共查询到20条相似文献,搜索用时 46 毫秒
1.
A novel scheme to joint phase noise (PHN) correcting and channel noise variance estimating for orthogonal frequency division multiplexing (OFDM) signal was proposed. The new scheme was based on the variational Bayes (VB) method and discrete cosine transform (DCT) approximation. Compared with the least squares (LS) based scheme, the proposed scheme could overcome the over-fitting phenomenon and thus lead to an improved performance. Computer simulations showed that the proposed VB based scheme outperforms the existing LS based scheme 相似文献
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为满足RFID射频收发器可灵活配置工作模式,并校准芯片工作频率的要求,设计了一种具有新型双缓冲存储结构和实现自适应频率校准(AFC)的可编程配置模块。采用双缓冲存储结构和数据同步方法简化设计,通过引入可变阶距因子改进自适应频率校准算法,使得频率锁定时间有效降低。采用TSMC0.18μm工艺进行后端设计并流片,芯片面积4mm2,供电电压1.8V。测试结果表明,该模块能正确完成芯片配置,AFC频率跟踪时间缩短到135μs以内。 相似文献
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Debarati Sen Saswat Chakrabarti R. V. Raja Kumar 《Wireless Personal Communications》2010,54(4):623-633
In this literature, we present a new method for estimating the coarse frequency offset in multi-band orthogonal frequency
division multiplexing (MB-OFDM) based ultra-wideband (UWB) communication systems. The proposed training based coarse frequency
offset (CFO) estimator performs an averaging of initial estimate over the multiple bands of transmission during estimation
process. The proposed multi-band averaging provides an improved estimation of approximately three times for band group 1 (BG1)
compared to our earlier proposed scheme. To prove the efficiency of the proposed scheme, the Cramer Rao lower bound (CRLB)
of the estimation error is calculated and compared with the simulation results. We illustrate the performance of MB-OFDM system
in terms of bit-error rate (BER) with multi-band averaged frequency synchronization (MBAFS) and compare with earlier reported
results for 100,000 noisy realizations in UWB channel model 2 (CM2). 相似文献
4.
Hyoung-Kyu Song 《Electronics letters》1999,35(5):380-382
A fast and exact frequency offset estimator (FOE) algorithm using peak phase error detection and frequency offset smoothing is proposed for time division multiple access (TDMA) systems. The proposed peak phase error detection scheme avoids the large phase errors which lead to poor FOE performance. To control the AFC, frequency offset smoothing using a simple filter is utilised. Simulation results show that the proposed algorithm is adequate for the frequency offset estimator of TDMA systems for burst data transmission 相似文献
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A fast adaptive frequency calibration (AFC) technique with self-calibration for fast-locking phase-locked loops is presented with frequency-selecting switches. The proposed AFC directly calculates the proper switch states of the voltage-controlled oscillator (VCO). It requires only six clock cycles of the reference oscillator regardless of the number of VCO switches to reach the final switch state in the ideal case. The proposed method counts the number of VCO cycles per reference clock period for the minimum VCO frequency (MIN) and the maximum VCO frequency (MAX) during the first four-clock periods. For the following two-clock periods, the proper states of the VCO switches are set to the calculated value from MIN, MAX and the desired division ratio for a target frequency (EST). A frequency synthesiser with the proposed AFC was implemented on a 0.18?µm CMOS process. The AFC time decreased from 40 to 0.4?µs employing the proposed scheme such that the total lock time is 40?µs with the loop bandwidth of 40?kHz. 相似文献
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Object‐based audio coding can provide new music applications with interactivity. To efficiently compress a lot of target audio objects, a subband‐based parametric coding scheme has been adopted for MPEG spatial audio object coding. In this letter, the time‐frequency (T/F) subband analysis structure is investigated. A reconfigured T/F structure is also proposed to enhance the generating performance of sound scenes such as ‘karaoke’ and ‘solo’ play in interactive music scenarios. From the experimental results, it was confirmed that the proposed scheme remarkably improves the SNR and sound quality. 相似文献
10.
Channel estimation for orthogonnl frequency division multiplexing(OFDM)systems operating over doubly selective channels is complicated by the existence of intercarrier interference(ICI).This paper extends the idea of estimating time-variant channel impulse response(CIR)via time-averaged CIR.proposed by Hijazi,and proposes a low-complexity channel estimation scheme with ICI suppression based on Karhnnen-Loeve basis expansion model(KL-BEM),which is in a more general form.In the proposed scheme,the KL-BEM coefficients are obtained through their numerical relationship with the time-averaged CIR.The estimation performance is improved by adopting an expectation-maximization(EM)-based iterative structure combined with a low-complexity ICI equalizer and canceller.Theoretical analysis and simulation results show that the proposed scheme achieves superior performance over the original one with lower computational complexity. 相似文献
11.
