Dragan I. Olcan

Open hardware for electrostatic discharge pre-compliance immunity testing is presented. This system is based on a digitally controlled high-voltage source featuring a custom-designed step-up transformer, a capacitive voltage multiplier, and an innovative printed pulse shaper. The voltage multiplier consists of a cascade arrangement of capacitors and diodes, allowing it to provide a constant output voltage in the range from −15 kV to 15 kV for the pulse shaper in accordance with the IEC 61000-4-2:2025 standard. The high-voltage source is designed for burst outputs, capable of stepping up constant voltages from 5 V to ±15 kV. The novel pulse shaper, printed on FR4 substrate, was designed and optimized using circuit analysis and full-wave electromagnetic solvers to generate standard current pulses for contact electrostatic discharges. Measurements, verified in an accredited electromagnetic compatibility laboratory, indicate that the proposed open-hardware electrostatic-discharge generator produces the required voltages and contact-discharge current pulses within standard tolerances. The design choices prioritize ease of reproducibility, manual assembly, and the use of widely available components. All production files and accompanying microcontroller software are publicly accessible and released under the CERN Open Hardware License to foster innovation, promote collaborative design practices and enable broader access to electrostatic discharge pre-compliance immunity testing.

This article proposes a novel Multiple Access (MA) scheme called Ramanujan Periodic-subspace Division Multiple Access (RPDMA) for subcarrier sizes $N = 2^{m},\ m\in \mathbb {N}$, to address the high Peak-to-Average Power Ratio (PAPR) in Orthogonal Frequency Division Multiple Access (OFDMA). Building on the properties of Ramanujan subspaces, we design transmitter and receiver models that allocate users on a subspace-wise basis, ensuring zero inter-user interference, providing inherent frequency diversity. We analyze the computational complexity of OFDMA, SC-FDMA, and RPDMA, and find that RPDMA has substantially lower per-user transmitter complexity than both OFDMA and SC-FDMA, while its receiver complexity is comparable to SC-FDMA and higher than that of OFDMA. We further introduce a generalized framework, termed Nested Periodic-subspace Division Multiple Access (NPDMA), which unifies both RPDMA and OFDMA under a common family of multi-carrier MA schemes. We derive the theoretical PAPR of RPDMA and demonstrate its superiority over OFDMA. The analysis is validated through numerical simulations under two multi-user scenarios with diverse Quality of Service (QoS) requirements. The results demonstrate that RPDMA achieves lower PAPR than both OFDMA and SC-FDMA, with users assigned larger subspaces benefiting from even greater PAPR reduction. We prove that both the sum and per-user Spectral Efficiency (SE) of RPDMA are identical to those of OFDMA and SC-FDMA. In terms of Bit Error Rate (BER), SC-FDMA achieves the best performance, while RPDMA still outperforms OFDMA as the SNR increases.

Pored tradicionalnih metoda za dijagnostikovanje preloma kostiju, u koje spadaju kompjuterska tomografija i magnetska rezonansa, istraživanje odgovarajućih dijagnostičkih metoda primenom elektromagnetskih sistema privlači sve više pažnje poslednjih godina. Ova tehnika zasniva se na merenju refleksije od antena i transmisije između antena postavljenih u okolini organa od interesa. U ovom radu prikazano je elektromagnetsko modelovanje preloma tibijalne kosti (lat. tibia) i pratećeg hematoma. Pokazano je kako pojednostavljivanje detaljnog modela potkolenice utiče na s-parametre antena, postavljenih u vazduhu oko modela, u frekvencijskom opsegu od 0,7 GHz do 1 GHz.

Prikazana je mogućnost rekonstrukcije bitova protokola HDMI signala analizom radijacione emisije magnetskog polja, što otvara mogućnost beskontaktne rekonstrukcije slike monitora računara. U radu je objašnjen HDMI protokol, kao i na koji način se vrši prenos signala. Prikazana je eksperimentalna postavka koja se sastoji od PCB HDMI test pločice za merenje signala, osciloskopa, pasivnih sondi i magnetske sonde. Takođe, prikazani su rezultati merenja, koji se sastoje od vremenskog prikaza protokola HDMI signala na osciloskopu, kao i vremenskog prikaza signala snimljenog sondom bliskog polja. Izvršena je obrada signala sa magnetske sonde, u cilju detekcije emisije magnetskog polja, određivanjem trenutka tranzicije stanja bitova na liniji i rekonstrukcije HDMI protokola. Na samom kraju izvedeni su zaključci eksperimenta.

An assessment of radio-frequency interference due to the emanated electromagnetic field and the time-domain waveforms of the currents drawn from the electric power distribution network was performed. Three constant-current switching-mode power-supply units were analyzed. These units are LED drivers that are widely available on the local market. The observed interference spanned the HF and VHF bands, i.e., from 10 kHz to 150 MHz, which are of particular concern for the amateur radio services. A computational electromagnetic model was analyzed and solutions for interference mitigation were demonstrated.

A multi-epoch mini-batch variant of the Levenberg-Marquardt algorithm (LMA) is proposed for an efficient training of large training sets applied in consensus deep neural network (Consensus DNN) of complex antenna models. In each training epoch the proposed approach divides whole training set into mini-batches and applies multiple iterations on each of them, where initial weights and biases are overtaken from the previously trained mini-batch. By appropriately selecting the mini-batch size and number of iterations per mini-batch, the adapted LMA enables shorter training time and higher accuracy than standard LMA. Owing to this adaptation the training of Consensus DNN is facilitated and its accuracy is improved.