In this paper, design and implementation issues for a network-oriented RF emitter localization system with array antenna are discussed. For hardware, the problem of array mismatch and RF/IF channel mismatch are introduced and the calibration schemes for solving those problems are also provided. For software, it is explained how to overcome the drawback of conventional MUltiple Signal Identification and Classification (MUSIC) algorithm in a point of identifying the number of received signals and problems such as Data Association Problem and Ghost Node Problem in regard to multiple emitter localization are presented with some approaches for getting around those problems. Finally, for implementation, a criterion for arranging each of sensors and a requirement for alignment of array antenna' orientation are also given.
Satellite coordinates are critical information in calculating the user’s location on the Global Navigation Satellite System (GNSS). This system estimates coordinates using ephemeris. Ephemeris is a value generated through satellite orbit estimation and does not indicate current satellite coordinates. When an unexpected problem or ephemeris modify problem occurs in the satellite operation, this results in a considerable error for the user. Ground reference stations apply a monitoring technique to prevent this problem. However, the current existing technique uses ground measurement estimated from ground reference stations, which inevitably incurs various errors. Error estimation can eliminate such errors, but in turn, this technique entails possible estimation error. As a result, the performance of this error detection technique decreases. Ground reference stations use distance values to detect satellite faults from the ground. This can also potentially reduce the detection performance as detection is dependent on geometrical arrangement and the direction of satellite faults. To resolve these two problems, the present study proposes a satellite orbit fault detection method using the Inter-Satellite Link (ISL) and the trigonometry law. We calculated test statistic and analyzed the sensitivity of our new method. Based on this, we identified the characteristics of our method. We calculated threshold and Minimum Detectable Error (MDE) based on statistical theories. Calculated values were tested through simulation. Finally, the performance of our method was confirmed through a quantitative comparison of sensitivity and MDE between the existing technique and our method.
Multipath reception remains a dominant source of ranging errors in Global Navigation Satellite Systems (GNSS). This phenomenon is generally considered undesirable in the context of GNSS, as multipath reception can significantly distort the shape of the correlation function. In this study, a model distortion of a correlation function is formulated, and a model-based multipath estimation (MBME) technique for GPS L1/L5 receivers is proposed in order to estimate parameters of multipath signals, such as amplitude and delay. The proposed MBME technique does not require any hardware modifications, and it can estimate parameters for both short- and long-delay multipath reception. This technique would prove to be very effective for short-delay multipath estimation, particularly where an L5 signal is available. Finally, we describe the results of a simulation to confirm the feasibility of the proposed technique.
The Korean government has a plan to build a new regional satellite navigation system called the Korean Positioning System (KPS). The initial KPS constellation is designed to consist of seven satellites, which include three geostationary Earth orbit (GEO) satellites and four inclined geosynchronous orbit (IGSO) satellites. KPS will provide an independent positioning, navigation, and timing (PNT) service in the Asia-Oceania region and can also be compatible with GPS. In the simulation for KPS, we employ 24 GPS as designed initially and 7 KPS satellites. Compared to the true orbit that we simulated, the averaged root mean square (RMS) values of orbit-only signal-in-space ranging errors (SISRE) are approximately 4.3 and 3.9 cm for KPS GEO and IGSO. Two different positioning solutions are analyzed to demonstrate the KPS performance. KPS standard point positioning (SPP) errors in the service area are about 4.7, 3.9, and 7.1 m for east (E), north (N), and up (U) components, respectively. The combined KPS+GPS SPP accuracy can be improved by 25.0%, 31.8%, and 35.0% compared to GPS in E, N, and U components. The averaged position errors for KPS kinematic precise point positioning (KPPP) are less than 10 cm. In the fringe of the KPS service area, however, the position RMS errors can reach about 40 cm. Unlike KPS, GPS solutions show high positioning accuracy in the KPS service area. The combined KPS+GPS can be improved by 28.7%, 27.1%, and 30.5% compared to GPS in E, N, and U components, respectively. It is noted that KPS can provide better performance with GPS in the Asia-Oceania region.
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