Earticle

본 논문에서는 기존의 GPS 항법 신호와 유럽에서 새롭게 추진되고 있는 갈릴레오 위성 항법 신호를 동시에 수신할 수 있는 광대역 고정밀 위성 항법 수신기의 RF 수신단 장치 설계 및 제작 결과에 대하여 기술하고 있다. 고정밀 광대역 위성 항법 수신기는 L‐대역 안테나, 항법 신호별 RF/IF 변환부, 그리고 고성능 기저대역 신호처리부로 구성되어진다. L‐대역 안테나는 1.1GHz~1.6 GHz를 수신할 수 있어야 하며, 항법 위성이 지평선 가까이에 있을 경우의 항법 신호를 수신할 수 있어야 한다. 갈릴레오 위성 항법 신호는 L1, E5, E6의 서로 다른 대역의 신호를 가지고 있으며, 신호 대역폭이 20MHz 이상으로 기존의 GPS위성 항법 신호보다 광대역이며, 따라서 수신기의 IF 주파수가 높아지며, 수신기의 처리 속도도 빨라져야 한다. 본 연구에서 개발한 수신기의 RF/IF 변환부는 단일 하향 변환기 구조의 디지털 IF 기술로 설계되었으며, IF 주파수는 위성 항법 신호의 최대 대역폭과 표본화 주파수 등을 고려하여 140MHz로 설정하였으며, 표본화 주파수는 112MHz로 설정하였다. RF/IF 변환부의 최종 출력은 디지털 IF 신호로서, IF 신호를 AD 변환기로 처리하여 얻게 된다. 본 연구에서 설계된 위성 항법용 고정밀 수신기 RF 수신단은 ‐130 dBm의 입력 신호에 대하여 40dB　Hz 이상의 C/N0 특성을 가지며, 40dB 이상의 동적 범위를 갖도록 자동 이득조절 장치가 포함되어 있다.

This paper describes the development of RF front‐end equipment of a wide band high precision satellite navigation receiver to be able to receive the currently available GPS navigation signal and the GALILEO navigation signal to be developed in Europe in the near future. The wide band satellite navigation receiver with high precision performance is composed of L‐band antenna, RF/IF converters for multi‐band navigation signals, and high performance baseband processor. The L‐band satellite navigation antenna is able to be received the signals in the range from 1.1 GHz to 1.6 GHz and from the navigation satellite positioned near the horizon. The navigation signal of GALILEO navigation satellite consists of L1, E5, and E6 band with signal bandwidth more than 20 MHz which is wider than GPS signal. Due to the wide band navigation signal, the IF frequency and signal processing speed should be increased. The RF/IF converter has been designed with the single stage downconversion structure, and the IF frequency of 140 MHz has een derived from considering the maximum signal bandwidth and the sampling frequency of 112 MHz to be used in ADC circuit. The final output of RF/IF converter is a digital IF signal which is generated from signal processing of the AD converter from the IF signal. The developed RF front‐end has the C/N0 performance over 40dB‐Hz for the ‐130dBm input signal power and includes the automatic gain control circuits to provide the dynamic range over 40dB.

A novel multistage pulse jamming suppression algorithm was proposed to solve the anti-pulse jamming problem encountered in navigation receivers. Based on the characteristics of the short duration of pulse jamming and distribution characteristics of satellite signals, the pulse jamming detection threshold was derived. From the experiments, it was found that the randomness of pulse jamming affects jamming suppression. On this basis, the principle of the multistage anti-pulse jamming algorithm was established. The effectiveness of the anti-jamming algorithm was verified through experiments. The characteristics of the algorithm include simple determination of jamming detection threshold, easy programming, and complete suppression of pulse jamming.

