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Nguyên tắc cơ bản của thiết kế mạch RF với tiếng ồn thấp dao động P5
Mixers are used to translate a signal spectrum from one frequency to another. Most modern RF/microwave transmitters, receivers and instruments require many of these devices for this frequency translation. The typical symbol for a mixer is shown in Figure
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Nguyên tắc cơ bản của thiết kế mạch RF với tiếng ồn thấp dao động P6
Power amplifiers consist of an active device, biasing networks and input and output reactive filtering and transforming networks. These networks are effectively bandpass filters offering the required impedance transformation. They are also designed to offer some frequency shaping to compensate for the roll-off in the active device frequency response if broadband operation is required. However the function of each network is quite different. The input circuit usually provides impedance matching to achieve low input return loss and good power transfer. ...
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Nguyên tắc cơ bản của thiết kế mạch RF với tiếng ồn thấp dao động P7
Modern large signal modelling packages offer extremely accurate results if good models are provided. However, they are often slow when optimisation is required. It would therefore be very useful to be able to optimise the performance of a circuit, such as the load network for a power amplifier, by being able to vary the important parameter values as well as the frequency and then to observe the waveforms on an ‘oscilloscope-like’ display in real time.
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GPS - đường dẫn quán tính và hội nhập P1
The ®ve basic forms of navigation are as follows: 1. Pilotage, which essentially relies on recognizing landmarks to know where you are. It is older than human kind. 2. Dead reckoning, which relies on knowing where you started from, plus some form of heading information and some estimate of speed. 3. Celestial navigation, using time and the angles between local vertical and known celestial objects (e.g., sun, moon, or stars) [115]. 4. Radio navigation, which relies on radio-frequency sources with known locations (including Global Positioning System satellites)...
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GPS - đường dẫn quán tính và hội nhập P2
This book is about GPS and INS and their integration. An inertial navigation unit can be used anywhere on the globe, but it must be updated within hours of use by independent navigation sources such as GPS or celestial navigation. Thousands of self-contained INS units are in continuous use on military vehicles, and an increasing number are being used in civilian applications. 2.1.1 Systems Other Than GPS
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GPS - đường dẫn quán tính và hội nhập P3
Signal Characteristics and Information Extraction Why is the GPS signal so complex? GPS was designed to be readily accessible to millions of military and civilian users. Therefore, it is a receive-only passive system for a user, and the number of users that can simultaneously use the system is unlimited. Because there are many functions that must be performed, the GPS signal has a rather complex structure.
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GPS - đường dẫn quán tính và hội nhập P4
The purpose of the receiver front end is to ®lter and amplify the incoming GPS signal. As was pointed out earlier, the GPS signal power available at the receiver antenna output terminals is extremely small and can easily be masked by interference from more powerful signals adjacent to the GPS passband. To make the signal usable for digital processing at a later stage, RF ampli®cation in the receiver front end provides as
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GPS - đường dẫn quán tính và hội nhập P5
GPS Data Errors SELECTIVE AVAILABILITY ERRORS Prior to May 1, 2000, Selective Availability (SA) was a mechanism adopted by the Department of Defense (DoD) to control the achievable navigation accuracy by nonmilitary GPS receivers. In the GPS SPS mode, the SA errors were speci®ed to degrade navigation solution accuracy to 100 m (2D RMS) horizontally and 156 m (RMS) vertically. In a press release on May 1, 2000, the President of the United States announced the decision to discontinue this intentional degradation of GPS signals available to the public. ...
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GPS - đường dẫn quán tính và hội nhập P6
History of Inertial Navigation Inertial navigation has had a relatively short but intense history of development, much of it during the half-century of the Cold War, with contributions from thousands of engineers and scientists.
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GPS - đường dẫn quán tính và hội nhập P7
It is an extremely effective and versatile procedure for combining noisy sensor outputs to estimate the state of a system with uncertain dynamics. For our purposes in this book: The noisy sensors may include GPS receivers and inertial sensors (accelerometers and gyroscopes, typically) but may also include speed sensors (e.g., wheel speeds of land vehicles, water speed sensors for ships, air speed sensors for aircraft, or Doppler radar), and time sensors (clocks).
