The invention discloses a micro spaceborne high dynamic GNSS receiver and a navigation method thereof. The receiver comprises an active antenna, a radio frequency front end processing module, a baseband signal digital processing module, a positioning solution module and a host computer monitoring interface. The navigation method comprises the steps that the active antenna converts a received GNSS electromagnetic wave signal into a current signal; the signal enters the radio frequency front end processing module through a band-pass filter, and undergoes amplification, frequency conversion, filtering and analog-to-digital conversion to finally acquire a digital intermediate frequency signal; the baseband signal digital processing module carries out capturing, tracking, bit synchronization and frame synchronization on the digital intermediate frequency signal to acquire a navigation measurement value and a navigation message; the positioning solution module carries out positioning solution to finally acquire the satellite information of a user; and the host computer monitoring interface displays a positioning observation value, the number of received satellites and the information of a PDOP value in real time. The micro spaceborne high dynamic GNSS receiver and the navigation method thereof have the advantages of high framework flexibility, rapid verification of an improved algorithm, low cost, small volume and light weight.

Micro spaceborne high dynamic GNSS receiver and navigation method thereof

The attitude information of ground vehicles, ie, heading and pitch information, can be used for many transport applications This information can be determined through various solutions of onboard sensors, including magnetic sensors, inertial sensors, GNSS equipment, and their combinations In order to find a cost-effective solution, we propose here a new toolbox named Vehicle Attitude Determination toolbox from the Intelligent Transportation And Geomatics group (iTAG_VAD) that determines vehicle dynamic heading and pitch using only one single-frequency GPS antenna, reducing costs while retaining an acceptable heading and pitch accuracy In this toolbox, by using the constraints of the vehicle motion and road geometry, two variations in a time-differenced measurement model, ie, Time-Differenced Carrier Phase (TDCP) and Time-Differenced Pseudorange (TDPR), are developed for heading and pitch determination The results show that both proposed TDCP- and TDPR-based models are able to provide an accurate heading and pitch estimation with a root mean square error below the one-degree level, which is sufficient for many land-based applications We describe the toolbox and its implementation in MATLAB in detail

Precise vehicle dynamic heading and pitch angle estimation using time-differenced measurements from a single GNSS antenna

The resolution of the integer phase ambiguity among a group of spatially separated sensors is considered, where the smallest inter-sensor spacing exceeds half wavelength ( $\lambda /2$ ) of a single-frequency signal. The sufficient condition that the integer phase ambiguities can be unambiguously determined is derived and verified numerically. The traditional receiver of a triplet is identified as a particular example of this general framework. An efficient strategy for averaging redundant virtual observations is outlined. The performance in terms of the success rate of ambiguity resolution is significantly improved due to the averaging process.

A $2q$ -Order Difference-Set Approach to Eliminate Phase Ambiguity of a Single-Frequency Signal

In spite of significant research in the development of efficient algorithms for three carrier ambiguity resolution, full performance potential of the additional frequency signals cannot be demonstrated effectively without actual triple frequency data. In addition, all the proposed algorithms showed their difficulties in reliable resolution of the medium-lane and narrow-lane ambiguities in different long-range scenarios. In this contribution, we will investigate the effects of various distance-dependent biases, identifying the tropospheric delay to be the key limitation for long-range three carrier ambiguity resolution. In order to achieve reliable ambiguity resolution in regional networks with the inter-station distances of hundreds of kilometers, a new geometry-free and ionosphere-free model is proposed to fix the integer ambiguities of the medium-lane or narrow-lane observables over just several minutes without distance constraint. Finally, the semi-simulation method is introduced to generate the third frequency signals from dual-frequency GPS data and experimentally demonstrate the research findings of this paper.

Three carrier ambiguity resolution : distance-independent performance demonstrated using semi-generated triple frequency GPS signals

With recent developments in global navigation satellite systems (GNSS), dual- and triple-frequency reception is becoming increasingly available. This can be used for ionospheric error removal, but further research efforts are required to successfully apply it to mitigate and detect errors caused by multipath and non-line-of-sight reception. To review the current state of the art on this topic, the previously published multi-frequency fusion methods for minimization of multipath and non-line-of-sight errors are summarized and classified. The main input is the pseudorange of each frequency, but in addition, three main categories of inputs are identified, i.e., signal-to-noise ratio, carrier-phase measurements, and correlator output. Existing works that use these parameters as input for frequency fusion mainly consider stationary applications, error detection, and the minimization of the carrier phase multipath error. To develop the state of the art to also suit dynamic scenarios and to reduce the errors further, the information contribution of each individual parameter needs to be studied, to prepare the way for a frequency fusion algorithm that combines these information contributions optimally.

Multi-Frequency GNSS Signal Fusion for Minimization of Multipath and Non-Line-of-Sight Errors: A Survey

The invention provides a DSP (digital signal processor)-based multi-system compatible GNSS (global navigation satellite system) receiver and a receiving system thereof, and aims to solve the problem of coverage blank of a single system. An all-frequency-point antenna receives a satellite signal of a navigation system and sends the satellite signal into a radio frequency unit; after the satellite signal is subjected to band-pass pre-filtering and low-noise amplification in the radio frequency unit, the satellite signal and a sine intrinsic signal generated by a local oscillator are mixed to realize down conversion to obtain an intermediate frequency signal; finally, an analog intermediate frequency signal is converted into a digital intermediate signal through an analog-digital converter, and the digital intermediate signal is sent into a base-band processing unit; the base-band processing unit carries out capturing and tracking on the digital intermediate signal output by the radio frequency module so as to obtain a Doppler observed quantity; besides, the digital intermediate signal is subjected to demodulation and dispreading, so that original navigation telegraph texts are acquired from the digital intermediate signal, and a pseudo range observed quantity is obtained; a positioning resolving unit is used for obtaining pseudo-range, Doppler and telegraph text parameter information for positioning and resolving, and after resolving, a positioning speed measurement result is sent to a user.