본 논문에서는 간섭상쇄 기능을 갖춘 지역전파항법 수신기의 GNSS (global navigation satellite system) 위성항법신호 획득성능을 분석하였다. GNSS 항법신호와 동일 주파수영역에 지역전파항법 신호를 사용하여 통합 항법을 수행할 경우 혼신에 의한 영향이 발생하나, 이는 순차적 간섭신호상쇄 알고리즘 등과 같은 간섭상쇄 기술을 통해 어느 정도 극복 가능하다. 하지만 J/S(jamming-to-signal ratio)가 클 경우 잔여 신호와 GNSS신호와의 교차상관 특성에 의해 신호획득 시 잘못 된 검출결과를 보일 수 있다. 본 논문은 Kasami코드를 사용할 경우 GNSS신호와의 혼신에 의한 신호획득 성능저하를 Monte Carlo 시뮬레이션을 통해 분석해 보았으며, 비교를 위해 GNSS Gold 코드의 신호획득 성능과 비교하였다.

This paper analyzed GNSS signal acquisition performance of a regional navigation receiver when an interference cancellation capability is applied. Intereference between the regional navigation and GNSS signal can be mitigated by the interference cancellation technique such as the successive interference cancellation (SIC) algorithm. However signal acquisition performance will be degraded when jamming-to-signal ratio (J/S) is large due to a cross-correlation properties of residual signals. In this paper we analyzed signal acquisition performance degradation due to the interference between the Kasami and GNSS Gold code signal. Monte Carlo simulation is used for the analysis and compared results with those of GNSS Gold code only condition.

Modernized GNSS signal structures tend to use tiered codes, and all GNSSs use binary codes as secondary codes. However, recently, signals using polyphase codes such as Zadoff-Chu sequence have been proposed, and are expected to be utilized in GNSS. For example, there is Tiered Differential Polyphase Code (TDPC) using polyphase code as secondary code. In TDPC, the phase of secondary code changes every one period of the primary code and a time-variant error is added to the carrier tracking error, so carrier tracking ambiguity exists until the secondary code phase is found. Since the carrier tracking ambiguity cannot be solved using the general GNSS receiver architecture, a new receiver architecture is required. Therefore, in this paper, we describe the carrier tracking ambiguity and its cause in signal tracking, and propose a receiver structure that can solve it. In order to prove the proposed receiver structure, we provide three signal tracking results. The first is the differential decoding result (secondary code sync) using the general GNSS receiver structure and the proposed receiver structure. The second is the IQ diagram before and after multiplying the secondary code demodulation when carrier tracking ambiguity is solved using the proposed receiver structure. The third is the carrier tracking result of the legacy GPS (L1 C/A) signal and the signal using TDPC.

Among the various error sources in positioning and navigation, the paper focuses on the modeling and prediction of receiver clock bias and then tries to achieve positioning based on simulated and predicted clock bias. With the SA off, it is possible to model receiver clock bias more accurately. We selected several types of GNSS receivers for test using ARMA model. To facilitate prediction with short and limited sample pseudorange observations, AR and ARMA are compared, and the improved AR model is presented to model and predict receiver clock bias based on previous solutions. Our work extends to clock bias prediction and positioning based on predicted clock bias using only 3 satellites that is usually the case under urban canyon situation. In contrast to previous experiences, we find that a receiver clock bias can be well modeled using adopted ARMA model. Test has been done on various types of GNSS receivers to show the validation of developed model. To further develop this work, we compare solution conditions in terms of DOP values when point positioning is conducted using 3 satellites to simulate urban positioning environment. When condition allows, height component is derived from other ways and can be set as known values. Given this condition, location is possible using less than 2 GNSS satellites with fixed height. Solution condition is also discussed for this background using mode of constrained positioning. We finally suggest an effective predictive time span based on our test exploration under varied conditions.

In this study, we implemented the data quality monitoring algorithm which is the previous step for real-time Global Navigation Satellite System (GNSS) correction generation and compared Global Positioning System (GPS) and BeiDou System (BDS). Signal Quality Monitoring (SQM), Data QM, and Measurement QM (MQM) that are well known in Ground Based Augmentation System (GBAS) were used for quality monitoring. SQM and Carrier Acceleration Ramp Step Test (CARST) of MQM result were divided by satellite elevation angle and analyzed. The data which are judged as abnormal are removed and presented as Root Mean Square (RMS), standard deviation, average, maximum, and minimum value.

This letter presents a filter for a car navigation system integrating a low-grade inertial measurements unit (IMU) and a global positioning system receiver. The filter is designed according to the state variables to be estimated and the usable measurements. The usable measurements change from case to case, and the estimative state variables also change due to the measurements; therefore, multiple models must be used for real environmental maneuvers. In this letter, four models for land navigation are chosen and switched by rearranging the system matrix and resetting the error covariance matrices.

