A Voltage Controlled Crystal Oscillator or a VCXO is a piece of electronic equipment whose oscillating or output frequency is altered whenever a control potential difference is given to it under a constant supply voltage. A VCXO comes with a crystal oscillator, supporting circuitry, and a varactor diode. The maximum change in the measure of the output frequency of VCXO over the change in control voltage under constant temperature and supply voltage – as said in ppm – is known as Pullability or Total Pulling Range.

Difference between VCXO and VCO

1. In the VCXO an oscillation frequency is generated according to the Crystal Properties while in the VCO it is generated through an electronic circuit.
2. The VCXO has got a narrow range of frequency while the VCO comes with a wide range of frequency.
3. VCXO has got higher stability, on the other hand, VCO has got lower stability.
4. VCXO has a lower phase noise while VCO has a higher phase noise.

Applications of VCXO

VCXOs have found their use in many applications. Here we have some of them:

• Narrowband PLLs – VCXO is used in narrow-band phase-locked loops where the requirement for the change on frequency is very small.
• Temperature Controlled Crystal Oscillators – VCXOs are mainly used in TCXOs, commonly known as Temperature Controlled Crystal Oscillators, where the temperature pay voltage is provided to a control terminal of the VCXO. Thus using this technique reduces the drift to a lot extent. It is to be noted that the use of VCXO is not that much good as a full oven-controlled crystal oscillator but still it can provide a slight up-gradation in its performance level.

VCXOs Specifications:

While specifying VCXOs the following parameters are normally taken into consideration.

1. Package – The voltage-controlled crystal oscillators come in different forms, thus it is important to specify the right package for the right product.

2. Pullability – The pullability is defined as the range of frequency over which the VCXO can be pulled for a defined change in control potential difference. For a given voltage, it is specified in terms of ppm (parts per million). VCXO having a small pullability value offers a lower phase noise and greater stability. While VCXOs with larger pullability value provides a larger tuning range.

3. Voltage Supply – It is important to mention the supply voltage to guarantee that it works inside the unit for which it is proposed. Ideally, it ought to have the option to work outside the normal resistance of the flexibly so that any slight jumble doesn't cause an issue.

4. Frequency – This is generally specified in MHz for all frequencies that are in the range of over 1.0MHz and in KHz for all frequencies that are below this. It is also important to specify the frequency to the right number of decimal spots to empower the producer to have the option to decide the necessary recurrence required.

This was all we have regarding VCXO Oscillators. Hope you liked going through it. Brands that manufacture them are ABRACON, Silicon Labs and, Crystek. Make sure to check them out using the links as provided.

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A Temperature Compensator Crystal Oscillator or a TCXO is a crystal oscillator that is designed to withstand high-temperature conditions. In a regular crystal oscillator the oscillation frequency fluctuates with the rise in temperature. The consequence of this is an unstable oscillation frequency. TCXO supports a stable oscillation frequency at high temperatures. For this, they take the help of a temperature compensation network which balances out the oscillation frequency at higher temperatures.

Performance figure of TCXO

Some of the most important performance figures of TCXO are as follows:

• Power Dissipation – The dissipation of power in a TCXO will be much greater as compared to an ordinary oscillator keeping in view of the additional circuitry needed. In addition to that the cost becomes greater. It should also be kept in mind that the cost is greater. It is also worth remembering that it will take a short period after start-up for the oscillator to stabilize. This might be of the order 100 ms, or conceivably more, subordinate upon the plan.

• TCXO PPM performance – As said earlier, the performance of TCXO temperature is much better as compared to a normal crystal oscillator. Ordinarily, figures of somewhere in the range of 10 and 40 times improvement can regularly be seen. Figures that are better than +1.5 (or -1.5) ppm over a temperature range of 0 to 70 degrees Celsius are much harder to achieve as they at that point fall into a high exactness classification where costs increment essentially.

