Design and simulation of digital channelized receivers in fractional Fourier domain

An approach is proposed to realize a digital channelized receiver in the fractional Fourier domain （FRFD） for signal intercept applications. The presented architecture can be considered as a generalization of that in the traditional Fourier domain. Since the linear frequency modulation （LFM） signal has a good energy concentration in the FRFD, by choosing an appropriate fractional Fourier transform （FRFT） order, the presented architecture can concentrate the broadband LFM signal into only one sub-channel and that will prevent it from crossing several sub-channels. Thus the performance of the signal detection and parameter estimation after the sub-channel output will be improved significantly. The computational complexity is reduced enormously due to the implementation of the polyphase filter bank decomposition, thus the proposed architecture can be realized as efficiently as in the Fourier domain. The related simulation results are presented to verify the validity of the theories and methods involved in this paper.

Design and Implementation of Partial Shared Digital Channelized Receiver

A novel efficient partial sharing channelization structure with odd and even stacking is designed and implemented. There are two special designs in the proposed structure. Firstly, by the intensive channel overlap design, for non-cooperative wideband signals, the proposed structure can achieve good parameter estimation accuracy and high probability of complete interception.Secondly, based on the partial sharing design developed in this paper, the computation burden of the proposed structure can be greatly reduced compared with the traditional directly implemented structures. Experiments and numerical simulations are conducted to evaluate the proposed structure, which shows its improvements over traditional methods in terms of field programmable gate arrays(FPGA) resource consumption and parameter estimation accuracy.

Constrained least squares algorithm for channel vector estimation in 2-D RAKE receiver

Based on the fact that the variation of tile direction of arrival (DOA) isslower than that of the channel fading, the steering vector of the desired signal is estimatedfirstly using a subspace decomposition method and then a constrained condition is configured.Traffic signals are further employed to estimate the channel vector based on the constrained leastsquares criterion. We use the iterative least squares with projection (ILSP) algorithm initializedby the pilot to get the estimation. The accuracy of channel estimation and symbol detection can beprogressively increased through the iteration procedure of the ILSP algorithm. Simulation resultsdemonstrate that the proposed algorithm improves the system performance effectively compared withthe conventional 2-D RAKE receiver.

A Fully Integrated 60GHz Four Channel CMOS Receiver with 7GHz Ultra-Wide Bandwidth for IEEE 802.11ad Standard

In this paper, a fully integrated CMOS receiver frontend for high-speed short range wireless applications centering at 60GHz millimeter wave （mmW） band is designed and implemented in 90nm CMOS technology. The 60GHz receiver is designed based on the super-heterodyne architecture consisting of a low noise amplifier （LNA） with inter-stage peaking technique, a single- balanced RF mixer, an IF amplifier, and a double-balanced I/Q down-conversion IF mixer. The proposed 60GHz receiver frontend derives from the sliding-IF structure and is designed with 7GHz ultra-wide bandwidth around 60GHz, supporting four 2.16GHz receiving channels from IEEE 802.1lad standard for next generation high speed Wi- Fi applications. Measured results show that the entire receiver achieves a peak gain of 12dB and an input 1-dB compression point of -14.SdBm, with a noise figure of lower than 7dB, while consumes a total DC current of only 60mA from a 1.2V voltage supply.

Channel aware receiver for next generation wireless communication system

We consider an iterative phase synchronization scheme based on maximum a posteriori probability algorithm.In classical approaches,the phase noise estimation model considers one sample per symbol at the channel and receiver.However,information theoretic studies suggested use of more than one sample per symbol at the channel and receiver for achieving higher performance.In this article,a soft-information aided iterative receiver is derived,which uses off-the-shelf blocks for detection and demodulation by keeping the complexity of the receiver acceptable.We consider here two samples per symbols at the channel and receiver in a pragmatic paradigm.It is shown that phase noise estimation can be significantly improved at the expense of modest processing overhead.Simulation results are presented for low-density parity check coded quadrature amplitude modulations.Our results show a significant performance improvement for strong phase noise values compared to classical receiver approaches.

