Frequency Distribution Amplifier 2017.01

1:8 frequency distribution amplifier based on LMH6702 and LMH6609 op-amps.

In particular the power-supply section using a common-mode choke, a Murata BNX025 filter, and low-noise regulators LT1963 and LT3015 seems to work quite well. I also used ferrites (2 kOhm @ 100 MHz) as well as an RC-filter on all supply pins. Perhaps overkill? Performance with the intended AC/DC brick is still to be verified.

Measurements around 10 MHz show a 1 dB compression at over 14 dBm and an IP3 of around 27 to 30 dBm. The gain extends beyond 100 MHz with some gain-peaking.

Some measurements of residual phase-noise with a 3120A phase-meter, at 10 MHz. My earlier distribution amplifier required shielding with aluminium foil as well as powering from a lead-acid battery to achieve a reasonably quiet phase-noise spectrum. These measurements were done with lab power-supplies for +/-12 V to the board and without any shielding.

Finally some measurements of gain vs. frequency with a Rigol spectrum analyzer.


White Rabbit Workshop, Amsterdam

I gave a talk at the White Rabbit Workshop in Amsterdam about our long link, ideas for fiber asymmetry calibration, and recent stability measurements. The slides are online.

I updated my earlier picture with the noise-floor of three different phase-noise measurement setups. The picture now includes a typical good OCXO trace and the CLK2 10MHz output of a GM-locked White Rabbit Switch (v4.2 firmware).


SRS FS710 noise measurement

Update: changing the main electrolytic capacitors as well as the tantalum caps around the 7805/7905 voltage regulators did not help. There is still about 600 mVpp of ripple on the +/- 13.9 VDC inputs to the regulators.

Here's a noise measurement on an old second-hand SRS FS710 distribution amplifier. I wonder if the excessive noise at 50 Hz and harmonics is within spec or a result of old age?

Measurement setup: 10MHz signal to a Mini-Circuits ZFSC-2-1+ splitter, one branch to 3120A REF-input, the other branch to the FS710 input, and FS710 output1 to the 3120A DUT input. Noise floor was measured with the same setup but bypassing the FS710.

Phase noise with AllanTools

I've looked at calculating phase-noise spectra with python - to be included in allantools. Here are some first results.


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