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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.
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.
In nearly all quartz clocks and watches, the frequency is 32 768 Hz, [1] and the crystal is cut in a small tuning fork shape on a particular crystal plane. [2] This frequency is a power of two ( 32 768 = 2 15 ), just high enough to exceed the human hearing range , yet low enough to keep electric energy consumption , cost and size at a modest ...
Allan variance is used as a measure of frequency stability in a variety of precision oscillators, such as crystal oscillators, atomic clocks and frequency-stabilized lasers over a period of a second or more. Short-term stability (under a second) is typically expressed as phase noise.
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.
Amongst the building blocks of a GPS Time and Frequency solution the oscillator is a key component [11] and typically they are built around an Oven Controlled Crystal Oscillator or a Rubidium based clock. The dominant factors influencing the quality of the reference oscillator are taken to be aging and temperature stability.
The crystal in combination with C 1 and C 2 forms a pi network band-pass filter, which provides a 180° phase shift and a voltage gain from the output to input at approximately the resonant frequency of the crystal. To understand the operation, note that at the frequency of oscillation, the crystal appears inductive.
Causes may include component aging, [1] changes in temperature that alter the piezoelectric effect in a crystal oscillator, or problems with a voltage regulator which controls the bias voltage to the oscillator. Frequency drift is traditionally measured in Hz/s. Frequency stability can be regarded as the absence (or a very low level) of ...