Dual Channel SIS Receiver of Trao Telescope

We have developed the dual channel receiver with 100GHz and 150GHz band, which is used to make the simultaneous observation with two bands. The SIS mixers are used in both bands. The constructed dewar for receiver has the performance with the vacuum of 10 -8 Torr and the temperature of 4 2K. The receiver noise temperature is 50K (DSB) for 100GHz band and 80K (DSB) for 150GHz band ,respectively. In order to achieve the simultaneous observations, the quasioptical system is precisely designed, and also evaluated by the measurement in the laboratory. We have observed the various sources using this receiver since October 1998. The relative pointing offset between two bands is 3″.

A Receiver Structure for Frequency-Flat Time-Varying Rayleigh Channels and Performance Analysis

This paper proposes a wavelet based receiver structure for frequency-flat time-varying Rayleigh channels, consisting of a receiver front-end followed by a Maximum A-Posteriori (MAP) detector. Discretization of the received continuous time signal using filter banks is an essential stage in the front-end part, where the Fast Haar Transform (FHT) is used to reduce complexity. Analysis of our receiver over slow-fading channels shows that it is optimal for certain modulation schemes. By comparison with literature, it is shown that over such channels our receiver can achieve optimal performance for Time-Orthogonal modulation. Computed and Monte-Carlo simulated performance results over fast time-varying Rayleigh fading channels show that with Minimum Shift Keying (MSK), our receiver using four basis functions (filters) lowers the error floor by more than one order of magnitude with respect to other techniques of comparable complexity. Orthogonal Frequency Shift Keying (FSK) can achieve the same performance as Time-Orthogonal modulation for the slow-fading case, but suffers some degradation over fast-fading channels where it exhibits an error floor. Compared to MSK, however, Orthogonal FSK provides better performance.

ITERATIVE RECEIVER FOR OFDM SYSTEMS BASED ON SEMI-BLIND CHANNEL ESTIMATION

In this paper we propose two iterative algorithms of joint channel estimation and symbol detection for Orthogonal Frequency Division Multiplexing (OFDM) systems. In which, superimposed pilot scheme is adopted and an initial Channel State Information (CSI) is obtained by employing a first-order statistic. In each subsequent iteration, we propose two algorithms to update the CSI. The Mean Square Error (MSE) of channel estimation and Bit Error Rate (BER) performance are given and simulation results demonstrate that the iterative algorithm using method B has good perform-ance approaching the ideal condition.

Iterative receivers for SFBC-OFDM systems with adaptive training scheme

This paper considers the design of iterative receivers for space-frequencyblock-coded orthogonal frequency division multiplexing (SFBC-OFDM) systems in unknown wirelessdispersive fading channels. An iterative joint channel estimation and symbol detection algorithm isderived. In the algorithm, the channel estimator performs alternately in two modes. During thetraining mode, the channel state information (CSI) is obtained by a discrete-Fourier-transform-basedchannel estimator and the noise variance and covariance matrix of the channel response is estimatedby the proposed method. In the data transmission mode, the CSI and transmitted data is obtainediteratively. In order to suppress the error propagation caused by a random error in identifyingsymbols, a simple error propagation detection criterion is proposed and an adaptive training schemeis applied to suppress the error propagation. Both theoretical analysis and simulation results showthat this algorithm gives better bit-error-rate performance and saves the overhead of OFDM systems.

A HIGH SENSITIVITY AND WIDE DYNAMIC RANGE ZERO-IF RF RECEIVER FOR COGNITIVE RADIO APPLICATION

This paper presents an RF receiver of zero-Intermediate Frequency(IF) architecture for Cognitive Radio(CR) communication systems.Zero-IF architecture reduce the image reject filter and IF filter,so it is excellent in low cost,compact volume,and low power dissipation.The receiver employs three digital attenuator and a high gain,high linearity low noise amplifier to achieve wide dynamic range of 70 dB and high receiving sensitivity of-81 dBm.A fully balanced I/Q demodulator and a differential Local Oscillator(LO) chips are used to minimize the negative effects caused by second-order distortion and LO leakage.In order to select an 8 MHz-channel from 14 continuous ones located in UHF band(694-806 MHz) accurately,approach of channel selectivity circuits is proposed.The RF receiver has been designed,fabricated,and test.The measured result shows that the noise figure is 3.4 dB,and the error vector magnitude is 7.5% when the input power is-81 dBm.

