Since mixer noise is one of the limiting factors using a mixer with low
flicker noise will help.
NIST found that a custom mixer using diode connected (collector base
short) 2N222As had a significantly lower flicker phase noise than either
the ZRPD1 or the 10534A.
They used off the shelf 1:5 impedance ratio transformers (probably from
Minicircuits).
Another issue is the flicker phase noise of any isolation amplifiers used.
This is particularly critical if each mixer uses its own isolation
amplifiers.
My current amplifier phase noise measurement setup (for measuring the
additive PN of a pair of well matched amplifiers) has a self noise of
around -170dBc/Hz @ 1Hz offset for a 10MHz input.
Ideally the additive phase noise of any isolation amplifiers should be
well below that of the mixers.
Bruce
ewkeh...@aol.com wrote:
Yes Bruce I have the paper. I am not suggesting to copy it verbatim but if
there is a way to reach reasonable priced 1 E-14 members of the list should
pipe in. I am willing to do an other board. the rest of the systems well
on its way. Einally after three years.
Bert Kehren
In a message dated 11/20/2012 3:28:57 P.M. Eastern Standard Time,
bruce.griffi...@xtra.co.nz writes:
ewkeh...@aol.com wrote:
The D/M is being revisited because of the counter performance. 1 E-13 is
easily attainable but the Czech IREE published a paper and claim 2 E-15.
Do you mean the paper ""optimization of dual-mixer time-difference
multiplier" ?
The ZCD developed in this is a bit of a kludge and is far from optimum.
Reverse engineering the circuit from the description given in the paper
isn't too difficult.
They claim an instrument limited ADEV of ~7E-15 @ 1s.
Do you have a copy of this paper?
Bert Kehren Miami
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