильное функционирование устройств. Представлены модули калибровки, используемые в программно-аппаратном комплексе (ПАК), который позволяет произвести оценку влияния электромагнитных помех (ЭМП) на электронные средства. Практическое искажение сигналов неизбежно, так как причиной помех может стать взаимное влияние элементов печатной платы (ПП) друг на друга, а также конфигурация самого рисунка дорожек ПП и её топологии. Рассматриваются модули, позволяющие выявить ряд ошибок по ранее полученным результатам и обеспечить калибровку комплекса с целью повышения точности оценки влияния самоиндукции и импеданса линии передач на вносимые искажения сигнала при различных конфигурациях трассировки печатной платы. Применение данного программно-аппаратного комплекса позволяет значительно сократить время, необходимое на разработку устройства и комплекс испытаний, что, в свою очередь, снижает финансовую нагрузку на выпуск единицы продукции, поскольку позволяет выявить недостатки устройств на стадии макетирования электротехнической продукции In the modern world, with the desire of all mankind to miniaturize electrical products without loss of power, one of the significant problems is the influence of electromagnetic interference on the stable functioning of devices. This article presents the calibration modules used in the software and hardware complex (SHC), which allows one to assess the influence of electromagnetic interference (EMI) on electronic means. The practical distortion of signals is inevitable since the cause of interference can be their mutual influence on each other, as well as the configuration of the printed circuit board pattern itself. The paper considers modules that allow identifying a number of errors based on previously obtained results and providing calibration of the complex in order to increase the accuracy of estimating the effect of self-induction and transmission line impedance on the introduced signal distortion in various configurations of the PCB trace. The use of this software and hardware complex can significantly reduce the development time and conduct tests that require financial costs since it allows one to conduct a number of experiments at the stage of prototyping electrical products

Accounting for Signal Distortion Biases for Wide-Lane and Narrow-Lane Phase Bias Estimation with Inhomogeneous Networks

Due to different designs of receiver correlators and front ends, receiver-related pseudorange biases, called signal distortion biases (SDBs), exist. Ignoring SDBs that can reach up to 0.66 cycles and 10 ns in Melbourne-Wübbena (MW) and ionosphere-free (IF) combinations can negatively affect phase bias estimation. In this contribution, we investigate the SDBs and evaluate the impacts on wide-lane (WL) and narrow-lane (NL) phase bias estimations, and further propose an approach to eliminating these SDBs to improve phase bias estimation. Based on a large data set of 302 multi-global navigation satellite system (GNSS) experiment (MGEX) stations, including 5 receiver brands, we analyze the characteristics of these SDBs The SDB characteristics of different receiver types for different GNSS systems differ from each other. Compared to the global positioning system (GPS) and BeiDou navigation satellite system (BDS), SDBs of Galileo are not significant; those of BDS-3 are significantly superior to BDS-2; Septentrio (SEPT) receivers show the most excellent consistency among all receiver types. Then, we apply the corresponding corrections to phase bias estimation for GPS, Galileo and BDS. The experimental results reveal that the calibration can greatly improve the performance of phase bias estimation. For WL phase biases estimation, the consistencies of WL phase biases among different networks for GPS, Galileo, BDS-2 and BDS-3 improve by 89%, 77%, 76% and 78%, respectively. There are scarcely any improvements of the fixing rates for Galileo due to its significantly small SDBs, while for GPS, BDS-2 and BDS-3, the WL ambiguity fixing rates can improve greatly by 13%, 27% and 14% after SDB calibrations with improvements of WL ambiguity fixing rates, the corresponding NL ambiguity fixing rates can further increase greatly, which can reach approximately 16%, 27% and 22%, respectively. Additionally, after the calibration, both WL and NL phase bias series become more stable. The standard deviations (STDs) of WL phase bias series for GPS and BDS can improve by more than 46%, while those of NL phase bias series can yield improvements of more than 13%. Ultimately, the calibration can make more WL and NL ambiguity residuals concentrated in ranges within ±0.02 cycles. All these results demonstrate that SDBs for phase bias estimation cannot be ignored and must be considered when inhomogeneous receivers are used.