The satellite navigation system was developed for the purpose of calculating the location of local users, starting with the Global Positioning System (GPS) in the 1980s. Advanced countries in the space industry are operating Global Navigation Satellite System (GNSS) that covers the entire earth, such as GPS, GLONASS, Galileo, and BeiDou, by establishing satellite navigation systems for each country. Regional Navigation Satellite Systems (RNSS) such as QZSS and NavIC are also in operation. In the early 2010s, only GPS and GLONASS could calculate location using a single system for location determination. After 2016, the EU and China also completed the establishment of GNSS such as Galileo and BeiDou. As a result, satellite navigation users can benefit from improved availability of GNSS. In addition, before Galileo and BeiDou's Full Operational Capability (FOC) declaration, they used combined navigation algorithms to calculate the user's location by adding another satellite navigation system to the GPS satellites. Recently, it may be possible to calculate a user's location for each navigation system using the resources of a single system. In this paper, we evaluated the performance of single system navigation and combined navigation solutions of GPS, GLONASS, Galileo, BeiDou and QZSS individual navigation systems using high-performance GNSS receivers.

최근 SA(Selective Availability)의 해제에 따른 GPS의 활용이 증대되면서 차량운행에 있어서도 저가 GPS 수신기의 활용이 활발하게 이루어지고 있으며, 일반 차량 운행자를 위한 상용화가 급속도로 이루어지고 있다. 하지만 저가 GPS수신기를 통한 실시간 위치정보의 제공은 실질적으로 상당한 오차를 포함하고 있다. 이는 저가 수신기가 가지고 있는 문제라 할 수 있다. 이에 본 연구에서는 저가 수신기와 정밀 측위용 이주파 수신기를 이용하여 측지분야에서 검증된 GPS측량방법을 통해 오차를 비교ㆍ분석하고 저가 수신기의 정확도 향상을 위한 방법을 제시하고자 하였다.

The Korea Augmentation Satellite System (KASS) satellite was successfully launched and service is being started. By receiving messages transmitted from the KASS satellite, users can employ the messages to improve positioning accuracy or to verify the integrity of Global Positioning System (GPS). In this paper, we propose a test method for a beam-formed GPS receiver developed to improve the survivability of KASS augmented messages that can enhance positioning accuracy even in an environment with jamming or interfering signals. Through the test method proposed in this paper, quantitative verification is performed for a beam-formed GPS receiver aimed at maintaining the augmented navigation solution to which KASS augmented messages are applied by tracking the KASS signal as much as possible under conditions where the jamming signal strength is gradually increasing. In addition, the proposed test method includes three conditions; first, a static lab test method for repeated verification of functions under the same conditions; second, a static outdoor test method for performance verification in an operating environment of a platform equipped with the beam-formed GPS receiver; and finally, a dynamic lab test method for performance verification of a moving platform equipped with the beam-formed GPS receiver toward a jammer. In this paper, we propose a method for simulating the jamming signal incident direction through the phase delay of an RF cable designed to prevent unintentional jamming signal emission in both lab and outdoor tests, and a method of applying test software for injecting a jamming signal to compare the survivability performance consistently according to the presence or absence of beamforming signal processing. Through the proposed test method, it was verified that the augmented navigation solution could be output for a longer time period when the beamforming signal processing was applied to the KASS satellite signal in the beam-formed GPS receiver.

본 논문에서는 무인 다중 항체의 자율 주행 기법을 제시하였다. 항체의 역할을 선두 항체와 추종 항체로 구분하고 정해진 목적지로 선두 항체가 이동하면 추종 항체가 선두 항체를 따라 이동하여 두 항체가 모두 목적지에 도달하도록 하는 기법이다. 주행 중 항체 사이의 거리는 일정하게 유지하도록 GPS 수신기와 초음파 센서를 사용하였다. 자율 주행 실험에 앞서, GPS 수신기로 얻은 위치로부터 계산한 방향의 정확도를 확인하는 실험을 수행하였다.