To satisfy the future demand for multi-target tracking in hemispherical coverage,a 32-element circular polarized semi-spherical conformal phased array antenna is present in this paper.Hemispherical and cylinder configuration is adopted to meet the communication requirements at low elevation angel.Activate corner domain and different element distributions are compared in detail to decide the optimum performance.Simulated results show that the gain is higher than 13.8 dBi and the gain flatness is less than 1.8 dB within the scanning range of 0°～90°,which indicates this spherical phased array antenna can be applied in the oc-casions of multi-target tracking in hemispherical coverage.

AbstractA waveguide power divider based on ridge waveguide to microstrip line transition is presented in this paper. To improve the isolation performance, a probe insulator is inserted into the contact face from the center of the waveguide side wall, also two chip resistors are mounted on a planar substrate and connected with the probe to absorb the coupled energy. The impedance transformation is accomplished by ridge waveguide to microstrip line transition, which is hidden in the waveguide. This proposed power divider shows merits of waveguide power dividers and substrate-integrated waveguide power dividers simultaneously, i.e. planar output ports, compact size, and high isolation. For verification, a power divider operating at the Ka-band is simulated, fabricated, and measured. The obtained results show the return loss and isolation are better than 10 and 20 dB, respectively. The measured insertion loss is <1.5 dB, including the insertion loss of waveguide to microstrip line transitions at the output port in the range of 34.6–39 GHz.

To meet the rapidly growing needs of current and future deep space exploration missions, China has developed three deep space stations: Jiamusi and Kashi, (China), and Argentina (South America), for providing continuous telemetry, tracking, and command (TT&C), reliable communication, and precise navigation services. Integrated with state-of-the-art technologies, these three deep space stations are not only powerful for transmission but also extremely sensitive for receiving. Many remarkable innovations and achievements were made during the construction process, including the beam waveguide (BWG), adjustable subreflector, high-power transmitter, cryogenic low-noise amplifier (LNA), antenna-arraying technique, digital baseband receiver, and interferometry. This article briefly reviews the system architecture, general performance, critical system design issues, and contributions made by these Chinese deep space stations (CDSSs) during Chang’e missions.

激光统一测控系统采用激光链路同时实现高速通信、高精度测距和时钟同步.为了实现激光统一测控系统,根据异步应答测距方法,设计研制了基于OOK体制的激光统一测控系统原理样机,样机包含两套激光模拟终端,分别向对方发送包含测量数据帧的激光调制信号,并记录发送测量数据帧和接收测量数据帧的本地钟时间,据此计算得到距离、钟差、相对频差的测量结果.样机有线对接试验表明,在码率为2.5 Gbit/s的双向激光通信条件下,测距随机误差为6.2 mm,测距系统误差为1.3 mm,钟差测量随机误差为27 ps,相对频差测量随机误差为2.7×10-13.该样机为激光统一测控设备的研制和应用提供了技术支撑.

Duplex laser communication system can achieve high-precision ranging and clock synchronization between terminals in spacecrafts with high data rate transmission. By measuring the transmission and arrival time of data frames during the detection of frame synchronization in laser communication, we resolved the range, time difference and frequency difference simultaneously. Furthermore, we designed a prototype of laser communication system with space and ground terminals separated by a free space to validate the ranging method for asynchronous transponders. For this duplex laser communication demonstration with data rate of 2.5 Gbps, we achieved very high precision with two-way ranging accuracy of 5.4 mm, frequency difference standard deviation of 3.4×10 -13 , and time difference standard deviation of 2.9 ns. Such high-precision ranging accuracy would be valuable for orbit determination, and the precise measurement of time and frequency difference could be used for disciplining the satellite clock by the high-stability ground clock.

With the development of laser communication technology, the integration of communication and ranging has become a trend in the field of satellite communication and deep-space exploration. Dual mixer time difference (DMTD) has various advantages of precise time resolution and low resource consumption as a method for measuring time difference, which is suitable for ranging in requirement of integration. In this paper, a high-precision ranging technology based on DMTD is proposed and implemented on hardware platform. This technology includes a clock data recovery module which provides synchronizing clock, a DMTD module and the interpolation algorithm which improve measurement accuracy jointly, and the ranging algorithm for the purpose of eliminating the periodic phase ambiguity. Simulation results demonstrate that the proposed technology can achieve higher ranging precision compared to the conventional method using tracking loop. The implementation results verifies the feasibility and the good performance of the proposed technology.

This Letter reveals the underlying relations of three state-of-the-art interval arithmetic (IA)-based algorithms for antenna array pattern upper bound estimation with excitation amplitude errors. Theoretical analysis proves that the matrix IA algorithm has better performance than both the rIA and circular IA algorithms. Mathematical derivations are presented in detail, and representative numerical examples are given for validating this conclusion.

A high-speed frequency-domain bit synchronization algorithm for parallel implementation is proposed in this paper, which is aimed at integrating high-speed laser communication with distance measurement. This algorithm which combines bit synchronization with the frequency-domain parallel matched filtering can make the output of filter only contain the data of optimum sampling points, so that the complexity of implementation will be obviously lower than parallel time-domain bit synchronization algorithm. Moreover, this algorithm adopts tracking timing adjustment to produce a better accuracy. A description of this algorithm is made in this paper, including formula derivation, implementation structure and simulation verification. Meanwhile, comparison between time-domain algorithm and frequency-domain algorithm is performed in this paper. According to the simulation results, this algorithm has a better performance.

