星上多载波解调技术研究

新一代具有星上处理的卫星将急剧降低地球站的复杂度,星上多载波解调(MCD)技术就是在星上分离出各个信道然后再独立解调。研究了星上多路信号即FDMA/QPSK信号的多载波技术,这是一种重要的星上处理技术,它包括频分多路信号的FFT分路算法、频偏估计、多路QPSK信号的全数字化解调算法和解调算法中的位定时恢复方法等。对主要的关键技术进行了计算机仿真。     

Multi-carrier demodulators for on-board processing satellites

A study of the digital transmultiplexor element of an on-board multi-carrier demodulator (MCD) results in design data for various architectures (FFT, tree etc.) which can be applied to a wide range of applications. A detailed design based on the latter for a 4 × 16 kb/s MCD for the U.K. T-SAT mobile OBP payload is presented. Implementation of the MCD using TMS320C25 signal processor technology has been performed and early test results are presented.     

Alternatives for on-board digital multicarrier demodulation

In this paper alternatives for digital multicarrier demodulators (MCD) suitable for advanced digital satellite communications systems are presented. The MCD permits the direct on-board interfacing of FDMA and TDM communication links by digital signal processing techniques. Two main functions are implemented by a MCD: demultiplexing (DEMUX) and demodulation (DEMOD). We focus here only on a digital implementation of the MCD, looking at its advantages, flexibility, better performance and VLSI integrability. The DEMUX may be implemented in a number of ways: the analytic signal method, fast Fourier transform with polyphase network technique, or multistage methods. For all the implementation methods considered it is shown that a certain degree of integration of DEMUX and DEMOD functions is possible. To this end, in the proposed MCD schemes the receiver pulse-shaping filter has been integrated in the DEMUX structure, reducing the overall implementation complexity. It is shown that, for the per-channel structure based on the analytic signal method, a highly modular and flexible implementation can also be achieved. Coherent demodulation is used to reduce the signal-to-noise ratio required to achieve a specified bit error rate. The coherent demodulation is carried out by using the maximum likelihood (ML) estimation method. Two different approaches to receiver synchronization have been studied. For the first, the carrier phase and symbol timing estimates are independently derived by suitable techniques. The second approach makes use of the maximum a posteriori probability method to estimate both the carrier phase and symbol timing of the receivied signal. In particular, for this technique it is shown that, by a suitable choice of the architecture of the digital coherent receiver, the ML demodulator can be integrated in the joint carrier and clock recovery circuit, with no increase in the overall system complexity. The digital architecture of the proposed MCD can be adapted to different digital modulation techniques. However, here we consider only the application for QPSK signals, as this modulation scheme is the most promising for digital satellite communications. A theoretical analysis and computer simulation have been used to evaluate the performance degradation of the proposed MCD, including finite-arithmetic implementation effects.     

Saw-based chirp fourier transform and its application to analogue on-board signal processing

This paper reports on the work done at ELAB-RUNIT on surface acoustic wave (SAW) on-board signal processing. The main processing is done by the analogue chirp Fourier transformer (CFT) and its inverse (ICFT). In a CFT, the input signal is transformed from an FDMA format to a TDM format and at the same time filtered by a filter bank. By multiplying and convolving the signal with chirp waveforms, the CFT is implemented by one bandpass cover filter and one chirp filter. The paper demonstrates that SAW reflector array compressors (RAC) built by ELAB-RUNIT have suitable chirp responses and adequate precision for digital satellite communication. Two applications are described. An on-board multicarrier demodulator (MCD) for 9·6 kb/s QPSK carriers and a processor for filtering, routeing and beam steering (FROBE) for flexible transparent repeaters. For MCDs the use of SAW CFTs leads to a power consumption for demultiplexing and A/D conversion of 15 mW per carrier with room for improvements. For transparent paylods, the FROBE leads to more flexibility and narrower guardbands than can be obtained by other analogue processors.     

