Temperature Compensated Crystal Oscillators TCXO deliver excellent temperature characteristics combined with low power consumption and fast warmup. Voltage Controlled Temperature Compensated Crystal Oscillators VCTCXO combine the same excellent temperature characteristics, low power consumption and fast warmup with a voltage control function to allow precise tuning of the output frequency after PCB assembly and later, to compensate for any effects of aging as well as offering the ability to pull back to nominal frequency where there is a change of circuit conditions.
Some of our TCXO models incorporate an analogue ASIC which provides a smoother signal when combined with a high order temperature compensation circuit. Rakon's commitment to quality and high performance has meant it has become the default standard for consumer GPS, emergency beacons, telecommunications infrastructure and many other performance critical applications.
We also offer a custom TCXO design and application service to meet specific customer requirements where characteristics such as frequency slope and perturbation specifications can be customised to satisfy specific applications. Sign In if you already have an account with us.The SiT further minimizes the loss of satellite lock by eliminating activity dips and micro jumps. Program oscillators to get instant samples, optimized performance, and fast prototyping Learn More.
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There are several characteristics peculiar to VCXOs. In generating a VCXO specification these apply in addition to the characteristics which define fixed frequency crystal oscillators.
It is sometimes referred to as Modulation Voltage, especially if the input is an AC signal. Deviation - This is the amount of frequency change which results from changes in control voltage.
For example. Transfer function sometimes referred to as Slope Polarity - This denotes the direction of frequency change vs control voltage.
A positive transfer function denotes an increase in frequency for an increasing positive control voltage, as in Figure 1 A. Conversely, if the frequency decreases with a more positive or less negative control voltage, as in Figure 1 B, the transfer function is negative. It is the ratio between frequency error and total deviation, expressed in percent, where frequency error is the maximum frequency excursion from the best straight line drawn through a plot of output frequency vs control voltage.
These limits are shown by lines "B" and "C".
TCXO vs. OCXO
The VCXO which produces the characteristic in Figure 3 uses an abrupt junction varactor diode with an applied unipolar control voltage positive in this case. Good VCXO design dictates that the voltage to frequency curve be smooth no discontinuities and monotonic. Modulation rate sometimes referred to as Deviation Rate or Frequency Response - This is the rate at which the control voltage can change resulting in a corresponding frequency change.
It is measured by applying a sinewave signal with a peak value equal to the specified control voltage, demodulating the VCXO's output signal, and comparing the output level of the demodulated signal at different modulation rates.CTS VCXO High-Performance Crystal Oscillator Products - TechTalk with Tom Griffin
The modulation rate is defined by Vectron as the maximum modulation frequency which produces a demodulated signal within 3 dB of that which is present with a Hz modulating signal. While non-crystal controlled VCOs can be modulated at very high rates greater than 1 MHz for output frequencies greater than 10 MHzthe modulation rate of VCXOs is restricted by the physical characteristics of the crystal.
While the VCXO's modulation input network can be broadened to produce a 3 dB response above kHz, the demodulated signal may exhibit amplitude variations of dB at modulation frequencies greater than 20 kHz due to the crystal.
Slope should be really called average slope if it is intended to define the total deviation divided by the total control voltage swing. Incremental sensitivity, often misnomerred Slope Linearity means the incremental change in the frequency vs control voltage.
It inherently resists being "pulled" deviated from its designed frequency. This results in degrading the inherent stability of the crystal in terms of its frequency vs temperature characteristic, its aging characteristic, and its short-term stability and associated phase noise characteristic.
Therefore, it is in the user's best interest not to specify a wider deviation than that absolutely required. Phase Locking - When a VCXO is used in phase lock loop application, the deviation should always be at least as great as the combined instability of the VCXO itself and the reference or signal onto which it is being locked. Vectron produces a line of VCXOs especially intended for use in phase lock loop applications described on the pages which follow.
It is rare that higher overtone, and therefore higher frequency crystals find application in VCXOs. Thus, VCXOs with output frequencies higher or lower than available from the appropriate crystal frequencies include frequency multipliers or dividers. General Note - While it is true of any type of crystal oscillator, it is especially important with VCXOs that the user not over-specify the product. The particular problem with VCXOs is that increased deviation results in degraded stability which can result in the need for still wider deviation, further degrading stability, resulting in a spiraling increase in the required deviation.
Search text: Contact us Login. Back to Product Table.Gain a better understanding on the differences between these two popular crystal oscillators. A crystal oscillator is an electronic oscillator circuit that uses the mechanical reverberation of a vibrating crystal typically a quartz crystal to create an electrical signal with precise frequency.
It is often used for stabilization applications, to help keep track of time, and to provide a stable clock signal for digital integrated circuits. To limit their level of influence, modified crystal oscillators are offered. Both offer excellent short-term stability, with limitations coming mostly from the electronic components that are included in the oscillator circuits, and affects brought on by aging of the crystal.
