基于FPGA的基带码发生器设计

设计一个基于FPGA的基带信号码发生器。首先简要介绍了单极性非归零码、双极性非归零码、单极性归零码、双极性归零码、差分码、交替极性码、分相码、传号反转码等8种基带码的基本特点,然后根据码型转换原理设计发生器模块。程序采用VHDL进行描述,并用Modelsim软件仿真实现所有功能,最后将功能集成到FPGA上,产生的基带码稳定、可靠,可满足不同数字基带系统传输需要。     

State assignment using programmable counters

The use of programmable counters in the state assignment of finite state machines is discussed. A systematic method is presented for maximising the use of such a counter and for minimising accordingly the storage of next state codes.<>     

State assignment of finite state machines for low powerapplications

The authors present an algorithm for the state assignment in finite state machines targeted for minimal switching power dissipation. The adjacent states are assigned codes closer in Hamming distance by our algorithm, which modifies the given state transition graph so that it can be embedded in an n-cube. Experimental results show that the switching activity obtained by the proposed method is better than the previous method     

一种自动生成状态机RTL代码的方法

集成电路设计中,状态机的代码实现具有一定规律性.根据该规律通过某种方法自动生成状态机RTL代码,可以提高设计设计效率.此项方法首先由Matlab中的Stateflow工具输入状态转移图,利用基于Tcl/Tk的软件提取其中有用信息,再进行状态机RTL代码生成,完成转换过程.该软件的成功设计和应用证明了此方法的可行性和实用性.     

Protection contre les erreurs en enregistrement magnétique numérique de télévision

In this paper the authors present the main problem of operating video tape recorders for television production, viz. picture degradations through multiple generations, which could be cancelled by using digital machines. Efficient error protection is mandatory. Burst error statistics are given as collected on a laboratory digital recorder as well as a physical interpretation. Different protection methods are used for luminance and colour differences, which results in sharing the available redundancy between two distinct coding systems. Adequate codes are selected through the use of two bounds stated as theorems. The main parameters of a possible system are presented. They are likely to be improved when further information is available to make an operating system practical.     

Comparison of Redundancy Reducing Codes for Facsimile Transmission of Documents

A comparison and a valuation of different redundancy reducing coding techniques for the digital transmission of facsimile documents on telephone lines is presented. Especially taken into account are those codes which have been submitted to the International Telegraph and Telephone Consultative Committee (CCITT) for standardization of digital group 3 facsimile machines. The reduction factor and the sensitivity of channel errors of these one- and two- dimensional codes have been investigated by computer simulations using the CCITT test documents and burst error patterns of real telephone lines. For a resolution of 1728 picture elements per line and 3.85 lines per mm one-dimensional run length coding proves to be the most economical solution. Using a higher vertical resolution of 7.7 lines per mm the effects of transmission errors are less visible in the received document and two-dimensional codes become more efficient. To achieve a transmission time of 1 min or less for a size A4 document a transmission bit rate of 4800 bits/s is required. For the higher vertical resolution a transmission time of 1 min cannot be guaranteed for all types of documents with this bit rate even if two-dimensional coding is used.     

Construction of Constrained Codes for State-Independent Decoding

Constrained sequence codes are widely used to meet constraints imposed by digital storage and communication systems. This paper develops an algorithm for the construction of constrained codes that admit state-independent decoding. By partitioning the code into a group of alphabets, one for each state, a codebook is developed using this algorithm that will allow the code to be decoded at the receiver without the need for state information. Finally, we use this algorithm to construct DCfree runlength-limited (RLL) codes, and we present two highly efficient state-independent decodable DC-free RLL codes.     

Synthesis of Circuits with Low-Cost Concurrent Error Detection Based on Bose-Lin Codes

This paper presents a procedure for synthesizing sequential machines with concurrent error detection based on Bose-Lin codes. Bose-Lin codes are an efficient solution for providing concurrent error detection as they are separable codes and have a fixed number of check bits, independent of the number of information bits. Furthermore, Bose-Lin code checkers have a simple structure as they are based on modulo operations. Procedures are described for synthesizing circuits in a way that their structure ensures that all single-point faults can only cause errors that are detected by a Bose-Lin code. This paper presents an efficient scheme for concurrent error detection in sequential circuits with no constraint on the state encoding. Concurrent error detection for both the state bits and the output bits is based on a Bose-Lin code and their checking is combined such that one checker suffices. Results indicate low area overhead. The cost of concurrent error detection is reduced significantly compared to other methods based on other codes.     

基于FPGA的CMI编码系统设计

提出了一种基于FPGA并利用Verilog HDL实现的CMI编码设计方法.研究了CMI码型的编码特点,提出了利用Altera公司Cyclone Ⅱ系列EP2C5Q型号FPGA完成CMI编码功能的方案.在系统程序设计中,首先产生m序列,然后程序再对m序列进行CMI码型变换.在CMI码型变换过程中,采用专用寄存器对1码的...     

The Effects of Digital Random Errors on the DMI Code Power Spectrum

The power spectrum of the DMI coded signal containing random errors is investigated. Results of experiments on DMI code transmission are given, confirming that low-frequency components increase according to line errors. These experimental results agree with the theoretical values for a wide error rate range. The investigation method presented in this paper can be applied to the error estimation of other line codes, such as CMI code.     

