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Logic kỹ thuật số thử nghiệm và mô phỏng P1
Things don’t always work as intended. Some devices are manufactured incorrectly, others break or wear out after extensive use. In order to determine if a device was manufactured correctly, or if it continues to function as intended, it must be tested. The test is an evaluation based on a set of requirements. Depending on the complexity of the product, the test may be a mere perusal of the product to determine whether it suits one’s personal whims, or it could be a long, exhaustive checkout of a complex system to ensure compliance with many performance and safety criteria. Emphasis may...
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Logic kỹ thuật số thử nghiệm và mô phỏng P2
Simulation is an imitative process. It is used to study relationships between parameters that interact in a system. In some cases it may point out errors that cause a design to respond incorrectly. In other cases it permits optimization of a design for maximum performance or economy of operation or construction. In still other situations, the system may be so complex that simulation is the only way that variables affecting the design, and their interaction with each other, can be controlled and studied. In order to imitate the behavior of a product or system, simulation employs models. A model is...
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Logic kỹ thuật số thử nghiệm và mô phỏng P3
Thus far simulation has been considered within the context of design verification. The purpose was to determine whether or not the design was correct. Were all the key control signals of the design checked out? What about the data paths, were all the “corners” or endpoints checked out? Are we confident that all likely combinations of events have been simulated and that the circuit model responded correctly? Is the design ready to be taped out? We now turn our attention to simulation as it relates to manufacturing test. Here the objective is to create a test program that uncovers defects...
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Logic kỹ thuật số thử nghiệm và mô phỏng P4
In Chapter 3 we looked at fault simulation. Its purpose is to evaluate test programs in order to measure their effectiveness at distinguishing between faulty and fault-free circuits. The question of the origin of test stimuli was ignored for the moment; we simply noted that test programs could be derived from test stimuli originally intended for design verification, or stimuli could be written specifically for the purpose of exercising the circuit to reveal the presence of physical defects, or stimuli could be produced by an automatic test pattern generator (ATPG). We now turn our attention to the ATPG. However, we...
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Logic kỹ thuật số thử nghiệm và mô phỏng P5
The previous chapter examined methods for creating sensitized paths in combinational logic extending from stuck-at faults on logic gates to observable outputs. We now attempt to create tests for sequential circuits where the outputs are a function not just of present inputs but of past inputs as well. The objective will be the same: to create a sensitized path from the point where a fault occurs to an observable output. However, there are new factors that must be taken into consideration. A sensitized path must now be propagated not only through logic operators, but also through an entirely new dimension—time....
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Logic kỹ thuật số thử nghiệm và mô phỏng P6
Digital circuits have always been designed to operate beyond the point where they could be reliably manufactured on a consistent basis. It is a simple matter of economics: By pushing the state of the art—that is, aggressively shrinking feature sizes, then testing them and discarding those that are defective—it is possible to obtain greater numbers of ICs from a single wafer than if they are manufactured with more conservative feature sizes (cf. Section 1.8 for more discussion on this practice). This strategy depends on having access to complex, and sometimes very expensive, test equipment. This strategy also depends on being...
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Logic kỹ thuật số thử nghiệm và mô phỏng P7
The first five chapters provided a survey of algorithms for logic simulation, fault simulation, and automatic test pattern generation. That was followed by a brief survey of tester architectures and strategies to maximize tester effectiveness while minimizing overall test cost. We now turn our attention to methods for combining the various algorithms and testers in ways that make it possible to achieve quality levels consistent with product requirements and design methodologies.
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Logic kỹ thuật số thử nghiệm và mô phỏng P8
Chapter 7 focused on methods for integrating design and test activities by capturing verification suites written by logic designers and converting them to test programs. For some ICs, especially those with reasonably high yield, test programs derived from a thorough design verification suite, combined with an IDDQ test (cf. Chapter 11), may produce quality levels that meet or exceed corporate requirements. When it is not possible, or practical, to achieve fault coverage that satisfies acceptable quality levels (AQL) through the use of design verification suites, an alternative is to use an automatic test pattern generator (ATPG). Ideally, one would like...
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Logic kỹ thuật số thử nghiệm và mô phỏng P9
Numerous ATPG algorithms and heuristics have been developed over the years to test digital logic circuits. Some of these methods can trace their origins back to the very beginnings of the digital logic era. Unfortunately, they have proven inadequate to the task. Despite many novel and interesting schemes designed to attack test problems in digital circuits, circuit complexity and the sheer number of logic devices on a die continue to outstrip the test schemes that have been developed, and there does not appear to be an end in sight, as levels of circuit integration continue to grow unabated. New methods...
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Logic kỹ thuật số thử nghiệm và mô phỏng P10
Memory is pervasive in digital products. Consider, for example, the personal computer (PC). It has main memory, video memory, translation ROMs, shadow ROMs, scratchpad memory, hard disk, floppy disk, CDROM, and various other kinds of storage distributed throughout. In addition, the die that contains the microprocessor may also contain one or more levels of cache. A typical PC is depicted in the block diagram of Figure 10.1. It is basically a memory hierarchy connected by several buses and adapters and controlled by a CPU. ...
