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.
上傳時間： 2013-11-29
上傳用戶：黑漆漆
The PCA9549 provides eight bits of high speed TTL-compatible bus switching controlledby the I2C-bus. The low ON-state resistance of the switch allows connections to be madewith minimal propagation delay. Any individual A to B channel or combination of channelscan be selected via the I2C-bus, determined by the contents of the programmable Controlregister. When the I2C-bus bit is HIGH (logic 1), the switch is on and data can flow fromPort A to Port B, or vice versa. When the I2C-bus bit is LOW (logic 0), the switch is open,creating a high-impedance state between the two ports, which stops the data flow.An active LOW reset input (RESET) allows the PCA9549 to recover from a situationwhere the I2C-bus is stuck in a LOW state. Pulling the RESET pin LOW resets the I2C-busstate machine and causes all the bits to be open, as does the internal power-on resetfunction.
上傳時間： 2014-11-22
上傳用戶：xcy122677
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.
上傳時間： 2014-04-02
上傳用戶：han_zh
收SP下行消息 A. 啟動MMSC偵聽端口 在模擬器界面的右下角的"Liten Port"文本框中輸入MMSC的偵聽端口，這個值是為接收SP發出的下行消息提供服務的端口號，比如："8080"，按下"Start"按鈕啟動MMSC偵聽服務。 B. 接收消息 接收的是從SP（API）發來的消息，處理后回一條響應消息。 2 模擬MMSC向SP發送上行消息 A. 選擇模擬器左邊界面的MessageType為“DeliverReq”； B. “Send To”文本框中輸入SP的上行地址，例如http://10.164.50.29:8888； C. 在界面中選擇輸入其他需要的字段，然后點擊“Send”按紐即可向SP上行地址發送上行消息。 3 模擬MMSC向SP發送遞送報告消息 A. 選擇模擬器左邊界面的MessageType為“DeliverReportReq”； B. “Send To”文本框中輸入SP的上行地址，例如http://10.164.50.29:8888； C. 在界面中選擇輸入其他需要的字段，然后點擊“Send”按紐即可向SP上行地址發送遞送報告消息。 4 模擬MMSC向SP發送閱讀報告消息 A. 選擇模擬器左邊界面的MessageType為“ReadReportReq”； B. “Send To”文本框中輸入SP的上行地址，例如http://10.164.50.29:8888； C. 在界面中選擇輸入其他需要的字段，然后點擊“Send”按紐即可向SP上行地址發送閱讀報告消息
上傳時間： 2014-01-16
上傳用戶：氣溫達上千萬的
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
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
The XML Toolbox converts MATLAB data types (such as double, char, struct, complex, sparse, logical) of any level of nesting to XML format and vice versa. For example, >> project.name = MyProject >> project.id = 1234 >> project.param.a = 3.1415 >> project.param.b = 42 becomes with str=xml_format(project, off ) "<project> <name>MyProject</name> <id>1234</id> <param> <a>3.1415</a> <b>42</b> </param> </project>" On the other hand, if an XML string XStr is given, this can be converted easily to a MATLAB data type or structure V with the command V=xml_parse(XStr).
標簽： converts Toolbox complex logical
上傳時間： 2016-02-12
上傳用戶：a673761058
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
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.
標簽： transmission simulation generates simulated
上傳時間： 2013-12-24
上傳用戶：希醬大魔王
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標簽： 源代碼
上傳時間： 2017-11-17
上傳用戶：wendingchang
