共查询到19条相似文献,搜索用时 125 毫秒
1.
位同步检测是实现全数字接收机开环定时恢复的关键技术。本文推导了基带PAM(脉冲幅度调制)信号的互相关函数,指出基带PAM信号的互相关函数中含有位同步信息,以此为依据得到了一种位同步检测算法。该算法可采用递归结构实现,且与载波相位误差无关。 相似文献
2.
该文提出了一种基于多途信道单通道接收的带通数据(波束或传感器输出)自相关函数的盲解卷积算法。该算法先通过复解调将带通信号频谱搬移到0频率附近,然后进行低通滤波和降采样率,得到其复基带信号。再针对单通道复基带信号,以其自相关函数在零延时之外某区间内的实部平方和最小为准则,推导出复基带多途信号盲解卷积的LMS自适应迭代算法。该方法能够适用于带通高斯信号和非高斯信号,与基于高阶统计量的方法相比,对源信号概率分布具有较宽的适用面,计算机仿真结果验证了该方法的正确性。 相似文献
3.
4.
5.
提出一种应用人工神经网络根据多路光学相关器相关面输出图像识别目标的方法.运用统计规律确定相关峰的位置,不但把自相关峰作为目标特征,还将互相关峰也引入了识别,并通过神经网络实现相关峰复杂特征的抽取.该方法能有效地排除目标背景干扰和器件性能波动的影响,实现了对目标的实时识别 相似文献
6.
为提高现有通信系统中高斯最小频移键控(GMSK)信号的接收性能,提出了一种基于后解码的GMSK相干解调方法.对于接收到的GMSK基带信号,首先完成相位和载波的同步,将信号的初始相位补偿到零相位;然后通过交替抽取GMSK基带信号的虚部与实部幅度采样值完成信息提取;最后通过后续解码处理完成信号解调.仿真表明,在误码率为10-3时,基于后解码的GMSK解调性能仅比预编码GMSK相干解调差0.5 dB,与传统基于维特比迭代处理的GMSK相干解调性能基本相当,但算法实现更为简化,有利于在现有非相干解调GMSK通信系统中的性能提升实现. 相似文献
7.
在GMSK信号线性近似的基础上,提出一种GMSK混合信号时延的并行估计算法.利用过采样混合信号的自相关函数建立平坦衰落条件下GMSK混合信号时延参数的并行估计方程组,并推导了并行时延估计的克拉美劳界.针对估计方程组中GMSK成型滤波器的复杂非线性特性,采用多项式拟合方法进行简化并利用收敛速度较快的梯度下降法进行数值求解.仿真结果表明该算法对GMSK混合信号时延参数的估计较准确,其估计误差方差与时延估计性能的克拉美劳界较为接近.该时延并行估计算法具有不需要前导字、计算量较小的优点,为混合信号的进一步盲处理打下基础,具有实际意义. 相似文献
8.
时差估计精度与信号在频域上的分布情况以及信号能量和噪声有关。多载波信号的频率信息和能量在频域上分布区间大,通过多载波信号的相参积累,可以有效利用信号在整个区间内的频域信息和能量来提高时差参数的估计精度,克服单载波信号带宽窄能量低导致的时差估计精度不高的问题.本文针对多载波基带信号的时差估计问题,在单载波基带信号互相关函数分析的基础上,推导了多载波基带信号互相关函数,并分析了其相位关系,通过相位补偿实现了多载波基带信号互相关函数的相参积累,并理论分析了多载波信号时差参数估计性能与信号各参数的关系。蒙特卡洛仿真表明,提出的多载波基带信号相参时差估计算法性能明显优于单载波信号的估计性能,性能改善情况与理论分析一致。 相似文献
9.
10.
为了克服二元联合变换相关器的取阈和实时性问题,采用微分运算与二元联合变换相关器结合的方法.联合功率谱中,由于干扰项随频率的变化率比需要的信息量随频率的变化率慢得多,因此可以采用微分方式削弱干扰项,增强互相关信号,对微分后的功率谱再进行二值化非线性处理得到优化功率谱,然后对优化功率谱进行傅里叶逆变换,得到目标和图像的相关输出.模拟实验结果表明,所提出的相关器能很好地抑制自相关峰,增强互相关峰,具有更强的鲁棒性.而且该方法在处理过程中,不需选择阈值,简单的微分及二值化操作使之具有更强的实时性. 相似文献
11.
A single-chip baseband waveform generator CMOS-LSI has been fabricated for use in the quadrature-type GMSK modulator, which is suitable for application to digital mobile communications. The LSI employs digital signal processing in realising such functions as Gaussian baseband filtering and phase integration. Digital/analogue convertors and auxiliary circuits, such as an internal-clock generator and carrier frequency adjuster, are also integrated onto the same chip. The LSI operates well below a bit rate of 110 Kbit/s when the power supply voltage is 5 V. 相似文献
12.