An analysis and experimental approach to MOS controlled diodesbehavior

The metal oxide semiconductor (MOS)-controlled diode (MCD) is a new class of power semiconductor diode that can achieve ideal diode performance. In this paper, experimental verification of the MCD key concept is presented for the first time by using commercially available power metal oxide semiconductor field effect transistors (MOSFETs) operating as MCDs. Measurements of the reverse recovery currents and reverse recovery charges of these “MCDs” are obtained and compared with the body diodes of the MOSFETs. These measurements suggest that MCDs can reduce the reverse recovery current, storage charge, and switching loss significantly. Optimized MCD performances at 1.2 kV, 2.4 kV, and 4.5 kV are also predicted based on numerical simulations. Ideal performance of the MCD close to that predicted by the device simulation should be obtained once an optimized MCD is developed     

空间相机软件在轨重注方法研究与实现

随着计算机技术和软件技术的发展,具有高度自治性和灵活性的实时嵌入式系统在航天领域的应用越来越广泛.对这些嵌入式系统往往具有较高的长时间运行的自治性和可靠性要求,因此,对系统在轨维护能力提出了迫切的需求.针对实时嵌入式系统在轨维护需求,提出了一种基于FPGA的嵌入式系统软件在轨重注方法.     

A multirate digital multicarrier demodulator: design,implementation, and performance evaluation

Frequency-division multiple access (FDMA) and single channel per carrier (SCPC) in the uplink and time-division multiplexing (TDM) in the downlink are employed in the system described. To interface FDMA in the uplink and TDM in the downlink, multicarrier demodulation (MCD) is required onboard the satellite. The operation of the onboard MCD is the separation of each individual channel and subsequent demodulation. The results, which concern onboard frequency demultiplexing and demodulation for low-bit-rate carriers, are constrained by the requirement that new-generation payloads could serve the stations already active in the INTELSAT Business System. A digital hardware design that implements an MCD that can process three channels at 4.4 Mb/s or 12 channels at 1.1. Mb/s is described. The test results confirm the MCD feasibility, and further improvements are expected from a semicustom implementation     

定标漫反射板实验室系统级BRDF测量方法

星上定标系统是卫星遥感器的重要组成部分,用于实现仪器的星上辐射定标等功能。介绍了安装在某一时间调制型傅里叶变换光谱仪上的星上定标系统,该星上定标系统采用漫反射板太阳辐射定标方法进行仪器在轨全口径、全光路、全视场的星上辐射定标。定标漫反射板在光谱仪光路最前端反射太阳光,通过已知的大气外太阳照度和漫反射板的双向反射分布函数BRDF确立辐亮度标准。定标漫反射板的BRDF需要在实验室进行精确测量。介绍了在光谱仪整机状态下使用太阳模拟器和标准漫反射板进行定标漫反射板实验室系统级BRDF测量的方法,对使用定标漫反射板系统级BRDF进行星上辐射定标时的绝对辐射定标精度进行了分析,绝对辐射定标精度能够满足5%的指标要求。     

Power limitation and high-power amplifier nonlinearities inon-board satellite communications systems

The authors discuss the problem of power limitation in on-board satellite communications systems. They consider the nonlinear characteristics of on-board high-power amplifiers and corresponding linearisation techniques. It is shown that, with the recent development of solid-state high-power amplifier designs and linearisation techniques for travelling wave-tube amplifiers, it is now possible to operate on-board amplifiers near to saturation without increasing their nonlinear effects     

GF5B热红外通道星上定标与验证

以GF5B卫星发射前实验室定标为基础,采用星上0级黑体定标数据,建立了适用于GF5B热红外通道的星上绝对辐射定标模型。通过对2022年01月12日星上黑体定标数据进行处理,获得成像仪热红外通道的绝对辐射定标系数。对星上定标系统精度进行分析,并采用地面同步烟台浮标数据对定标结果进行精度验证,结果表明,在轨后星上定标系统的绝对定标精度为0.9 K;星地验证结果显示B11和B12通道亮温的偏差分别为0.33、0.77 K。说明基于星上黑体的定标方法具有较好的精度,定标结果可靠,可满足遥感数据定量化应用的需要,为实时准确获取热红外通道定标系数提供了方法借鉴。     

On-board digital signal processing technologies for present and future SCPC systems

Devices and architectures for on-board SCPC (single channel per carrier) multi-carrier demodulators suitable for use in satellites to be launched between the present and the year 2000 are discussed in the light of trends in the development of device technology towards lower on-board weight and power consumption. It is shown that at the present time (equivalent to about 1990 for on-board use). The choice of demodulation scheme depends on the number of channels available for regeneration on board the satellite. The total weight and power consumption for several suitable on-board multicarrier demodulation schemes are predicted for 1990, 1995 and 2000, as functions of the number of channels to be regenerated.     

