Typical Minicircuits SMT RF amps have a phase noise at best 20dB worse
(@10Hz offset) than the mixer/phase detector.
Their reverse isolation is quite low (<<40dB)
The principle reason that the Czech DMTD has such low internal noise is
due to the absence of any isolation amplifiers.
They use the outputs of a 2 way splitter to drive the LO inputs of the
mixers.
A output to output isolation of 40dB or more at 10MHz is possible with
some minicicuits splitters (e.g. SYPS-2-1).
The ZRPD1 has an RF1 - RF2 isolation of around 70dB at 10MHz.
With a channel to channel isolation of around 110dB for a 2x ZRPD1 +
Splitter combination isolation amplifiers may not be necessary.
Bruce
Bruce Griffiths wrote:
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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Bruce
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