Copyright: 1996 - 2024
BSEE - KB3UON
RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling
2 MB. Its primary purpose was to provide me with ready access to commonly needed
formulas and reference material while performing my work as an RF system and circuit
design engineer. The World Wide Web (Internet) was largely an unknown entity at
the time and bandwidth was a scarce commodity. Dial-up modems blazed along at 14.4 kbps
while tying up your telephone line, and a nice lady's voice announced "You've Got
Mail" when a new message arrived...
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down mixer - RF Cafe Forums
RF Cafe Forums closed its virtual doors in 2012 mainly due to other social media
platforms dominating public commenting venues. RF Cafe Forums began sometime around
August of 2003 and was quite well-attended for many years. By 2010, Facebook and
Twitter were overwhelmingly dominating online personal interaction, and RF Cafe
Forums activity dropped off precipitously. If the folks at
phpBB would release a version with integrated
sign-in from the major social media platforms, I would resurrect the RF Cafe Forums,
but until then it is probably not worth the effort. Regardless, there are still
lots of great posts in the archive that ware worth looking at.
Below are the old forum threads, including responses to the original posts.
|-- Amateur Radio
Gripes & Humor
-- CAE, CAD, &
Test & Measurement
Post subject: down mixer Posted: Thu Oct 19, 2006 2:54 am
Joined: Thu Oct 19, 2006 2:42 am
iam a novice to this RF design field.
I am doing a down mixer( active, folded mixer).
I am facing a huge
difficulty in meeting gan and noise figure specs.
it is a low IF
1)How can I get a good noise figure with
out losing the gain??
2) How to measure the output DC offset
for the mixer??
Post subject: Active
mixer noise figurePosted: Thu Oct 19, 2006 3:47 pm
Joined: Wed Feb 22, 2006 3:51 pm
One problem that mixer designers often encounter with noise figure
is that all mixers (except specially-designed "image reject mixers")
quite happily down-convert noise from the image frequency as well as
the desired frequency. In a low-IF system, you can't filter out the
image frequency. That means that even with perfect devices, you'd have
a baseline 6 dB noise figure - and it would get worse from there.
In general, the rule is that resistance is the source of noise.
In a BJT, that particularly means rbb', in FETs you have channel resistance.
A good noise figure in a mixer is hard to get - which is why the standard
design for an RF system establishes the noise figure in the pre-mixer
DC offset can occur because of device mismatching or lack
of symmetry - are you designing an IC or a discrete circuit? DC offset
can vary with signal amplitudes - what condition drives your spec?
Posted: Fri Oct 20, 2006 5:39 pm
Fri May 19, 2006 5:01 am
Just a quick thought: dual conversion? This will yield better
Post subject: mixer dc offsetPosted: Fri Oct 27, 2006 9:16
Joined: Thu Oct 19, 2006 2:42 am
this mixer is for a radio IC.
spectreRF for my simulations.
how to measure the DC offsets for my
down conversion mixer??
if u have any paper(s) related to its measurement,
pls post them..