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Logic kỹ thuật số thử nghiệm và mô phỏng P11
Test strategies described in previous chapters relied on two concepts: controllability and observability (C/O). Good controllability makes it easier to drive a circuit into a desired state, thus making it easier to sensitize a targeted fault. Good observability makes it easier to monitor the effects of a fault. Solutions for solving C/O problems include scan path and various ad-hoc methods. Scan path reduces C/O to a combinational logic problem which, as explained in Chapter 4, is a solved problem (theoretically, at least)....
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Logic kỹ thuật số thử nghiệm và mô phỏng P12
The first 11 chapters of this text focused on manufacturing test. Its purpose is to answer the question, “Was the IC fabricated correctly?” In this, the final chapter, the emphasis shifts to design verification, which attempts to answer the question, “Was the IC designed correctly?” For many years, manufacturing test development and design verification followed parallel paths. Designs were entered via schematics, and then stimuli were created and applied to the design. Design correctness was confirmed manually; the designer applied stimuli and examined simulation response to determine if the circuit responded correctly. Manufacturing correctness was determined by simulating vectors against...
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Laser điốt được phân phối thông tin phản hồi và các bộ lọc du dương quang P1
Communication is a process in which messages, ideas and information can be exchanged between two individuals. From the early days when languages were developed, the methods people use to communicate have experienced a dramatic evolution. Nowadays, rapid transmission of information over long distances and instant access to various information sources have become conspicuous and important features of our society.
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Laser điốt được phân phối thông tin phản hồi và các bộ lọc du dương quang P2
The rapid development of both terrestrial and undersea optical fibre networks has paved the way for a global communication network. Highly efficient semiconductor injection lasers have played a leading role in facing the challenges of the information era. In this chapter, before discussing the operating principle of the semiconductor distributed feedback (DFB) laser diode (LD), general concepts with regard to the principles of lasers will first be presented.
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Laser điốt được phân phối thông tin phản hồi và các bộ lọc du dương quang P3
The introduction of semiconductor lasers has boosted the development of coherent optical communication systems. With the built-in wavelength selection mechanism, distributed feedback semiconductor laser diodes with a higher gain margin are superior to the Fabry– Perot laser in that a single longitudinal mode of lasing can be achieved. In this chapter, results obtained from the threshold analysis of conventional and singlephase-shifted DFB lasers will be investigated. In particular, structural impacts on the threshold characteristic will be discussed in a systematic way. ...
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Laser điốt được phân phối thông tin phản hồi và các bộ lọc du dương quang P4
In Chapter 3, eigenvalue equations were derived by matching boundary conditions inside DFB laser cavities. From the eigenvalue problem, the lasing threshold characteristic of DFB lasers is determined. The single %/2-phase-shifted (PS) DFB laser is fabricated with a phase discontinuity of %/2 at or near the centre of the laser cavity. It is characterised by Bragg oscillation and a high gain margin value. On the other hand, the SLM deteriorates quickly when the optical power of the laser diode increases. This phenomenon, known as spatial hole burning, limits the maximum single-mode optical power and consequently the spectral linewidth....
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Laser điốt được phân phối thông tin phản hồi và các bộ lọc du dương quang P5
In the previous chapter, the transfer matrix method (TMM) was introduced to solve the coupled wave equations in DFB laser structures. Its efficiency and flexibility in aiding the analysis of DFB semiconductor LDs has been explored theoretically. A general N-sectioned DFB laser model was built which comprised active/passive and corrugated/planar sections. In this chapter, the N-sectioned laser model will be used in the practical design of the DFB laser. The spatial hole burning effect (SHB) [1] has been known to limit the performance of DFB LDs. As the biasing current of a single quarterly-wavelength-shifted (QWS) DFB LD increases, the gain...
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Laser điốt được phân phối thông tin phản hồi và các bộ lọc du dương quang P6
The flexibility of the transfer matrix method allows one to evaluate the spectral behaviour of a corrugated optical filter/amplifier and the threshold characteristic of a laser source. To extend the analysis into the above-threshold biasing regime, the transfer matrix has to be modified so as to include the dominant stimulated emission. Based on a novel numerical technique, the above-threshold DFB laser model will be presented in this chapter. Using a modified transfer matrix, the lasing mode characteristics of DFB LDs will be determined....
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Laser điốt được phân phối thông tin phản hồi và các bộ lọc du dương quang P7
The above-threshold lasing characteristics of DFB semiconductor laser diodes were presented in the previous chapter using a modified transfer matrix. Instead of using an averaged carrier concentration, the inclusion of the actual carrier distribution allows phenomena such as the spatial hole burning effect and non-linear gain to be included. In the analysis, a parabolic gain model and high-order carrier recombination were assumed. Lasing mode characteristics such as the longitudinal distribution of carrier density, photon density, refractive index and the internal field intensity were shown for various laser structures....