Asynchronous laser transponders algorithm is an emerging technology for high-precision laser ranging. This paper presents an improved algorithm based on the previous asynchronous laser transponders algorithm. The clock frequency deviation between the satellite and ground is taken into account, and two pairs of lasers are used to calculate the ranging result in the improved algorithm, thus getting a more accurate result. Besides, the improved algorithm can also calculate the time difference, clock frequency deviation between two terminals and the satellite movement radial velocity. We apply both the improved algorithm and previous algorithm to a laser ranging experiment to calculate the ranging result respectively and compare the ranging errors. According to the experimental results, compared with the previous algorithm, the improved algorithm can reduce ranging error, which verifies the accuracy and engineering feasibility of this algorithm.

The high-speed deep space communication is one of the key technologies for deep space exploration. Laser communication system equipped with sensitivity of single photon will improve existing deep space communication speed. However, laser communication at single photon level needs to consider not only the effect of transmission environment, but also the performance of used single photon detector and the photon number distribution. As a new single photon detector, superconducting nanowire single photon detector (SNSPD) outperforms the traditional semiconducting SPDs at near infrared wavelengths, and has high detection efficiency, low dark count rate, low timing jitter, high counting rate, etc. The SNSPD can be used for detecting single photons efficiently, rapidly and accurately. In this paper, we introduce the system detection efficiency and dark count rate of SNSPD based on the photoelectric detecting model without considering the effect of atmospheric turbulence, establish the mathematical model of bit error, and put forward the formula of system bit error rate. What should be emphasized is that the bit error rate is an important parameter for measuring the performance of laser communication system. Error is partly from background thermal radiation and circuit electromagnetic interference; in addition, error appears when photons reach the surface of device without being absorbed to successfully produce resistance area or photons are absorbed but there occurs no response. As a result, the calculation of bit error rate includes the whole process of photoelectric conversion. In order to analyze how to affect the size of system bit error rate, first we simulate two factors of the formula, i.e., light intensity and laser pulse repetition frequency. The results show that the light intensity has the greatest influence on error bit rate. With the light intensity increasing from 0.01 to 1000 photon/pulse, the error bit rate significantly decreases from 10-1 to 10-7 level. The influence of laser pulse repetition frequency is restricted by the light intensity, which declines with the increase of pulse repetition frequency. Then we measure the error bit rate experimentally, which validates the simulation model. However, when increasing light intensity or speed, experimental bit error rate is about 10-4 times higher than simulation result. The reason may be that the insufficiency of actual communication modulation extinction ratio of optical signal to the background noise through optical fiber increases the dark count rate. The above model and experimental results could be the foundation of high-speed deep space laser communication such as moon-earth and Mars-earth based on SNSPD.

由弹体自旋产生的弹载天线的旋转是引起地面测控站多普勒测速误差的一个重要因素.根据线极化信号接收原理,对弹载天线旋转条件下接收的左旋和右旋信号多普勒偏差进行了理论推导和分析.分析结果表明:左/右旋接收信号将产生幅度相等、极性相反的多普勒偏差,多普勒偏差的均值与弹载天线旋转速率在数值上相等,多普勒偏差的方差随着目标视线与天线转轴之间夹角的增大而增大.为验证理论分析结果,开展了天线转台模拟实验,实验测量得到的多普勒偏差的均值和方差与理论分析结果基本一致.最后,根据理论分析和模拟实验结果,提出在实际任务中,可采用左旋和右旋多普勒偏差均值差的一半分别对左/右旋信号的多普勒进行补偿,以减小弹载天线旋转对测速精度的影响.

The intermediate frequency(IF) bandwidth is an important influencing factor on the demodulation performance of FM telemetry receiver.The influence of IF bandwidth is studied for both non-coherent demodulation and multi-symbol detection by means of the simulation analysis.To optimize the bit-error-rate performance of demodulation,the recommended typical parameter of IF bandwidth is put forward,which is almost 1.2 times bit-rate.At last,the simulated results are validated by the hardware testing.

The principle of measurement of the G/T of telemetry systems using sun source is introduced and a practical method of measurement is proposed.Analysis is given on parameters including sun flux,K1gene and K2gene and calculation method is given for engineering application.Taking a model of telemetry system as an example,test results with the sun source method and beacon tower method are compared and analyzed.Analysis of the test results shows that the repeating error of G/T measured with the sun source method is less than 0.4 dB and the difference from that of the beacon tower method is smaller than 0.6 dB.Therefore,the sun source method is theoretically correct and feasible and can be widely used in test of telemetry systems.

Following a brief introduction of turbo-code frame synchronization in CCSDS recommendations and ASM(Attached Sync Marker),the performance of autocorrelation function and peak-side lobe is analyzed.Then,a new ASM pattern with better autocorrelation function is proposed.Simulation and analysis of ASM detection in noisy environment shows that the new ASMs with a length of 128 bits and 192bits have much better synchronization performance than CCSDS ASMs with the same length.

Following a brief description of multi-h CPM system,a new demodulation algorithm is proposed based on Viterbi algorithm and Maximum Likelyhood Sequence Detection method.Based on simulation analysis,Bit-Error-Rate(BER) curves and spectrum of multi-h CPM are acquired.The results show that multi-h CPM schemes with appropriate modulation indices obtain a better performance than PCM-FM systems in terms of BER and spectrum efficiency.The approach is of high significance for application in high bit rate telemetry systems.