Optimum 4-Transmit-Antenna STBC/SFBC with Angle Feedback and a Near-Optimum 1-Bit Feedback Scheme

A 4-antenna transmit diversity scheme based on space time/frequency block coding (STBC/SFBC) with 1-bit feedback is proposed. We first describe the optimum scheme with angle feedback. We then identify the condition under which choosing between only two choices of angles effectively eliminates the larger between the real and imaginary parts of the interference term. Simulation shows that the 1-bit feedback scheme achieves near-optimum performance.     

Adaptive feedforward/feedback architectures for multiuser detectionin high data rate wireless CDMA networks

We consider the design and performance of nonlinear minimum mean-square-error multiuser detectors for direct sequence code-division multiple-access (CDMA) networks. With multiple users transmitting asynchronously at high data rates over multipath fading channels, the detectors contend with both multiple-access interference (MAI) and intersymbol interference (ISI). The cyclostationarity of the MAI and ISI is exploited through a feedforward filter (FFF), which processes samples at the output of parallel chip-matched filters, and a feedback filter (FBF), which processes detected symbols. By altering the connectivity of the FFF and FBF, we define four architectures based on fully connected (FC) and nonconnected (NC) filters. Increased connectivity of the FFF gives each user access to more samples of the received signal, while increased connectivity of the FBF provides each user access to previous decisions of other users. We consider three methods for specifying the FFF sampling and propose a nonuniform FFF sampling scheme based on multipath ray tracking that can offer improved performance relative to uniform FFF sampling. For the FC architecture, we capitalize on the sharing of filter contents among users by deriving a multiuser recursive least squares (RLS) algorithm and direct matrix inversion approach, which determine the coefficients more efficiently than single-user algorithms. We estimate the uncoded bit-error rate (BER) of the feedforward/feedback detectors for CDMA systems with varying levels of power control and timing control for multipath channels with quasi-static Rayleigh fading. Simulations of packet-based QPSK transmission validate the theoretical BER analysis and demonstrate that the multiuser RLS adapted detectors train in several hundred symbols and avoid severe error propagation during data transmission mode     

Interference suppression for DS/CDMA

A direct-sequence spread spectrum (DS/SS) receiver for suppressing multiple-access interference in direct-sequence code-division multiple-access (DS/CDMA) communication systems is introduced. The proposed receiver does not require knowledge of other users' spreading codes, timing, or phase information. Moreover, the receiver allows the number of taps to be chosen independently of the processing gain and, hence, is easily applicable to CDMA systems employing either a small or a large processing gain. Performance analysis, including average probability of error and signal-to-noise ratio, is provided, and results are presented for systems varying from lightly loaded (for example, eight user/255 chip) to heavily loaded (for example, 50 user/200 chip). Performance results indicate that the proposed receiver outperforms the linear correlation receiver and, in many cases, it does so by a considerable margin     

Low-pass biquadratic filters with high suppression rate

Low-pass biquadratic filters providing a high attenuation rate in the stopband are presented. This feature achieves better high frequency parameters, even with conventional (e.g. low consumption) active elements. Analysis and improvements of the Sallen-Key filter, as well as a biquadratic filter based on the second generation current conveyor CCII are also presented. The optimisation relies on the parasitic transfer zeros elimination.     

Performance Verification of Successive Interference Cancellation for STBC MIMO-OFDM System with Channel Correlation

Multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) transmission can improve both the transmission capacity and performance due to diversity gain. However, when the antennas are close to each other in a MIMO-OFDM system, the diversity order will be decreased because of channel correlation. In the paper performance of various detection methods for space–time block code (STBC) MIMO-OFDM with channel correlation are evaluated, including the conventional Alamouti full matrix detection, the modified diagonal matrix detection, the least square-zero forcing (LS-ZF) detection, and the successive interference cancellation (SIC). The paper also verify that the SIC detection can still keep excellent detection performance under large channel correlation.

Clustered OFDM with channel estimation for high rate wireless data

Clustered OFDM can provide in-band diversity gain for wideband wireless communication systems. It is a promising technique for high rate packet data access over wideband mobile wireless channels. Due to the smaller size of each cluster for clustered OFDM than for classical (nonclustered) OFDM, edge effects can be very large. In this letter, we present new transforms for channel estimators in clustered OFDM systems. The new transforms are independent of the channel delay profiles and can effectively mitigate the edge effects. It is shown by computer simulation that the performance of clustered OFDM with the estimator using the new transforms is very close to the performance with the optimum estimator that is determined by the individual channel delay profile. Furthermore, clustered OFDM with the new estimator is almost as good as classical OFDM with transmit diversity     

Code-aided interference suppression for DS/CDMA communications. I.Interference suppression capability

