高约束度卷积码的一种译码方法及其性能

本文提出了高约束度卷积码的一种新的译码方法──状态扩展（ＳＳＤ）方法。该方法先将译码状态扩展一倍，再用最大似然维特比译码原理进行译码，目的是通过增加储存量来减少运算量。ＳＳＤ方法度量值迭代简单，判决输出方便。文中以约束度分别为Ｋ＝７和Ｋ＝９的两种卷积码为例，讨论ＳＳＤ译码方法、性能及用ＤＳＰ器件的实现问题，并得出了几个结论。     

数字信号处理器的算法与结构特点

随着大规模集成电路和计算机技术的飞速发展，数字信号处理器（ＤＳＰ）技术已经渗透到各种领域，包括计算机语音学、计算机视觉、计算机多媒体技术、超文本数据传输等领域。从事ＤＳＰ研究和设计的工程师在工作中面临的主要问题就是如何选用ＤＳＰ芯片，这既需要对具体产品规格有清楚的了解，又需要对各种ＤＳＰ芯片的性能和特长有比较全面的了解。在很多情况下，ＤＳＰ的特性主要由其ＭＩＰＳ速度来描述，但由于一种ＤＳＰ器件的指令并不一定等同于弓一种ＤＳＰ器件，因此仅考虑ＭＩＰＳ常常会导致不正确的结论。与ＤＳＰ器件能力有关的其…     

基于自适应滤波的DPSK解调方法及性能

本文研究了一种基于自适应滤波（ＡＤＦ）算法的解调差分相移键控（ＤＰＳＫ）信号的方法,用常用的最小均方误差（ＬＭＳ）自适应算法,研究了自适应解调（ＡＤＥＭ）方法对ＤＰＳＫ信号的解调及其性能,计算机模拟结果表明,自适应ＤＰＳＫ解调比传统的ＤＰＳＫ相干解调性能优越,便于用数字信号处理技术实现。     

数字信号处理器件发展概况

本文对数字信号处理器件在国内市场上的发展状况进行了介绍，对国内两大主流数字信号处理器件的主要器件的主要结构特点和应用领域进行了分析和比较，对最新信号处理器件的发展动态进行了说明，为ＤＳＰ器件的初不者了解ＤＳＰ概况提供捷径，为选用ＤＳＰ器件进行设计的研究人员提供了一定的理论指导。     

SSPD器件及其应用

以ＣＬ１２８Ｅ型ＳＳＰＤ线列阵为例，介绍了ＳＳＰＤ器件的工作原理，主要特性及其应用。     

19.2kbit／s CDPD调制解调器

提出了一种基于蜂窝数字分组数据（ＣＤＰＤ）系统的无线分组ｍｏｄｅｍ即ＣＤＰＤｍｏｄｅｍ的软硬件实现方案。采用高速数字信号处理器芯片,在系统可编程器件,ＧＭＳＫｍｏｄｅｍ芯片、９００ＭＨｚ射频模块及其他相关器件,实现了ＣＤＰＤｍｏｄｅｍ中子网相关会聚协议,移动数据链路协议,媒质接入控制协议和物理层协议,提供了实验样机的测试结果,并对结果进行了分析。     

KDP反常声光衍射几何关系的研究

讨论了ＫＤＰ晶体在三个主轴坐标平面内的反常声光衍射几何关系，计算了中心频率在２００ＭＨｚ以下ＫＤＰ声光器件的各设计参数以及性能参数。     

扩频芯片Z2000中的编码与解码

介绍了扩频收发芯片Ｚ２０００中的差分编码和ＤＢＰＳＫ，ＤＱＰＳＫ的解码原理。     

适合于本体微机械加工的改进的MOSIC工艺

介绍标准ＩＣ工艺与使用ＫＯＨ或ＥＤＰ（乙二胺－焦儿苯酚混合物）进行本体微机械加工的集成方法。钼被用作最终金属化材料是因为它具有耐ＫＯＨ或ＥＤＰ腐蚀的本领。采用真空退火为的是增强钼对氮化物层的粘附性，这对ＫＯＨ腐蚀是非常重要的。实验表明这些特殊工艺步骤对ＭＯＳ器件特性毫无影响     