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Laser điốt được phân phối thông tin phản hồi và các bộ lọc du dương quang P8
Although today microwave and optical engineering appear to be separate disciplines, there has been a tradition of interchange of ideas between them. In fact, many traditional microwave concepts have been adapted to yield optical counterparts. The laser, as an optical device that plays a key role in optoelectronics and fibre-optic communications, grew from the work of its microwave predecessor, the maser (microwave amplification by stimulated emission of radiation) [1]. The operating principle behind the laser is very similar to that of the microwave oscillator....
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Laser điốt được phân phối thông tin phản hồi và các bộ lọc du dương quang P9
In Chapter 8 we introduced transmission-line laser modelling (TMLM). In this chapter, TLLM will be modified to allow the study of dynamic behaviour of distributed feedback laser diodes, in particular the effects of multiple phase shifts on the overall DFB LD performance. We can easily model any arbitrary phase-shift value by inserting some phaseshifter stubs into the scattering matrices of TLLM. This helps to make the electric field distribution and hence light intensity of DFB LDs more uniform along the laser cavity and hence minimise the hole burning effect. ...
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Laser điốt được phân phối thông tin phản hồi và các bộ lọc du dương quang P10
In recent years, advances in wavelength division multiplexing (WDM) and dense wavelength division multiplexing (DWDM) technology have enabled the deployment of systems that are capable of providing large amounts of bandwidth [1]. Wavelength tunable optical filters appear to be the key components in realising these WDM/DWDM lightwave systems. Optical filtering for the selection of channels separated by 2 nm is currently achievable, and narrower channel separations will be possible in the near future with improved technology [2–3]....
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Laser điốt được phân phối thông tin phản hồi và các bộ lọc du dương quang P11
Optical tunable filters are key components of the future dense wavelength division multiplexed (WDM) optical fibre networks. In such a network a number of information channels are simultaneously transmitted through a single fibre by putting each channel on a different optical carrier wavelength. The wavelength filter allows a single or multiple channel(s) to be isolated at the receiving or routing node. The tunability of the filter allows for dynamic network reconfiguration and increases versatility of the system....
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Laser điốt được phân phối thông tin phản hồi và các bộ lọc du dương quang P12
In this book, the performance characteristics of distributed feedback semiconductor laser diodes and optical tunable filters based on DFB laser structures have been investigated. As discussed in Chapter 1, these lasers can be used as optical sources and local oscillators in coherent optical communication networks, in which a stable single mode (in both the transverse plane and the longitudinal direction) and narrow spectral linewidth become crucial. Based on the interaction of electromagnetic radiation with a two-energy-band system, the operating principles of semiconductor lasers were reviewed in Chapter 2. With partially reflecting mirrors located at the laser facets, a Fabry–Perot laser...
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Nguyên tắc cơ bản của lượng tử ánh sáng P1
Light is an electromagnetic wave phenomenon described by the same theoretical principles that govern all forms of electromagnetic radiation.
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Nguyên tắc cơ bản của lượng tử ánh sáng P2
SIMPLE OPTICAL COMPONENTS A. Reflection and Refraction B. Transmission Through Optical Components C. Graded-Index Optical Components INTERFERENCE A. Interference of Two Waves B. Multiple-Wave Interference POLYCHROMATIC LIGHT A. Fourier Decomposition B. Light Beating
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Nguyên tắc cơ bản của lượng tử ánh sáng P3
Can light be spatially confined and transported in free space without angular spread? Although the wave nature of light precludes the existence of such an idealization, light can take
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Nguyên tắc cơ bản của lượng tử ánh sáng P4
PROPAGATION OF LIGHT IN FREE SPACE A. Correspondence Between the Spatial Harmonic and the Plane Wave B. Transfer Function of Free Space C. Impulse-Response Function of Free Space OPTICAL FOURIER TRANSFORM A. Fourier Transform in the Far Field B. Fourier Transform Using a Lens DIFFRACTION OF LIGHT A. Fraunhofer Diffraction *B. Fresnel Diffraction IMAGE FORMATION A. Ray-Optics Description of Image Formation B. Spatial Filtering C. Single-Lens Imaging System HOLOGRAPHY
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Nguyên tắc cơ bản của lượng tử ánh sáng P5
ELEMENTARY ELECTROMAGNETIC WAVES A. Plane, Spherical, and Gaussian Electromagnetic Waves B. Relation Between Electromagnetic Optics and Scalar Wave Optics ABSORPTION AND DISPERSION A. Absorption B. Dispersion C. The Resonant Medium PULSE PROPAGATION IN DISPERSIVE MEDIA
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Nguyên tắc cơ bản của lượng tử ánh sáng P6
POLARIZATION DEVICES A. Polarizers B. Wave Retarders C. Polarization Rotators Augustin Jean Fresnel (1788-1827) advanced a theory of light in which waves exhibit transverse vibrations. The equations describing the partial reflection and refraction of light are named after him. Fresnel also made important contributions to the theory of light diffraction.
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