Co-channel interference rejection for MIMO-OFDM systems

A method based on the maximum a posteriori probability （MAP） criterion is proposed to estimate the channel frequency response （CFR） matrix and interference- plus-noise spatial covariance matrix （SCM） for multiple input and multiple output orthogonal frequency division multiplexing （MIMO-OFDM） systems. An iterative solution is proposed to solve the MAP-based problem and an interference rejection combining （IRC） receiver is derived to suppress co-channel interference （CCI） based on the estimated CFR and SCM. Furthermore, considering the property of SCM, i. e., Hermitian and semi-definite, two schemes are proposed to improve the accuracy of SCM estimation. The first scheme is proposed to parameterize the SCM via a sum of a series of matrices in the time domain. The second scheme measures the SCM on each subcarrier as a low-rank model while the model order can be chosen through the penalized-likelihood approach. Simulation results are provided to demonstrate the effectiveness of the proposed method.

UWB System Based on the Modified Gegenbauer Function in MISO Channel

In this paper, we propose a new multi-user Rake receiver, based on the interference mutualization with a matrix representation for Multiple Input Single Output MISO channel. The proposed system used the Modified Gegenbauer functions in order to generate the signal and to ensure the multi users transmission system. The new proposed receiver allows, using the temporal and special diversity, to avoid the interferences between symbols and to improve the system performances in terms of Bit Error Rate BER and interferences between users with a low algorithm complexity. The proposed solution is based on the classical Rake receiver associated with the equalizer receiver. In order to adapt the Rake approach, in single detection case and in multi users Ultra Wide Band environment, we propose a multi-user Rake receiver using the matrix form. Our proposed system is evaluated in terms of channel effects and multi users’ interferences.

Performance of terahertz channel with multiple input multiple output techniques

Terahertz(THz) communication is being considered as a potential solution to mitigate the demand for high bandwidth. The characteristic of THz band is relatively different from present wireless channel and imposes technical challenges in the design and development of communication systems. Due to the high path loss in THz band,wireless THz communication can be used for relatively short distances. Even,for a distance of few meters( > 5 m),the absorption coefficient is very high and hence the performance of the system is poor. The use of multiple antennas for wireless communication systems has gained overwhelming interest during the last two decades.Multiple Input Multiple Output( MIMO) Spatial diversity technique has been exploited in this paper to improve the performance in terahertz band. The results show that the Bit Error Rate( BER) is considerably improved for short distance( < 5 m) with MIMO. However,as the distance increases,the improvement in the error performance is not significant even with increase in the order of diversity. This is because,as distance increases,in some frequency bands the signal gets absorbed by water vapor and results in poor transmission. Adaptive modulation scheme is implemented to avoid these error prone frequencies. Adaptive modulation with receiver diversity is proposed in this work and has improved the BER performance of the channel for distance greater than 5 m.

ROBUST OPTIMIZATION OF TRANSMIT/RECEIVE BEAMFORMER FOR MIMO DOWNLINK WITH IMPERFECT CSI AT BASE STATION

A robust scheme is proposed to jointly optimize transmit/receive beamformers for Mul-tiple Input Multiple Output(MIMO) downlinks where the available Channel State Information(CSI) at Base Station(BS)(CSIBS) is imperfect.The criterion is to minimize the sum Mean Square Error(sum-MSE) over all users under a constraint on the total transmit power,which is a non-convex and non-linear problem.Observing from the first order optimization condition that the optimal trans-mit/receive beamformers are mutually dependent,the transmit/receive beamformers for each user are updated iteratively until the sum-MSE is minimized.Simulation results indicate that the proposed scheme can effectively mitigate the system performance loss induced by imperfect CSIBS.