A code-aided technique for the simultaneous suppression of narrow-band interference (NBI) and multiple-access interference (MAI) in direct-sequence code-division multiple-access (DS/CDMA) networks is proposed. This technique is based on the linear minimum mean-square error (MMSE) algorithm for multiuser detection. The performance of this technique against MAI has been considered previously. In this paper, its performance against NBI as well as combined NBI and MAI is addressed. Specifically, the performance of this technique against three types of narrow-band interferers, namely, multitone interferers, autoregressive (AR) interferers, and digital interferers, is analyzed. The NBI suppression performance of this method is then compared with performance bounds of the linear and nonlinear estimator-subtracter NBI suppression techniques. It is seen that this method outperforms all of the previous linear or nonlinear methods of NBI suppression, while simultaneously suppressing the MAI     

24位A／D转换称重数据采集系统

研究一种用于组合秤和选别秤的高精度数据采集系统,采用具有24位分辨率的Σ-Δ模数转换器高性能片上系统(SoC)MSC1210和应变式称重传感器设计称重数据采集系统。该系统可应用于组合称重设备、选别设备,并具有精度较高,可靠性较强的特点。     

24位A/D转换称重数据采集系统

研究一种用于组合秤和选别秤的高精度数据采集系统,采用具有24位分辨率的∑-△模数转换器高性能片上系统(SoC)MSC1210和应变式称重传感器设计称重数据采集系统.该系统可应用于组合称重设备、选别设备,并具有精,度较高,可靠性较强的特点.     

Joint equalization and interference suppression for high data ratewireless systems

Enhanced Data Rates for Global Evolution (EDGE) is currently being standardized as an evolution of GSM in Europe and of IS-136 in the United States as an air interface for high speed data services for third generation mobile systems. In this paper, we study space-time processing for EDGE to provide interference suppression. We consider the use of two receive antennas and propose a joint equalization and diversity receiver. This receiver uses feedforward filters on each diversity branch to perform minimum mean-square error cochannel interference suppression, while leaving the intersymbol interference to be mitigated by the subsequent equalizer. The equalizer is a delayed decision feedback sequence estimator, consisting of a reduced-state Viterbi processor and a feedback filter. The equalizer provides soft output to the channel decoder after deinterleaving. We describe a novel weight generation algorithm and present simulation results on the link performance of EDGE with interference suppression. These results show a significant improvement in the signal-to-interference ratio (SIR) performance due to both diversity (against fading) and interference suppression. At a 10% block error rate, the proposed receiver provides a 20 dB improvement in SIR for both the typical urban and hilly terrain profiles     

FM/TV Interference into rate 1/2 FEC encoded SCPC/QPSK

This paper presents some results obtained in laboratory measurements of interference caused by FM television signals to encoded SCPC/QPSK carriers. Certain parameters, such as the TV energy dispersal excursion, the frequency spacing between wanted and interfering carriers, the SCPC bit rate, etc., were varied during the measurements in order to study their influence on the amount of interference suffered by the SCPC channel. Computer simulations were also carried out in order to analyse and interpret measurement results obtained in some cases. Conclusions are drawn on the use of a possible interference criterion when rate 1/2 convolutional encoding and soft decision Viterbi decoding is used in the SCPC system as well as on the expected improvement with frequency offset.     

Information-guided channel-hopping for high data rate wireless communication

In this letter, we introduce information-guided channel-hopping, a new scheme for high data rate communication over Rayleigh fading channel using multiple transmit antennas. This scheme is proposed based on the fact that the independence character of multi-channel can be used as an additional information transmitting channel, and the maximum likelihood decoding can be achieved in a simple way by decoupling of the signals conveyed by different methods. The analysis results prove that the capacity behavior of this scheme is better than that of the space-time block coding for more than two transmit antennas.     

A monolithic 8-bit A/D converter with 120 MHz conversion rate

A monolithic 8-bit flash A/D converter is described which digitizes a 40-MHz signal at a conversion rate of over 100 MHz. To obtain full resolution and high accuracy at ultrahigh speed operation, a three-stage comparator with small talk back and other new logic circuits were designed. The process used is a self-aligned bipolar technology. Signal-to-noise ratio of 45 dB was measured at the 30-MHz input frequency.     

Robust Optimal Cross-Layer Designs for TDD-OFDMA Systems with Imperfect CSIT and Unknown Interference: State-Space Approach Based on 1-bit ACK/NAK Feedbacks

Cross-layer designs for OFDMA systems have been shown to offer significant gains of spectral efficiency by exploiting the multiuser diversity over the temporal and frequency domains. In this paper, we shall propose a robust optimal cross-layer design for downlink TDD-OFDMA systems with imperfect channel state information at the base station (CSIT) and unknown interference in slow fading channels. Exploiting the ACK/NAK (1-bit) feedbacks from the mobiles, the proposed cross-layer design does not require knowledge of the CSIT error statistics or interference statistics. To take into account of the potential packet error due to the imperfect CSIT and unknown interference, we define average system goodput (which measures the average b/s/Hz successfully delivered to the mobile) as our optimization objective. We formulate the cross-layer design as a state-space control problem. The optimal power, optimal rate and optimal user allocations are determined as the output equations from the system states based on dynamic programming approach. Simulation results illustrate that the performance of the proposed closed-loop cross-layer design is very robust with respect to imperfect CSIT, unknown interference, model mismatch as well as channel variations due to Doppler.     

