Ronald Stephens

12 posts
Ronald Stephens is the former president of Q-Tech Corporation. He has degrees in Physics, Math and Operations Research and 47 years of experience in the crystal oscillator industry. He is a former chairman of the EIA’s Piezoelectric Products Group and the Piezoelectric Conference and Exhibition. In 2017 the IEEE Frequency Control Symposium awarded him the C.B. Sawyer Memorial Award “For decades of entrepreneurial leadership in the frequency control industry.

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…

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…

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…

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…

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…

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…

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…

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…

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…

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.