Voltage Controlled Oscillators- Fine Tuning The Communication SystemsThe technological world, which helps communication ac...
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Voltage Controlled Oscillators- Fine Tuning The Communication Systems

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A Voltage Controlled Oscillator (VCXO) is a component for reference timing used in virtually all wireless systems. A VCXO has the capability to fine-tune the output frequency within a certain range, even after the device is already populated in a system.

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Voltage Controlled Oscillators- Fine Tuning The Communication Systems

  1. 1. Voltage Controlled Oscillators- Fine Tuning The Communication SystemsThe technological world, which helps communication across geographical boundaries easier and faster, isnot as simple as it sounds. Understanding the intricacies of the network and the components, which gointo making communication lines with clarity of voice and speech, is itself a Herculean task.A Voltage Controlled Oscillator (VCXO) is a component for reference timing used in virtually allwireless systems. A VCXO has the capability to fine-tune the output frequency within a certain range,even after the device is already populated in a system. With the varactor diode as the principal variable ortuning element, the VCO is tuned across its band by a dc voltage applied to the diode. This fine-tuning ofa clock frequency within an electronic system is used to synchronize the receiving system with atransmitting system, which is not at the same location. Synchronous communication standards likeSONET and GiGe require extremely tight timing control. These standards are found everywhere fromlong-haul, wide-area network (WAN) global communication to the metro-area network (MAN) found incities and neighborhoods. An error in the timing between the receiver and transmitter translates to biterrors, dropped transactions and systems coming to a grinding halt. An example is a phone call. Whenyou talk on your mobile phone while driving, the wireless infrastructure is moving your call from onebase station or repeater to another to maintain contact. If any of the base stations or repeaters were out ofsynch, the call would be dropped or larger pieces of the conversation would be lost.Voltage controlled oscillators (VCXO) are generally made of quartz crystals, but recent technologicaldevelopments have led to the usage of silicon oscillators with MEMS technology. Generally used forperforming a clock and data recovery function, a VCXO is used with receivers or wireless base stationsand with consumer electronic devices and set top boxes. Two main specifications with a VCXO are pullrange and linearity. The crystal oscillator offers an output frequency pull range up to 200PPM, buttypically only 10-15PPM for higher precision VCXOs. An all-silicon VCXO offers significantly greaterpull range up to 1600PPM. This wide pull range will enable new applications as more system designsrealize the availability of a VCXO with such a large pull range. However, a wide pull range is not veryappealing if the linearity is poor. Fortunately, this is not the case with MEMS VCXOs. Linearity istypically 1%, resulting in a monotonic pull range over the entire 1600 PPM. This represents a 10-to-20-times improvement compared to a quartz-crystal VCXO with a 200PPM pull range. MEMS Oscillatorsare flexible and facilitate innovation of in telecom clock synchronization, wireless networking, FPGA-based systems and various other applications.An all-silicon VCXO showcases a number of other unique key features such as configurability, frequencyand supply-voltage flexibility, plastic packaging, and drop-in, pin-to-pin compatibility to existing quartzcrystal VCXOs.Learn more about :- Clock Oscillator & TCXO

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