• TCXO package – TCXOs can be supplied in several packages depending upon the requirements of the end-user as well as the way they have been designed. The most well-known type of development is to build the circuit on a little printed circuit board that can be housed in a plat metal bundle. This is then reasonable for mounting onto the fundamental circuit leading body of the general hardware. As the crystal is sealed itself, this implies fixing of the general TCXO bundle isn't basic, or even required for most applications.

• Output format and level - With numerous TCXOs being utilized for driving advanced circuits, a large portion of the little oscillator bundles produce what is named a clipped sine wave. This is suitable for driving a logic circuit, but in many instances it is recommended to put it through a logic buffer to make sure that it is sufficiently square. The output is generally an open collector circuit. On the off chance that a sine wave output is needed, at that point this must be picked at the start and it will confine the decision accessible.

• Power Requirements – The actual requirement of power depends on the particular device. Many works from provisions of 3 V, and may draw as meager as 2 mA, even though this will rely on the general kind, the producer and the specific gadget picked.

This was all we have regarding the TCXO oscillator. Hope you liked going through it. Brands that manufacture them are ABRACON, TXC Corporation, and AVX. Check them out using the links as provided.

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A crystal oscillator is said to be an electrical oscillator circuit that utilizes the mechanical resonance of a vibrating crystal made up of piezoelectric material to establish an electrical signal with an exact frequency. This frequency is found to be useful in providing a stable clock signal in digital integrated circuits, keeping a track of time (in quartz wristwatches), and to settle frequencies for radio receiver and transmitters. The most widely recognized kind of piezoelectric resonator utilized is the quartz crystals, so oscillator circuits consolidating them got known as crystal oscillators, but other piezoelectric materials including polycrystalline ceramics are utilized in comparable circuits.

A crystal oscillator, particularly that utilizes quartz crystal, works by mutilating the crystal by an electric field when a potential difference is applied to the electrode. This property is known as inverse piezoelectricity or electrostriction. As soon as the electric field is taken off, the quartz that is oscillating at a precise frequency returns to its previous shape and generates an electric field. This can even set up a voltage. The consequence is that this quartz crystal starts to act like an RLC circuit but with a much higher value of Q.

Quartz crystals are produced for frequencies ranging from a few tens of Kilo Hertz to hundreds of MegaHertz. It is estimated that more than 2 Billion crystals are produced per year. Most of them have found their use in consumer devices like clocks, computers, wristwatches, cellphones, and radios. These crystals are also used inside measuring and texting equipment like oscilloscopes, signal generators, counters, etc.

Operation

A crystal is defined as that solid where all its constituent atoms, ions, or molecules are packed in regular order, repeated pattern in all its 3 dimensions.

Whenever a crystal made up of quartz is cut and mounted properly, it very well may be made to contort in an electric field by applying a voltage to a terminal close or on the crystal. As said earlier, this property is known as Electrostriction. When the field is removed, it sets up an electric field as it gets back in its initial shape. Thus, it behaves like an RLC circuit, made up of a capacitor, resistor, and an inductor.

One more advantage of quartz is that its size and elastic constants change in such a manner that the frequency reliance on temperature can be extremely low. The specific characteristic depends on two things: the angle at which the quartz is cut (with respect to its crystallographic axes) and the mode of vibration. As a result, the resonant frequency of the plate (depending on size) does not vary much. This conveys that a quartz filter, oscillator, or a clock remains accurate. For basic applications, the quartz oscillator is mounted in a temperature-controlled holder known as Crystal Oven. It can also be mounted on shock absorbers to forestall irritation by outer mechanical vibrations.

This was all we have for Crystal Oscillator. Hope you liked this article. Brands that manufacture them are ABRACON, ECS Inc, and IQD. Make sure to visit them using the links as provided.

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Standard clock oscillators are believed to be the heart of frequency control products and XON serves with a wide range of Crystal Oscillators (XOs) worldwide. Whether your need is for a simple clock or you want it in developing a mission-critical system, we have the best clock oscillators for you.

