Inside Frequency Control

One is definitely the loneliest number. So what's better, a single (OCXO) or double oven controlled crystal oscillator (DOCXO)?

One of the core challenges any RF engineer faces is maintaining frequency stability in crystal oscillators. In an ideal world, an oscillator would transmit at the desired frequency indefinitely and without deviation… but of course, we don’t live in an ideal world, and frequency drift is a real problem in many applications.

There are a number of factors that can cause an oscillator to deviate from the correct frequency, but frequency drift is not an insurmountable issue. There are various approaches engineers can take to improve stability. In this article, we'll discuss the best approaches to maintaining a high degree of stability your in crystal oscillators.

Will a crystal oscillator operate outside its specified temperature range? This is a common question and the short answer is: yes, but it's complicated.

If, for example, a crystal oscillator is specified over 0 to 60 °C, it will most likely perform without any issues over -40 to 85 °C. But it's possible that it will fall outside its specified stability. This may not matter if the application needs just a stable frequency rather than an accurate frequency.

RF engineers would love to get their hands on an ideal crystal oscillator circuit. That is, a quartz crystal oscillator that transmits at the designated frequency for the entire life of the device without any frequency deviation. Unfortunately, that ideal circuit world is a mathematical fantasy.

There are many factors that contribute to quartz oscillator stability and frequency drift issues. To prevent these problems as much as possible, it's important to have a firm understanding of precise frequency stability. This will give you the tools to keep your applications performing optimally. But there's another problem...

There are many different types of crystal oscillators. OCXOs, TCXOs, and VCXOs are some of the most common types of oscillators. Each have their own advantages and disadvantages. One of the core responsibilities of a lead RF engineer is to pick the oscillators that are an optimal fit for their designs and applications.

If you want to be able to fine-tune your frequency source and get a stable, dependable signal, a voltage-controlled crystal oscillator (VCXO) might be just the solution you’re looking for. Let’s explore the benefits of the VCXO and how you can put them to work in your designs.

There are 7 key factors to understanding successful crystal oscillator circuit design. These include:

1. Series circuit
2. Crystal load capacitance
3. Parallel circuit
4. Drive level
5. Frequency vs. mode
6. Design considerations
7. Negative resistance

GPS disciplined oscillators (GPSDO) are some of today's most trusted and accurate sources of timing. These powerful devices (sometimes called GPS clocks) consist of a high-quality stable oscillator and a GPS receiver. The GPSDO works by disciplining (or steering) the oscillator output to a GPS device or GNSS satellite signal via a tracking loop.

We'll be honest, crystal oscillators aren't the easiest topic to understand. That's mostly because there's a wide variety of crystal oscillator types that do different things, in different ways, for different purposes. This is largely due to their almost endless applications. From satellite communications in space, to military & defense, to telecom and more... there are so many different needs for crystal oscillators. 

In this post, we'll cover the most common types of crystal oscillators, which include:

• Oven controlled crystal oscillators (OCXO)
• Temperature compensated oscillators (TCXO)
• Voltage controlled oscillators (VCXO)
• Clock oscillators (XO)
• And some other key types within these categories

I know it sounds like a lot to cover, but don't worry! We're about to make things a whole lot easier for you. By the end of this post, you'll learn the basic uses, advantages, and limitations of each crystal oscillator type.

Virtually all electronic components benefit from mass production. As it turns out, it’s harder to benefit from buying a few parts compared to buying many. This is true for the production and ordering of Oven-Controlled Crystal Oscillators (OCXOs). There are several important advantages to buying these in bulk instead of in small quantities, including lower setup costs, shorter lead times, and reduced impact of supply chain issues.