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An OCXO inside an HP digital frequency counter Miniature crystal oven used to stabilize the frequency of a vacuum-tube mobile radio transmitter. A crystal oven is a temperature-controlled chamber used to maintain the quartz crystal in electronic crystal oscillators at a constant temperature, in order to prevent changes in the frequency due to variations in ambient temperature.
Crystal oscillators can be manufactured for oscillation over a wide range of frequencies, from a few kilohertz up to several hundred megahertz.Many applications call for a crystal oscillator frequency conveniently related to some other desired frequency, so hundreds of standard crystal frequencies are made in large quantities and stocked by electronics distributors.
A crystal oscillator is an electronic oscillator circuit that uses a piezoelectric crystal as a frequency-selective element. [1] [2] [3] The oscillator frequency is often used to keep track of time, as in quartz wristwatches, to provide a stable clock signal for digital integrated circuits, and to stabilize frequencies for radio transmitters and receivers.
For example, most computers require independent clocks for processor timing, disk I/O, serial I/O, video generation, Ethernet I/O, audio conversion, and other functions. [ 3 ] Clock generators are usually specialised for their applications, including the number and selection of frequencies, various auxiliary features, and package configurations.
A combination of quartz based reference oscillator (such as an OCXO) and modern correction algorithms can get good results in Holdover applications. [23] The holdover capability then is provided either by a free running local oscillator, or a local oscillator that is steered with software that retains knowledge of its past performance. [23]
Rakon Limited is a technology company founded in 1967 that designs and manufactures frequency control products, primarily quartz crystals and temperature-compensated crystal oscillators (), [1] oven controlled crystal oscillators and voltage controlled crystal oscillators (). [2]
Due to the sub 1 ppm accuracy of this type of crystal oscillator specialist packaging must be used to ensure good ageing and temperature shock characteristics. Example applications are for use in low power or battery operated consumer electronic products such as GSM or CDMA mobile phones, or GPS satellite navigation systems.
The low frequency flicker noise affects the phase noise because the flicker noise is heterodyned to the oscillator output frequency due to the non-linear transfer function of active devices. The effect of flicker noise can be reduced with negative feedback that linearizes the transfer function (for example, emitter degeneration).