###### Abstract
The \(\Delta\)VLBI measurements were derived from the interference fringes of the radar echo [9]. However, in recent years, there has been no successful implementation of lunar and deep space exploration in Russia. Despite this, it is anticipated that they will continue their lunar exploration activities in the future. In China, VLBI has been extensively applied to the Chang'E series lunar explorations and its first Mars exploration. VLBI technology was first verified using the TT&C signal of the Chang'E-1 spacecraft with a bandwidth of about 1 MHz [10]. The Differential One-way Range (DOR) signals were set up according to the CCSDS specification in the Chang'E-2 mission [11]. The X-band \(\Delta\)DOR on-orbit experiment was conducted, achieving an interferometry delay accuracy of about 0.5 ns [12]. The Same-Beam Interferometry (SBI) experiment was conducted during the Chang'E-3 mission, yielding a post-processing differential phase delay accuracy of approximately 1 pico-second. On the basis of these measurement data, the relative positioning accuracy of the Chang'E-3 lunar probe reached up to roughly 1 m [13; 14; 15]. Subsequent experiments involving multi-probe and multi-signal interferometry technology were executed in Chang'E-4 and Chang'E-5. The accuracy of orbit determination was increased to the order of hundreds of meters by the comprehensive utilization of ranging, range-rate, and VLBI interferometry delay measurement for trans-earth or trans-lunar trajectory [16; 17; 18; 19; 20; 21]. In the Tianwen-1 exploration, the average error of the \(\Delta\)DOR time-delay was about 0.11 ns [22], and the positioning accuracy of the rover was up to 100 m [23]. However, with the ongoing advancement of deep space exploration, the distance between explorers and ground stations is progressively increasing, which leads to significantly weak downlink signals, thereby limiting the measuring performance of ground-based systems. The primary challenges in deep space exploration include enhancing the comprehensive utilization of downlink signal power to extend the exploration distance and improve the measurement accuracy. In the realm of deep space radio measurement, the predominant technical methods for improving weak signal processing capabilities encompass regenerative pseudo-code technology and antenna array technology. Additionally, it is useful to increase antenna aperture, transmission power on the spacecraft, and integration time. At present, the maximum aperture of the commonly used antenna in deep space exploration is 70 m. Any further enlargement of the aperture would substantially escalate the system construction costs. The increase in transmission power on the spacecraft is limited by current manufacturing levels. While the increase in integration time can improve the influence of thermal noise, it is constrained by the accuracy of the probe's predicted ephemeris. Antenna array technology is generally used to improve the performance of data transmission in the communication field. Due to the requirement of radio measurement for the system's phase center, the combined signal of an antenna array is difficult to use directly for measurement. Regenerative pseudo-code technology was originally designed to improve the ranging accuracy in the field of deep space exploration. It simultaneously improves the measurement accuracy and resolves the ambiguity problem associated with ranging. In the current trend of signal multiplexing in deep space exploration, the regenerative pseudo-code technology can be combined with traditional radio measurement technology to enhance the weak signal processing capability of the system. CCSDS specifications recommend that the frequency spacing between the two sets of DOR beacon signals and the carrier in the X-band downlink signal is approximately \(\pm\)3.8 MHz (denoted as \(\pm\)DOR\({}_{1}\)) and \(\pm\)19.2 MHz (denoted as \(\pm\)DOR\({}_{2}\)), respectively [24; 25].