Test Board Data
After powering the RF pre-amp at 6V and replacing the coupling capacitors on the RF power amp with 10 nF, broadband caps, the power output for 5 dBm input looked like this:
Note that the attenuator protecting the spectrum analyzer input is not calibrated out, so 0 dBm on the graph is actually 30 dBm.
Under the same conditions but with 0 dBm input, the power output looked like this (here, the attenuator is calibrated out):
TTL control of RF output and RF frequency source works fine with the optocouplers. Saw switching up to max. frequency of the SRS function generator. Switching delay is between 40-60 ns, which meets the spec of the optocoupler. The production version of the board will use a faster optocoupler to reduce delay to about 10 ns.
Analog control of the variable attenuator works with the differential sense using an instrumentation amplifier. The response time for small attenuation changes is < 6 us, which agrees with the data provided by the manufacturer. We should able to get intensity locking bandwidths of 100-200 kHz with sufficiently fast detectors.
External modulation of the VCO frequency is also working with the differential sense from an instrumentation amplifier. I was able to see the modulation easily using the JQI's spectrum analyzer and I'll post the data eventually.
Still need to double check the effectiveness of these new input methods in reducing 60 Hz noise.