توجه: محتویات این صفحه به صورت خودکار پردازش شده و مقاله‌های نویسندگانی با تشابه اسمی، همگی در بخش یکسان نمایش داده می‌شوند.
۱VLSI Architecture of Lifting–Based Nonseparable 2D Discrete Wavelet Transform
اطلاعات انتشار: سیزدهیمن کنفرانس مهندسی برق ایران، سال
تعداد صفحات: ۶
In this paper, we propose an architecture that performs non–separable discrete wavelet transform (DWT) using a lifting scheme for (5,3) and (9,7) wavelets, the two major filters proposed in JPEG2000. It exploits advantages of lifting scheme such as low number of calculation and hardware similarity of forward and inverse DWT. The proposed architecture also inherits the characteristics of non–separable basis functions, such as compatibility with two–dimensional image scanning, and low latency and smaller hardware due to absence of transposition. The proposed hardware is a unified high throughput regular architecture, capable of executing (5,3) filter in lossless mode and (9,7) filter in lossy mode. It
computes multilevel DWT while generating four outputs per cycle for (5,3) filter and two outputs per cycle for (9,7) filter. This architecture requires only one simple processor element and can achieve 100% utilization of hardware resources. The schedules of designed architecture have been
generated manually. It has been simulated in system level and implemented in VHDL.<\div>

۲Algorithm and VLSI Architecture of Wavelet Vector Quantization
اطلاعات انتشار: سیزدهیمن کنفرانس مهندسی برق ایران، سال
تعداد صفحات: ۶
In this paper, we present an algorithm and VLSI hardware of a real–time image compression that is based on Vector Quantization (VQ) of Discrete Wavelet Transform (DWT) coefficients. Containing the hardware of both Wavelet and VQ, this architecture is capable of performing real–time image compression for grayscale and 24 bit color image with a resolution of 1024×1024 pixels. The algorithm of 2D DWT is lifting–based nonseparable 2D DWT. Difference–Codebook Binary Tree Search VQ (DC–BTSVQ) is used in the algorithm that lead to a high speed encoder. Binary Tree Search VQ (BTSVQ) also requires low hardware in VLSI implementation. The proposed real–time Wavelet Vector Quantization (WVQ) algorithm combines the multistage VQ (MSVQ) and the classified VQ (CVQ). The MSVQ encodes the lowest frequency subbands of wavelet coefficients and has the advantage of the robustness to wireless channel fading. The CVQ encodes other higher frequency subbands and results the high coding efficiency.<\div>

۳Using Weighted Multilevel Wavelet Decomposition for Wideband Spectrum Sensing in Cognitive Radios
اطلاعات انتشار: نوزدهمین کنفرانس مهندسی برق ایران، سال
تعداد صفحات: ۵
Cognitive radio is defined as a paradigm for wireless communication in which either a network or a wireless node changes its transmission or reception parameters to communicate efficiently avoiding interference with the other users. Cognitive Radio (CR) introduces the idea of system awareness and intelligence adaptability in order to provide more efficient spectrum utilization especially in spectrum scarcity environment. One of the key CR functionalities is the spectrum sensing, which allows CRs to monitor radio environment and detect unused spectrum. Accuracy and speed of estimation are keys to select appropriate spectrum sensing technique. Conventional spectrum estimation techniques based on Fourier transform have a lack of performance in case of low frequency resolution, large variance of estimated power and large side lobes. Some other methods that improve these deficiencies would increase the complexity of the system, which is not desired. In this paper, we utilized an energy detection based spectrum sensing method which reduced the complexity of the system while improving the performance of the CR. Multi level wavelet decomposition is used to divide the signal into different frequency resolution and each scale level is taken into account according to its importance in the edge detection procedure. Simulation results revealed that in comparison to state of the art similar methods, the proposed method reduces the complexity while improving the performance.<\div>

۴New low current mismatch and wide output dynamic range charge pump
نویسنده(ها): ،
اطلاعات انتشار: نوزدهمین کنفرانس مهندسی برق ایران، سال
تعداد صفحات: ۵
Conventional charge pumps suffer from current mismatch that increases reference spur in Phase Locked Loops (PLL). Some previously introduced methods reduce this mismatch by cost of output voltage dynamic range limitation. This paper proposes a new charge pump structure with low current mismatch while having wide output dynamic range. High accurate current matching is done using high–gain low power amplifiers in feedback configuration where it’s wide output dynamic range is obtained by using triode–region transistors in current mirrors. Circuit level simulation results in standard 0.18μm CMOS technology with 1.8 V supply voltage has been provided to verify the effectiveness of the proposed structure<\div>

۵An Improved Active Mixer Architecture for Millimeter Wave Applications
نویسنده(ها): ،
اطلاعات انتشار: International Journal Information and Communication Technology Research، سوم،شماره۲، Mar ۲۰۱۱، سال
تعداد صفحات: ۱۰
Modified active mixer architecture is presented in this paper which improves the gain and noise figure of the mixer considerably. The architecture of the mixer allows wide band operation from very low frequencies up to millimeter – wave regime. Also the proposed architecture makes it possible to use older process options for implementing high frequency mixers with acceptable performance. Simulations using 0.18u RF technology files show the efficiency of the mixer. The technology files are based on BSIM 3(V3.2) .Accurate transistor and passive component models are obtained by augmenting the technology files with the results of Electromagnetic field solvers.
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