La compression d’images embarquée pour les missions spatiales

On-board space instruments produce more and more high amount of data due to the increase in both resolution and number of bits per pixel, not compensated by the reduced swath. Due to the stringent limitations (in terms of mass and power) which apply to on-board equipment, it is essential to reduce to a minimum the on-board sto-rage capacity and the on-board transmission rate needed to fullfill the mission: on-board image compression is a very powerful tool to optimise the resources. The availability, for spaceborne applications, of highly integrated circuits allows to implement on board very sophisticated real-time compression schemes and then to improve the performances of on-board compression. The whole image chain (from the sensor to the on-ground post-processing such as déconvolution and denoising) has to be considered in order to select the compression algorithm and the compression ratio. This article presents the compression algorithms, selected or currently studied, for space missions, and the methods of image quality evaluation.     

海洋参数星上快速处理方法及典型应用研究

海洋相关参数的遥感反演对灾害预警等有重要作用。随着硬件的发展,星上实时处理成为可能。海洋参数中,海面风场和浪场占据了重要地位。本文的研究,首先对星上处理进行说明,并叙述星上环境的仿真方法。然后针对台风海面风场和海面浪场,使用散射计、辐射计联合观测以及高度计的观测,进行星上快速处理的实现方法研究。对选取的方法,使用卫星遥感数据,在星上仿真环境下实现运行。结果表明,研究中使用的方法能有效实现星上处理。在“通导遥”一体化趋势下,该方法的应用将有效辅助自动的实时决策,实现灾害预警。下一步研究将实现更多参数的星上平台仿真。      

Improving clustering performance using multipath component distance

The problem of identifying clusters from MIMO measurement data is addressed. Conventionally, visual inspection has been used for cluster identification, but this approach is impractical for a large amount of measurement data. For automatic clustering, the multipath component distance (MCD) is used to calculate the distance between individual multipath components estimated by a channel parameter estimator, such as SAGE. This distance is implemented in the well-known KMeans clustering algorithm. To demonstrate the effectiveness of the choice made, the performance of the MCD and the Euclidean distance were compared by clustering synthetic data generated by the 3GPP spatial channel model (SCM). Using the MCD significantly improved clustering performance     

Limiting electromagnetic interference due to on-board devices from on-bench tests

Electromagnetic interference due to on-board devices may differ from what can be expected after on-bench tests. An approach, aimed at ensuring that the on-board device performance is satisfactory, is presented. It is based on the computation of new limits for on-bench tests and is illustrated in a very simple configuration.     

基于特征检测和小波变换的SAR图象的智能压缩

在地质普查、安全监控等众多任务中，合成孔径雷达成像系统产生着海量的图象数据．必须通过有限的通道传回地面，迫切需要一个能从图象的信息中自动检测目标或兴趣区域的智能压缩技术。为此，本文提出了一种基于标准特征检测方法的Bayes网络融合检测方法检测兴趣区域，并据此对图象的小波分解系数进行变化和编码，从而既实现高压缩，又保持了关键区域图象的质量。     

A novel strategy for preparing a selective back surface field of n-type emitter wrap through solar cells

In the present study, we have developed a novel mixed co-diffusion (MCD) process by which to prepare a selective back surface field (BSF) of n-type emitter wrap through (EWT) solar cells, which combines a plasma enhanced chemical vapor deposition (PECVD) phosphorus-doped n-type microcrystalline silicon as the dopant source, with a low temperature thermal oxidation (LTO) process. Through comparison between our MCD process and a standard co-diffusion (SCD) process, a BSF with a shallow doping depth of 0.56 µm and high doping concentration of 1.9×10²⁰ at/cm³ is easily obtained by the MCD process under the low temperature of 750 ℃. Therefore, the MCD process is shown to reduce the number of high temperature processes, which cannot produce dopant redistribution, and can accurately control the doping concentrations and depths of the BSF and emitter. In addition, the novel method also eliminates the boron-rich layer, which induces misfit dislocations and bulk lifetime degradation, without extra chemical treatment. Therefore, the MCD process' open circuit voltage, short circuit current density, conversion efficiency and fill factor of the solar cells are respectively increased by 7 mV, 6 mA/cm², 2% and 2%. These results indicate that the MCD process is a novel and potential agent for the SCD process.     

磁致圆二向色性对法拉第旋转器消光比的影响

从磁光材料的介电张量出发,分析了法拉第旋转器消光比与磁致圆二向色性的关系,在此基础上,讨论了铋钙钒BiCaInVIG法拉第旋转器磁致圆二向色性对光隔离器隔离度、插入损耗的影响.