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The Prof’s Posts

20 posts
November 15, 2023
3 min read

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…
October 31, 2023
3 min read

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…
October 17, 2023
2 min read

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…
September 19, 2023
4 min read

Unleashing the Mystery of Crystal Cuts

Distinguished Guest Professor: Bernd Neubig, AXTAL Consulting When faced with quartz crystal data sheets or catalogs, you inevitably are confronted with the term “crystal cut.” What is this all about? This article will serve to clarify the significance of crystal cuts in the performance of crystal oscillators. In the most common applications quartz crystals are used as a core element to generate a stable frequency. Besides the stability over time (so-called aging), the frequency stability vs. temperature is a primary factor. Therefore, from the early beginning, researchers have looked on the parameters which determine frequency stability over temperature. Quartz crystals…
August 17, 2023
3 min read

The MCXO Is Finally Ready for Space

The latest advances in radiation-hardened digital components have enabled the development of MCXOs that, for the first time, can replace larger, high-power-consuming OCXOs in low-earth orbit (LEO) New Space applications Introduction The last post in this series explored the benefits of microcomputer-compensated crystal oscillators (MCXOs) when compared to (oven-controlled) OCXOs. This post introduces the first MCXO that combines clever engineering design with rad-hardened digital components to qualify for New Space applications. Developing Space-Qualified MCXOs When developing MCXOs in the early 2000s, the space- and rad hard-level digital components needed were very expensive, which meant an MCXO space-level product would sell…
August 1, 2023
4 min read

Comparing OCXOs to MCXOs

Oven-controlled (OCXO) and microprocessor-controlled (MCXO) crystal oscillators each provide exceptional frequency stability over a wide temperature range, using very different approaches. Introduction This post will describe the technology behind OCXOs and MCXOs and delve into the Size, Weight and Power (SWaP) benefits provided by MCXOs. The next article in this series will introduce the first space-qualified MCXO for low-earth orbit (New Space) applications. Crystal Oscillator Stability All crystal oscillators are based on the very stable frequency vibrations of a piezoelectric quartz crystal resonator. Usually, the crystals and their associated circuitry are carefully designed and crafted so that the quartz crystal…
July 6, 2023
4 min read

MEMS vs. Crystal Oscillators: It’s All in the Application

Putting timing and frequency control technologies in their proper place Introduction Precision frequency control and timing are essential to all modern electronics technology. Almost every electronic device you can imagine depends on a precision clock; without precision oscillator clocks, all electronic communication would stop. This article compares the benefits of the latest precision clock technologies as they perform in different applications. The Evolution of Precision Clocks Introduced in the 1920’s, the quartz crystal oscillator has long been the workhorse amongst electronic timing devices.  A newer type of oscillator that has been in development since the 1960s and available in production…
June 1, 2023
3 min read

Crystal Oscillators 101

Quartz is relatively abundant in nature and easy to grow in a very pure form. What sets it apart from other piezoelectric crystals is that it can be made to vibrate in very controlled and stable ways. Thus, a properly fashioned quartz resonator can act as an ultra-stable mechanical frequency source that can be coupled to an electronic oscillator circuit.
May 3, 2023
2 min read

Does anybody really know what time it is? (Part 2)

Quantum physics took the mysteries of time to a whole other level. Is time continuous or discrete? Is there a minimum size of time duration, a sort of quantum of time? Is time fundamental or is it an emergent phenomenon, or is it an illusion? Many scientists now think that time is not fundamental but that it emerges out of nothingness. Of course, nothingness itself is being redefined. Completely empty space is now thought to be a quantum foam, with virtual particles popping into and out of existence randomly and continuously. When these virtual particles happen to interact with each…
April 3, 2023
2 min read

Does anybody really know what time it is? (Part 1)

Precise time keeping is of the utmost importance in science and technology and has been since the beginning of recorded time. Yet no one really knows what time is. If you look up the word “time” in a good dictionary you will see one of the longest entries, with dozens of definitions. St. Augustine, in 400 AD, said “What, then, is time? If no one asks me, I know; if I wish to explain to him who asks, I know not.” Time is what a clock measures. The first clocks were natural phenomena, like the sun rising and setting and…