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Q-Tech & Axtal News

12 posts
May 14, 2025
2 min read

Oranges, Apples and Cherries in Timing Oscillator Noise Specs

There’s a popular saying that goes, “lies, damned lies and statistics.” While this statement is perhaps a bit strong to apply to the inconsistencies of engineering specifications, when dealing with oscillator noise specs, there is an issue of comparing oranges, apples and cherries. An important part of engineering design is delivering the required performance for the application at the least cost. The emergence of MEMS (Micro-Electro-Mechanical-System) oscillators has enabled dramatic cost reductions in many digital consumer and commercial products. But in many high-performance applications, there’s no replacement for quartz oscillators. When it comes to specifying and measuring phase noise and…
February 15, 2024
2 min read

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…
January 16, 2024
2 min read

The Benefits of Using Multiple-Output Space Clocks

The use of multiple-output low-noise clocks provides three major advantages to space OEMs. Multiple-output clocks used in a space application must meet the same specs as single-output space-qualified devices. Q-Tech produces multiple differential output LVDS full-space clocks at up to 200 MHz, and also CMOS full-space multiple output clocks at up to 125 MHz, in frequency. The QT625 LVDS series offers two up to 12 synchronous outputs from one flatpack package, and the CMOS version up to four outputs. By providing all outputs through the utilization of one ultra-precision, hermetically sealed quartz crystal resonator, no expense is spared in designing…
December 5, 2023
5 min read

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…
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…