共查询到18条相似文献,搜索用时 109 毫秒
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正交相移键控(QPSK)调制解调方式广泛应用于深空通信、数字卫星通信等高速系统中,高动态QPSK信号具有较大的多普勒载波频偏,针对现有的解调算法对QPSK信号频偏估计范围小、精度较低等问题,提出了一种改进的高动态QPSK信号解调算法。该算法利用基于Zoom-FFT的Quinn频率估计算法对载波频偏进行估计,将频偏估计分为粗估计和精估计两个过程,对估计所得频偏进行补偿后利用Costas环完成载波同步。在MATLAB中对算法进行了仿真,仿真结果表明,该算法能够实现对高动态大频偏QPSK信号的有效捕获,与传统的解调方式相比,该算法对载波频偏的估计范围更大,且具有更高的频偏估计精度和更好的误码性能。 相似文献
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针对通信接收中的载波同步问题,提出一种基于Fitz算法的改进载波频偏估计算法.分析了Fitz算法频偏估计方法中估计范围受限的原因,针对性地提出了改进方法,利用离散傅里叶变换(DFT)算法得到基准频偏,以此修正大间隔自相关函数估计频偏,保持了Fitz算法的估计精度优势,极大地扩展频偏估计范围,同时具有低的信噪比门限.最后给出了改进算法的实现步骤,并通过MATLAB仿真实验证明了算法的有效性. 相似文献
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在多输入多输出-正交频分复用(MIMO-OFDM)系统中载频同步是个关键问题.考虑在该类系统中,存在着多个不同的载波频偏这个具有普遍适应性的模型,为了估计多个不同的频偏,提出了一种导频设计方案-子波段方法,将多个频偏的估计问题转换为一组单个频偏估计问题,从而降低了复杂度,同时可以有效地抑制载波间干扰和天线间干扰,提高载波频偏估计性能. 相似文献
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This paper examines the effect of timing errors on QPSK/FDMA signals regenerated by a SAW-based group demodulator. The presence of a timing offset not only degrades the performance of that channel, but also increases the amount of its interference into other channels. Time windowing of the input to the chirp Fourier transform is shown to reduce the impact of the timing errors, but at the cost of an increased output noise variance. Measurements are presented for the bit-error rate (BER) performance of a single channel with a fixed timing offset using a surface acoustic wave (SAW) group demodulator based on the convolve-multiply-convolve (CMC) configuration with Kaiser-Bessel windowing 相似文献
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The use of π/4 quadrature phase-shift keying(QPSK) modems for satellite sound broadcast systems (SSBS) broadcasting to mobile or portable receivers is proposed. Three different differential detectors (including the FM-discriminator followed by integrate-sample-and-dump filter) and a novel coherent detector are discussed. The degradation caused by the frequency offset between the local oscillator and the unmodulated carrier in the baseband differential detector is studied. The performance of both coherently and differentially detected π/4-QPSK in a Gaussian channel is also studied. It is shown that with a frequency offset of more than 3% of the symbol rate, the performance degradation is more than 1 dB at 10-4. The out-of-band power of the nonlinearly amplified bandlimited π/4-QPSK signals is reduced from -13 dB to -37 dB if a 2-dB output back-off amplifier is used instead of a hardlimiter. The performance of the π/4-QPSK is equivalent to that of QPSK, although the π/4-QPSK has the advantage of less spectrum restoration after nonlinear amplification. The coherent demodulator and differential decoder avoid the three-level detection and achieve the same bit-error-rate (BER) performance as DEQPSK with a simple circuit 相似文献
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Dong Han Yuanjin Zheng 《Circuits and Systems II: Express Briefs, IEEE Transactions on》2009,56(9):719-723
