共查询到18条相似文献,搜索用时 203 毫秒
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针对频域信道测量中测量仪器引入的不确定度进行了深入分析。矢量网络分析仪是频域信道测量中最重要的测量仪器,测量前必须进行自校准。深入分析不同校准方法所引入的测量不确定度是合理选择自校方法的量化依据。测量不确定度分析基于蒙特卡洛法。由于在频域信道测量中需要对多个频点进行测量,而各频点间的测量结果存在较强的相关性,因此在应用蒙特卡洛法的基础上引入了基于协方差矩阵的分析方法,从而考虑了相关性的影响,给出了更为准确合理的不确定度分析,最终有效地指导了自校方法的合理选择。实验表明,是否考虑相关性,对信道参数的测量不确定度有较大影响。基于对测量不确定度的定量分析,可以得出直通校准是更适合于信道测量的矢网自校准方法的结论。 相似文献
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采用多输入多输出(MIMO)结构和空时编码可以使水声通信系统获得分集增益,改善系统性能。针对水声信道中的频率选择性衰落,研究了一种用于MIMO水声通信系统的空时分组扩展编码方案(STBSC),利用正交扩频编码克服了水声信道中多径干扰对空时分组编码(STBC)信号正交性的破坏。给出了方案的系统模型和实现框图,采用MIMO水声模型对方案的性能进行了仿真。仿真结果表明,STBSC方案在多径水声信道中可以得到完全发射分集。最后介绍了方案的水库试验,试验结果表明了方案的有效性。 相似文献
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为实现高速水下通信,提出了一种基于VBLAST(贝尔实验室垂直分层空时)编码的水声MIMO(多输入多输出)通信技术。该技术通过在发射端和接收端同时采用多个阵元进行多发多收,借助空间复用,可有效解决水下通信系统带宽资源缺乏的难题,使系统在不增加带宽的条件下成倍提高数据传输速率。在水声MIMO通信系统的接收端,提出采用带有二阶数字锁相环、基于自适应空时判决反馈均衡的相干解调技术。该技术可有效克服水声MIMO信道中的多径干扰及同频干扰,且能自适应跟踪信道变化。仿真及湖试结果证明了所提水声MIMO高速通信技术的良好性能。 相似文献
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目前大多数多参数监护仪血压参数的测量都是基于振荡法的无创血压测量.针对无创血压的检测校准,国内还没有相应的国家标准,只有电子血压计检定规程.这个规程只考虑静态血压,而没有考虑动态血压.对动态无创血压监护参数进行的检测校准,可以最大限度地保障临床使用的安全、准确、可靠. 相似文献
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本文介绍了一种利用计数器校准时间继电器延时误差的方法。操作简便、准确度高,通过测量结果的不确定度评定,证明该方法完全满足时间继电器延时误差的校准要求,是目前国内用于校准时间继电器延时误差较先进、方便实用的方法。 相似文献
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为了准确测量无线电测定业务(RDSS)通道零值,提出一种基于循环相关处理的测试方法.采用真实的RDSS信号作为测试信号,对导航卫星RDSS业务通道输入和输出进行同步过采样,然后对采样后的输入和输出信号进行希尔伯特变换、载波旋转,对载波旋转后输入输出信号进行循环相关处理,搜索相关峰值,由峰值点确定循环位移量,最后结合采样频率和测试系统的标校时延,计算得到了RDSS业务通道零值.提出的测试方法采样频率10GHz时,其测量不确定度优于0.2ns. 相似文献
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A spread spectrum measurement system using a surface acoustic wave convolver has been used to measure radio wave propagation in steel works at 1.75 GHz with an echo delay resolution of ≈20 ns. Due to the high metal content of the factory halls, path loss is found to be small and its exponent to range between 1.1 and 2.3 only. We observed a delay spread between 82 and 548 ns depending on the size of the steel mill, its construction and machinery. Characterizing the radio channel by a stochastic delay line model the echo amplitude probability distribution is found to fit a Rician or log-normal distribution rather than a Rayleigh distribution. The fit of the amplitude distributions is determined by a χ2 hypothesis test. From the channel impulse response the coherence bandwidth is deduced to range between 2.4 and 27.4 MHz 相似文献
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Shahid Bashir Mohammed H. Alsharif Imran Khan Mahmoud A. Albreem Aduwati Sali Borhanuddin Mohd Ali Wonjong Noh 《计算机、材料和连续体(英文)》2021,66(1):263-274
With the development of wireless mobile communication technology,
the demand for wireless communication rate and frequency increases year by
year. Existing wireless mobile communication frequency tends to be saturated,
which demands for new solutions. Terahertz (THz) communication has great
potential for the future mobile communications (Beyond 5G), and is also an
important technique for the high data rate transmission in spatial information network. THz communication has great application prospects in military-civilian
integration and coordinated development. In China, important breakthroughs have
been achieved for the key techniques of THz high data rate communications, which
is practically keeping up with the most advanced technological level in the world.