TCXOs are used to provide a higher level of temperature stability than the standard crystal oscillator XO. Power consumption is greater with the TCXO and the cost is more, too, but these matters are inconsequential when you consider the fact that it effectively addresses the aforementioned environmental factors, and delivers a much more reliable signal than a normal XO.
Included is a temperature sensor that — when the temperature changes — will apply a small correct voltage to a varactor, which then produces a frequency that is equal and opposite to the change in frequency produced by the temperature. This counterbalance-based circuitry allows the TCXO to continue to provide a stable frequency without being influenced by environmental factors.
The warm-up allows all of the components to reach thermal equilibrium and ensures that the device delivers a precise signal. Those worried about power consumption will be pleased to hear that power used during this stage is for the most part, nominal. To remove the affects of an aging crystal, TCXOs come with an external adjustment that enables the frequency to be reset periodically.
Time between these calibration adjustments varies based upon the level of accuracy required, but average recommendations are every six months to a year. Shorter periods can be used if higher levels of accuracy are necessary. Applying temperature compensation can be problematic, too, because the temperature coefficient of the crystal changes with temperature.
This version of crystal oscillator is typically used with tasks that require precise frequency, such as controlling radio transmitter frequency, cellular base stations and military communications equipment. To ensure that that it is optimized for a higher internal operating temperature, the crystal used in an OCXO is typically made from a special cut AT- or SC-cut. A thermistor temperature sensor is used to control the power of the heater and ensure that a precise temperature within the oven is maintained constantly.
While having a precisely regulated, temperature controlled environment all but guarantees top tier performance of the crystal, one should keep in mind that having everything together in an enclosed oven-like unit means that an OCXO is physically larger than a TCXO. As such, it cannot be used in many of the TCXO-appropriate miniature applications.
A longer warm-up period is required when using an OCXO because the oven will only begin to operate once it hits a precise temperature some OCXO heaters actually require about an Amp of power during this time. Such a high level of power consumption means that an OCXO cannot be run solely on batteries. As with the TCXO, periodic calibrations are required every six months to a year. They are a terrific solution for portable units that necessitate a reasonably accurate source.
Learn more about Electronic Products Magazine. Gain a better understanding on the differences between these two popular crystal oscillators BY JEFFREY BAUSCH A crystal oscillator is an electronic oscillator circuit that uses the mechanical reverberation of a vibrating crystal typically a quartz crystal to create an electrical signal with precise frequency. Calibration To remove the affects of an aging crystal, TCXOs come with an external adjustment that enables the frequency to be reset periodically.
Power consumption A longer warm-up period is required when using an OCXO because the oven will only begin to operate once it hits a precise temperature some OCXO heaters actually require about an Amp of power during this time.A crystal oscillator is an electronic oscillator circuit that uses the mechanical resonance of a vibrating crystal of piezoelectric material to create an electrical signal with a precise frequency.
Temperature Compensated Crystal Oscillators (TCXOs & VCTCXOs)
The most common type of piezoelectric resonator used is the quartz crystal, so oscillator circuits incorporating them became known as crystal oscillators,  but other piezoelectric materials including polycrystalline ceramics are used in similar circuits.
A crystal oscillator, particularly one using a quartz crystalworks by distorting the crystal with an electric fieldwhen voltage is applied to an electrode near or on the crystal; a property known as electrostriction or inverse piezoelectricity.
When the electric field is removed, the quartz—which oscillates at a precise frequency—generates an electric field as it returns to its previous shape, and this can generate a voltage. The result is that a quartz crystal behaves like an RLC circuitbut with a much higher Q.
Quartz crystals are manufactured for frequencies from a few tens of kilohertz to hundreds of megahertz. More than two billion crystals are manufactured annually. Quartz crystals are also found inside test and measurement equipment, such as counters, signal generatorsand oscilloscopes. A crystal oscillator is an electronic oscillator circuit that uses a piezoelectric resonator, a crystal, as its frequency-determining element.
Crystal is the common term used in electronics for the frequency-determining component, a wafer of quartz crystal or ceramic with electrodes connected to it. A more accurate term for it is piezoelectric resonator.
Crystals are also used in other types of electronic circuits, such as crystal filters. Piezoelectric resonators are sold as separate components for use in crystal oscillator circuits. An example is shown in the picture. They are also often incorporated in a single package with the crystal oscillator circuit, shown on the righthand side. Piezoelectricity was discovered by Jacques and Pierre Curie in Paul Langevin first investigated quartz resonators for use in sonar during World War I.
The first crystal-controlled oscillatorusing a crystal of Rochelle saltwas built in and patented  in by Alexander M.
TCXO Vs. OCXO Oscillators
Pierce and Louis Essen. Quartz crystal oscillators were developed for high-stability frequency references during the s and s. A number of firms started producing quartz crystals for electronic use during this time.