基于特征值的动态数字信道化子带检测算法

动态数字信道化接收结构通过检测所有子带,判断信号是否存在,为综合滤波器组处理提供依据,因此子带检测在接收结构中起着关键作用。针对传统检测算法存在低信噪比(signal-to-noise ratio,SNR)下检测性能不高的问题,依据随机矩阵理论,提出了基于最大最小特征值之差与平均特征值之比的检测算法,利用平均特征值和最小特征值的极限分布规律来推导算法的检测门限。其次,根据所有子带数据获取的特征值信息对所提算法进行了优化。最后,在动态数字信道化接收结构中,分析不同因素下算法的性能,表明了所提算法能够克服低SNR的影响,子带检测的性能更好。

缓蚀剂对雷达T/R组件腐蚀行为的影响

T/R组件作为雷达系统的重要组成部分,在严酷海洋大气环境的侵蚀作用下,容易发生腐蚀,从而导致雷达系统性能下降,甚至引发故障。基于实测的某型机雷达舱环境数据,编制加速腐蚀试验环境谱,针对喷涂和未喷涂TFHS-20缓蚀剂的T/R组件开展当量加速腐蚀对比试验,并以收发通道芯片的微观腐蚀形貌、铝合金外壳蚀坑深度、T/R组件收发性能和输出功率等为指标参数,表征缓蚀剂对T/R组件腐蚀行为的影响。结果表明,TFHS-20缓蚀剂仅使T/R组件的输出功率降低0.59%~0.78%、接收增益降低0.11 dB~0.21 dB,缓蚀剂对T/R组件收发性能影响非常小。未喷涂缓蚀剂的T/R组件,在加速腐蚀试验的第4周期时,发射通道性能和接收通道功能失效;喷涂缓蚀剂的T/R组件,在加速腐蚀试验的8个周期时,接收通道功能失效。所以,TFHS-20缓蚀剂能够有效地提高T/R组件的使用寿命。

双线偏振雷达机外定标信号源故障研究

文章对双偏振天气雷达定标链路进行了简要阐述,分析了标定信号源故障对雷达回波、动态范围及噪声温度产生的影响,提出了一种通过断离定标信号源输入法快速诊断故障的方法,列举了一例典型的双偏振多普勒天气雷达标定信号源故障个例并进行分析,给出了标定信号源被感应雷击损害的处理方法,同时也给出了灾害性天气过程中信号源故障的快速修复方法,为其他台站处理相似故障提供思路和借鉴。

基于信噪比和噪声功率密度测量的射频接收通道状态检测方法

针对传统射频接收通道中靠近天线射频前端的故障检测代价大,检测颗粒度受限等问题,提出了一种基于噪声功率密度测量的射频接收通道状态检测方法。利用噪声系数与增益的级联迭代关联特性,实现对射频接收通道中各单元故障的准确定位。对技术原理进行了理论推导,并构建测试系统验证了方法的可行性与有效性。与传统方法相比,该方法可减少自检电路设计复杂度,减少链路上各个单元自检成本,并可消除自检盲区,实现对故障单元的准确定位。

基于深度学习的高效矿井MIMO信号检测研究

针对智能接收机检测效率低的问题,提出了一种基于深度学习的高效矿井MIMO信号检测模型,该模型由非线性映射网络以及纠错网络共同组成。非线性映射网络实现接收信号到二进制比特信号的初步恢复,纠错网络用于纠正非线性映射网络恢复的错误信号,提升信号检测精度。通过搭建矿井MIMO通信系统对该模型的性能进行了验证,仿真结果表明,在模拟矿井MIMO通信环境中,在发射端调制方式,信道编码方式改变以及信道环境变化时其性能优于传统接收机。同时,相对于深度接收机模型,该模型具有更高的检测效率。这项研究为解决智能接收机译码效率低的问题提出了一个新的解决方案,并在复杂的矿井场景中证明了该模型的性能优势。