The unguided transmission of information using electromagnetic waves at radio frequency (RF) is often referred to as wireless communications, the first demonstration of which took place at the end of the 19th cen- tury and is attributed to Hertz. The technology was, shortly thereafter, commercialised by, amongst others, Marconi in one of the first wire- less communication systems, i.e., wireless telegraphy. In the first half of the 20th century the technology was developed further to enable more than the mere transmission of Morse code. This first resulted in uni- directional radio broadcasting and several years later also in television broadcasting.
標(biāo)簽： Imperfections RF
上傳時(shí)間： 2020-06-01
上傳用戶：shancjb
Intensive development of digital technologies coincided in time with the beginning of the new era in telecommunications. It made possible to formalize many proce- dures of data exchange and to atomize some operations which made providing of serviceandmakeworkofmanytelecommunicationworkersmucheasier. Somenew telecommunication technologies were born out of the necessity for use of specific configurations of network elements and networks, as well as for a possibility of providing maximum characteristics of efficiency combined with high requirements to the stability of operation, the overcoming of different catastrophic situations and deadlockconditions,such as failuresand ”pending”of the networkandthe like. The thresholdbetweeninformationsystems andtelecommunicationsystems has become practically invisible. It resulted in such a new term as ”infocommunication”
標(biāo)簽： Telecommunication+Systems
上傳時(shí)間： 2020-06-01
上傳用戶：shancjb
When 3GPP started standardizing the IMS a few years ago, most analysts expected the number of IMS deploymentsto grow dramatically as soon the initial IMS specifications were ready (3GPP Release 5 was functionallyfrozenin the first half of 2002and completedshortly after that). While those predictions have proven to be too aggressive owing to a number of upheavals hitting the ICT (Information and Communications Technologies) sector, we are now seeing more and more commercial IMS-based service offerings in the market. At the time of writing (May 2008), there are over 30 commercial IMS networks running live traffic, addingup to over10million IMS users aroundthe world; the IMS is beingdeployedglobally. In addition, there are plenty of ongoing market activities; it is estimated that over 130 IMS contracts have been awarded to all IMS manufacturers. The number of IMS users will grow substantially as these awarded contracts are launched commercially. At the same time, the number of IMS users in presently deployed networks is steadily increasing as new services are introduced and operators running these networks migrate their non-IMS users to their IMS networks.
標(biāo)簽： Multimedia Subsystem The IMS 3G IP
上傳時(shí)間： 2020-06-01
上傳用戶：shancjb
The continuing explosive growth in mobile communication is demanding more spectrally efficient radio access technologies than the prevalent second generation (2G) systems such as GSM to handle just the voice traffic. We are already witnessing high levels of mobile penetration exceeding 70% in some countries. It is anticipated that by 2010 more than half of all communications will be carried out by mobile cellular networks. On the other hand, the information revolution and changing life habits are bringing the requirement of commu- nicating on a multimedia level to the mobile environment. But the data handling capabilities and flexibility of the 2G cellular systems are limited.
標(biāo)簽： Planning Network UMTS
上傳時(shí)間： 2020-06-01
上傳用戶：shancjb
I can remember buying my first electronic calculator. I was teaching a graduate level statistics course and I had to have a calculator with a square root function. Back in the late 1960s, that was a pretty high-end requirement for a calculator. I managed to purchase one at the “educational discount price” of $149.95! Now, I look down at my desk at an ATmega2560 that is half the size for less than a quarter of the cost and think of all the possibilities built into that piece of hardware. I am amazed by what has happened to everything from toasters to car engines. Who-da-thunk-it 40 years ago?
標(biāo)簽： Beginning Arduino for
上傳時(shí)間： 2020-06-09
上傳用戶：shancjb
