[time-nuts] low noise multiplication to 100 MHz

jimlux jimlux at earthlink.net
Thu Jan 21 09:43:01 EST 2016


My tiny 100 MHz low noise OCXOs are unexpectedly delayed at the mfr, and 
I'm looking at alternative schemes.
One is to get 10 or 20 MHz OCXOs (typically in stock) and multiply them 
up. I've got the Wenzel ap notes on 2diode and using HCMOS (and I've 
used the packaged Wenzel multipliers), and I think I have some spare 
board real estate on another board.

The 2diode multiplier describes using 1n5711 or 1n914, but I was 
wondering if anyone has run this sort of multiplier up to 100 MHz?

What sort of symmetry does the resulting waveform have (yeah, it's 
basically a filtered sinewave, because you're picking a harmonic, but 
I've been surprised before)?




I'm driving an FPGA and a couple of ADCs.  The ADCs have differential 
input that is 10kohms with 9pF in parallel offset from ground in the 
usual way (we're using a transformer and appropriate bias resistors). 
Not a 50 ohm load, in any case.  And it wants a clock that is high for 
about 47.5% to 52.5% in one mode and much wider (30%-70% in another).. I 
need to check.

The FPGA is less critical noise-wise, and has a AD8138 buffer in any 
case, which can fix a variety of evils.






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