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GPS - đường dẫn quán tính và hội nhập Part 8
We now consider the following, practical aspects of Kalman ®ltering applications: 1. how performance of the Kalman ®lter can degrade due to computer roundoff errors and alternative implementation methods with better robustness against roundoff; 2. how to determine computer memory, word length, and throughput requirements for implementing Kalman ®lters in computers; 3. ways to implement real-time monitoring and analysis of ®lter performance;
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GPS - đường dẫn quán tính và hội nhập P8
Differential GPS (DGPS) is a technique for reducing the error in GPS-derived positions by using additional data from a reference GPS receiver at a known position. The most common form of DGPS involves determining the combined effects of navigation message ephemeris and satellite clock errors [including the effects of selective availability (SA), if active] at a reference station and transmitting pseudorange corrections, in real time, to a user's receiver. The receiver applies the corrections in the process of determining its position [63]....
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Phân tích tín hiệu P5
Transforms and Filters for Stochastic Processes In this chapter, we consider the optimal processing of random signals. We start with transforms that have optimal approximation properties, in the least-squares sense, for continuous and discrete-time signals, respectively. Then we discuss the relationships between discrete transforms, optimal linear estimators, and optimal linear filters.
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Phân tích tín hiệu P6
Filter banks are arrangements low pass, bandpass, and highpass filters used of for the spectral decomposition and composition of signals. They play an important role in many modern signal processing applications such as audio and image coding. The reason for their popularity is the fact that they easily allow the extractionof spectral components of a signal while providing very efficient implementations. Since most filter banks involve various sampling rates, they are also referred to as multirate systems....
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Phân tích tín hiệu P7
Short-Time Fourier Analysis A fundamental problem in signal analysis is to find the spectral components containedin a measuredsignal z ( t ) and/or to provide information about the time intervals when certain frequencies occur. An example of what we are looking for is a sheet of music, which clearly assigns time to frequency, see Figure 7.1. The classical Fourier analysis only partly solves the problem, because it does not allow an assignment of spectralcomponents to time. Therefore one seeks other transforms which give insight into signal properties in a different way. ...
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Phân tích tín hiệu P8
Wavelet Transform The wavelettransform was introduced at the beginning of the 1980s by Morlet et al., who used it to evaluate seismic data [l05 ],[106]. Since then, various types of wavelet transforms have been developed, and many other applications ha vebeen found. The continuous-time wavelet transform, also called the integral wavelet transform (IWT), finds most of its applications in data analysis, where it yields an affine invariant time-frequency representation.
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Phân tích tín hiệu P9
Non-Linear TirneFrequency Distributions In Chapters 7 and 8 twotime-frequencydistributions were discussed: the spectrogram and the scalogram. Both distributions are the result of linear filtering and subsequent forming of the squared magnitude. In this chapter time-frequency distributions derived in a different manner will be considered. Contrary to spectrograms and scalograms, their resolution is not restricted by the uncertainty principle. Although these methods do not yield positive distributions in all cases, they allow extremelygood insight into signal properties within certain applications. ...
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Xử lý hình ảnh kỹ thuật số P1
CONTINUOUS IMAGE MATHEMATICAL CHARACTERIZATION In the design and analysis of image processing systems, it is convenient and often necessary mathematically to characterize the image to be processed. There are two basic mathematical characterizations of interest: deterministic and statistical. In deterministic image representation, a mathematical image function is defined and point properties of the image are considered. For a statistical image representation, the image is specified by average properties. The following sections develop the deterministic and statistical characterization of continuous images. Although the analysis is presented in the context of visual images, many of the results can be extended to general two-dimensional...
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Xử lý hình ảnh kỹ thuật số P2
PSYCHOPHYSICAL VISION PROPERTIES For efficient design of imaging systems for which the output is a photograph or display to be viewed by a human observer, it is obviously beneficial to have an understanding of the mechanism of human vision. Such knowledge can be utilized to develop conceptual models of the human visual process. These models are vital in the design of image processing systems and in the construction of measures of image fidelity and intelligibility.
