Inside Frequency Control

What is a Swept Quartz Crystal?

Like many other things, radiation can impact a crystal oscillator's frequency. This is because radiation physically alters the quartz crystal inside the oscillator (changes position of weakly bound compensators that change the elastic constants of quartz). In some cases, radiation can even impact the crystal series resonance. The increase of resonance can be serious enough to cause the oscillator to stop oscillating if the crystal isn't radiation resistant. When a quartz crystal is manufactured to be radiation resistant, the crystal is referred to as a swept quartz crystal.

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

1. Series circuit
2. Load Capacitance
3. Parallel Circuit
4. Drive Level
5. Frequency vs mode
6. Design Considerations
7. Negative Resistance

In this post, we're going to cover the basics of oscillator design and each of the 7 key components of great crystal oscillator circuit design.

What if I told you that specifying more Electronic Frequency Control (EFC) than you need could actually be hurting you pocketbook? Well, it very well may be! Paying attention to whether your supplier is using AT cut vs SC cut crystals will help you save money in the long run with OCXOs.

Ahh the mysterious OCXO. What the heck is an OCXO anyway? What's it good for? When should you use one in your electronic system design? These questions and more will all be answered in this post.

Quartz crystal oscillators are the high and mighty option for low phase noise and added frequency stability in circuit design. Yes, simple oscillators like those made with resistor-capacitor (RC) or inductor-capacitor (IC) resonators are fine for some circuits. But if you're dealing with higher performance applications in aerospace, military, and space industries... you're going to want a higher performance crystal oscillator that can maintain low phase noise & strong stability. Otherwise, you'll risk deviating from the very specific (and many times critical) center frequency selected for your design.

Want to know what's better than a crystal oscillator? A crystal oscillator combined with Electronic Frequency Control (EFC). Of course, it really comes down to your specific application and what requirements you're looking for to determine if EFC would be a good addition to your crystal oscillator circuit design, and if so, which method is best for you.

There are 4 options to choose from when selecting an Electronic Frequency Control method for your crystal oscillator. These 4 options are

1. Pulse Width Modulation & Low Pass Filter
2. Reference RF Signal & Phase Locked Loop (PLL)
3. Voltage Divide
4. Digital-to-Analog Converter (DAC)

In this post, let's take a closer look at each option and compare the pros and cons between them.

GPS Disciplined Oscillators (GPSDO) are one 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.

The harsh truth is, selecting the wrong quartz crystal oscillator can quickly kill any design. With the wide variety of options and specs available in the market today, selecting the perfect crystal oscillator for your design can be a difficult and time consuming task.

 

The development of crystal oscillators has literally changed the world. Technically that can (and is) said about many things. But think about it! Without crystal oscillators, we may have never seen precision timing in clocks, wide and clear radio broadcasts, or important communication methods within military and space programs.

Imagine how different our world might be without these now commonplace technologies. 

We can't possibly be the only intelligent life-forms in this infinite universe, can we? I mean, there's still plenty of exploring to do in our own solar system let alone nearby stars, our entire galaxy, and surrounding galaxies. Will our current deep space communication efforts, like Voyager 1, ever stumble across alien life so us humans can say, "Hi! We're here!"? Or will it take so long that our messages would be more like, "Hi! We were here!"? 

Let's explore some current communication efforts to make contact with aliens and how they work.