SMA40 Tour Magne – Crystal Oscillator


  • Low-phase noise crystal oscillator
  • For use in Pound-Drever-Hall
  • EOM phase-modulator driver
  • Phase-reference for mixer input
  • Low-distortion sinewave source
  • Fixed-frequency ranging from 3 MHz to 30 MHz
  • 3 chassis-isolated outputs
  • Fixed 0-dBm reference output
  • 2 variable level outputs rated at +17 dBm max.
  • DC-voltage control of level over 40 dB
  • DC-voltage control of phase-shift over 200°
  • Pure analog design – free of digital noise
  • EMI noise immunity
  • Ideal for rapid prototyping
  • All schematics included

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The SMA40 module is a low-phase noise crystal oscillator. The module was designed for use in laser frequency stabilizations where the frequency offset  between the laser source and the resonance of the reference cavity requires tight and quick control.
In a Pound-Drever-Hall setup, the SMA40 provides the RF oscillating signals required for the frequency error discriminator. Thus, the module is used both for the phase modulator as well as for the mixer.
Three outputs are available on the front panel. The LO and PM signals are respectively fed to the RF mixer and phase modulator inputs. Their power levels can be adjusted within a 40 dB range using either the respective DC-control voltage or the front panel trimmer. The Reference output is a copy (0-dBm) of the oscillator signal. The phase shift between the LO and PM signals can be controlled over 200 degrees using either the front panel trimmer or the dedicated DC-control voltage. The oscillating frequency is set at the factory between 3 MHz and 30 MHz. Because each output use an RF-isolator, single-ended loads can be
driven without introducing ground-loops.
Like all SM-Series modules, the SMA40 is shipped with the schematic diagrams of its electronic circuitry providing all required information for advanced users.


See also