In this paper, the trend of digital TV transmitters in the world is introduced and analyzed in detail. The digital adaptive pre-correction technology used in digital TV transmitters, LDMOS technology, N+1 technology and transmitter cooling technology, etc., and the advantages of using these new technologies are discussed.
Faced with the rapid development of GPS tracking, wireless Internet, mobile communications, PDP (plasma) display and TV studio technology, digital TV transmission technology appears to be slower. However, in recent years, driven by the digital TV market, the launch of digital TV services in the United Kingdom, the United States, Spain, Canada and other countries and the digital TV boom in the world have also made great progress in TV transmission technology.
Early digital TV transmitters simply replaced analog Vision/Sound exciters with external COFDM or 8-VSB exciters, replacing RF output filters and Vision/Sound duplexers with RF band filters. But recently, some large TV transmitter manufacturers have designed and produced a new generation of digital TV transmitters with new concepts and technologies. The main features are as follows:
1. Digital adaptive pre-correction technology (DAP or RTAC)
Digital adaptive pre-correction techniques have been applied to digital television transmitters manufactured by manufacturers in the United States and Europe. THALES in Europe (formerly THOMCAST, a subsidiary of Thomson) called Digital Auto-Adaptive Pre-correction (DAP); HARRIS in the US called Automatic Digital Correction - Real-Time adaptation correction (Enter Automatic Digital correction-Real Time Adaptive correction referred RTAC). Digital adaptive correction technology refers to the performance of the transmitter to the best state within a few minutes of starting the transmitter without human intervention, and the system can also monitor and automatically correct the signal from the transmitter. Fluctuations such as aging, temperature, and the failure of the transmitter itself ensure that the transmitted signal is always in a high-index state, making maintenance very simple.
2. Widely used high power LDMOS transistors in power amplifiers
LDMOS (Lateral Diffused Metal Oxide Semiconductor) is a laterally diffused metal oxide semiconductor. At first, LDMOS technology was developed for 900MHz cellular phone technology. The continuous growth of the cellular communication market guarantees the application of LDMOS transistors, and the LDMOS technology continues to mature and the cost is continuously reduced. Therefore, in most cases, it will replace the bipolar type in the future. Transistor technology.
Compared with bipolar transistors, the gain of the LDMOS transistor is higher, the gain of the LDMOS transistor can reach more than 14dB, and the bipolar transistor is 5~6dB, and the gain of the PA module using the LDMOS transistor can reach about 60dB. This indicates that fewer devices are required for the same output power, thereby increasing the reliability of the amplifier.
Rectifier bridge is to seal the rectifier tube in a shell. Points full bridge and half bridge. The full bridge connects the four diodes of the connected Bridge Rectifier circuit together. The half bridge is half of four diode bridge rectifiers, and two half bridges can be used to form a bridge rectifier circuit. One half bridge can also be used to form a full-wave rectifier circuit with a center-tapped transformer. Select a rectifier bridge to consider. Rectifier circuit and operating voltage.
Bridge Rectifier
Bridge Rectifier,Original Bridge Rectifier,Full Bridge Rectifier ,Diodes Bridge Rectifier,Single Phase Rectifier Bridge, Three Phase Bridge Rectifier
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