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.
Back in 2016, we wrote one of our most popular posts covering 12 popular Software Defined Radios or SDRs. While the previous post still holds some extremely valuable information, a lot has changed in 3 years... especially the technology related to SDRs. So we thought it was time for an update.
RF engineers would love to get their hands on ideal crystal oscillator circuits. 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, having a firm understanding of precise frequency stability will help give you the tools to keep your applications performing optimally. But there's another problem...
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.
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.
Precise timing across a variety of networks and industries is becoming a necessity. Both operationally and legally. It's actually pretty amazing to see the evolution of timing & frequency control throughout different industries. There's been significant timing innovations over the past 5-10 years alone.
Do you know all about Atomic Clocks in space and how they work? If not, it's about TIME you do. (Haha. Ha. Ha...)
Timing is everything when it comes to GPS satellites and other space applications. Even just a one microsecond error in timing can lead to an error of 300 meters on the ground. Atomic clocks can maintain very precise timing, making them a great timing solution for GPS and other LEO satellites.
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
- Pulse Width Modulation & Low Pass Filter
- Reference RF Signal & Phase Locked Loop (PLL)
- Voltage Divide
- 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.
Surface Acoustic Wave (SAW) filters offer a reduced size, weight, & cost compared to other filter technologies. However, there are many tradeoffs that need to be considered when selecting a SAW filter for your system design.
What are SAW filters? What are some common SAW filter applications? How are SAW filters used for mobile communications? We'll answer these questions and more in this post.
Topics: RF Technology
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.