AOM/EOM Driver. Description. Specifications

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1 Page 1 of 5 AOM/EOM Driver Description The AOM/EOM driver is a high power RF amplifier which provides the necessary power level to drive an eletro-optical modulator (EOM) or an acousto-optical modulator (AOM). This driver needs to provide up to 2W of RF power adjustable over a 24dB range. The EOM driver also has the option of an amplitude stabilization circuit to minimize oscillator AM noise in the optical field leaving the EOM. It can optionally implement an independent DC bias adjust which can be used to adjust the RF AM in the optical field. The frequency stabilization circuit requires a low noise RF detector. The presented design uses a combination of series and shunt diode detectors in a differential arrangement to effectively quadruple the response. A parallel chain of diodes is used to both compensate for temperature drifts and to remove a bias. Under nominal RF load this detector then has zero output and can directly be used in a compensation network to control a variable RF attenuator ahead of the detector. A relatively high bias current is applied to the diodes to minimize Johnson and flicker noise. Two modules are envisioned: (i) a unit to accurately measure the RF AM noise, and (ii) a unit to stabilize the RF AM. These units are closely related by sharing the RF detector chain. Two RF detectors are implemented per unit. For the RF AM stabilization one serves as a in-loop and one serves as an out-of-loop measurement. The out-of-loop detector servos its bias and is therefore AC coupled. The bias of the in-loop detector is adjusted externally which is used to set the RF level at the output. The RF chain consists of a RF preamlifier, a voltage-controlled attenuator, a high power amplifier and two in series directional couplers which feed the two RF detectors. The attenuator is used to control the RF power up to 100kHz. A report describing the measured performance can be found in T v1. Specifications Frequency range: Input: 5 MHz MHz minimum 10 dbm nominal N female High power output: 33 dbm max. N female 20 db attenuation min. 1 db step size enable switch/led RF power monitor: monitor output power range at least 40 db output: 0V - 10V single ended Phase noise:

2 Page 2 of 5 Frequency Phase noise spec 10 Hz -120 dbc/hz 100 Hz -155 dbc/hz 1 khz -165 dbc/hz 10 khz -165 dbc/hz Amplitude noise (standard): Frequency AM noise spec 10 Hz -140 dbc/hz 100 Hz -150 dbc/hz 1 khz -150 dbc/hz 10 khz -150 dbc/hz Physical: Power: stand-alone for example: satellite box from Hamilton Metalcraft +27V/+31V (3-5V above RF power amplifier requirement) and +17V Negative rails: Symmetric -27V/-31V and -17V Amplitude stabilization (optional) Compensation network: AC coupled or fixed DC bias +/-0.5dB range Bandwidth: approximately 100 khz Amplitude noise: Frequency AM noise spec 10 Hz -165 dbc/hz 100 Hz -170 dbc/hz 1 khz -170 dbc/hz 10 khz -170 dbc/hz Test input:

3 Page 3 of 5 AM stabilization circuit error point offset Differentially sensed Bandwidth: 200 khz on/off switch BNC female Test outputs (2): Before and after excitation point Single-ended Bandwidth: 100 khz BNC female DC bias (optional) Input: Differentially sensed Bandwidth: 100 khz on/off switch 2-pin LEMO Output: Added to high power RF output 1Hz/30Hz pole/zero Noise: < 10 nv/rthz (100kHz bandwidth) Modeling Circuit model Circuit model files Spice model T v1 T v1 spice model Drawings Assembly RF AM Measurement: Schematics (rev A ) Assembly files (rev A ) D A D A

4 Page 4 of 5 Test Procedure EOM/AOM Driver: Schematics (rev A ) Assembly files (rev A ) Test Procedure Common: Half-width 2U enclosure (rev A ) Half-width 2U enclosure (rev A ) TBD D A D A TBD D v1 D v1 Panels RF AM Measurement: Front panel drawing (rev A ) Front panel CAD (rev A ) Rear panel drawing (rev 1) Rear panel CAD (rev 1) Rear mounting plate drawing (rev 1) Rear mounting plate CAD (rev 1) EOM/AOM Driver: Front panel drawing (rev 1) Front panel CAD (rev 1) Rear panel drawing (rev 1) Rear panel CAD (rev 1) Rear mounting plate drawing (rev 1) Rear mounting plate CAD (rev 1) Rear mounting plate drawing (rev 2) Rear mounting plate CAD (rev 2) Rear mounting plate adapter 1 drawing (rev 1) Rear mounting plate adapter 1 CAD (rev 1) Rear mounting plate adapter 2 drawing (rev 1) Rear mounting plate adapter 2 CAD (rev 1) D A D A D v1 D v1 D v1 D v1 D v1 D v1 D v1 D v1 D v1 D v1 D v2 D v2 D v1 D v1 D v1 D v1 Boards

5 Page 5 of 5 EOM/AOM Driver Attenuator Schematics (rev A ) EOM/AOM Driver Attenuator Files (rev A ) RF AM Stabilization Schematics (rev A ) RF AM Stabilization Files (rev A ) EOM/AOM Driver Servo Schematics (rev A ) EOM/AOM Driver Servo Files (rev A ) EOM/AOM Driver Power Schematics (rev A ) EOM/AOM Driver Power Files (rev A ) D A D A D A D A D A D A D A D A aligo: EomAomDriver (last edited :56:22 by localhost)

AM Stabilized RF Amplifier Driver

LIGO T00074 AM Stabilized RF Amplifier Driver SURF Project Final Report August 00 Jing Luo Mentor: Daniel Sigg Co Mentor: Paul Schwinberg Abstract: The AOM/EOM driver is a high power RF amplifier used