Doppler estimation is a key link in the synchronization process of GMSK spread spectrum communication system receivers in the context of burst transmission. Given the extremely short information transmission time associated with short-duration burst GMSK spread spectrum communication systems, the synchronization segment structure of the system receiver is built. Based on this, a Doppler estimation algorithm adapted to the short-time burst synchronization segment structure is designed. The short-time burst Doppler estimation algorithm model is established. The algorithm formula is derived and the algorithm model is theoretically analyzed. The implementation process of the algorithm for Doppler estimation is described in detail, and the algorithm is simulated. The experimental results demonstrate that the Doppler estimation accuracy of the algorithm can reach 97.2% when the signal-to-noise ratio is 1 dB, and it exceeds 99% when the signal-to-noise ratio is greater than or equal to 3 dB. These findings validate the effectiveness and feasibility of the algorithm in GMSK spread spectrum communication systems within the context of burst transmission. It also shows that the Doppler estimation algorithm can still achieve superior accuracy even under weak signal conditions within the communication system.

For a long time, the modular design has been the mainstream implementation method of missile-borne telemetry and control equipment. However, there is no uniform standard for information interaction between modules. The development unit defines it according to its own technical and signal characteristics. The way of definition directly affects or determines the difficulty of implementing missile-borne telemetry and control equipment. In order to develop an efficient internal interconnection technology for missile-borne telemetry and control equipment, so that the connection of modules is simpler and more efficient, and the degree of generalization is higher when the performance requirements of missile-borne telemetry and control equipment become more complex, this paper divides the missile-borne telemetry and control equipment into three core modules and function expansion modules,and defines an efficient module-level bus interface form and protocol. The bus includes the input and output of primary power supply, secondary power supply, and internal cross-linked signals. The signal interaction adopts the form of a half-duplex bus. Each module can access the bus online and edit the bus online. Through design and experimental verification, the bus design method simplifies the external interface of the missile-borne telemetry and control equipment, and enables convenient and efficient online generation of telemetry PCM (Pulse Code Modulation) code stream. The function expansion module can be freely added or reduced without increasing the hardware burden of the bus interface, making the missile-borne telemetry and control equipment highly versatile.

In order to ensure the communication security of users and improve the high latency of traditional solutions in the integrated network of space and ground. In this paper, we propose a lightweight certificateless key agreement scheme. Firstly, we analyze the certificateless key agreement protocol system model. Based on the characteristics of the integrated network of space and ground, it is proposed that the protocol needs to satisfy some security requirements such as two-way authentication, anti-replay, and integrity. Then, we choose a lightweight certificateless encryption scheme. Base on the encryption scheme, we propose a key agreement protocol to meet the resource and security requirements of the integrated network of space and earth. Finally, we prove the proposed key agreement protocol security conducted on the BAN logical analysis, and compare the protocol performance with software simulation. The results show that the solution not only meets the network security requirements, but also provides fast and efficient negotiation.

With the continuous progress of satellite internet and China's aerospace TT&C technology, aerospace TT&C networks are developing towards intelligence and integration, making great progress in autonomous TT&C, resource allocation, and other aspects. Therefore, establishing an intelligent space-ground integrated network is an important goal for the future development of China's aerospace industry. In this paper, the relevant principles and technologies of tracking orbit, telemetry, and telecommand in intelligent space TT&C network are introduced. At the same time, combined with the space data link standard protocol proposed by CCSDS, TM, TC, AOS, Proximity-1, and USLP standards are introduced in detail, and the technology and practical application of different standards are analyzed. This paper introduces the working principle and technical requirements of space TT&C system from the view of the data link layer and physical layer, and provides reference and prospects for the research of the intelligent space-ground integrated satellite TT&C communication network in China.

With the increasing demand for multi-function and multiband operation, more antennas have been employed in different electronic systems, which inevitably results in difficulties in antenna arrangement and severe interference. As a key technique of radio-frequency aperture integration, ultrawideband (UWB) antennas provide an effective solution to this problem. A novel miniaturized UWB H-plane ridged horn antenna with end-fire radiation property is proposed in this paper. In order to broaden the operating bandwidth, an exponential ridge is employed and the cutting-off frequency of the rectangle waveguide is significantly reduced. By extending a hyperbola-shaped dielectric lens from the horn aperture, nearly uniform aperture phase distribution is achieved along the Hplane, which leads to a significant enhancement of the end-fire gain. This antenna has a compact form factor of only 0.57 λ_L×0.45 λ_L×0.11 λ_L and it maintains a wide operating bandwidth ranging from 0.8 GHz to 18 GHz. Moreover, the simulated cross polarization discrimination across the operating bandwidth is better than 30 dB. The antenna structure features a low profile, good stability, and easy fabrication, which can greatly facilitate its integration with metallic structures and missiles. Compared with other reported end-fire antennas, the proposed design shows remarkable superiority in terms of its electrical size and performance.

Accurate prediction of ionospheric clutter is of great significance in improving the target detection performance of high-frequency surface wave radar. This paper proposes a short-term prediction model of ionospheric clutter using the Opposite Artificial Rabbits Optimization optimized Gated Recurrent Unit (OARO-GRU) network. Firstly, based on the a priori knowledge that ionospheric clutter received by high-frequency surface wave radar has chaotic characteristics, the input and output sample sets of the GRU network are constructed using the phase space reconstruction technique. Then, two improvement strategies, namely, the opposition-based learning and the Cauchy-based mutation, are incorporated to enhance the optimization capability of the original ARO, which is used to optimizthe GRU network with the values of three hyperparameters including the number of hidden layer nodes, the initial learning rate, and the maximum number of iterations. Finally, the optimized GRU network is retrained and fed into the test sample set for testing. The model is evaluated based on the given evaluation metrics. The experimental results show that compared with the other seven comparison forecast models, the proposed OARO-GRU network model has obvious superiority in prediction accuracy and reliability, and provides a new idea and method for effectively improving the target detection performance of high-frequency surface wave radar.

The living environment of satellite navigation and positioning equipment is increasingly complex and severe,all kinds of electronic countermeasures,interference and deception are very fierce,and man-made interference has become the focus of satellite navigation and positioning security and confrontation. In view of the shortcomings of traditional means to effectively deal with the complexity, comprehensiveness and systematization of interference,the paper ,based on the analysis of OODA ring theory and practice transformation, combined with the overall counter process of interference and anti-interference in complex environment, optimized operation, coupled with satellite navigation and positioning security and counter, innovative satellite navigation and positioning security and counter non-directional circular link which is based on environment awareness, screening isolation, detection and recognition, performance evaluation, strategic planning, counter attack-return visit feedback, reperception. The seven links of expansion and mapping are analyzed and demonstrated. By introducing the concepts of loop and undirected, the operation mechanism of nested iteration and guided transmission of cyclic outer loop and loop in link is not only realized, but also the freedom of the inner loop is optimized, so that links are interconnected and independent, and loop but not directed, effectively enhance the safety of satellite navigation and positioning and the robustness of confrontation. The design idea of the paper can accelerate the realization of the dynamic closed-loop loop of cyclic link, improve the overall efficiency of countermeasure, and has certain reference value in practical application and technology demonstration.