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Low Phase Noise Crystals
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Vectron International's Ultra Low Noise (ULN) crystals are developed beginning with the consideration of specific resonator design parameters and selection of raw materials. ULN crystals are then manufactured via a dedicated production process with processing steps and process criteria chosen to control the variables that affect phase noise performance. The resulting is Ultra Low Noise crystal resonators that will ensure consistent and superior performance for the most demanding applications. Standard offerings are available at common frequencies, and custom frequencies and small lot orders can be supported.

Key Features

  • 3rd OT from 5 to 60MHz
  • 5rd OT from 10 to 150MHz
  • Standard operating temperature range: −45 to 80°C
  • AT, SC, and IT Cuts
  • RoHS & WEEE compliant packaging
  • Radiation hardened swept quartz available for space applications
Applications

  • Signal Generators
  • Network/Spectrum Analyzers
  • Frequency References
  • Radar Systems
  • Military Radios
  • Electronic Warfare
  • Navigation
  • Satellite Receivers/Transceivers

Guidance on Crystal Selection

For a system designer to achieve the very best jitter, ADEV, MTIE, or signal–to–noise ratio in their system, a high Q crystal resonator is frequently necessary.

The close–in noise of an oscillator is where the crystal performance is generally dominant for a given oscillator circuit. AT–Cut crystals can provide good close–in phase noise, but SC–Cut crystals are generally employed to achieve good performance in the noise floor as they can handle higher power levels.

Overtone designs are generally used in low noise applications for their higher Q and better aging rates compared to fundamental modes. 3rd Overtone designs are common from 5MHz to 45MHz and 5th Overtone designs are common from 50MHz to 150MHz.

Photo of the XR-U product packages Photo of the XR-R product packages

Technical Information

As shown in the figure below, the noise floor is almost independent of the crystal frequency for oscillators which do not employ frequency multiplication. Thus for low noise floor applications, the highest frequency crystal which satisfies longterm stability requirements should generally be used. However, when a higher frequency application specifically requires minimum close–in phase noise, lower frequency crystals may often be multiplied to advantage. This is so because close–in phase noise is disproportionately better than the noise performance obtained using higher frequency crystals.

Photo of noise floor plot

Note that the introduction of a varactor diode and moderate Q crystal, used typically in TCXO and VCXO products, result in poorer close–in noise performance when compared with fixed frequency non–compensated crystal oscillators.

View our Phase Noise Application Note


Lead Products

10MHz 3rd OT SC–Cut:

  • Package: XR–U (HC37/TO–8)
  • Aging: 100ppb 1st year
  • Aging Rate: <5ppb/day after 7 days
  • Phase Noise:
        −105dBc/Hz @ 1Hz
        −135dBc/Hz @ 10Hz
        −155dBc/Hz @ 100Hz
  • g–sensitivity: 1.5ppb/g

10 MHz 3rd overtone SC Cut phase noise plot

100MHz 5th OT SC–Cut:

  • Package: XR–R (HC35/TO–5)
  • Aging: 500ppb 1st year
  • Aging Rate: <5ppb/day after 14 days
  • Phase Noise:
        −100dBc/Hz @ 1Hz
        −130dBc/Hz @ 10Hz
        −155dBc/Hz @ 100Hz

100 MHz 5th overtone SC Cut phase noise plot

Phase Noise Measurement of Crystals

For many applications our crystals are capable of meeting the desired phase noise performance by design. For the most demanding applications, phase noise of the crystals can be measured on a sample or 100% basis.

The Crystal phase noise is measured by temporarily installing the unit in a low noise oscillation circuit. Pass/Fail limits can then be applied at offsets from 10Hz to 100kHz with our software. Phase noise plots can be supplied with the units, if desired.

Crystal Phase Noise set & HP-5052B Network Analyzer Analysis Software screen shot

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