Universal signal simulation method for multi-target VLBI track measurement verification

Abstract

The invention provides a universal signal simulation method for multi-target VLBI track measurement verification. The method comprises the following steps of simulating an intermediate frequency signal of a target source in a time domain to obtain an intermediate frequency digital signal, the target source being a switchable detector and a radio power source; and processing the intermediate frequency digital signal to generate a simulation result of the baseband signal. According to the universal signal simulation method for the multi-target VLBI track measurement verification, the whole process of intermediate frequency signal simulation is processed in a time domain, a radio power source and detector baseband signal simulation function is achieved at the same time, unification of radio power source and detector beacon simulation is achieved, and the universal signal simulation method is suitable for simulating a deep space exploration VLBI alternating observation mode; in addition, by starting simulation from the intermediate frequency signal, calculation and storage complexity can be remarkably reduced, and engineering feasibility is achieved.

Description

technical field [0001] The invention belongs to the field of astrometry, and in particular relates to a general signal simulation method for multi-target VLBI orbit measurement verification. Background technique [0002] Very long baseline interferometry (VLBI) is a technical method with high resolution and high measurement accuracy that appeared in the late 1960s, and is widely used in astrophysics, astrometry and deep space exploration, etc. field. figure 1 It is the basic schematic diagram of VLBI. Two radio telescopes on the same baseline receive signals from detectors or radio sources, and the signal delay is obtained through correlation, so that the spatial position of the signal source can be further obtained. [0003] my country used VLBI technology in the first lunar exploration project in 2007, which played an important role in the smooth implementation of the mission. With the deepening of the lunar exploration project and the development of deep space explorat...

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Problems solved by technology

[0025] 2) In addition, from the point of view of specific implementation, because the simulation technology of Datasim is designed and implemented according to the idea of ​​DiFX related processing inverse process (that is, first decimal sampling correction, then into time domain signal, and then inverse fringe rotation), Its applicability has several limitations:

[0026] 1) First use the radio source delay model to calculate the range of the time domain signal and then do subsequent processing to generate the baseband signal (that is, step 3 of the simulation process of the Datasim module first determines the start and end time of the time domain signal, and step S4 generates the baseband real signal) , which means that Datasim can only simulate single-shot power supply signals but cannot simulate multi-shot power supply signals;

[0027] 2) Datasim simulation starts from the frequency domain. For the radio source signal, it is generally considered to be a Gaussian white noise signal, and its spectrum is known, so this kind of processing is feasible, but for the detector differential one-way ranging (Differential One- Way Range, DOR) signals and digital transmission signals are often given in the form of time domain, and the corresponding frequency domain form is relatively complicated, which is not suitable for processing from the frequency domain, so the method starting from the frequency domain is not universal;

[0028] 3) Datasim simulation includes two transformations from frequency domain to time domain, and one time domain to frequency domain transformation (step 2 includes a frequency domain to time domain transformation, step 3 includes a time domain to frequency domain transformation, and a frequency domain to frequency domain transformation Time domain transformation), the processing is more cumbersome, which affects the simulation efficiency;

[0029] 4) Mark5B is currently the main data format used by the CVN network. Datasim only generates VDIF format data, which cannot meet the testing and use requirements of the CVN network.

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