13.
GMSK is the world's most widely used modulation technique for mobile digital telephony and digital wireless applications. We describe two GMSK modulator structures, the voltage controlled oscillator (VCO) and the quadrature modulator structure. The tremendous advantages of the quadrature modulator structure for practical GMSK modulator implementations are emphasized. We present the results of computer simulations and hardware experimental measurements performed on GSM-standardized IC chips which are used by several million subscribers in order to illustrate the operation of a GMSK modulator. Since quadrature modulator structures are used in nearly all practical GMSK chipsets, the properties of this structure are of wide interest. In this paper we highlight the crosscorrelation properties of the GMSK in-phase and quadrature-phase baseband signals, which are part of the quadrature modulator structure. While uncorrelated in-phase and quadrature-phase baseband signals are used in traditional QPSK and OQPSK modulated systems, we demonstrate that there is strong crosscorrelation between the in-phase and quadrature-phase baseband signals. The crosscorrelation is stronger if the observation interval is shorter. Nonobvious quadrature modulator/radio crosscorrelation advantages were patented by Kato/Feher (1986). Design with crosscorrelated quadrature transmitter is “contrary to the wisdom of classical linear communications theory”. Crosscorrelated quadrature modulated systems include FQPSK-KF and GMSK 相似文献
14.
15.
M. J. Kesoulis C. S. Koukourlis J. N. Lygouras D. Soudris J. N. Sahalos 《International Journal of Communication Systems》2009,22(8):971-987
The design and hardware implementation of a multi‐carrier Gaussian minimum shift keying (GMSK) modulator, based on a direct digital synthesizer, suitable for global system for mobile (GSM) base station applications is described. The synthesizer does not only generate the baseband GMSK signal, but also delivers it at a low IF. Special care has been taken in order to minimize the required memory of the synthesizer. The hardware implementation is mainly based on a field programmable gate array device (FPGA) and a D/A converter. The number of carriers depends on the size of the FPGA. Finally, the hardware implementation of a two‐carrier modulator is given. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
16.
17.
Zhi Ding Ge Li 《Selected Areas in Communications, IEEE Journal on》1998,16(8):1493-1505
This paper focuses on the study of blind equalization global system for mobile communications (GSM) systems using a single antenna. In order to utilize the well-known linear system model in conventional studies of blind equalization, an equivalent baseband quadrature amplitude modulation (QAM) approximation is used for the nonlinear GMSK signal in GSM systems. Since the GMSK signal in GSM has very little excess bandwidth to warrant oversampling, a derotation scheme is developed to create two subchannels for each received GMSK signal sampled at the baud rate. Linear approximation of the GMSK signal makes the traditional QAM blind equalization system model applicable for GSM. Derotation induces channel diversity without an additional antenna and reduces the number of necessary radio frequency (RF) receivers (sensors) without increasing hardware or computational costs. Several second-order statistical and higher order statistical methods of blind equalization are adopted for GSM signals 相似文献
18.
目前接收机基于环路的多径抑制主要采用窄相关和HRC技术,而在实际应用中HRC技术对不同调制方式的现代导航信号采取的相关间隔也不同。针对上述问题,通过对几种现代导航信号的鉴相范围和多径抑制性能进行分析,给出在现代导航信号中HRC鉴别器算法相关间隔的优化设计方法。仿真可见:不同现代导航信号下HRC相关间隔的优化选取也不同;带宽较宽时,鉴相范围随相关间隔增大而增大,多径抑制性能随相关间隔减小而提高;带宽较窄和相关间隔较小时,在一定鉴相范围内减小相关间隔并不会再提高现代导航信号的多径抑制性能。提出的相关间隔的优化方法具有创新性,研究成果具有重要理论价值并已应用到GNSS接收机中。 相似文献
19.
《IEEE transactions on information theory / Professional Technical Group on Information Theory》1979,25(2):170-178
A method for evaluating the average error probability in digital fiber optic transmission systems is described. It takes into account the statistical properties of the main impairments that affect the information signal, i.e., shot noise (dark current included), thermal noise, and intersymbol interference. Unlike other methods, the analysis of shot-noise statistics does not entail the second-moment characterization alone, but uses a number of moments sufficient to evaluate the error probability with a high degree of accuracy. For this purpose it is shown how the cumulants of shot noise and intersymbol interference of any order can be computed. The baseband pulse response and the statistical distribution of the avalanche-photodetector gain are assumed to be available. Moreover, techniques for exploiting the cumulants are given; knowledge of the cumulants allows one to compute the probability of error by means of Gaussian numerical integration rules. Finally, some results and comparisons are reported. 相似文献