共查询到19条相似文献,搜索用时 343 毫秒
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针对星载统一S频段(Unified S-band, USB)测控应答机遥控接收高动态问题,提出了一种USB接收设备的设计方法。该方法基于AD9361+现场可编程逻辑门阵列(Field Programmable Gate Array, FPGA)硬件平台,采用并行+串行快速傅里叶变换(Fast Fourier Transform, FFT)实现信号载波频率捕获,载波环路使用2阶锁频环(Frequency Lock Loop, FLL)辅助3阶锁相环(Phase Lock Loop, PLL)环路进行跟踪,遥控副载波环路采用2阶PLL环进行跟踪。对方法的可行性进行了理论推导,使用Matlab进行仿真,结果表明该方法可以满足多普勒动态不小于32 kHz/s下遥控数据解调要求。 相似文献
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介绍了跟踪与数据中继星系统(TFDRSS)中用户星TDRSS/USB双模应答机的功能和组成,在传统USB应答机和扩频应答机的基础上设计了一种数字化的星载TDRSS/USB双模应答机,具有TT&C和TDR两种工作模式.接收机采用了中频数字化的载波跟踪和解扩解调、伪码快速捕获和精确跟踪方法;发射机的相干载波产生和PM调制采用直接数字频率合成(DDS)方法;两种模式下共用了收发通道和部分FPGA.资源.新的设计方法使应答机的调试难度、稳定性、载波和伪码捕获速度、跟踪精度、测距时延误差、功耗、重量等指标均有改善. 相似文献
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叉积鉴频器的输出频率范围比较窄,捕获信号以后的多普勒频偏可能不在其跟踪范围内。针对此问题,提出了使用四相鉴频器( FQFD )算法辅助已经成型的二阶锁频环加三阶锁相环模型。首先,利用四相鉴频器的非线性特性将接收信号频偏大步长牵引到较低范围,然后使用锁频环消除其大部分动态性,最后利用锁相环跟踪精度高的特点实现高动态二进制偏移载波( Binary Offset Car-rier,BOC)信号载波的快速准确跟踪。在分析各跟踪模块算法的基础上,讨论了其本身的热噪声误差、动态适应力以及最优带宽等相关问题,理论分析和仿真结果验证了该方法比原有跟踪算法提高了300 Hz左右的鉴频范围,并且跟踪效果良好。 相似文献
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本文介绍了一种高动态多普勒条件下载波的捕获与跟踪算法。使用又积鉴频法对载波作初捕,实现载波的快速捕获,利用锁频锁相环实现对载波的精确跟踪。分析了噪声及载波动态性对环路的影响。仿真结果验证了该方法的正确性及有效性。 相似文献
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Chun-Ting Lin Sheng-Peng Dai Chen J. Po Tsung Shih Peng-Chun Peng Sien Chi 《Photonics Technology Letters, IEEE》2008,20(13):1106-1108
This letter demonstrates the feasibility of a novel direct detection microwave photonic vector modulation scheme for the radio-over-fiber (RoF) system. Unlike the traditional double-sideband with optical carrier suppression modulation scheme, which can carry only the on-off keying data format, the proposed scheme encodes the electrical vector signal on either the upper sideband (USB) or the lower sideband (LSB) only and a pure optical subcarrier on the other sideband. Therefore, phase and amplitude information will be preserved after direct detection. A frequency doubling scheme is employed to reduce the cost of RoF systems. Additionally, the relative intensity between USB and LSB can be easily tuned by adjusting the individual power of electrical driving signals to optimize the performance of the optical radio-frequency signals. A proof-of-concept experiment is conducted by using a 1.25 Gb/s BPSK signal at a carrier frequency of 20 GHz. After transmission over 50-km single-mode fiber, the receiver sensitivity penalty is less than 0.5 dB. 相似文献
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Orthogonal frequency-division multiplexing (OFDM) systems are highly sensitive to synchronization errors. We introduce an algorithm for the blind estimation of symbol timing and carrier frequency offset in wireless OFDM systems. The proposed estimator is an extension of the Gini-Giannakis (see IEEE Trans. Commun., vol.46, p.400-411, 1998) estimator for single-carrier systems. It exploits the cyclostationarity of OFDM signals and relies on second-order statistics only. Our method can be applied to pulse shaping OFDM systems with arbitrary time-frequency guard regions, OFDM based on offset quadrature amplitude modulation, and biorthogonal frequency-division multiplexing systems. We furthermore propose the use of different subcarrier transmit powers (subcarrier weighting) and periodic transmitter precoding to achieve a carrier frequency acquisition range of the entire bandwidth of the OFDM signal, and a symbol timing acquisition range of arbitrary length. Finally, we provide simulation results demonstrating the performance of the new estimator 相似文献
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《Broadcasting, IEEE Transactions on》1988,34(3):398-406
The author presents a simple yet accurate method of verifying, and if necessary adjusting, the frequency deviation of the visual carrier and of the aural subcarriers without having to resort to the indirect method of carrier Bessel null. The method proposed is a direct method in that it measures the actual deviation of the FM carrier when this carrier is modulated with video test signals. This assures optimum use of the available transponder bandwidth for single or dual video operation. Tables and charts are provided for determining the levels of test tones for any frequency deviation of the main carrier or aural subcarrier 相似文献
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设备时延测量的新方法 总被引:2,自引:2,他引:0
讨论了连续波转发器设备时延 (距离零值 )测量技术 ,重点研究了利用测量副载波调制边带侧音相位完成中频调制转发应答机绝对距离零值测量的工作原理 ,并介绍了适用于各种形式应答机(包含中频调制转发应答机 )的距离零值通用测量方法 ,分析了测量方法误差。 相似文献
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针对 GPS 接收机发生 SEL 事件后的温度升高问题,在卫星轨道漂移分析基础上, 重点考察卫星应答机的 AGC 电压与载波锁定的温度敏感特性,并确定载波锁定的温度上限,进而提出 GPS 接收机的降级应用方案,关闭轨道电路板。结果表明,应答机载波锁定时的 AGC 电压应在 0.82V 以下,对应卫星应答机温度不超过 26.2°C;轨道电路板断电后,GPS 接收机定位与守时功能正常,工作温度在 20.5°C 以下,发生 SEL 事件的概率降低;GPS 接收机温度对于卫星应答机的影响明显减弱,应答机在原有上行约束下的载波锁定时长优于 150s,满足上行遥控注入时限需求。降级应用方案已施行于大数量卫星集中监控与管理。 相似文献
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文中对OFDMA系统中的子载波分配方法进行了研究,介绍了两种子载波分配方法的原理,对两种子载波分配方法进行了仿真,结果显示在频率选择性衰落信道中交织分配的OFDMA系统要比块分配的OFDMA系统获得更多的频率分集.给出了交织OFDMA系统上行链路的信号结构,由于发射机和接收机之间存在的载波频率偏移(CFO)将会影响子载波间的正交性,对多用户的CFO估计提出了一种估计算法,仿真的结果显示所提出的算法具有较好的性能. 相似文献