Modulation Transfer Spectroscopy (MTS) Module

This repository contains the KiCad 7 design files of a module for MTS error-signal generation. The module provides a frequency modulated RF signal applicable to AOM-based MTS. The signal is generated by a VCO. The carrier frequency is locked to a stable reference in a low-bandwidth PLL. A frequency modulation at a frequency exceeding the PLL bandwidth is added to the input of the VCO. The board also contains a section for phase-sensitive demodulation of the error signal including a 4th order filter. The PCB is used with a DDS board providing the carrier signal as well as signals for modulation and phase-sensitive demodulation (Gra&Afch AD9959).

The module features:

• Frequency modulated RF output for AOM

  • Carrier frequency: 110 to 130 MHz

  • Modulation frequency: 0.1 to 10 MHz

  • Modulation index: 1.8 max.

• Variable gain photodetector amplifier: 0 dB to 20 dB / 100 MHz

• Internal demodulation with 4th order filter (0.75 MHz)

• Error signal output

  • Voltage range: ±1 V @ 50 Ohm

  • Output noise level: <50 nV/√Hz

Versions

The VCO type determines the output frequency range of the AOM signal.

• 110MHz_VCO (master): 100 to 140 MHz

• 80MHz/200MHz_VCO: 60 to 110 MHz or 140 to 250 MHz. This version can be found here

• 80MHz/200MHz_VCO_Rev1.2: deprecated version

Design Files

The design files can be found on the releases page and include the following resources:

• Schematics as a PDF
• Gerber files
• Pick & place position files
• Bill of materials as a CSV file and also as an interactive HTML version

The latest revision of those files can be found here.

Assembly

The PCB and the DDS are placed in a standard 19''-rack mount unit. Display and controls of the DDS board are moved to the frontpanel as intended by the manufacturer. Use the rotary encoder breakout board for this task. See frontpanel/ folder for drawings and BOM.

Assembly units (see BOM for details)

• MTS module PCB

• Gra&Afch AD9959

• Rotary encoder breakout board

• Fischer rack mount unit

Requirements

• Dual power supply

  • +15 V (0.5 A typ.)
  • - 15 V (0.1 A typ.)

• 19-inch rack mount (e.g. Fischer Elektronik BGT384)

Related work

T. Preuschoff, Laser Technologies for Applications in Quantum Information Science, Ph.D. thesis, TU Darmstadt, 2023, https://tuprints.ulb.tu-darmstadt.de/23242/

License

This work is released under the CERN OHL v.1.2 See www.ohwr.org/licenses/cern-ohl/v1.2 or the included LICENSE file for more information.