Therefore, further intensifying efforts on the development of THz communication
have the strategic importance for China in leading the development of future wireless communication techniques and the standardization process of Beyond 5G. This
paper analyzes the performance of the MIMO channel in the Terahertz (THz) band
and a discrete mathematical method is used to propose a novel channel model.
Then, a channel capacity model is proposed by the combination of path loss and
molecular absorption in the THz band based on the CSI at the receiver. Simulation
results show that the integration of MIMO in the THz band gives better data rate
and channel capacity as compared with a single channel. 相似文献
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Garcia-Garcia L. Lindmark B. Jalden N. Orlenius C. 《Microwaves, Antennas & Propagation, IET》2007,1(6):1160-1169
We compare different methods of evaluating arrays for multiple-input multiple-output (MIMO) systems through calculation of the MIMO capacity of a compact antenna array for mobile or WLAN applications at 1766 MHz and comparing it to a reference array of four mono- poles. Three different methods were used: evaluation using radiation patterns and a channel model, measurements in a reverberation chamber and simultaneous measurement of radio channel data using the two arrays. We conclude that all methods give very similar relative results and that the main difference in the two arrays is the 1.3 dB lower radiation efficiency of the compact array. The channel measurements also show that the arrays provide between 80% and 90% of the capacity of a 4 times 4 MIMO system. 相似文献
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McWatters D.A. Lutes G. Caro E.R. Meirong Tu 《IEEE transactions on instrumentation and measurement》2001,50(1):40-46
The Shuttle Radar Topography Mission (SRTM) is an interferometric synthetic aperture radar system that flew on the space shuttle in February 2000, SRTM has an inboard antenna in the shuttle cargo bay and an outboard antenna at the end of a 60-m mast, extending from the cargo bay. In order to meet the elevation mapping accuracy requirement, the relative phase delay between the radar signals received via the outboard channel, compared with the inboard channel has to be known to within 80 at 5.3 GHz. This paper describes the design solutions and constraints, the devices, the analysis, and validation used to implement an optical calibration loop for SRTM. The calibration method involves injecting a tone into one panel of the inboard antenna, and sending an optical copy of the tone via a fiber-optic cable to be injected into the outboard antenna. A portion of the optical signal is reflected off an outboard partial mirror and travels back via the fiber to the inboard calibration system. There, it is converted back into a radio frequency tone and its phase is compared with the phase of the original tone. As the temperature of the mast fiber changes, a phase error is detected in the phase comparator. This error is used to control a custom designed optical phase shifter connected in series with the mast fiber. This phase-locked-loop guarantees that the phase of the calibration tone at the outboard stages within 1° relative to the phase of the calibration tone at the inboard antenna 相似文献
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Silverstein SD Ceperley DP 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2003,50(7):795-804
This work develops a class of ultrasound phase aberration correction/autofocusing algorithms that are based upon the properties of the covariance matrix of the channel signals for time-delay focused resolution/speckle cells. The scaled covariance matrix SCM algorithms are designed to blindly estimate and correct focusing timing errors due to thin layers of unanticipated fatty tissue located in the near field of the transducer array. An important aspect of the algorithm is that the scaling of the covariance matrix elements fundamentally establishes a channel independent phase reference relative to which the aberrant channel phases are estimated. The model development involved the combination of a rigorous mathematical analysis of the scattering of ultrasound in random scattering media and extensive statistical simulation studies with phase aberrations imposed upon both the transmit and received channel signals. Under the assumption of a near field aberration model, the statistical simulation analyses showed that the SCM algorithms in simulation are capable of accurately estimating relative time delay channel errors with RMS timing errors up to /spl sim/62 ns, with interchannel correlation lengths as short as 1.4 mm. 相似文献
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Bit error performance of turbo trellis coded/continuous phase modulation (TTC/CPM) is investigated for multiple input multiple output (MIMO) channels. The performance of TTC/CPM for 16-continuous phase frequency shift keying (CPFSK) over AWGN and Rician channels (for Rician channel parameter K=10 and 4 dB) is given for 1Tx-1Rx, 2Tx-1Rx and 2Tx-2Rx antenna combinations. Channel capacities of TTC-16CPFSK signals are obtained for these antenna configurations. TTC/CPM over MIMO fading channels is found to be very good, especially for low power applications 相似文献