Won-Gyu Song Jong-Tae Lim 《Broadcasting, IEEE Transactions on》2003,49(4):398-402
In this paper, we address the problem of estimating a rapidly-varying channel in orthogonal frequency division multiplexing (OFDM) systems. To handle rapid variation within a transmission block, we propose a novel pilot-based estimation scheme which uses channel interpolation. In addition, we develop a simple Doppler frequency estimation scheme. We show that the proposed scheme has better performance in the high-Doppler frequency by simulations. 相似文献
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A two-channel 140 Mbit/s coherent optical FDM transmission system with a new frequency stabilisation scheme has been developed. In this scheme, low frequency modulation is applied to transmitter laser diodes to lock them at the resonances of a Fabry-Perot interferometer, and a high speed IF AFC circuit is used to eliminate the system performance degradation due to this low frequency modulation. The measured BER is 10/sup -9/ for a received signal power of -41 dBm and no crosstalk between channels is observed with a channel spacing of 4.0 GHz.<> 相似文献
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《Mechatronics》2007,17(9):524-532
Angular acceleration estimation and its application in acceleration feedback control are investigated experimentally in the paper. In combination of Newton Predictor (NP) with Kalman Filter (KF), a new predictive estimator for angular acceleration, called Newton Predictor Enhanced Kalman Filter (NPEKF) is proposed. This estimator provides a wide bandwidth and a small phase lag of the estimated acceleration while attenuating noises. Based on the estimated acceleration an acceleration feedback control (AFC) is presented for multiple degree-of-freedom (DOF) mechatronic system. The design of AFC is specified in terms of its stability and ability in suppressing dynamic disturbances. Experiments are conducted on a 2-DOF direct-drive manipulator. The frequency responses of the acceleration estimated by NP, KF and NPEKF are compared with those of the measured acceleration via linear accelerometer. The performance of AFC using the estimated acceleration is assessed against that using the measured acceleration. This study has shown that the proposed NPEKF estimator is able to supply the AFC with reliable required acceleration. 相似文献
14.
A cooperative Bayesian and lower bound estimation in dynamic framed slotted ALOHA algorithm for RFID systems
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Mustapha Benssalah Mustapha Djeddou Brahim Dahou Karim Drouiche Abdelmadjid Maali 《International Journal of Communication Systems》2018,31(13)
A novel estimation scheme that combines Bayesian and lower bound estimating radio frequency identification tag population size is proposed. The developed methodology is based on the fusion between the Bayesian and lower bound estimating techniques. It turns out that the fusion rule is built up thanks to an existing linear relationship between the cited techniques. Simulation results show that the developed technique significantly improves the accuracy of the estimating tag quantity and presents less estimation error. Also, the resulting advanced dynamic framed slotted ALOHA protocol considerably improves the performance and efficiency of the radio frequency identification anti‐collision compared with the most recent protocols using others estimating methods. 相似文献
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针对双基地MIMO雷达目标定位问题,该文提出一种基于三阶张量分解的快速多目标定位算法。该算法首先将匹配滤波输出转化为三阶张量,并对其进行降维预处理,然后利用交替最小二乘(ALS)算法估计收发阵列流型矩阵和多普勒矩阵,最后通过谱估计算法恢复目标收发角和多普勒频率。同时利用线性搜索加快ALS算法的收敛速度。与现有算法相比,该算法避免了2维谱峰搜索和协方差矩阵估计,得到的目标三参数自动配对,不仅提高了估计性能,而且有效降低了运算量和存储量。仿真结果证明了所提算法的有效性和优越性。 相似文献
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针对正交频分复用(OFDM)系统中的信道时变,基于时变信道的分段线性近似模型,提出一种改进的OFDM时变信道估计方案。该方案通过采用期望最大化(EM)迭代算法来提高符号平均信道脉冲响应的估计精度,从而提高时变信道估计的性能;此外,在迭代过程中进行带状子载波间干扰抑制,不仅进一步提高了时变信道估计的性能,而且降低了实现复杂度。理论分析和仿真结果表明,该算法以较低的复杂度代价有效提高了时变信道OFDM系统的性能。 相似文献
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In this paper, we consider a new channel sounding scheme for opportunistic scheduling with the use of reduced channel information
in the uplink of orthogonal frequency division multiplexing (OFDM)-based wireless systems. To reduce signaling overhead for
the sounding, we propose a two step channel sounding process considering the correlation characteristic in the time and frequency
domain; called pre-sounding and main-sounding. Signal-to-noise power ratio (SNR) of each subchannel is first estimated through
the pre-sounding process. Then, a main-sounding signal is sent over subchannels having high SNR but not highly correlated
to each other. Since it is possible to extract the whole channel information from partial one by exploiting the channel correlation,
the proposed scheme can significantly reduce the sounding signaling overhead without noticeable performance degradation compared
to the full sounding scheme. Simulation results show that the proposed scheme provides significant performance improvement
over conventional schemes especially when the channel is highly correlated in the time and frequency domain. 相似文献
18.
Deping Huang Wei Li Jin Zhou Ning Li Junyan Ren Jinghong Chen 《Analog Integrated Circuits and Signal Processing》2014,79(2):207-217
The automatic frequency calibration (AFC) technique is routinely used in wideband frequency synthesizers that contain multiple voltage-controlled oscillator (VCO) tuning curves. In this paper, a counter-based AFC that uses a time-to-digital converter (TDC) in the counting process is developed. The TDC is able to capture the fractional VCO cycle information within the counting window. This significantly improves the frequency detection accuracy over the existing counter-based AFC techniques. In addition, a quantitative model is developed to determine the minimally required error-free AFC calibration time for a given VCO tuning curve characteristic. An AFC circuit using the proposed TDC-based counter is designed in a 0.13-μm CMOS technology. Simulation results show that the proposed AFC significantly improves the frequency detection accuracy and consequently for a given frequency detection resolution reduces the AFC calibration time. The simulated error-free AFC time is <2.5 μs with a frequency resolution of 0.04 %. 相似文献
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《Broadcasting, IEEE Transactions on》2009,55(1):84-94