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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My Hobby Website:
Laser Receiver - 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: Laser Receiver Posted: Fri Aug 11, 2006 6:20
Joined: Fri Aug 11, 2006 6:07 am
I need to design a laser receiver circuit which would receive
laser pulses in the red region of the spectrum (around 630nm wavelegth),
the laser pulses carry an RF ripple of around 315MHz. I built a current
to voltage converter using a transimpedance amplifier with resistor
feedback and simulated it on Multisim, it seems to be working fine.
But I have a couple of problems, firstly, the transimpedance amplifier
is an inverting amplifier so I need to reinvert the signal or get it
straight the first time with minimum distortion. Secondly, I need to
find a way to have two outputs for the device, one giving the equivalent
output voltage of the signal (DC with a 315MHz ripple) and the other
with AC coupling (just the 315MHz ripple). And the last problem is that
I need to make the system as noise-immune as possibe. If anyone can
help me or point me to where I can find something that would help I'd
appreciate it a lot.
Posted: Fri Aug 11, 2006 7:55 am
Fri Feb 17, 2006 12:07 pm
Location: London UK
first reaction is try to separate the dc from the 315MHz components
at as early a stage as possible.
What is the source/spectrum of the
Posted: Fri Aug 11, 2006 8:15 am
Aug 11, 2006 6:07 am
Well, there's no specific source,
it's just thermal noise, shot noise and other regular sources of interference.
I can put two parallel transimpedance amplifiers, one to separate the
RF alone and the other just to convert the signal to voltage as a whole,
but the problem is that I get a weird transient of a relatively low
frequency whenever there's a pulse transition when I try to separate
the RF alone, I guess it's due to the presence of the L and C in the
transimpedance amplifier, I'm still trying to figure out how to remove
Post subject: Posted: Fri Aug
11, 2006 1:14 pm
Joined: Fri Aug 11, 2006 6:07
I think I was able to do it but I just have one more
question left. I'm supposed to add an enable signal to the circuit,
what would be the best way to implement that? Is it through a transistor
that passes Vcc to the whole circuit when it receives the needed signal
or through a transistor that passes the output signal when it receives
the enable signal?
Post subject: Posted:
Fri Aug 11, 2006 1:23 pm
Joined: Mon Jun
27, 2005 2:02 pm
To answer to your last question, I recommend to use the first option,
i.e. to control over the Vcc supply voltage. This will promise a full
isolation and will block any leakage or residual signals to the output.