一种基于PC机的多DSP系统设计

文章给出一种用三片ＴＭＳ３２０Ｃ５０构成，基于ＰＣ机的多ＤＳＰ系统，该系统既能适应并行信号处理，又能适应流水信号处理。介绍了数据采集电路，ＤＳＰ器件间的数据通信设计，以及ＤＳＰ器件与ＰＣ机的接口电路，最后给出两种具体应用实例。     

A differential-delay SAW correlator for combined DSSS despreadingand DPSK demodulation

The design of a novel SAW (surface-acoustic-wave) component for the noncoherent detection of DS/SS (direct-sequence spread-spectrum) signals with a DPSK (differential phase-shift keying) modulation format is presented. In the considered differential-delay correlator, both the correlation function for despreading and the delay function for DPSK demodulation are merged into a single device. Due to the absence of a separate delay line, no bandwidth-limiting effects no high insertion losses occur in the delay branch of the DPSK demodulator. In addition, an exact match between the correlator output and its one-symbol-delayed replica is obtained. Experiments on an ST-quartz differential-delay correlator with a center frequency of 98.5 MHz, a chip rate of 12.3 MHz and a symbol rate of 195.4 kb/s demonstrated the operation of the device     

Analysis and design of a DPSK optical heterodyne receiver in the presence of laser phase noise and frequency detuning

This paper is concerned with the analysis and design of an improved differential heterodyne optical receiver for differentially-encoded binary PSK (briefly, DPSK) signals in a coherent lightwave communication system. In the first part of the paper, we discuss the relevant design criteria to be employed when dealing with asynchronous heterodyne receivers for ASK, FSK or DPSK optical signals. In particular, we introduce a convenient definition of the signal-to-noise ratio at the data detector input to be assumed as the system performance measure when the non-negligible linewidth of the transmit/receive laser sources are to be taken into account. Following this design approach, we show that by properly modifying the traditional delay-and-multiply DPSK receiver, i. e. by allowing the delay to be a fraction of the symbol interval, we can considerably reduce the performance degradation caused by laser phase noise. We show thus that the superior power-efficiency of DPSK can be traded in favour of a decreased sensitivity to phase noise through a proper choice of the differential detector delay. In this respect, our results reveal that DPSK may still be competitive with other modulation formats even with non-negligible linewidth sources. In the last part of the paper, the behaviour of the optimized DPSK, ASK and large-deviation FSK data demodulators in the presence of a quasistationary frequency detuning of the local laser is also discussed under the same set of conditions as in the previous analysis. The results can be employed to derive accurate design requirements for the AFC loop of the receiver.     

Tolerances and Receiver Sensitivity Penalties of Multibit Delay Differential-Phase Shift-Keying Demodulation

Multibit delay demodulation of differential-phase shift-keying (DPSK) is finding applications in polarization interleaved modulation, optical time-domain multiplexing (OTDM), and multisymbol DPSK demodulation. Little attention has been paid to the degradation in tolerance and power penalty associated with multibit delay demodulation. We assess experimentally, numerically, and analytically the power penalties and tolerances associated with multibit delay DPSK demodulation. Numerical and analytical results show that the power penalty scales by a small factor of 0.2-0.35 dB per integer bit delay due to laser linewidth (LW) while experimental back-to-back results show a significant 1.2 dB per integer bit delay due to frequency offset penalty of longer bit delays. Frequency offset tolerance scales as 1/bit-delay and the delay-mismatch tolerance decreases by 20% for delays longer than 1 bit. A simple analytic model accounts for the combined effect of LW, frequency offset, and amplified spontaneous emission.     

FSR优化后的DPSK解调的研究

文章仿真验证了在差分相移键控(DPSK)解调时,通过调整延时线干涉仪(DLI)两臂的相对延迟来优化自由光谱范围(FSR),使其大于传输比特率,能够获得比传统1 bit延迟更好的传输性能,并得到了FSR的最优值.优化FSR后的DPSK解调系统时光信噪比(OSNR)灵敏度和色度色散容限范围均有改善,对偏振模色散(PMD)的容忍度没有明显提高.     

