Welcome to the Crystal Oscillator Professor

This blog is about the nuts and bolts of time and frequency control, and especially about the details of crystal oscillators, which are particularly fascinating devices. This blog will explore how timing systems using crystal oscillators work, and how to use, specify and troubleshoot crystal oscillators, as well as tracking and discussing the exciting new developments in the field.

Activity Dips and How to Avoid Them

Commercial grade quartz crystal oscillators can sometimes exhibit problems known as “activity dips” that occur only at very specific temperatures. If you never happen to operate at exactly the problem temperature, you will never see the problem. But what is an activity dip? It’s a relatively sudden increase in the crystal’s resistance, (a perturbation) in the quartz crystal’s series resistance and frequency characteristics over temperature. Generally, activity dips are caused by an interfering mode of vibration (coupled mode) in the quartz crystal. A coupled mode bleeds energy from the main mode if and when its frequency coincides with the frequency…

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The Benefits of Using Multiple-Output Space Clocks

The use of multiple-output low-noise clocks provides three major advantages to space OEMs. Board Space Savings. First, they save PC board space in the end equipment design. Instead of using up to 12 separate crystal oscillators, only one package is needed. This is of major significance in efforts to reduce the size of satellite electronic equipment. This also saves engineering time at the OEM because it is no longer necessary to carefully design and coordinate the outputs of different clock oscillators, with that work being done internally already in the multiple output clock. High Performance. Second, multiple output clocks tailored…

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Radiation Effects on Crystals and Oscillators – Part 4

In this fourth and final lecture, the Professor will discuss radiation impacts on the entire crystal oscillator assembly.. Up until now we have not discussed the effects of radiation on oscillator components other than the quartz crystals. Radiation effects on other electronic components is a more complicated subject, because all active devices (semiconductors, transistors, digital electronic devices, etc.) are subject to degradation due to several types of radiation. Some of the major types of radiation of interest are: TID Total Ionizing Dose (TID) is the cumulative absorbed dose in a given material resulting from the energy of ionizing radiation at…

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Radiation Effects on Crystals and Oscillators – Part 3

In this third lecture, the Professor will review the four regions of the “spacescape” and how the radiation levels are an important consideration in device selection. Defining the Spacescape The “spacescape” can be defined as comprising four distinct regions. In a whitepaper published in 2020, several key parameters are discussed that are considered in making the optimum crystal oscillator selection for each region – phase noise & jitter; size, weight & power (SWaP); stability; and radiation tolerance. When it comes to the latter, this chart defines to industry standard for total ionizing dose (TID) radiation in each region. Environment or…

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Radiation Effects on Crystals and Oscillators – Part 2

In this second lecture, the XOProf will discuss the processes used to optimize crystal oscillator performance in the face of potentially damaging levels of radiation in space applications. Radiation Effects on the Quartz Crystal There are two separate things to consider, first, the effects of radiation on quartz crystal resonators, and then the effects of radiation on all other components in the oscillator circuit. In this section we will address the former. Concerning the quartz crystal itself, the good news is that, unlike many electronic components, the quartz crystal resonator will not die, it will not cease to operate due…

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Radiation Effects on Crystals and Oscillators – Part 1

In this first “lecture” on this important topic, the Professor will define what is meant by radiation, what types of radiation are potential causes of damage and how radiation levels are characterized and quantified. Radiation Basics First, what do we mean by radiation? For our purposes, radiation is the transmission of energy through space in the form of either subatomic particles or electromagnetic waves. Subatomic particles include electrons, neutrons, protons and ions. Just for confusion purposes, electrons are sometimes referred to as beta particles and helium ions as alpha particles. Electromagnetic waves, in ascending order of frequency and descending order of wavelength include:  radio…

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White Paper Maps Out Spacescape Challenges in XO Selection

This informative white paper describes how the regions of the spacescape from low-earth orbit to deep space affect the selection of crystal oscillators. Subscribe to The Crystal Professor blog and we'll send you a free copy.