Abstract：Aiming at the real-time problems of signal acquisition, attitude calculation and data output of laser gyro strapdown inertial navigation system, the data input and output of IMU, odometer, altimeter and GPS/BeiDou are analyzed. RS-232 serial interface and CAN bus interface are generally used for data exchange, which are difficult to meet the high-speed real-time sampling of sensors. The paper puts forward a high-speed data access mode of FPGA dual port RAM+dual DSP to output navigation data in real time according to the clock synchronization cycle, which can effectively solve the bottleneck problem of data transmission, processing and transmission to various devices. The highest output frequency attitude rate can reach 100 kHz~2 000 kHz, and realize the rapid response ability of attitude state of strapdown navigation system. Experiments and simulations show that this method can greatly improve the cycle calculation ability of the system and the maneuverability of the carrier.

Abstract：With the development of space technology, the technology of satellite navigation system is also improving. Inter satellite link is a wireless network with precise measurement and data transmission functions between navigation satellites. As an important means to improve the survivability of navigation system, it is very important for the construction of satellite navigation system. As an important part of inter satellite link technology, inter satellite link routing algorithm has become one of the main research fields and directions of inter satellite link technology. According to the actual operation scenario of the inter satellite link system, combined with the characteristics of the inter satellite link network, considering a variety of evaluation indexes such as data transmission delay and satellite node load, based on the idea of breadth first algorithm, supplemented by a variety of pruning strategies, this paper proposes a multi evaluation factor based routing planning algorithm. The algorithm can find the first N optimal paths in high dynamic time-varying networks. At the same time, this paper analyzes and validates the planning results of routing algorithm from many aspects, such as the number of paths between nodes, the situation of nodes building chains, the cost of path overhead and so on, so as to provide a theoretical basis for the selection of paths in the inter satellite link routing planning.

Abstract：With the development of compatibility and interoperability of global navigation satellite system, the implementation of satellite navigation receiving terminal with compatibility and interoperability performance is very important. In this paper, a dual frequency compatible and interoperable terminal is designed and implemented for CDMA navigation signal. The terminal parameters are set by terminal control software. The digital processing module is realized by general digital front-end module, parallel multi-channel acquisition based on time-domain, and multi-phase correlator, and the positioning function is further realized. The terminal has the characteristics of strong universality and fast acquisition speed, which lays a hard ware foundation for improving the continuity, integrity and availability of services.

Abstract：Galileo system provides commercial services including precise point positioning and authentication through E6B/C signals. In January 2019, the European Union announced the spreading code of the Galileo system′s E6B/C signal. This article refers to the European Union′s published document of the E6B/C signal and describes the carrier frequency, modulation scheme, primary codes, secondary codes, data coding scheme, and message structure. This article introduces the scheme of acquisition and tracking of the E6B/C signal, which acquires the E6B/C signals in the sky through the short-time correlation and FFT scheme,then uses the narrowband-wideband power ratio method and moments method to estimate the CNR of E6C and E6B.At the same time, this paper analyzes the current E6B message information that transmitted by current satellites. It shows that Galileo′s E6B signal has not yet started to provide PPP services.

Abstract：Landslide and debris flow are the most frequent deformation geological disasters in our country. It is an important safety issue to establish a high-precision, real-time and stable monitoring system. Aiming at the problem of low efficiency of the traditional GNSS-RTK landslide monitoring system as the number of observation nodes increases and the alarm leakage caused by the simultaneous displacement of the base station and observation station, a double-layer landslide monitoring system based on GNSS-RTK technology is proposed. The double-layer landslide monitoring system based on GNSS-RTK technology is proposed. On the basis of the traditional landslide monitoring system, the new system adds a micro network observation system in some important node areas, which is improved from the previous "point" monitoring to the micro area "surface" monitoring, and realizes the deformation data collection based on GNSS-RTK technology and data transmission based on Lora and LTE technology. The test results show that the data transmission is reliable and efficient, and the measurement accuracy of the system can reach millimeter level, which can meet the requirements of landslide monitoring. The density of observation nodes and the length of baseline in the micro area of the observation station can be adjusted to meet the needs of different environments.

Abstract：Because the designed frequency band of Geosynchronous synthetic aperture radar(GEO SAR) satellite signal possibly shares or overlaps with the frequency band of various Global Navigation Satellite System(GNSS) signals which have been put into use, the ground GNSS receiver may be subject to the pulse radio frequency interference generated by GEO SAR signal. In order to evaluate the influence of GEO SAR signal on the performance of GNSS ground receiver, a parametric theoretical model based on International Telecommunication Union(ITU) related standards is proposed in this paper. The model uses the "source-path-receiver" analysis method to extract parameters from the three aspects of GEO SAR signal, signal propagation path and receiver model for interference evaluation. Then, according to ITU standards, the influence of high-orbit SAR signal as additive pulse radio frequency interference on the performance of GNSS receiver is evaluated. Taking the representative B3I signal as an example, this paper evaluates the performance of different types of B3I receivers for GEO SAR signal under the condition of the assumed design parameters. The results show that the performance of the receiver decreases slightly in the presence of high-orbit SAR signal interference, but it can still work normally.

Abstract：Based on 0.18 μm RFCMOS technology, a high linearity low noise amplifier(LNA) for low voltage GPS receivers was designed. By using the trans-conductance derivative superposition technique with bulk bias control, the adjustment accuracy of auxiliary transistor was remarkably improved. An extra capacitance is added between gate and source nodes of input transistor in a parallel manner to reduce the effect of second-order harmonic on IMD3. In addition, folded cascade structure is adopted to make the circuit work under low voltage conditions. The simulation results shown that the LNA achieves a 6.63 dBm IIP3, a noise figure of 1.53 dB, a 13.16 dB power gain, the input and output return losses are -32.43 dB and -24.58 dB at 1.575 GHz with the core LNA consuming 8.78 mW at 0.9 V power supply.

Abstract：The existing Beidou signal receiver has a low-noise amplifier scheme in the S-band, and the noise figure is between 1.5 dB～1.7 dB under the condition of meeting the gain requirements and the noise performance can be further optimized. The scheme studies a low noise amplifier(LNA) based on a high-bandwidth millimeter wave tube. The tube is based on NPN broadband silicon germanium RF transistor process. Amplifier uses two-stage conjugate matching to achieve the best balance between circuit noise and gain，and uses LDO circuit linear regulated output to minimize power supply noise. ADS software simulation, Altium designer board and actual measurement of Agilent noise analyzer show that it′s single-stage amplifier has a minimum noise figure of 0.4 dB. At 2.492 GHz, the maximum gain of the solution is 32 dB, and the corresponding noise figure is 1.23 dB. The low-noise amplifier scheme is applied to the front end of Beidou user receiver, which can effectively improve the system noise performance and improve the signal receiving efficiency.

Abstract：With the construction of BDS III satellite nearing completion, Beidou service will transition smoothly to be provided mainly by BDS III system. The B2b signal interface document was announced on December 27, 2019. B2b signals are divided into two types: B2b signal that provides basic navigation services and PPP-B2b signal that provides precise point positioning services. Based on the B2b signal interface control file, this paper introduces the B2b signal information structure, message type, and analysis results of satellite signals in the sky, and gives the positioning accuracy results of B2b signals. The PPP-B2b information in the sky is also analyzed. This article also explores the Q branch signal of B2b.