Features

• Extreme Shock, Vibration, and Temperature (ranging from -55 degrees Celsius to 125 degrees Celsius).
• 3^rd overtone crystal designs as well as low phase noise fundamental.
• High Reliability / COTS / High Temperature options (up to 200 degree Celsius).
• Ultra-low phase noise and jitter; as low as -170dBc/Hz, to 22fs.
• Industrial and automotive-grade products; operating temperature to -40 degrees Celsius to 125 degrees Celsius.
• Standard output types – HCSL, HCMOS, LVDS, and LVPECL.
• Real-time clock reference at the rate of 32.768 kHz with the option for ultra-low current (10 microampere maximum).

Applications

• Radar application and military communication.
• Data storage and networking equipment.
• Automotive electronics – Mobile multimedia systems and car infotainment.
• 100G, 40G, 10G, and SyncE Ethernet protocols.
• Industrial controllers – M2M communications.
• Wireless communications – Zigbee, Bluetooth, Wi-Fi protocols.
• Measurement and Test instrumentation.
• Base station infrastructures.
• Medical monitoring devices.
• PCI Express.
• Energy monitoring equipment like - Gas and water meters, smart electric meters.
• FPGA and microcontroller frequency reference.
• IoT (Internet of Things) applications.

This was all we have regarding the standard clock oscillator. Hope you liked going through the article. Brands that manufacture these oscillators are ABRACON, Microchip, and SiTime. Check them out using the links as provided.

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A temperature-controlled chamber utilized in maintaining the quartz crystal present in the electronic crystal oscillators (at constant temperature) is known as a crystal oven. Its main aim is to cease any changes in the frequency because of varieties in encompassing temperature. An oscillator of this category is known as Oven-Controlled Crystal Oscillator (OCXO; Here “XO” is an old short form for “crystal oscillator”). This kind of oscillator gets the greatest frequency stability possible using a crystal. They are used generally to manage the frequency of cellular base stations, radio transmitters, equipment for military communications as well as in measuring frequency precisely.

Description

Quartz crystals have found its wide use in electronic oscillators to manage the frequency generated precisely. The frequency of vibration of a quartz crystal resonator depends completely on its dimensions. When there is a change in temperature, it leads to the thermal expansion of the resonator. This results in the change of frequency of the signal produced. The coefficient of thermal expansion is very low in quartz, still, the change in temperature is the major cause of the difference in frequency in the oscillator.

The oven comes with the crystal and some electrical heating elements. It is also thermally insulated. Other electrical equipments present inside the circuit are likewise helpless against temperature float, thus, the whole oscillator circuit is enclosed inside the oven. A thermistor temperature sensor in a closed-loop control circuit is utilized to make sure that the oven is kept at a desired precise temperature as well as to manage the power of the heater. The oven is said to start its work above ambient temperature and because of it the oscillator generally requires a warm-up time after the power is supplied to reach its operating temperature. The frequency will not have the full rated stability during this warm up time.

The operating temperature chosen for the oven is that at which the slope of Crystal’s Frequency Vs. The temperature curve is Zero. SC-cut (Stress-Compensated) or AT- crystals are utilized. The SC-cut has a wide range of temperatures over which the near-zero temperature coefficient is accomplished and along these lines lessens warmup time. Instead of resistance heating elements, power transistors are used for the heaters. The power output of these transistors is not proportional to the square of the current but only to the current. This linearizes the gain of the control loop.

One of the temperatures which is common for a crystal is 75 degree Celsius. But depending on the setup it may vary between 30 to 80 degrees Celsius.

Most standard commercial crystals are indicated to an ecological temperature of 0 to 70 degrees Celsius and the industrial ones are generally specified to -40 to +85 degrees Celsius.

This was all we have regarding OCXO Oscillators. Hope you liked reading it. Brands that manufacture them are ABRACON and ECS Inc. Do give a check to these manufacturers using the links as provided. 

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