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The investigation of the propagation channel is becoming more and more important in mod-
ern wireless communication. The demand for spectral efficiency motivates exploitation of
all channels that can possibly be used for communications. Nowadays, a common trend for
designing physical layer algorithms is to adapt the transceiving strategy, either by maximizing
the diversity gains or by utilizing the coherence of the channels to improve the signal-to-noise
power ratio.
標簽：
Characterization
Propagation
Channel
上傳時間：
2020-05-31
上傳用戶：shancjb
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為了提高超高頻RFID系統中閱讀器在低信噪比的情況下仍具有較高的識別能力,提出一種基于FPGA系統結合軟件無線電方法實現超高頻RFID射頻前端電路方案。超高頻射頻識別系統必須符合EPC Class 1generation 2標準,所設計的電路系統以Xilinx公司的XC6SLX16-2CSG324FPGA芯片為硬件基礎,將數字基帶調制解調和中頻濾波電路在FPGA系統中設計實現,重點闡述了射頻前端電路的設計結構、AD/DA轉換電路,以及數字濾波器的設計。實驗結果表明,所設計的超高頻RFID閱讀器簡化了前端電路系統結構,提升了穩定性,增強了抗干擾能力。該電路系統在信噪比較低的情況下,能夠較好地實現915MHz頻率的射頻接收和發送。In order to improve the reader UHF RFID system still has a higher ability to identify,in the case of low signal-to-noise ratio.The UHF RFID systems must comply with EPC Class 1 generation 2 standard.In this paper,the design of the circuit system based on Xilinx＇s XC6SLX16-2CSG324 FPGA chip,and presents UHF RFID RF front-end circuit with software radio based on FPGA system.Digital baseband modem and IF filter circuit is designed and implemented in the FPGA system,and focused on designing the structure of the RF front-end circuit,AD/DA conversion circuits,and digital filter.Experimental results show that the UHF RFID reader de...
標簽：
915mhz
超高頻
rfid
閱讀
射頻
前端
電路
設計
上傳時間：
2022-04-17
上傳用戶：shjgzh
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This demonstration illustrates the application of adaptive filters to signal separation
using a structure called an adaptive line enhancer (ALE). In adaptive line
enhancement, a measured signal x(n) contains two signals, an unknown signal
of interest v(n), and a nearly-periodic noise signal eta(n). The goal is to remove
the noise signal from the measured signal to obtain the signal of interest.
標簽：
demonstration
application
illustrates
separation
上傳時間：
2014-09-08
上傳用戶：2525775
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All inputs of the C16x family have Schmitt-Trigger input characteristics. These Schmitt-Triggers are intended to always provide proper internal low and high levels, even if anundefined voltage level (between TTL-VIL and TTL-VIH) is externally applied to the pin.The hysteresis of these inputs, however, is very small, and can not be properly used in anapplication to suppress signal noise, and to shape slow rising/falling input transitions.Thus, it must be taken care that rising/falling input signals pass the undefined area of theTTL-specification between VIL and VIH with a sufficient rise/fall time, as generally usualand specified for TTL components (e.g. 74LS series: gates 1V/us, clock inputs 20V/us).The effect of the implemented Schmitt-Trigger is that even if the input signal remains inthe undefined area, well defined low/high levels are generated internally. Note that allinput signals are evaluated at specific sample points (depending on the input and theperipheral function connected to it), at that signal transitions are detected if twoconsecutive samples show different levels. Thus, only the current level of an input signalat these sample points is relevant, that means, the necessary rise/fall times of the inputsignal is only dependant on the sample rate, that is the distance in time between twoconsecutive evaluation time points. If an input signal, for instance, is sampled throughsoftware every 10us, it is irrelevant, which input level would be seen between thesamples. Thus, it would be allowable for the signal to take 10us to pass through theundefined area. Due to the sample rate of 10us, it is assured that only one sample canoccur while the signal is within the undefined area, and no incorrect transition will bedetected. For inputs which are connected to a peripheral function, e.g. capture inputs, thesample rate is determined by the clock cycle of the peripheral unit. In the case of theCAPCOM unit this means a sample rate of 400ns @ 20MHz CPU clock. This requiresinput signals to pass through the undefined area within these 400ns in order to avoidmultiple capture events.For input signals, which do not provide the required rise/fall times, external circuitry mustbe used to shape the signal transitions.In the attached diagram, the effect of the sample rate is shown. The numbers 1 to 5 in thediagram represent possible sample points. Waveform a) shows the result if the inputsignal transition time through the undefined TTL-level area is less than the time distancebetween the sample points (sampling at 1, 2, 3, and 4). Waveform b) can be the result ifthe sampling is performed more than once within the undefined area (sampling at 1, 2, 5,3, and 4).Sample points:1. Evaluation of the signal clearly results in a low level2. Either a low or a high level can be sampled here. If low is sampled, no transition willbe detected. If the sample results in a high level, a transition is detected, and anappropriate action (e.g. capture) might take place.3. Evaluation here clearly results in a high level. If the previous sample 2) had alreadydetected a high, there is no change. If the previous sample 2) showed a low, atransition from low to high is detected now.
標簽：
Signal
Input
Fall
Rise
上傳時間：
2013-10-23
上傳用戶：copu
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Abstract: Specifications such as noise, effective number of bits (ENOB), effective resolution, and noise-free resolution inlarge part define how accurate an ADC really is. Consequently, understanding the performance metrics related to noise isone of the most difficult aspects of transitioning from a SAR to a delta-sigma ADC. With the current demand for higherresolution, designers must develop a better understanding of ADC noise, ENOB, effective resolution, and signal-to-noiseratio (SNR). This application note helps that understanding.
