What is an OCXO and what are the benefits?

What is an OCXO?

OCXO stands for Oven Controlled Xtal Oscillator. An OCXO is a type of crystal oscillator that uses either an oven or another heat source to maintain a constant temperature around the crystal which enables it to generate a stable and accurate output frequency. The OCXO achieves the Freq. Vs temp by tightly maintaining the temperature of the crystal at a temperature above the highest operating temperature.

The crystal is the heart of the oscillator, and its performance is affected by temperature changes. The oven in an OCXO is typically a small chamber surrounding the crystal and is heated by a small heater and monitored by a temperature sensor, which maintains the temperature of the oven around a set point. The temperature change inside the oven is typically very small, over the specified temperature.

In some cases, copper may be used as a conductor to transfer heat to the oven chamber in order to maintain a constant temperature. This is usually done through a copper thermal link, which is a copper strip that connects the oven to the crystal resonator. This copper strip can be heated to a specific temperature, which will in turn heat the crystal resonator to the same temperature, keeping it stable. This approach eliminates the need for an oven, which can help to reduce the size and power consumption of the oscillator

An OCXO can achieve 0.5 ppb over a wide temperature range by:

• Maintaining the crystal to a tight temperature, better than 1,000:1 for the higher performance ovens.
• Setting the temperature of the oven where the crystal slope is close to zero.?Typically, < 5ppb/°C.
• For a 100°C temperature?? 100°C/1,000 ? 0.1°C ? 0.1°C x 5ppb/°C ? 0.5 ppb

OCXOs are generally more expensive and larger than other types of crystal oscillators as they use a more precise crystal and more circuitry for the oven temperature/frequency control.

They also have a longer start-up time as it takes time for the oven to reach the set temperature, but when stable it is the most accurate of the quartz oscillator circuit types

OCVCXO stands for oven-controlled voltage-controlled crystal oscillator. It is a type of oscillator that uses a crystal as its frequency-determining element and a control circuit to maintain a constant temperature for the crystal.

The Vcontrol, or voltage control input, is used to adjust the frequency of the oscillator. It can be part of an automatic frequency control (AFC) system or adjusted manually using a potentiometer. The accuracy of the frequency can be improved by using a regulated supply reference.

The Benefits of an OCXO?

The main advantage of an OCXO is its high-frequency stability and accuracy. The temperature of the crystal is kept constant generating an output frequency that is stable and accurate making it ideal for applications that require precise timing and an accurate output frequency.

The main benefits of an OCXO include:

• High-frequency stability and accuracy: The temperature of the crystal is kept constant, which ensures that the output frequency is stable and accurate. This makes OCXOs ideal for applications that require precise timing and frequency, such as telecommunications, GPS, and test and measurement equipment.
• Long-term stability: The oven maintains the temperature of the crystal, which prevents the crystal from drifting over time meaning that it can maintain its accuracy over a long period of time, making it suitable for applications where long-term stability is required.
• Wide temperature range: Offer good frequency stability over a wide temperature range, which makes them suitable for applications that are exposed to temperature changes.
• Versatility: OCXOs can be used in a variety of applications that require a stable and accurate time base, such as telecommunications, test and measurement, navigation, and industrial control systems.
• Low-Phase Noise: One of the main benefits of OCXOs is that they have low-phase noise, which means that they produce a very stable and clean signal. This makes them ideal for use in applications where a stable signal is essential.

What Applications use OCXOs?

While OCXOs are generally more expensive and larger than other types of crystal oscillators, they can be useful in some applications where the stability, accuracy, and long-term stability outweigh the cost and size considerations. OCXOs are widely used in a variety of applications that require a stable and accurate time base. Some common applications that use OCXOs include:

• Telecommunications: OCXOs provide a stable and accurate clock signal for digital signal processing and data transmission. They are also used in frequency synthesisers and modems.
• GPS: They are used in GPS receivers to provide a stable and accurate clock signal for timing and navigation. They are also used in GPS base stations to provide a reference frequency for the GPS signal.
• Test and measurement: They generate a stable and accurate time base for frequency measurements, time domain reflectometry, and other applications.
• Industrial control systems: OCXOs are used in industrial control systems to provide a stable and accurate clock signal for timing and control.
• Military and aerospace: They provide a stable and accurate time base for navigation, guidance, and control systems.
• Audio and video equipment: OCXOs offer a stable and accurate clock signal for digital signal processing and data transmission.
• Atomic clocks: An OCXO is used as a cleanup in situations where high-precision frequency generation is required, such as in communications systems or GPS receivers which results in more accurate frequency generation.
• Networking equipment: Used in networking equipment such as routers and switches to provide a stable and accurate clock signal for data transmission and processing.

Overall, OCXOs are widely used in a variety of applications that require a stable and accurate time base and long-term stability. They are particularly useful in applications that are sensitive to temperature changes, vibration, and shock, and in applications where long-term stability is a priority.

In summary, an OCXO is a type of crystal oscillator that uses an oven to maintain a constant temperature around the crystal. This allows the oscillator to produce a stable and accurate output frequency, making it ideal for applications that require precise timing and frequency.

Raltron's portfolio of OCXOs covers frequencies ranging from 1 MHz to 200 MHZ with frequency stability between ±0.5ppb to ±0.1ppm. Extended Temperature ranges from -40°C to +105°C and offers all standard voltages. Products are available in both through-hole and SMD.

Raltron is one of the fastest-growing manufacturers of frequency components. The company offers one of the broadest lines of quartz crystals and crystal-based products from simple resonators to precision oscillators, such as OCXO, VCXO, and TCXO. In addition, Raltron’s portfolio extends to RF products such as LTCC Filters, Baluns, Band-Pass Filters, and both Chip Antennas and Stub / Patch Antennas.

Raltron offers full technical support with two application engineering teams and failure analysis labs based in Miami and Shenzhen (China).