Using what are now considered primitive methods, aboutcrystal units were produced in the United States during Shortages of crystals during the war caused by the demand for accurate frequency control of military and naval radios and radars spurred postwar research into culturing synthetic quartz, and by a hydrothermal process for growing quartz crystals on a commercial scale was developed at Bell Laboratories.
By the s virtually all crystals used in electronics were synthetic. InJuergen Staudte invented a photolithographic process for manufacturing quartz crystal oscillators while working at North American Aviation now Rockwell that allowed them to be made small enough for portable products like watches.
Although crystal oscillators still most commonly use quartz crystals, devices using other materials are becoming more common, such as ceramic resonators. A crystal is a solid in which the constituent atomsmoleculesor ions are packed in a regularly ordered, repeating pattern extending in all three spatial dimensions. Almost any object made of an elastic material could be used like a crystal, with appropriate transducerssince all objects have natural resonant frequencies of vibration.
For example, steel is very elastic and has a high speed of sound. It was often used in mechanical filters before quartz. The resonant frequency depends on size, shape, elasticityand the speed of sound in the material.
High-frequency crystals are typically cut in the shape of a simple rectangle or circular disk. Low-frequency crystals, such as those used in digital watches, are typically cut in the shape of a tuning fork.
For applications not needing very precise timing, a low-cost ceramic resonator is often used in place of a quartz crystal. When a crystal of quartz is properly cut and mounted, it can be made to distort in an electric field by applying a voltage to an electrode near or on the crystal. This property is known as electrostriction or inverse piezoelectricity. When the field is removed, the quartz generates an electric field as it returns to its previous shape, and this can generate a voltage.
The result is that a quartz crystal behaves like an RLC circuitcomposed of an inductorcapacitor and resistorwith a precise resonant frequency. Quartz has the further advantage that its elastic constants and its size change in such a way that the frequency dependence on temperature can be very low. The specific characteristics depend on the mode of vibration and the angle at which the quartz is cut relative to its crystallographic axes.Welcome, Guest. Please login or register. Did you miss your activation email?
This topic This board Entire forum Google Bing. Print Search. My apologies to Lightages, I seemed to have tuned your thread into a pissing contest about oscillators. A control voltage was supplied to center the frequency to the nominal of the crystal as close as I could get it. In my area, this means that it is effectively disciplined to GPS.
It had been up and running for about 6 months. We started the measurements, and disconnected the antenna.
The unit went into holdover and then into free running mode. This is showing TDEV of the three. This is the frequency error or the TS The first 6mHz spike is the change over form locked to hold over.
The second spike is the unit going form holdover to free running. No offset or drift compensation was applied to this data. This is the frequency error or the OCXO. You can see even though the oscillator has a single oven there is still a temperature dependance. All the measurements were under regular building HVAC. Notice the magnitude of the spike of the Rb oscillator vs the scale in this graph. Vgkid Super Contributor Posts: Country:.
What gear are you using to graph that. If you own any North Hills Electronics gear, message me. Dago Frequent Contributor Posts: Country:. I don't have the equipment to measure close in phase noise correctly. We are mostly concerned with wander.
I'm interested to get one of the FEIs and do a comparison. It would be a stretch to delicate a counter to it for that amount of time Lightages Supporter Posts: Country: Canadian po.A Quartz crystal oscillator is used to create an electrical signal, as well as providing a precise frequency. The crystal oscillators supplied by Euroquartz are popular for their ability to keep track of time. The circuit of the Quartz crystal oscillators is integrated too. When deciding which oscillator is best for your application, Euroquartz make the process easier, allowing you to choose a crystal or a temperature controlled oscillator.
The TCXO Oscillator can reliably keep track of time and is one of the most cost-effective oscillators on the market. This is a miniature 4 pad SMD which is a high-specification product that is low cost.
Euroquartz supply this Quartz crystal oscillator in a variety of frequencies- click here to find out more! This type of oscillator offers greater stability and precision, making it a reliable choice for military equipment. Euroquartz has an extensive range of oscillators available for you to choose from, including the YH oscillator. This type of oscillator is an example of a crystal oven which provides little disruption. The oscillator features a low phase noise and has a frequency range of 10MHz right up to 30MHz.
Check out the crystal oven today! The design of the crystal oven and the temperature controlled products is very different. In addition to this, the design of the TCXO Oscillator is designed to stabilise frequency and maintain precision but the crystal oven is designed to operate at a specific temperature and is designed to be long-lasting.
The warm-up period of the two varies. The crystal oven takes longer to warm up than the temperature controlled oscillator because it operates best when it reaches a certain temperature. The TCXO generates a thermal equilibrium which allows it to work so efficiently. Needless to say, everything requires careful consideration and regular maintenance, however, any Quartz crystal oscillator from Euroquartz requires periodic testing.
This testing is recommended every 6 to 12 months, it merely depends on the device itself. The calibration of the Quartz crystal oscillator is dependent on a number of factors, one of which being the accuracy of the oscillator. If the device has high electrical sensitivity, there needs to be regular calibration to ensure that maximum functionality is achieved.
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