Wide-range high-precision Doppler measuring method for deep space exploration

Abstract

The invention relates to a wide-range high-precision Doppler measuring method for deep space exploration. An analog PM_BPSK signal of a transmitting end can form a cycle-repeated dual-signal block. Areceiving end converts the received signal into a digital baseband signal. Firstly, FFT calculation is carried out on the digital baseband signal, and a Doppler frequency rough estimation value of thesignal is obtained according to the FFT result. Secondly, according to the obtained rough estimation value, after an original digital baseband signal is subjected to frequency integer correction, andcompensation, a residual carrier signal is obtained through narrow-band filtering, and the residual carrier signal is subjected to conjugate complex correlation fine estimation operation on the basisof the double-signal block to obtain a Doppler fine estimation value. Thirdly, the rough estimation value and the fine estimation value are subjected to fitting to obtain the wide-range high-precision Doppler estimation value. Compared with a traditional Doppler estimation method, the wide-range high-precision Doppler measuring method has the advantages that the measurement efficiency, the measurement range and the measurement precision are all considered, the measurement range is large, the measurement precision is high, the software complexity is low, and the application prospect is wide.

Description

technical field [0001] The invention relates to the field of inter-device communication in the field of deep space exploration, in particular to a method for realizing wide-range high-precision Doppler measurement by using a subcarrier modulation mode in the inter-device communication. Background technique [0002] When vibration sources such as sound, light and radio waves move relative to the observer, the vibration frequency received by the observer is different from the frequency emitted by the vibration source. This phenomenon is called the Doppler effect. When the transmitter emits a pulse wave with a fixed frequency to scan the air, if it encounters a moving target, there will be a frequency difference between the frequency of the echo and the frequency of the transmitted wave, which is called the Doppler frequency. According to the size of the Doppler frequency, the radial relative motion speed of the target to the transmitter can be measured; according to the time d...

AI Technical Summary

Problems solved by technology

[0006] Two-way Doppler frequency measurement is an active measurement technology. The measuring station transmits signals to the target detector. The detector is equipped with a transponder, which locks the frequency of the received signal and then transmits it to the measuring station. The measuring station passes Doppler counting. The principle can calculate the Doppler frequency of the detector. The disadvantage of this method is that if a cycle skip occurs at a certain moment, it will directly affect the counting result and make the measurement deviate.

The three-way measurement mode is similar to the two-way measurement mode, the only difference is that the signal transmission and reception are completed by two different stations, so although the cycle skipping phenomenon can be avoided, the cost of two stations is required

For a large elliptical orbit satellite moving at high speed, its Doppler is changing all the time, so the actual measurement error will be relatively large, which will affect the final orbit measurement accuracy

If the ultra-long-order FFT method needs to take into account the wide range and high-precision indicators, more than 217 FFT operations are required. For satellite application environments with strict power consumption and cost requirements, the required hardware resources are too expensive; Gemini Segment phase measurement method, such as the patent "a dual-sub-segment phase difference frequency estimation method and its device" (CN104076200A), due to the limitations of the algorithm itself, cannot take into account the dual requirements of measurement range and measurement accuracy; there is also a patent: "Carrier Doppler High-precision measurement method for Le and its rate of change (CN201711173235)", using three-stage Doppler spectrum estimation, the first two stages of 2048-point FFT and the third stage using 4096-point FFT, the final measurement accuracy is 1.953Hz about 2Hz, The accuracy cannot reach 10mHz, and the required carrier-to-noise ratio is above 40dB. For suppressed carrier modulation such as BPSK and QPSK, the carrier-to-noise ratio and signal-to-noise ratio are relatively close, so the required signal-to-noise ratio is high, and at the same time The synchronization problem of the modulated signal is not considered in the scheme. If the integral processing is performed directly, the measurement will deteriorate sharply. Therefore, this method is difficult to meet the high-precision measurement needs of deep space exploration and low signal-to-noise ratio.

"Underwater Acoustic OFDM Doppler Factor Accurate Estimation Method (CN103618686A)", by designing a special OFDM frame format, adding CW single-frequency signals, and using three-stage Doppler spectrum estimation to gradually reduce the range and gradually improve the accuracy, its first The first level uses CW, and the last two levels use autocorrelation and cross-correlation algorithms respectively, and use the search method to estimate the third level. In addition, the required signal power is not given in the paper, and the implementation complexity is relatively high, so , it is also difficult to guarantee the high-precision measurement requirements under low signal-to-noise ratio

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