HI
I have no direct experience with the Minicircuits "active mixers", but
I have used some of their amplifier chips. I suspect they use their
own amps.
The amps I worked with had significant phase noise issues when driven
within 6db of their 1db compression point. They were "ok" at low
drive levels. More or less then went from 3 db noise figure to a > 20
db nf as you went from -20 dbm to 0 dbm output on a +7 dbm amplifier.
Bob
On Nov 11, 2009, at 7:39 PM, Magnus Danielson wrote:
Bruce Griffiths wrote:
Hej Magnus
To confuse matters Minicircuits use the term active mixer for a
conventional diode mixer that uses amplifiers on the LO and/or RF
ports to boost signal levels.
While it confuses matters, it is usefull to know about them, since
they may be good for some designs, but maybe not for DMTD designs.
I have argued that keeping a buffer-amplifiers (not to be confused
with the -120 dB isolational amp) just at the mixer will relief the
issues of VSWR to tempco. Also, getting that extra boost is also
good. Needs to have meaningfull phasenoise to be usefull thought.
Whereas I was referring to mixers like gilbert cell mixers as
active mixers.
I was making the same distinction. Passive JFET mixers is just
another variant to using schottkydiodes.
With the Minicircuits so called active mixers one needs to measure
their phase noise in order to make meaningful comparisons.
Indeed. Their target is probably not considering cutting edge DMTD
systems.
Cheers,
Magnus
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