by Ramon M. Cerda, VP of Engineering
Quartz-based oscillators (crystal oscillators) have a virtual monopoly in the electronic industry as the premier frequency-control source of choice. This monopoly goes back nearly 100 years. Today, there is still no other frequency-control technology that comes close in terms of volumes produced each year. The quartz crystal oscillator global market is expected to reach $3.2 billion by 2020 [1]. The use of MEMS-based oscillators is the only technology that has started to nibble at the heels of this competitive frequency-control industry. However, MEMS-based oscillators have higher phase noise/jitter than their quartz-based counterparts [2], making them unusable in many applications.
Quartz is a mineral composed of silicon and oxygen (SiO2) whose piezoelectric property was discovered in 1880 by the Curie brothers, Jacques and Pierre. Yes, the famous Madame Curie was the wife of Pierre Curie and, in fact, both received the Nobel Prize for Physics in 1903 for discovering the elements of Radium and Polonium. A quartz crystal unit is made by placing two electrodes on a slab of quartz and placing it in a hermetically sealed package, just like making a sealed capacitor. It was in 1918 that Professor Walter Guyton Cady recognized that a quartz crystal unit can be used as a resonator to control and stabilize the frequency of an oscillator and for making filters [2]. Amateur radio hobbyists started using quartz crystal oscillators in the late 1920s.
WWII was the catalyst for mass production of crystal units and the numbers made have risen each year since then. Today, billions of crystal units are made each year to satisfy the ever increasing demand, from electronic products requiring multiple crystal oscillators, from cell phones to TVs to cars, to name a few. We have become reliant upon this thriving monopoly, and without the crystal unit, the electronic world would face a global financial collapse.
The quartz crystal unit has no across-the-board replacement. MEMS-based oscillators have improved, but they cannot replace the quartz crystal in many applications. I see quartz-based oscillators being around for another 100 years (at least). It is hard to predict when quartz-based oscillators will lose their monopoly, but it has been the goal of many semiconductor companies to dethrone quartz technology. The Holy Grail of frequency control is an all-silicon solution; MEMS-based oscillators look like the first serious contender.
References:
[1] MarketsandMarkets, www.marketsandmarkets.com
[2] Cerda, Ramon M, “Understanding Quartz Crystals and Oscillators,” Artech House 2014, Chapter 4.
(424)