標簽：
ENOB
模數轉換器
上傳時間：
2013-10-16
上傳用戶：x18010875091
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鎖定放大是微弱信號檢測的重要手段。基于相關檢測理論，利用開關電容的開關實現鎖定放大器中乘法器的功能，提出開關電容和積分器相結合以實現相關檢測的方法，并設計出一種鎖定放大器。該鎖定放大器將微弱信號轉化為與之相關的方波，通過后續電路得到正比于被測信號的直流電平，為后續采集處理提供方便。測量數據表明鎖定放大器前級可將10-6 A的電流轉換為10-1 V的電壓，后級通過帶通濾波器級聯可將信號放大1×105倍。該方法在降低噪聲的同時，可對微弱信號進行放大，線性度較高、穩定性較好。
Abstract:
Lock-in Amplifying（LIA）is one of important means for weak signal detection. Based on cross-correlation detection theory， switch in the swithched capacitor was used as multiplier of LIA， and a new method of correlation detection was proposed combining swithched capacitor with integrator. A kind of LIA was designed which can convert the weak signal to square-wave， then DC proportional to measured signal was obtained through follow-up conditioning circuit， providing convenience for signal acquisition and processing. The measured data shows that the electric current（10-6 A） can be changed into voltage（10-1 V） by LIA， and the signal is magnified 1×105 times by cascade band-pass filter. The noise is suppressed and the weak signal is amplified. It has the advantages of good linearity and stability.
標簽：
開關電容
鎖定放大器
上傳時間：
2013-11-29
上傳用戶：黑漆漆
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All inputs of the C16x family have Schmitt-Trigger input characteristics. These Schmitt-Triggers are intended to always provide proper internal low and high levels, even if anundefined voltage level (between TTL-VIL and TTL-VIH) is externally applied to the pin.The hysteresis of these inputs, however, is very small, and can not be properly used in anapplication to suppress signal noise, and to shape slow rising/falling input transitions.Thus, it must be taken care that rising/falling input signals pass the undefined area of theTTL-specification between VIL and VIH with a sufficient rise/fall time, as generally usualand specified for TTL components (e.g. 74LS series: gates 1V/us, clock inputs 20V/us).The effect of the implemented Schmitt-Trigger is that even if the input signal remains inthe undefined area, well defined low/high levels are generated internally. Note that allinput signals are evaluated at specific sample points (depending on the input and theperipheral function connected to it), at that signal transitions are detected if twoconsecutive samples show different levels. Thus, only the current level of an input signalat these sample points is relevant, that means, the necessary rise/fall times of the inputsignal is only dependant on the sample rate, that is the distance in time between twoconsecutive evaluation time points. If an input signal, for instance, is sampled throughsoftware every 10us, it is irrelevant, which input level would be seen between thesamples. Thus, it would be allowable for the signal to take 10us to pass through theundefined area. Due to the sample rate of 10us, it is assured that only one sample canoccur while the signal is within the undefined area, and no incorrect transition will bedetected. For inputs which are connected to a peripheral function, e.g. capture inputs, thesample rate is determined by the clock cycle of the peripheral unit. In the case of theCAPCOM unit this means a sample rate of 400ns @ 20MHz CPU clock. This requiresinput signals to pass through the undefined area within these 400ns in order to avoidmultiple capture events.
標簽：
C16x
微控制器
輸入信號
時序圖
上傳時間：
2014-04-02
上傳用戶：han_zh
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Prony算法工具箱。Prony方法是用一組指數項的線性組合來擬和等間距采樣數據的方法,可以從中分析出信號的幅值、相位、阻尼因子、頻率等信息。considerations including data preprocessing, model order selection, model order selection criteria, signal subspace selection, signal and noise separation, root inspection and assessing residuals. The PTbox provides flexibility to compare and display analysis results simultaneously for several parameter variations.
標簽：
Prony
considerations
including
data
上傳時間：
2015-09-11
上傳用戶：lizhizheng88
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This simulation script set allows for an OFDM transmission to be
simulated. Imagetx.m generates the OFDM signal, saving it as a
windows WAV file. This allows the OFDM signal to be played out a sound
card and recorded back. Imagerx.m decodes the WAV to extract the
data.
settings.m contains all the common settings to specify all the
simulation parameters such as FFT size, number of carriers,
input data source file, input and output WAV files, etc.
標簽：
transmission
simulation
generates
simulated
上傳時間：
2013-12-15
上傳用戶：dyctj
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In this project we analyze and design the minimum mean-square error (MMSE) multiuser receiver for uniformly quantized synchronous code division multiple access (CDMA) signals in additive white Gaussian noise (AWGN) channels.This project is mainly based on the representation of uniform quantizer by gain plus additive noise model. Based on this model, we derive the weight vector and the output signal-to-interference ratio (SIR) of the MMSE receiver. The effects of quantization on the MMSE receiver performance is characterized in a single parameter named 鈥漞quivalent noise variance鈥? The optimal quantizer stepsize which maximizes the MMSE receiver output SNR is also determined.
標簽：
mean-square
multiuser
receiver
project
上傳時間：
2014-11-21
上傳用戶：ywqaxiwang
