Electronic Navigation Research Institute

Automatic Dependent Surveillance—Broadcast (ADS-B) is a position broadcast system for air traffic control. Although ADS-B outperforms traditional radars, positional verification—a technique used to check the validity of the position report—is necessary to detect anomaly information. A popular approach is using time difference of arrival (TDOA). However, many receiver sites are necessary to achieve higher detection performance. Therefore, performance enhancement by additional angle of arrival (AOA) measurement is proposed in this study. First, the conventional and proposed methods were mathematically modeled in a unified framework. Then, benefit of the proposed method compared with the conventional method was evaluated in numerical simulation. Finally, measurement-based analysis were conducted to consider practical implementation of the method and demonstrated its feasibility.

The fabrication of millimeter-wave lens antennas based on three-dimensional (3D) printing technology has the advantage of low cost. Using this technology, we have developed several types of 3D-printed W-band reflector Fresnel lens antennas based on acrylonitrile butadiene styrene (ABS) plastic filaments. However, these ABS plastic filaments, which are commonly used in 3D printers, exhibit relatively high dielectric loss. To overcome this problem, a reflector Fresnel lens antenna with a gain of more than 35 dBi has been proposed for the millimeter-wave radar applications (S. Futatsumori, 40th International Review of Progress in Applied Computational Electromagnetics, pp. 1–2, May 2024). In this study, we fabricate a 250-mm-diameter 3D-printed reflector Fresnel lens antenna designed using the finite-difference time-domain (FDTD) method and compare the FDTD-analysis results with those obtained from measurement. Initially, the design of the W-band reflector Fresnel lens antenna is discussed. Then, the difference in the FDTD analysis and measured results is presented.

As a crucial element within hydraulic systems, the condition monitoring of electro-hydraulic proportional servo valves is indispensable for ensuring safety and mission success. These systems often operate in harsh environments characterized by high temperatures and intense vibrations, which can lead to performance deterioration over time. Moreover, in dynamic applications, the system's duty cycle may not follow a periodic pattern, resulting in irregular degradation measurements that further complicate health assessment. To tackle these challenges, we propose a novel Transformer-based method specifically designed for this task, with the aim of assessing the health status of electro-hydraulic proportional servo valves under various operating conditions. This method is intricately linked with the electro-hydraulic proportional servo working model and degradation model that we have developed, enabling the evaluation of the current internal health status of hydraulic valves. The effectiveness of the proposed approach has been validated through experiments.

Abstract The S-520-27 sounding rocket was launched from the Uchinoura Space Center in Kagoshima, Japan at 23:57 JST on July 20, 2013. This sounding rocket was launched to verify the hypothesis of the nighttime medium-scale traveling ionospheric disturbance (MSTID) generation mechanism, in which electromagnetic interaction in the ionospheric E and F regions is thought to play an important role. The detrended total electron content (dTEC) map identified the MSTID structure as a northwest – southeast band structure at the time of the rocket launch. This band structure disappeared 30 min after launch, indicating that the rocket was observing the disappearance process of MSTID. The wavefront direction was assumed to be 164.90 ° in azimuth from the dTEC map. The electric field detector on board the rocket observed low-frequency electric fields from DC to 50 Hz in situ. The obtained data were analyzed, and the detrend electric field was derived. The electric field was analyzed by decomposing the MSTID into components perpendicular and parallel to the wavefront. In the low-plasma-density region, the perpendicular and parallel components of the electric field are southwestward and northwestward, respectively. Conversely, in the-high-plasma-density region, the perpendicular and parallel components are the northeastward and southeastward, respectively. These electric fields generated the E × B drift in the equalization direction of the Pedersen conductance gradient of the MSTID. The results show that the electric field played an important role in the disappearance of the MSTID.