Scalp attached tangential magnetoencephalography using tunnel magneto-resistive sensors

Non-invasive human brain functional imaging with millisecond resolution can be achieved only with magnetoencephalography (MEG) and electroencephalography (EEG). MEG has better spatial resolution than EEG because signal distortion due to inhomogeneous head conductivity is negligible in MEG but serious in EEG. However, this advantage has been practically limited by the necessary setback distances between the sensors and scalp, because the Dewar vessel containing liquid helium for superconducting sensors requires a thick vacuum wall. Latest developments of high critical temperature (high-Tc) superconducting or optically pumped magnetometers have not allowed scalp-attached MEG due to cold or hot temperatures at the sensing point, respectively. Here we applied tunnel magneto-resistive (TMR) sensors that operate at room temperature. Improvement of TMR sensitivity with magnetic flux concentrators enabled scalp-attached and scalp-tangential MEG to target the largest signal component produced by the neural current below. In a healthy subject, our single-channel TMR-MEG system clearly demonstrated the N20m, the initial cortical component of the somatosensory evoked response after median nerve stimulation. Multisite measurement confirmed a spatially and temporally steep peak of N20m, immediately above the source at a latency around 20 ms, indicating a new approach to non-invasive functional brain imaging with millimeter and millisecond resolutions.

Real-Time Multirate Filtering of Digitized Torque Signals on Tiva Microcontroller using Fixed-Point Design with MATLAB

Correct bone screw torque is critical for positive patient outcomes after orthopaedic surgery. Models of the screwing process have been developed to allow a smart screwdriver to optimise the insertion torque. Experimental data is required to test these models, so a test-rig has been developed. Accurate torque measurement is a key part of the test-rig. An FIR filter was designed for this torque signal, implemented on the test-rig, and compared theoretically and experimentally to a mean filter and to no filtering. The FIR and mean filters both performed well, with the FIR achieving better theoretical results, and the mean filter achieving better experimental results. Better understanding of the noise structure and potential signal distortion would be required to improve the FIR filter or to conclusively compare it against the mean filter, however both perform sufficiently well for this application.

A Low Complexity Non-Distortion Clipping Technique PAPR Reduction of MIMO-OFDM Systems

Amplitude clipping is one of the techniques used to reduce PAPR. This technique does not demand side information; therefore, there is no reduction in the system's data throughput. However, it leads to additional distortion (in-band signal distortion and out-of-band radiation). To overcome this problem, low complexity non-distortion clipping technique is proposed for MIMO-OFDM system. The main concept of this proposed method is how to convert the generated distortion (in-band and out-of-band signals distortion) when using clipping at transmitter to impulse noise (error), which is possible by using a simple coding technique to cover error at the receiver. The proposed method does not clip the signal in time domain. The clipping use for discrete samples directly after IFFT. Simulation outcome detects that the proposed non-distortion clipping technique provides an efficient reduction in PAPR, best performance compared with conventional clipping technique, and less cost and complexity.

Sensitivity and Adjustment Model of Electrocardiographic Signal Distortion Based on the Electrodes’ Location and Motion Artifacts Reduction for Wearable Monitoring Applications

Wearable vital signs monitoring and specially the electrocardiogram have taken important role due to the information that provide about high-risk diseases, it has been evidenced by the needed to increase the health service coverage in home care as has been encouraged by World Health Organization. Some wearables devices have been developed to monitor the Electrocardiographic in which the location of the measurement electrodes is modified respect to the Einthoven model. However, mislocation of the electrodes on the torso can lead to the modification of acquired signals, diagnostic mistakes and misinterpretation of the information in the signal. This work presents a volume conductor evaluation and an Electrocardiographic signal waveform comparison when the location of electrodes is changed, to find a electrodes’ location that reduces distortion of interest signals. In addition, effects of motion artifacts and electrodes’ location on the signal acquisition are evaluated. A group of volunteers was recorded to obtain Electrocardiographic signals, the result was compared with a computational model of the heart behavior through the Ensemble Average Electrocardiographic, Dynamic Time Warping and Signal-to-Noise Ratio methods to quantitatively determine the signal distortion. It was found that while the Einthoven method is followed, it is possible to acquire the Electrocardiographic signal from the patient’s torso or back without a significant difference, and the electrodes position can be moved 6 cm at most from the suggested location by the Einthoven triangle in Mason–Likar’s method.

Reconfigurable Antenna Array Direction Finding System Based on a Fast Search Algorithm

In a traditional antenna array direction finding system, all the antenna sensors need to work or shut down at the same time, which often leads to signal crosstalk, signal distortion, and other electromagnetic compatibility problems. In addition, the direction-finding algorithm in a traditional system needs a tremendous spectral search, which consumes considerable time. To compensate for these deficiencies, a reconfigurable antenna array direction finding system is established in this paper. This system can dynamically load part or all of the antennas through microwave switches (such as a PIN diode) and conduct a fast direction of arrival (DOA) search. First, the hardware structure of the reconfigurable antenna is constructed. Then, based on the conventional spatial domain search algorithm, an improved transform domain (TD) search algorithm is proposed. The effectiveness of the system has been proven by real experiments, and the advantage of the system has been verified by detailed simulations.