基于TMS320F2812 光伏并網(wǎng)發(fā)電模擬裝置PROTEL設(shè)計(jì)原理圖+PCB+軟件源碼+WORD論文文檔,硬件采用2層板設(shè)計(jì)，PROTEL99SE 設(shè)計(jì)的工程文件，包括完整的原理圖和PCB文件，可以做為你的學(xué)習(xí)設(shè)計(jì)參考。 摘要：本文實(shí)現(xiàn)了一個(gè)基于TMS320F2812 DSP芯片的光伏并網(wǎng)發(fā)電模擬裝置，采用直流穩(wěn)壓源和滑動(dòng)變阻器來(lái)模擬光伏電池。通過(guò)TMS320F2812 DSP芯片ADC模塊實(shí)時(shí)采樣模擬電網(wǎng)電壓的正弦參考信號(hào)、光伏電池輸出電壓、負(fù)載電壓電流反饋信號(hào)等。經(jīng)過(guò)數(shù)據(jù)處理后，用PWM模塊產(chǎn)生實(shí)時(shí)的SPWM 波，控制MOSFET逆變?nèi)珮蜉敵稣也ā１疚挠肞I控制算法實(shí)現(xiàn)了輸出信號(hào)對(duì)給定模擬電網(wǎng)電壓的正弦參考信號(hào)的頻率和相位跟蹤，用恒定電壓法實(shí)現(xiàn)了光伏電池最大功率點(diǎn)跟蹤（MPPT），從而達(dá)到模擬并網(wǎng)的效果。另外本裝置還實(shí)現(xiàn)了光伏電池輸出欠壓、負(fù)載過(guò)流保護(hù)功能以及光伏電池輸出欠壓、過(guò)流保護(hù)自恢復(fù)功能、聲光報(bào)警功能、孤島效應(yīng)的檢測(cè)、保護(hù)與自恢復(fù)功能。系統(tǒng)測(cè)試結(jié)果表明本設(shè)計(jì)完全滿定設(shè)計(jì)要求。關(guān)鍵詞：光伏并網(wǎng)，MPPT，DSP Photovoltaic Grid-connected generation simulator Zhangyuxin，Tantiancheng，Xiewuyang(College of Electrical Engineering, Chongqing University)Abstract: This paper presents a photovoltaic grid-connected generation simulator which is based on TMS320F2812 DSP, with a DC voltage source and a variable resistor to simulate the characteristic of photovoltaic cells. We use the internal AD converter to real-time sampling the referenced grid voltage signal, outputting voltage of photovoltaic, feedback outputting voltage and current signal. The PWM module generates SVPWM according to the calculation of the real-time sampling data, to control the full MOSFET inverter bridge output sine wave. We realized that the output voltage of the simulator can track the frequency and phase of the referenced grid voltage with PI regulation, and the maximum photovoltaic power tracking with constant voltage regulation, thereby achieved the purpose of grid-connected simulation. Additionally, this device has the over-voltage and over-current protection, audible and visual alarm, islanding detecting and protection, and it can recover automatically. The testing shows that our design is feasible.Keywords: Photovoltaic Grid-connected，MPPT，DSP 目錄引言 11. 方案論證 11.1. 總體介紹 11.2. 光伏電池模擬裝置 11.3. DC-AC逆變橋 11.4. MOSFET驅(qū)動(dòng)電路方案 21.5. 逆變電路的變頻控制方案 22. 理論分析與計(jì)算 22.1. SPWM產(chǎn)生 22.1.1. 規(guī)則采樣法 22.1.2. SPWM 脈沖的計(jì)算公式 32.1.3. SPWM 脈沖計(jì)算公式中的參數(shù)計(jì)算 32.1.4. TMS320F2812 DSP控制器的事件管理單元 42.1.5. 軟件設(shè)計(jì)方法 62.2. MPPT的控制方法與參數(shù)計(jì)算 72.3. 同頻、同相的控制方法和參數(shù)計(jì)算 8
標(biāo)簽： tms320f2812 光伏 并網(wǎng)發(fā)電 模擬 protel pcb
上傳時(shí)間： 2021-11-02
上傳用戶：
? LLC series-resonant Half-bridge: operationand significant waveforms? Simplified model (FHA approach)? 300W design example
上傳時(shí)間： 2021-11-22
上傳用戶：
This Section covers the design of power transformers used in buck-derived topologies: forward converter, bridge, half-bridge, and full-wave centertap. Flyback transformers (actually coupled inductors) are covered in a later Section. For more specialized applications, the principles discussed herein will generally apply.
上傳時(shí)間： 2021-12-16
上傳用戶：fliang
通過(guò)采用無(wú)橋PFC和半橋LLC諧振變換器作為數(shù)字開(kāi)關(guān)電源的主變換拓?fù)?基于STM32系列微控制器的全數(shù)字控制PFC和DC-DC變換器,首先對(duì)數(shù)字化開(kāi)關(guān)電源方案進(jìn)行對(duì)比,然后闡述了200W數(shù)字開(kāi)關(guān)電源整體方案,并對(duì)數(shù)字開(kāi)關(guān)電源的無(wú)橋PFC和半橋LLC變換器進(jìn)行系統(tǒng)研究。By using a bridgeless PFC and a half-bridge LLC resonant converter as the main conversion topology of the digital switching power supply,the all-digital control PFC and DC-DC converter based on the STM32 series of microcontrollers,firstly the digital switching power supply scheme is compared,and then the overall scheme of 200 W digital switching power supply is expounded, and the bridgeless PFC and half-bridge LLC converter of digital switching power supply are systematically studied.
標(biāo)簽： 數(shù)字開(kāi)關(guān)電源
上傳時(shí)間： 2022-04-02
上傳用戶：qingfengchizhu
該步進(jìn)電機(jī)驅(qū)動(dòng)器又稱為EasyDriver，EasyDriver能夠?yàn)閮杉?jí)步進(jìn)電機(jī)提供大約每相750mA（兩極一共1.5A）的驅(qū)動(dòng)。它默認(rèn)設(shè)置為8步細(xì)分模式（所以如果你的電機(jī)是每圈200步，你使用EasyDriver時(shí)默認(rèn)為每圈1600步），更多細(xì)分模式可以通過(guò)將MS1或MS2兩個(gè)接腳接地進(jìn)行設(shè)置。這是一種基于Allegro A3967驅(qū)動(dòng)芯片的細(xì)分?jǐn)嗦菲鳌?duì)于此設(shè)計(jì)的完整規(guī)格，請(qǐng)查閱A3967的參數(shù)表。它的最大每相電流從150mA到750mA。可以采用的最大驅(qū)動(dòng)電壓大概是30V，其中包括板載5V的調(diào)壓器，所以只需要一個(gè)電源。質(zhì)優(yōu)價(jià)廉，這玩意兒只要十幾美元，比你自己制作電路板更便宜。步進(jìn)電機(jī)驅(qū)動(dòng)器設(shè)計(jì)特色：· A3967 Microstepping Driver· MS1 and MS2 pins broken out to change microstepping resolution to full, half, quarter and eighth steps (defaults to eighth)· Compatible with 4, 6, and 8 wire stepper motors of any voltage· Adjustable current control from 150mA/phase to 700mA/phase· Power supply range from 6V to 30V. The higher the voltage, the higher the torque at high speeds
標(biāo)簽： 步進(jìn)電機(jī) 驅(qū)動(dòng)器 pcb 驅(qū)動(dòng)
上傳時(shí)間： 2022-04-27
上傳用戶：
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