According to the optimization problem of power amplifier output power, linearity and other performance indicators, this paper proposes an improved three-level cascade overall design framework, ...designed by the load traction method, source traction method and power back-off method for the driver stage and final stage power. The amplifier better improves the output power and linearity of the system and the high-gain pre-stage power amplifier is designed by the small-signal S-parameter method. After the performance analysis, simulation design, physical production and testing of the cascaded power amplifier, the output power of the system is 15W. This paper implements high power, high gain, high linearity power amplifier design, and applies this result to BeiDou Navigation Satellite System (BDS).
In the satellite signal acquisition and tracking, the locally reproducible ranging code plays an important role. For the newly launched Beidou-3 satellite in China, a method for implementing the B2a ...signal ranging code generator in FPGA is proposed. Taking the B2a ranging code of Beidou-3 satellite as the research object, the design principle of the B2a ranging code generator is explained in detail, which includes the analysis of the key modules of the Weil code and the Gold code generator. The FPGA is modularly designed to be scalable The B2a ranging code generator module, through the reserved register initialization interface, can realize the ranging code of different PRN satellites, solving the complex problem of generating arbitrary satellite number ranging codes, for the design of Beidou No. 3 navigation receiver Certain reference significance.
The Beidou satellite navigation receiver needs to receive Beidou signals efficiently in a complex environment, and the design of receiver front-end is the key link. According to the Beidou receiver ...front-end system indicators, such as noise figure, gain, etc., we propose a low-noise amplifier design scheme which is based on Infineon's broadband NPN RF bipolar transistor BFP740FED, and employ ADS to simulation and optimization tests. The results show that the low noise amplifier has a noise factor NF < 0.7dB, gain Gain > 35dB, gain flatness less than 0.5dB, input-output standing wave ratio less than 1.5 in the B3 band. This system has high noise performance of the amplifier, which can support the further development of Beidou navigation receiver application.
The BeiDou system has been providing a regional navigation service since 27 December 2012. The Global Navigation Satellite System (GNSS) user community will benefit from combined Global Positioning ...System (GPS)/BeiDou positioning due to improved positioning accuracy, reliability and availability. But to achieve the best positioning solutions, precise weights of the GPS and BeiDou observations are important since this involves the processing of measurements from two different satellite systems with different quality. Currently, a priori variances are typically used to determine the weights of different types of observations. However, such an approach may not be precise since many un-modelled errors are not accounted for. The Helmert variance component estimation method is more appropriate in this case to determine the weights of GPS and BeiDou observations. This requires high redundant observations in order to obtain reliable solutions, which will be a concern in the case of insufficient numbers of visible satellites. To address this issue, a weighting approach is proposed by a combination of the Helmert method and a moving-window average filter. In this approach, the filter is applied to combine all epoch-by-epoch weight estimates within a time window. As a result, more precise and reliable weights for GPS and BeiDou observations can be obtained at every epoch. Both static and kinematic tests in open sky and under tree environments are conducted to assess the performance of the new weighting approach. The results indicate significantly improved positioning accuracy.