Dual-frequency multi-constellation (DFMC) satellite-based augmentation system (SBAS) is a new SBAS standard for aeronautical navigation systems. It supports aircraft navigation from the enroute to approach phases via the L1 and L5 frequencies (1575.42 and 1176.45 MHz). Although the ionosphere-free (IF) combination in the DFMC SBAS operation removes the first-order ionospheric delays in the pseudorange measurement, remaining terms including the satellite-clock offset errors and higher-order ionospheric (HOI) delays are still unaccounted for. The DFMC SBAS accuracy and integrity can be affected by the HOI effects, especially during severe ionospheric disturbances. In this work, we present the local DFMC SBAS corrections with and without the mitigation of HOI delays. We first estimate the HOI delay terms using the received pseudorange followed by separate satellite and receiver bias estimations based on the minimum sum-variance technique. The integrity terms can then be obtained. The performances of DFMC SBAS using the global navigation satellite system (GNSS) data including GPS, Galileo, and QZSS are evaluated using obtained GNSS data at stations in Thailand on the ionospheric quiet and disturbed days. The results show that with the HOI mitigation, the vertical positioning errors (VPE) on the quiet and disturbed days can be improved by 12% and 9%, whereas the vertical protection levels (VPL) are improved by 16% and 21%, respectively. In addition, we perform a preliminary assessment of DFMC SBAS based on the International Civil Aviation Organization (ICAO) requirements of two categories: Localizer Performance with Vertical guidance (LPV-200) and Category I precision approach (CAT-I) showing promising results.

System Wide Information Management (SWIM) provides a digital data-sharing infrastructure that includes the standardization of the data format and exchange protocol internationally so that the required information can be shared among related civil aviation stakeholders efficiently and safely. In our project, we study the availability of the Aeronautical Mobile Airport Communications System (AeroMACS) as a wireless medium to achieve Aircraft Access to SWIM (AAtS) around the airport. We carried out flight experiments with an AeroMACS prototype and SWIM test bed over Sendai City to confirm the possibility of expanding AeroMACS coverage. In this paper, we focus on tracking, antenna placement and handover evaluations. First, the results of tracking tests show that our system can track the aircraft by using only ADS-B position reports and keep the communication link between the base station and the aircraft. Second, the results of antenna placement tests show that both the main and sub antennas for large aircraft should be mounted at the bottom of the aircraft body to obtain higher combined gain. On the other hand, the main and sub antennas for small aircraft should be mounted at the bottom and top of the aircraft body respectively, to obtain diversity gain during the aircraft turn. Third, the results of handover tests show that our system needs parameter optimization regarding handover in the air. Finally, we demonstrate SWIM-based information sharing over extended AeroMACS coverage.

This paper discusses the influence of the scattering order of electromagnetic waves on the performance of the ray-tracing method (RTM). ILS Localizer (LOC) is a ground-based navigation aid to guide aircraft in airports. LOC emits analogue signals, and transmitted signals are distorted by multipaths caused by obstacles. To numerically simulate the interference of electromagnetic waves in ILS systems, an appropriate scattering order must be considered to obtain results close to the actual values. In this paper, we show differences of scattering orders and their effects on the numerical results of RTM. Based on the numerical results, we discuss the elements of the electromagnetic field that are vitally important in simulating LOC signal interference using RTM.

We present a framework capable of generating required navigation performance authorization required approach (RNP AR APCH) procedures by using a combination of the optimal version of the path-planning rapidly-exploring random tree (RRT*) algorithm and Dubins paths. Procedures are generated by taking into account design constraints defined by the international civil aviation organization (ICAO) procedures for air navigation services -aircraft operations (PANS-OPS). The framework is used to compute several approach procedures for two airports in Japan, Kumamoto and Kitakyushu airports. Several feasible procedures are successfully obtained in a low amount of computational time, many of them resembling the actual procedures published in the selected airports. The output of our framework represents a valuable input for procedure designers, who could later refine the obtained results with specific flight-procedure-design software.

Millimeter-wave (mmWave) imaging is an emerging technology that has recently gained a lot of attention due to its potential applications in various fields, including security. MmWave imaging enables the detection of objects that are typically difficult to observe using traditional imaging techniques. A reconstructed target image can be obtained by analyzing the recorded amplitude and phase of the scattering behavior from illuminated objects with a Fast-Fourier Transform (FFT) based scheme using a dielectric lens. Experiments have been performed to show the effectiveness of the proposed systems for not only the single object but also for multiple targets with different distances. In agreement with theory, the experiments reveal that the object can be identified and reconstructed, yielding promising results.