The Simplest Crystal is the Best Crystal

Despite over a decade of research and development in MEMS and circuit-based alternatives, the crystal resonator remains the foundation of reference oscillators for higher-performance applications such as telecom infrastructure.  However, telecoms applications push crystal resonator performance requirements to a point where standard crystals cannot physically be produced.  In response to the explosion of the Internet over the last decade, crystal manufacturers were forced to move to alternative resonator structures in order to produce reference oscillators high enough in operating frequency and low enough in phase jitter to satisfy the demands of 10/40 GBit Ethernet, SONET, xDSL, WiFi and similar broadband data transport applications.

The inverted mesa crystal resonator has become the standard for telecom reference oscillators. Entrenched reference oscillator manufacturers such as SEIKO Epson, Kyocera, NDK, KDS, Rakon and Pericom have grown to rely upon inverted mesa crystals for their telecoms infrastructure customers.  Formed as a well structure with an ultra-thinned center region, the inverted mesa crystal can resonate in fundamental mode up to about 300 MHz.  However, this well structure results in an extremely thin resonator which is susceptible to increased phase jitter, temperature instability and is much more susceptible to aging effects.  And inverted mesa crystals cost more than 10 times a standard AT-cut crystal - making the inverted mesa resonator the cost driver in high-performance reference oscillators.

Glacier’s AnyFrequency™ integrated circuit eliminates the need for inverted mesa crystals in high-performance reference oscillators.  Utilizing a standard AT-cut crystal resonating in the 10-50 MHz range, Glacier’s synthesizers can be configured to produce output frequencies spanning the 10-1500 MHz range with phase jitter performance in the 1ps range critical to telecoms applications.  And AnyFrequency™ synthesizers achieve this performance while consuming 25% of the power associated with MEMS or ring oscillator-based reference oscillators.  In a package with less than 50% of their competitors’ footprints.

The last 15 years of increasingly difficult reference oscillator performance requirements have driven crystal resonator production to its extreme limits - while compromising cost, size and many critical reference oscillator performance parameters.  Glacier’s AnyFrequency™ synthesizers bring high-performance reference oscillators back from the extreme - and thus are key enablers of the ongoing expansion of Internet capacity.

(Inverted mesa crystal image courtesy of Electronic Design © 2001)

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