Lots of ambiguities in un-differenced (UD) model lead to lower calculation efficiency, which isn’t appropriate for the high-frequency real-time GNSS clock estimation, like 1Hz. Mixed differenced ...model fusing UD pseudo-range and epoch-differenced (ED) phase observations has been introduced into real-time clock estimation. In this contribution, we extend the mixed differenced model for realizing multi-GNSS real-time clock high-frequency updating and a rigorous comparison and analysis on same conditions are performed to achieve the best real-time clock estimation performance taking the efficiency, accuracy, consistency and reliability into consideration. Based on the multi-GNSS real-time data streams provided by multi-GNSS Experiment (MGEX) and Wuhan University, GPS+BeiDou+Galileo global real-time augmentation positioning prototype system is designed and constructed, including real-time precise orbit determination, real-time precise clock estimation, real-time Precise Point Positioning (RT-PPP) and real-time Standard Point Positioning (RT-SPP). The statistical analysis of the 6h-predicted real-time orbits shows that the root mean square (RMS) in radial direction is about 1–5cm for GPS, Beidou MEO and Galileo satellites and about 10cm for Beidou GEO and IGSO satellites. Using the mixed differenced estimation model, the prototype system can realize high-efficient real-time satellite absolute clock estimation with no constant clock-bias and can be used for high-frequency augmentation message updating (such as 1Hz). The real-time augmentation message signal-in-space ranging error (SISRE), a comprehensive accuracy of orbit and clock and effecting the users’ actual positioning performance, is introduced to evaluate and analyze the performance of GPS+BeiDou+Galileo global real-time augmentation positioning system. The statistical analysis of real-time augmentation message SISRE is about 4–7cm for GPS, whlile 10cm for Beidou IGSO/MEO, Galileo and about 30cm for BeiDou GEO satellites. The real-time positioning results prove that the GPS+BeiDou+Galileo RT-PPP comparing to GPS-only can effectively accelerate convergence time by about 60%, improve the positioning accuracy by about 30% and obtain averaged RMS 4cm in horizontal and 6cm in vertical; additionally RT-SPP accuracy in the prototype system can realize positioning accuracy with about averaged RMS 1m in horizontal and 1.5–2m in vertical, which are improved by 60% and 70% to SPP based on broadcast ephemeris, respectively.
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Earth rotation parameters (ERPs) are fundamental to geodetic and astronomical studies. With its high measurement accuracy and stability, the Very Long Baseline Interferometry (VLBI) plays an ...irreplaceable role in estimating the ERPs and maintaining the earth reference frame. However, the imperfect global station distribution, observation discontinuity, and vast cost of the VLBI make the GNSS a more attractive technique. In 2020, the third generation of the BeiDou Navigation System (BDS), namely BDS-3, was constructed completely. In this study, we conducted a series of experiments to estimate Earth’s rotation parameters based on the continuous BDS-3 observation data, the discontinuous VLBI observation data, and the combined BDS-3 and discontinuous VLBI observation data. We used two methods, namely the weighted averaging method and the normal equation combination method, to obtain ERP combination solutions. The results are compared with the International Earth Rotation and Reference Systems Service (IERS) EOP 20C04 at 00:00:00 UTC. Final results show that (a) the estimation accuracy becomes stable when the number of BDS-3 tracking stations is more than 40. At the same time, both the number of stations and the volume of polyhedrons formed by the observing stations affect the accuracy of the ERPs estimated by the BDS-3 or VLBI. (b) Results have also shown that the inclusion of the BDS-3 IGSO and GEO satellites contributes little to the ERP estimation. (c) For the BDS-3-only MEO satellites solution, the root mean square (RMS) was 113.2 µas, 102.8 µas, and 13.1 µs/day for X-pole coordinate, Y-pole coordinate, and length of day (LOD), respectively. For the VLBI solution, the RMSs of the X-pole, Y-pole, and LOD were 100.4 µas for the X-pole, 94.2 µas for the Y-pole, and 14.1 µs/day. The RMS was 82.6 µas, 70.3 µas, and 10.5 µs/day for the combined X-pole, Y-pole, and LOD using the weighted averaging method. It was 78.2 µas, 62.6 µas, and 8.6 µs/day when the normal equation combination method was applied. This demonstrates that by taking advantage of the BDS-3 and VLBI technique combinations, accuracy in estimating the ERPs can be improved over that using either of them, in addition to enhanced stability and reliability.
