Joko Suryana

Mid-air charging is a key enabler for persistent unmanned aerial vehicle (UAV) operation in 5G-enabled aerial networks, but practical microwave wireless power transfer (WPT) is constrained by how the receive rectenna can be integrated on small multi-rotor airframes. This paper investigates a distributed tiled rectenna architecture in which compact circularly polarized rectenna tiles are placed across the UAV body and arms to relax aperture constraints and reduce attitude-dependent reception. The prototype is experimentally characterized via per-tile received-power measurements under controlled pointing offsets and inter-tile coupling measurements, revealing non-uniform illumination and generally low coupling within the adopted spacing. Using these measured RF characteristics, a non-uniformity-aware scaling framework is developed to estimate the aggregated DC bus voltage of series-connected multi-tile configurations based on an empirical RF-to-DC conversion mapping. The results indicate that the proposed distributed tiled rectenna provides a viable and scalable receive-side approach for practical mid-air UAV charging using microwave WPT.

The variation in the k-factor value significantly influences the performance of unmanned aerial vehicle (UAV) air-to-ground point-to-point line of sight (A2G PTP LOS) communications over a Rician channel at 1,800 MHz using quadrature phase shift keying (QPSK) modulation and orthogonal frequency division multiplexing (OFDM) techniques. The research emphasizes the impact of the k-factor, which quantifies the dominance of the line-of-sight component over multipath scattering. The variation in the k-factor significantly influences UAV A2G PTP LOS communication performance for the empirical model (EM), as it involves precise measurements of the received power level in dBm from UAV to ground control station (GCS) across varying distances and altitudes. We introduce a method to compute the k-factor by assessing the ratio of the line-of-sight signal power to the multipath signal power, thereby enhancing channel modeling accuracy. Empirical analysis shows a strong correlation between bit error rate (BER) and signal-to-noise ratio (SNR) with differing k-factor values; a higher k-factor of 16.3 markedly improves performance, virtually eliminating errors at a 10 dB SNR, while a lower k-factor of 2.39 still shows significant errors at a 30 dB SNR. These results highlight the necessity of optimizing the k-factor in UAV A2G PTP LOS systems to ensure stable and reliable communication under diverse operational conditions.

The demand for advanced direction-finding systems operating in the 2-18 GHz frequency range has surged due to their role in cellular, satellite, and military applications. This increased demand has also led to a rise in illegal transmissions within this spectrum, highlighting the need for accurate signal detection and localization. This paper discusses the design and analysis of a compact antipodal Vivaldi antenna (AVA) aimed at detecting illegal transmitters within the 2-18 GHz band. Direction-finding systems require antennas with wide bandwidth, high gain, and directional radiation patterns to meet performance criteria. The Vivaldi antenna, with its tapered slot design, offers these features, making it ideal for precise signal detection. Designed on an FR-4 substrate with a relative permittivity of 4.6, the antenna's performance was optimized using CST Microwave Studio software. The antenna was fabricated using wet etching on a copper conductor. Measurement results show that the antenna exhibits a directional radiation pattern, with a maximum gain of 10.527 dBi at 8 GHz, surpassing the simulated gain of 8.12 dBi, and an average measured gain of 5.975 dBi, exceeding the design requirement of 4 dBi. Operating effectively across a 2.7-18 GHz range, the antenna achieves a bandwidth of 15.3 GHz, fulfilling 95.625% of the specified range. Despite minor shifts in the reflection coefficient due to dielectric permittivity variations in the FR-4 substrate, the antenna demonstrates strong performance for direction-finding applications. This study highlights the AVA's potential for high-performance detection of illegal transmitters and discusses design challenges and opportunities for optimization

The advent of quantum computers marks the beginning of the quantum 2.0 era. Unlike classical computers, quantum computers have faster and more efficient computational abilities, enabling them to break classical encryption such as the RSA (Rivest-Shamir-Adlemar) algorithm in a matter of minutes. To address this threat, a quantum communication system is required, which possesses quantum properties as well. The urgency of developing an independent and autonomous quantum communication system is crucial for a country. In this research, a transmitter for quantum communication based on faint pulse laser is developed. A weakened laser diode is used as the photon source. The laser diode weakening is achieved using a laser driver that generates short-duration pulse signals. By combining AND and XOR logic gates in such a way that when given a square wave input, the output of the logic gate system can produce short-duration pulses. The information in this communication system consists of randomly implemented keys, realized using the myRIO board and serving as a subsystem for random port selection. The designed laser driver produces pulse signals with a width of 128 nanoseconds and an amplitude of 1.5168 V. Additionally, the random port selection subsystem has been successfully designed using the myRIO board. Random numbers from ‘0’ to ‘3’ are generated uniformly. From 100 observation samples, an expected value of 1.445 and a variance of 0.911 are obtained. In the subsequent research, observations of single photon and the generated keys will be conducted.

The measurement room and far field calculation of the antenna to be measured are some of the factors that cause the antenna test results to be inaccurate. The room conditions that allow the test results to be unsuitable can be caused by external interference or reflections from electromagnetic waves. RF anechoic chamber of sufficient size can solve this problem, so that it reflects the true characteristics of the antenna being measured. However, the very high price for the procurement of the RF anechoic chamber facilities is the reason why not all educational laboratories have them. The Radio and Microwave Telecommunication Laboratory (LTRGM) designed and implemented an RF anechoic chamber with dimensions of 6.1 meters long, 4.88 meters wide and 4.27 meters high, using CRAM SFC and C-RAM Cornerblok absorbers. From the design specifications and implementation of the materials used, an RF anechoic chamber is built with a frequency range that can be measured between 1GHz - 40GHz, which can be used for satellite applications (27.5GHz, 31 GHz), cellular terrestrial networks (28GHz, 38GHz), network routing (23GHz , 3GHz), short-range radar (24 - 24.5GHz), and the maximum dimensions of the RF device tested are 50cm ² .

In this paper, 10 × 10 MIMO antennas have been designed for access point and handset application. Then, the proposed 10 × 10 MIMO antennas have been implemented on a low cost FR-4 substrate. These antennas realizes a good performance under MIMO situations with low mutual coupling (<;15 dB) and low correlation coefficient (<;0,5). This paper also presents indoor field performance measurement which consists of diversity simulation, power delay profile channel measurement, and throughput analysis. The diversity simulation and power delay profile result show that even though the channel has a lot of obstacle, MIMO system still can mitigate the multipath fading effect by selecting the best signal. The throughput using MIMO result show that up to 120 times throughput gain compared to single antenna transmission. Thus, we can conclude that MIMO antenna system is a promising technology for 5G networks in order to compensate the multipath fading effect and increase the throughput.