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.
標簽： Imperfections RF
上傳時間： 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”
上傳時間： 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.
標簽： Multimedia Subsystem The IMS 3G IP
上傳時間： 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.
上傳時間： 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?
上傳時間： 2020-06-09
上傳用戶：shancjb
基于TMS320F2812 光伏并網發電模擬裝置PROTEL設計原理圖+PCB+軟件源碼+WORD論文文檔,硬件采用2層板設計，PROTEL99SE 設計的工程文件，包括完整的原理圖和PCB文件，可以做為你的學習設計參考。 摘要：本文實現了一個基于TMS320F2812 DSP芯片的光伏并網發電模擬裝置，采用直流穩壓源和滑動變阻器來模擬光伏電池。通過TMS320F2812 DSP芯片ADC模塊實時采樣模擬電網電壓的正弦參考信號、光伏電池輸出電壓、負載電壓電流反饋信號等。經過數據處理后，用PWM模塊產生實時的SPWM 波，控制MOSFET逆變全橋輸出正弦波。本文用PI控制算法實現了輸出信號對給定模擬電網電壓的正弦參考信號的頻率和相位跟蹤，用恒定電壓法實現了光伏電池最大功率點跟蹤（MPPT），從而達到模擬并網的效果。另外本裝置還實現了光伏電池輸出欠壓、負載過流保護功能以及光伏電池輸出欠壓、過流保護自恢復功能、聲光報警功能、孤島效應的檢測、保護與自恢復功能。系統測試結果表明本設計完全滿定設計要求。關鍵詞：光伏并網，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驅動電路方案 21.5. 逆變電路的變頻控制方案 22. 理論分析與計算 22.1. SPWM產生 22.1.1. 規則采樣法 22.1.2. SPWM 脈沖的計算公式 32.1.3. SPWM 脈沖計算公式中的參數計算 32.1.4. TMS320F2812 DSP控制器的事件管理單元 42.1.5. 軟件設計方法 62.2. MPPT的控制方法與參數計算 72.3. 同頻、同相的控制方法和參數計算 8
標簽： tms320f2812 光伏 并網發電 模擬 protel pcb
上傳時間： 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.
上傳時間： 2021-12-16
上傳用戶：fliang
通過采用無橋PFC和半橋LLC諧振變換器作為數字開關電源的主變換拓撲,基于STM32系列微控制器的全數字控制PFC和DC-DC變換器,首先對數字化開關電源方案進行對比,然后闡述了200W數字開關電源整體方案,并對數字開關電源的無橋PFC和半橋LLC變換器進行系統研究。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.
標簽： 數字開關電源
上傳時間： 2022-04-02
上傳用戶：qingfengchizhu
該步進電機驅動器又稱為EasyDriver，EasyDriver能夠為兩級步進電機提供大約每相750mA（兩極一共1.5A）的驅動。它默認設置為8步細分模式（所以如果你的電機是每圈200步，你使用EasyDriver時默認為每圈1600步），更多細分模式可以通過將MS1或MS2兩個接腳接地進行設置。這是一種基于Allegro A3967驅動芯片的細分斷路器。對于此設計的完整規格，請查閱A3967的參數表。它的最大每相電流從150mA到750mA。可以采用的最大驅動電壓大概是30V，其中包括板載5V的調壓器，所以只需要一個電源。質優價廉，這玩意兒只要十幾美元，比你自己制作電路板更便宜。步進電機驅動器設計特色：· 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
上傳時間： 2022-04-27
上傳用戶：