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At present, the research on the tracking performance of navigation receivers is based on the conditions of single-frequency interference, however, the space electromagnetic environment is ...complicated, and so it is necessary to study the effect of the navigation receiver under multifrequency interference. Through the analysis of the blocking interference mechanism of the navigation receiver and the mathematical model of the tracking loop, the effect model under in-band and out-of-band multifrequency interference is established, when the satellite tracking is missing. The Beidou navigation receiver is used as the experiment object to build a multifrequency interference effect experiment platform, and the carrier-to-noise ratio ( C / N 0 ) threshold is used as the criterion for the satellite tracking missing, Finally, the model is verified with the experimental data, the error of the model under tri-frequency out-of-band interference exceeds 3 dB. For reducing the model error, the corrected model is proposed, and the corrected model errors are less than 1 dB. The model is helpful to predict the satellite signal status in the navigation receiver under complex electromagnetic environments.
This study shows the way of ionospheric data usage obtained from 2 Tables using D2 NAV message Chinese BeiDou system. It was identified particular algorithms for Table’s calculation. Authors also ...suggested data Table 2 modification and special algorithms useful for that Table. It was given calculated examples for BeiDou system Tables as well as for new suggested system.
Arctic sea ice has long been a focal point of scientific research globally, with sea ice thickness (SIT) recognized as a critical parameter for predicting local marine environments, climate dynamics, ...and ensuring the safety of maritime transport. This study focuses on the retrieval of SIT, utilizing an established two-layer (sea ice-seawater) global navigation satellite system-reflectometry (GNSS-R) model and is extended to new data from Fengyun-3E (FY-3E) satellite. The research introduces an innovative empirical approach aimed at reducing reliance on ancillary data, allowing for stand-alone SIT retrieval solely based on GNSS-R data. This work underscores the potential for developing a practical semi-empirical model and parameterization scheme for SIT estimation through GNSS-R data. Furthermore, FY-3E has the capability to process signals from both the BeiDou Navigation Satellite System (BDS) and the global positioning system (GPS). Compared to the reference SIT, for the training set the root-mean-square error (RMSE) and correlation coefficient (Formula Omitted) between GPS-R SIT and reference are 0.1347 m and 0.8087, respectively, and for the test set, they are 0.1442 m and 0.7821. Based on BDS-R data, for the training set the RMSE and Formula Omitted are 0.1325 m and 0.8152, and for the test set, they are 0.1289 m and 0.8063, respectively. Experimental results indicate that BDS-based outcomes slightly outperform those obtained using GPS in the context of SIT retrieval.
The BeiDou Global Navigation Satellite System (BDS-3) can provide PPP-B2b satellite-based Precise Point Positioning (PPP) real-time service to the Asia–Pacific region via PPP-B2b signal transmitted ...from the three Geostationary Earth Orbit (GEO) satellites. This paper provides a comprehensive evaluation of the accuracies of the satellite’s precise real-time orbit and clock products, including BDS-3 PPP-B2b precise products and the precise real-time products provided by four IGS centers (CAS, DLR, GFZ, and WHU). In addition, the influences of these real-time precise satellite products on the PPP positioning accuracy with single-frequency and dual-frequencies are also studied. Furthermore, the accuracies of broadcast ephemeris and IGS ultra-rapid products are studied, as well as their impact on PPP accuracies. Results illustrate that the orbits accuracies of PPP-B2b orbits are 9.42 cm, 21.26 cm, and 28.65 cm in the radial, along-track, and cross-track components, which are slightly lower than those of real-time orbits provided by the four IGS centers. However, the accuracy of PPP-B2b clock biases is 0.18 ns, which is higher than those provided by IGS Real-Time Service (RTS). In the static positioning test, the 3D positioning accuracy of B1I+B3I dual-frequencies PPP and B1C single-frequency PPP are centimeter-level while using PPP-B2b service, which is slightly lower in horizontal components compared to those obtained based on IGS RTS products. The results of the dynamic vehicle test indicate that the positioning accuracies of B1I+B2b dual-frequency PPP are about 50 cm and 120 cm in horizontal and vertical components, which are close to those of B2b single-frequency PPP using PPP-B2b service. Generally, the PPP-B2b orbit and clock accuracies on real-time PPP present similar performance to that based on IGS RTS.
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