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Xử lý hình ảnh kỹ thuật số P3
PHOTOMETRY AND COLORIMETRY Chapter 2 dealt with human vision from a qualitative viewpoint in an attempt to establish models for monochrome and color vision. These models may be made quantitative by specifying measures of human light perception. Luminance measures are the subject of the science of photometry, while color measures are treated by the science of colorimetry.
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Xử lý hình ảnh kỹ thuật số P4
IMAGE SAMPLING AND RECONSTRUCTION In digital image processing systems, one usually deals with arrays of numbers obtained by spatially sampling points of a physical image. After processing, another array of numbers is produced, and these numbers are then used to reconstruct a continuous image for viewing. Image samples nominally represent some physical measurements of a continuous image field, for example, measurements of the image intensity or photographic density. Measurement uncertainties exist in any physical measurement apparatus....
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Xử lý hình ảnh kỹ thuật số P5
DISCRETE IMAGE MATHEMATICAL CHARACTERIZATION Chapter 1 presented a mathematical characterization of continuous image fields. This chapter develops a vector-space algebra formalism for representing discrete image fields from a deterministic and statistical viewpoint. Appendix 1 presents a summary of vector-space algebra concepts.
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Xử lý hình ảnh kỹ thuật số P6
IMAGE QUANTIZATION Any analog quantity that is to be processed by a digital computer or digital system must be converted to an integer number proportional to its amplitude. The conversion process between analog samples and discrete-valued samples is called quantization. The following section includes an analytic treatment of the quantization process, which is applicable not only for images but for a wide class of signals encountered in image processing systems.
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Xử lý hình ảnh kỹ thuật số P7
SUPERPOSITION AND CONVOLUTION In Chapter 1, superposition and convolution operations were derived for continuous two-dimensional image fields. This chapter provides a derivation of these operations for discrete two-dimensional images. Three types of superposition and convolution operators are defined: finite area, sampled image, and circulant area. The finite-area operator is a linear filtering process performed on a discrete image data array.
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Xử lý hình ảnh kỹ thuật số P8
UNITARY TRANSFORMS Two-dimensional unitary transforms have found two major applications in image processing. Transforms have been utilized to extract features from images. For example, with the Fourier transform, the average value or dc term is proportional to the average image amplitude, and the high-frequency terms (ac term) give an indication of the amplitude and orientation of edges within an image.
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Xử lý hình ảnh kỹ thuật số P9
LINEAR PROCESSING TECHNIQUES Most discrete image processing computational algorithms are linear in nature; an output image array is produced by a weighted linear combination of elements of an input array. The popularity of linear operations stems from the relative simplicity of spatial linear processing as opposed to spatial nonlinear processing. However, for image processing operations, conventional linear processing is often computationally infeasible without efficient computational algorithms because of the large image arrays....
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Xử lý hình ảnh kỹ thuật số P10
IMAGE ENHANCEMENT Image enhancement processes consist of a collection of techniques that seek to improve the visual appearance of an image or to convert the image to a form better suited for analysis by a human or a machine. In an image enhancement system, there is no conscious effort to improve the fidelity of a reproduced image with regard to some ideal form of the image, as is done in image restoration.
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Xử lý hình ảnh kỹ thuật số P11
IMAGE RESTORATION MODELS Image restoration may be viewed as an estimation process in which operations are performed on an observed or measured image field to estimate the ideal image field that would be observed if no image degradation were present in an imaging system. Mathematical models are described in this chapter for image degradation in general classes of imaging systems. These models are then utilized in subsequent chapters as a basis for the development of image restoration techniques. ...
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Xử lý hình ảnh kỹ thuật số P12
POINT AND SPATIAL IMAGE RESTORATION TECHNIQUES A common defect in imaging systems is unwanted nonlinearities in the sensor and display systems. Post processing correction of sensor signals and pre-processing correction of display signals can reduce such degradations substantially (1). Such point restoration processing is usually relatively simple to implement. One of the most common image restoration tasks is that of spatial image restoration to compensate for image blur and to diminish noise effects. References 2 to 6 contain surveys of spatial image restoration methods. ...
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Xử lý hình ảnh kỹ thuật số P13
GEOMETRICAL IMAGE MODIFICATION One of the most common image processing operations is geometrical modification in which an image is spatially translated, scaled, rotated, nonlinearly warped, or viewed from a different perspective.
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