Ring-down Box

Application of the ring-down box

You can measure the finesse of a resonator with the ring-down box without locking the resonator!

Advantages

super fast (see characterization)

without locking the resonator

Measurement Method

Evaluation

Use this formula to analyse the datapoints with : time, : delay time

Afterwards calculate the finesse with with : free spectral range.

Electronic setup

max. Input PD-voltage: +5V or -5V

Output TTL (Name: inv. Q): 5V

Power voltage: +/-15 or +/-18V (max.)

Switch A: unten = Eingang invertierend, oben = deaktiviert

Switch B: unten = Ringdown Messung, oben = dauer-reset

Explanation of the operating principle

Electronic drawing: Electronic drawing_Ring_down_Box

Characterization

List of components

Inverter: LT1363

Invert negative input voltage to positive

Datasheet_LT1363

Power supply: +/-5V

Comparator: AD8561

Compare input voltage and threshold value

Datasheet_AD8561

Power supply: +/-5V

High speed timing: 7ns @ 5V

Flip-Flop: SN74HC74

Output of trigger

Datasheet_SN74HC74

Power supply: +5V

High speed timing: 15ns

1x XLR connector

1x Power supply +/-5V

1x single switch

1x double switch

3x BNC connctors

1x Potentiometer

1x big red button

2x 8-pin IC socket

1x 14-pin IC socket

3x PSK 3-pin cables

5x 100n capacitors

some resistors (3x 100k, 1x 4.7k, …)

1x Al-box

2x PCBs

Microwave switch

Control of RF signal to the AOM

Mixer typ: SRA-1+ (Datasheet_SRA-1+)

1x Resistor (100 Ohm)

2x diodes (type: 1N4748)

1x diode (type: Z3,9V)

3x BNC connectors

1x Al-Box

Connect all ground pins to ground, also the housing

Do NOT build it like this

Rather build it like this:
Make sure that the input and output are as far apart as possible and the connections to the switch form a straight line. Otherwise the input line acts as an antenna and a part of the rf signal passes to the output if the switch is closed. For the same reason, try to make the wires within the box as short as possible.

Also make sure to solder the shielding of the IC directly to the box. It makes the switch work A LOT better.