A 0.35-/spl mu/m CMOS analog turbo decoder for the 40-bit rate 1/3 UMTS channel code

This work presents the design and the test results of an analog decoder for the 40-bit block length, rate 1/3, Turbo Code defined in the UMTS standard. The prototype is fully integrated in a three-metal double-poly 0.35-/spl mu/m CMOS technology, and includes an I/O interface that maximizes the decoder throughput. After the successful implementation of proof-of-concept analog iterative decoders by different research groups in both bipolar and CMOS technologies, this is the first reported prototype of an analog decoder for a realistic error-correcting code. The decoder was successfully tested at the maximum data rate defined in the standard (2 Mb/s), with an overall power consumption of 10.3 mW at 3.3 V, going down to 7.6 mW with the decoder core operated at 2 V, and an extremely low energy per decoded bit and trellis state (0.85 nJ for the decoder core alone).     

一种遥感卫星高码速VCM数传信道的均衡技术

在基于第二代数字卫星视频广播协议（DVB-S2）标准的遥感卫星可变编码调制（VCM）高码速数传信道中,宽带信号的大失真、大频偏和低信噪比会导致解调器载波环路不锁定。传统的DVB-S2解调器并不能解决这个问题。在载波环路前增加一个均衡器补偿失真,可以让载波环路稳定锁定。为了克服载波环路前信号的频偏和相偏对均衡器的影响,提出了一种均衡技术,利用起始序列（SOF）和导频的先验信息进行双重自相关变换,设计了一种新的误差函数和迭代过程。仿真结果表明,该均衡技术可在该应用条件下支持解调稳定工作。     

Efficient 6-bit A/D converter using a 1-bit folding front end

An efficient analog-to-digital (A/D) converter architecture that uses a 1-bit folding front end is described. The folder is realized using a zero-crossing detector and transmission gates. The problem arising from the nonideality of the folding operation is handled in a special way. The use of a single folder in front rather than the conventional approach of using multiple folders results in a significantly smaller input capacitance. The architecture has been used for realizing a 7S-Msamples/s, 6-bit A/D converter for local-area-network application. The prototype has been implemented in a 0.5-μm single-poly, triple-metal digital CMOS technology. It occupies an area of 1 mm² and has a power consumption of 110 mW from a 3.3-V supply     

A floating-gate comparator with automatic offset adaptation for 10-bit data conversion

We present a novel voltage comparator that uses nonvolatile floating-gate charge storage for either offset ing or automatic programming of a desired offset. We exploit the negative feedback mechanism of pFET hot-electron injection to achieve fully automatic offset cancellation. The adaptation guarantees an input offset less than the input-referred noise level regardless of initial device offset for a typical 8.3% observed injection mismatch. In addition, we demonstrate the ability to accurately program a desired offset. The design has been fabricated in a commercially available 0.35-/spl mu/m process. Experimental results confirm the ability to reduce the variance of the initial offset by two orders of magnitude and to accurately program a desired offset with maximum observed deviation 728 /spl mu/V and typical deviation 109 /spl mu/V. The mean offset is reduced by a factor of 416 relative to fabricated chips directly from the foundry and by a factor of 202 relative to UV-irradiated chips. Adaptation is fast, with settling time typically under 50 ms and scaling inversely with the exponential of the injection voltage. We achieve controlled injection to accurately program the input offset to voltages uniformly distributed from -1 to 1 V. The comparator exhibits a 5 ns propagation delay and consumes 270 /spl mu/W.     

高重复率卫星激光测距中后向散射干扰及规避

大气后向散射对高重复率卫星激光测距（Satellite Laser Ranging,SLR）的回波接收产生干扰且随测量频率增加愈发严重,已成为制约SLR工作频率提升的关键因素之一。根据大气散射雷达探测方程,分析了探测系统接收到的大气后向散射光功率及对回波接收的影响,以上海天文台现有收发分离的SLR系统为平台,通过试验验证了分析的合理性;据此厘清后向散射干扰产生时序,给出基于激光发射时序控制的后向散射规避方法。通过在高重复率距离门控电路中添加激光点火信号产生模块,并实时判断后向散射干扰情况以控制点火信号是否延迟输出,基于FPGA（Field Programmable Gate Array）完成了后向散射自动规避电路,成功应用在上海天文台高重复率SLR的常规观测中,实现了对散射的完全规避,且对Lageos等重点激光卫星的平均点火频率下降率低于2%,具有很好的推广应用价值。