An ultralow-power Gaussian frequency-shift keying (GFSK) demodulator with large tolerance for process variations and wide coverage of data rate for low-intermediate-frequency (low-IF) wireless receivers is presented. A novel multithreshold linear phase quantization technique is proposed to improve the demodulator sensitivity and relax the tradeoff between the selection of the IF and the data rate. A dynamic threshold slicer is employed to efficiently overcome the dc drifts caused by the input frequency offset. The demodulator achieves 490-mV input dc offset cancellation, 800-kHz frequency offset tolerance, and data rate coverage from 100 kb/s to 2 Mb/s. The measured signal-to-noise ratio (SNR) is 16.0 dB for a 0.1% bit error rate (BER) and a 0.25 modulation index. The demodulator has been fabricated in a 0.18-mum complimentary metal-oxide-semiconductor process with only 0.14-mm2 active area and 450-muA current drawn from a 1.8-V power supply. 相似文献
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针对QPSK信号的相干解调器中存在载波捕获错锁的实际工程问题,研究了目前常用的防错锁方法;在此基础上,提出了一种改进的中频信号数字频域处理方法,通过设计合适的等效滤波器,并对数字锁相环载波频率增加限制条件,有效地降低了载波捕获时发生错锁的概率。仿真试验结果和实际工程系统均验证了该防错锁优化方法的可行性。 相似文献
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用TMS320C6x实现2M路QPSK信号全数字化整体解调算法研究 总被引:2,自引:1,他引:1
本文提出并证明了一种群路FDMA/QPSK(SCPS/QPSK)信号全数字化整体解调的新方法,该方法根据信道构成特点和信号调制方式,将直接分路法和常规多相FFT分离法相结合,构成了一种简化的等效多相FFT分路方法,接着将输出的数字信号直接送到数字式解调器,实现了多载波信号的全数字化整体解调,其特点是软件和硬件结构简单、系统计算量小,且易于DSP实时实现,现已用该算法进行了32路FDMA/QPSK信号整体解调的计算机仿真实验,结果表明该方法是可行的;目前已用最新数字信号处理器TMS320C6201硬件板对此方法的关键技术进行了实时仿真. 相似文献
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The design of a blind receiver for coded orthogonal frequency-division multiplexing communication systems in the presence of frequency offset and frequency-selective fading is investigated. The proposed blind receiver iterates between a Bayesian demodulation stage and a maximum a posteriori channel decoding stage. The extrinsic a posteriori probabilities of data symbols are iteratively exchanged between these two stages to achieve successively improved performance. The Bayesian demodulator computes the a posteriori data symbol probabilities, based on the received signals (without knowing or explicitly estimating the frequency offset and the fading channel states), by using Markov chain Monte Carlo (MCMC) techniques. In particular, two MCMC methods-the Metropolis-Hastings algorithm and the Gibbs sampler-are studied for this purpose. Computer simulation results show that the proposed Bayesian blind turbo receiver can achieve good performance and is robust against modeling mismatch 相似文献
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Imperfect carrier synchronization causes a performance loss for coherent phase-shift-keyed (PSK) communications. This detection loss is greater for quaternary signaling (QPSK) than for the binary case (BPSK). The use of an offset form of QPSK, also known as double-biphase modulation, is shown to yield a probability of bit error in detection that is equal to the average of the detection performances for BPSK and conventional QPSK. Because of frequency instabilities in communications systems, it is sometimes difficult to obtain carrier synchronization with sufficiently low jitter to preclude significant detection losses. The use of offset QPSK in lieu of conventional QPSK modulation is shown to lower by almost 3 dB the required SNR of the synchronizer phase reference for satisfying a specified value of allowable detection loss. 相似文献
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一种QPSK解调器(松尾环)的研制 总被引:1,自引:0,他引:1
本文是一种四相调相QPSK解调器(松尾环)的研制报告.该锁相环电路新颖、制作容易、性能优良,尤其适用于载波频率较高的卫星通信、微波通信设备中,是一种新型的QPSK解调器.目前在国外一些卫星设备中已有所应用.文中对松尾环的理论分析到实际电路制作给予了较详细的论述. 相似文献