An efficient convolutional coding/decoding strategy for channelswith memory

Many digital communication channels are affected by errors that tend to occur in bursts. A great deal of work has been devoted to finding good burst-error-correcting codes and developing burst-error-correcting schemes. However, burst-error-correcting codes are generally not effective for long bursts. Some burst-error-correcting schemes suffer long delay in decoding. Others are very sensitive to random errors in the guard space. Most of these schemes are not adaptive to channel conditions. A new adaptive scheme is proposed to overcome these drawbacks. The scheme employs a combination of two complementary punctured convolutional (CPC) codes. One of the codes is used for burst detection and for channel state estimation, and both codes are used for error correction. The proposed scheme is analyzed over a two state Markov chain channel model. Unlike existing burst-error-correcting schemes, it is shown that the proposed scheme is adaptive to channel conditions and less sensitive to errors in the guard space. For the same delay, the proposed scheme offers better performance than the interleaving schemes. When the channel is heavily corrupted by bursts, the improvement is even more pronounced     

Robust modem and coding techniques for FM hybrid ICOC DAB

The design of robust modem and FEC (forward error correction) code techniques with application to the transmission of an FM hybrid analog/digital in-band on-channel (IBOC) digital audio broadcast (DAB) signal is presented here. The FEC codes are derived from an original lower rate convolutional code (R=1/3). The original code is segmented into a pair of “complementary” components, which form independent codes, each with a higher rate (less redundancy) than the base code. The exploitation of channel state information (CSI) and special interleaving techniques are described for application to FM hybrid IBOC DAB with its unique interference environment and selective fading due to multipath. Simulation results confirm the robustness of the design     

A new edge detector for CMI optical fiber transmission withimproved jitter tolerance

An edge detecting scheme for coded mark inversion (CMI) line codes which can reject wrong slot errors is proposed. This scheme looks at data transitions over one-and-a-half symbol durations and makes a binary decision based on the most likely transition pattern. An analysis and measurement results for the bit-error-rate performance of this scheme over an optical fiber link which show improvements in the detector tolerance against symbol timing jitters are presented     

Sequential lookahead method for digital counters

In the design of synchronous digital counters the carry chain which starts from the least significant digit determines the maximum clock speed. Various schemes for implementing the carry calculation have been proposed to minimise the time of that computation. The author describes a new technique which uses additional state bits to aid in the carry calculation. This is shown to give a useful increase in clock speed over conventional combinational logic based carry lookahead techniques. The technique is also applicable to general finite state machines     

Minimization of mealy finite state machines via internal state merging

The problem of minimizing Mealy finite state machines (FSMs) arises when digital devices based on programmable logic integrated circuits are synthesized. A distinctive feature of the approach proposed is that merging of two states is used and an FSM is represented as a transition list. The conditions used to merge states, the functioning identity and the FSM’s behavior determinacy, are presented. Situations leading to wait state formation caused by state merging are discussed. The algorithms for minimizing the internal states, transition paths, and input variable of FSMs are described. The features of application of the method proposed are discussed.     

A possible concept of how present radiated emission standards could be amended in order to protect digital communication services

Present radiated emission standards are developed to protect analog communication services. Finding a new detector for electromagnetic interference (EMI) measurements with adequate weighting properties to quantify the effect of disturbance on digital communication services, is one important issue in the evolution of present radiated emission standards in order to protect digital communication services. Recent measurement and simulation results indicated that the RMS detector exhibits a response that can be correlated to the interference impact on digital communication systems that do not use error-correcting codes, or codes of block or convolutional type. In this paper, we show that this conclusion is also valid for systems using the more complicated concatenated codes. The codes investigated so far cover a representative and relevant selection of codes employed in practical digital systems. Therefore, the proposed concept to amend existing radiated emission standards is considered valid.     

数字声音信号参数的选择及码率压缩

为了实现模拟声音信号向数字声音信号的转化,需经过抽样、量化和编码3个步骤,为达到用最少的数码传递最大的信息量,必须对声音信号进行压缩.介绍了数字声音信号有关参数的选择依据和基本方法、码率压缩的理论基础和基本方法以及应用.     

Finite-state modulation codes for data storage

The authors provide a self-contained exposition of modulation code design methods based upon the state splitting algorithm. They review the necessary background on finite state transition diagrams, constrained systems, and Shannon (1948) capacity. The state splitting algorithm for constructing finite state encoders is presented and summarized in a step-by-step fashion. These encoders automatically have state-dependent decoders. It is shown that for the class of finite-type constrained systems, the encoders constructed can be made to have sliding-block decoders. The authors consider practical techniques for reducing the number of encoder states as well as the size of the sliding-block decoder window. They discuss the class of almost-finite-type systems and state the general results which yield noncatastrophic encoders. The techniques are applied to the design of several codes of interest in digital data recording     

基于数字相关算法的动平衡测试系统的研究

针对大型旋转机械动平衡，从数字相关算法的角度深入地研究了多路动平衡测试仪器的信号处理算法在数字信号处理器（DSP）上的实现问题。充分利用DSP内部资源，开发了以DSP为核心的严格同步八通道数据采集系统，通过信号处理可以准确地从通频振动信号中提取出基频信号的幅值和相位，文中给出了具体软件处理思想和流程。