Offset DPSK with differential phase detector in satellite mobilechannel with narrow-band receiver filter

An expression is derived for the error probability of M-ary offset differential phase-shift keying (DPSK) with the differential phase detector and narrowband receiver filter in the satellite mobile (Rician) channel, which includes as special cases the Gaussian and land mobile (Rayleigh) channels. The error probability is computed as a function of various system parameters for M=2, 4, and 8 symbols and third-order Butterworth receiver filter. Both symmetric and conventional DPSK systems are considered. The optimal normalized bandwidth is close to 1.0. Symmetric and conventional DPSK differ significantly in error probability only for M=2 and in the lower range filter bandwidth. In most cases, symmetric DPSK outperforms conventional DPSK. This was particularly noted when the time delay between the specular and diffused signal components was taken into account     

3 Gbit/s optically preamplified direct detection DPSK receiver with 116 photon/bit sensitivity

For the first time experimental bit error rate curves are presented for an optically preamplified direct detection differential phase and shift keying (DPSK) communication link. DPSK offers approximately 6 dB peak power sensitivity improvement over more traditionally optically preamplified on/off keying (OOK). Using an erbium doped fibre preamplifier, a fibre Fabry-Perot filter, an optical DPSK demodulator consisting of a fibre-optic Mach-Zehnder interferometer with a 1 bit differential delay, and a balanced receiver, a sensitivity of 116 photon/bit was obtained. To the authors' knowledge these results represent the first demonstration of optically preamplified DPSK with better sensitivity than previously reported multigigabit per second heterodyne DPSK and approximately 3 dB more sensitivity on a peak power basis than previously reported preamplified OOK systems.<>     

A Fiber-Based All-Optical 3R Regenerator for DPSK Signals

Analysis of an all-optical 3R regenerator for differential phase-shift keying (DPSK) signals is presented. Incoming DPSK signals impaired by noise are first demodulated to on-off keying (OOK) signals by a delay interferometer. The amplitude of the OOK signals is then stabilized by a fiber-based all-optical 2R regenerator. In a subsequent nonlinear fiber, locally generated optical clock pulses are phase-modulated by the stabilized OOK pulses and are output as regenerated signals. It is shown that significant phase-noise suppression is achieved by strong amplitude regeneration     

5 Gbit/s direct optical DPSK modulation of a 1530-nm DFB laser

5 Gb/s direct optical differential-phase-shift-keying (DPSK) modulation of a 1530-nm distributed feedback (DFB) laser is demonstrated using injection current modulation with a bipolar signal format. Delay demodulation is performed using an interferometer with a delay time T equal to the duration of one bit. The input and differentially encoded nonreturn to zero (NRZ) signals are shown. The bipolar modulation current signal is basically the time derivative of the NRZ signal. There was no degradation of the optical DPSK signal due to thermal frequency modulation of the laser. The direct DPSK modulation technique avoids the insertion loss and systems complexity of external DPSK modulators     

Combining DPSK and duobinary for the downstream in 40-Gb/s long-reach WDM-PONs

We propose and demonstrate combining differential phase-shift keying (DPSK) and duobinary transmission for the downstream in 40-Gb/s long-reach wavelength division multiplexed-passive optical networks (WDM-PONs) in order to provide robust transmission performance in the backhaul section and simple detection at the ONUs. DPSK is deployed in the trunk span as it provides stronger robustness to fiber nonlinearity. Duobinary is used in the access span where its higher chromatic dispersion tolerance relieves the need for dispersion compensation. All-optical multichannel modulation format conversion from DPSK to duobinary is realized in the local exchange in a single delay interferometer to reduce system cost. Single and multi-channel 80-km long-reach DPSK transmission and up to 5-km duobinary access transmission are experimentally demonstrated at 40 Gb/s. The proposed approach shows great potential for future high data rate optical access networks.     

Nearly Shot-Noise-Limited Performance of Dual-Channel Linear Optical Sampling for Ultrafast DPSK Signals

This paper describes a newly developed dual-channel linear optical sampling technique for observing ultrafast optical differential phase-shift keying (DPSK) signals. As the proposed measurement scheme offsets two parallel interferometers by a relative delay corresponding to 1-symbol length of the DPSK signal, the measured phase distribution reflects the signal quality which is determined by the phase difference between adjacent symbols. This technique, based on interferometric optical gating by local short-pulses, also offers ultrafast measurement at symbol rates of greater than 100 Gsymbol/s. Moreover, its detection sensitivity can reach the shot noise limit. The waveform degradation caused by the coherence of the light source and the pattern effect of the phase modulator is successfully observed in continuous waves and 10-Gsymbol/s nonreturn-to-zero DPSK signals, and the constellation measurement is demonstrated for a 160-Gsymbol/s return-to-zero DPSK signal. Measurement system noise is also discussed for characterizing the detection sensitivity, and the nearly shot-noise-limited performance is experimentally verified.