Frequency Mixers Wisdom
Double Balanced Ring Diode Mixers
Almost all of the mixers in iLIGO and the 40m lab are the ring diode mixers that are sold by Mini-Circuits. Exceptions are the WFS Demod boards which use solid-state Gilbert cell mixers.
We use mixers for a lot of different things:
- Demodulation of PDH signals - this may be also called 'carrier suppressed AM detection'
- Phase Locking of two sinusoidal signals (e.g. phase locking two lasers or two electronic oscillators)
- AM noise measurements of an oscillator - the same oscillator drives the LO and RF inputs of a mixer with in-phase signals.
On all of the iLIGO style LSC-Demod boards, we use Level 17 mixers.
Some places in the PSL, we used to have Level 23 mixers.
The ZP-3MH is a level 13 mixer with a very good linearity.
Approved Coaxial Mixers for General Lab Use
Rather than try to figure out what you need each time you buy mixers, instead, just use the following table:
Level 7 mixers |
|
|
ZAD-3 |
0.025-200 MHz |
BNC |
ZP-1 |
2-600 MHz |
BNC |
ZFM-2 |
1-1000 MHz |
? |
Level 13 mixers |
|
|
ZP-3MH |
0.15-400 MHz |
BNC |
ZX05-1MHW-S+ |
0.5 -600 MHz |
SMA |
Don't get mixers with a higher level than 13. You don't need any more RF power. If you think that the SNR is going to scale linearly with the mixers LO voltage you need to go back to radio electronics school.