DSP-based multi-system compatible GNSS receiver and receiving system thereof

Carrier phase Ambiguity Resolution (AR) is the key to GNSS attitude determination. The baseline length is a readily available and widely used constraint. The traditional long-short baseline AR method resolve the integer ambiguity using the baseline length constraint on condition that the short baseline length is shorter than half of the carrier wavelength. In this contribution, we propose the Dual Frequency Long-Short Baseline (DFLSB) AR method for GNSS attitude determination. The dual frequency integer ambiguity is resolved by combining the restriction of short baseline constraint, Wide Lane (WL) integer ambiguity and the relationship of the dual frequency carrier phase. The main advantage of DFLSB method is increasing the short baseline length limit from 0.0951m to 0.431m compared to the traditional long-short baseline AR method. We analyze the error characteristic on the short baseline length and the dual frequency carrier phase relationship in numerical to find the maximum short baseline length limit of DFLSB method and the maximum tolerance of carrier phase measurement error. Both static open sky and dynamic land vehicle experiments were carried out to demonstrate the proposed algorithm and evaluate its performance. As a comparison, the performance of single epoch C-LAMBDA was recorded. In static open sky environment, the integer ambiguity resolution success rate of both DFLSB and C-LAMBDA method can reach 100% due to the good geometry and data quality. In dynamic urban environment, the integer ambiguity resolution success rate of DFLSB method is about 15% higher than C-LAMBDA at a price of an additional antenna. The mean computational time of DFLSB method is two orders of magnitude lower than that of C-LAMBDA method.

Dual frequency long-short baseline ambiguity resolution for GNSS attitude determination

The performance of the Global Navigation Satellite System (GNSS) compass is related to the quality of carrier phase measurement. How to process the carrier phase error properly is important to improve the GNSS compass accuracy. In this work, we propose a dual frequency carrier phase error difference checking algorithm for the GNSS compass. The algorithm aims at eliminating large carrier phase error in dual frequency double differenced carrier phase measurement according to the error difference between two frequencies. The advantage of the proposed algorithm is that it does not need additional environment information and has a good performance on multiple large errors compared with previous research. The core of the proposed algorithm is removing the geographical distance from the dual frequency carrier phase measurement, then the carrier phase error is separated and detectable. We generate the Double Differenced Geometry-Free (DDGF) measurement according to the characteristic that the different frequency carrier phase measurements contain the same geometrical distance. Then, we propose the DDGF detection to detect the large carrier phase error difference between two frequencies. The theoretical performance of the proposed DDGF detection is analyzed. An open sky test, a manmade multipath test and an urban vehicle test were carried out to evaluate the performance of the proposed algorithm. The result shows that the proposed DDGF detection is able to detect large error in dual frequency carrier phase measurement by checking the error difference between two frequencies. After the DDGF detection, the accuracy of the baseline vector is improved in the GNSS compass.

A Dual Frequency Carrier Phase Error Difference Checking Algorithm for the GNSS Compass

With the rapid development of the GNSS receiver's performance, almost all the commercial receivers have the ability of hot start. The main algorithm of fast positioning is how to get the position before frame synchronization when hot start. Because of the incomplete information of the pseudorange calculation before frame synchronization, the pseudorange is calculated by its estimation of integer millisecond part and inside millisecond part. If the estimation is wrong, the position error will be huge because of the huge pseudorange error, and it need to be researched and improved further. Firstly, the principle of fast positioning when hot start is introduced, the estimation and combination of pseudorange before frame synchronization and the correction of the position of satellite because of the unknown of the send time are derived in detail. The influence of the shift of general position and coarse receiver time error to fast positioning is discussed, the result shows the accuracy of fast positioning when the shifting is not abnormal and original least squares are nearly the same. When the pseudorange combination is just in the middle of a millisecond, a little shift of general position and coarse receiver time error will lead to a huge estimation error in pseudorange. For the gross error coming from the misestimating of the pseudorange, robust least squares are proposed to correct the gross error, the result of the simulation shows it's an effective way to correct the gross error.

An approach of gross error elimination in GNSS receiver hot start

The A/D converter with high-precision and reliable is the key core device to realize the acquisition of aircraft analog signal. By controlling the fusing state of the repair and adjustment fuse, the connection relationship between the benchmark debugging element, clock debugging element and ADC nuclear repair and adjustment capacitor can be accurately controlled. In the process of fracture of fuse wires at high temperature, if the spacing is too small and the stress is released, individual poly-crystalline fragments are able to contact each other, resulting in abnormal decline of fuse impedance, which will lead to error of data collection. Aiming at the early elimination of fuse fragmentation impedance anomalies, a defect elimination method based on Arrhenius temperature stress acceleration model is proposed. According to the Weibull failure probability distribution model, the number of fault components in the fault batch is predicted and confirmed by FIB test process, which improved the reliability of A/D converter.

Shuo Liu

Papers

DSP-based multi-system compatible GNSS receiver and receiving system thereof

Dual frequency long-short baseline ambiguity resolution for GNSS attitude determination

A Dual Frequency Carrier Phase Error Difference Checking Algorithm for the GNSS Compass

An approach of gross error elimination in GNSS receiver hot start

Reliability Analysis and Fault Prediction of A/D Converter Based on Acceleration Model