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Laser Receiver - RF Cafe Forums

Because of the high maintenance needed to monitor and filter spammers from the RF Cafe Forums, I decided that it would be best to just archive the pages to make all the good information posted in the past available for review. It is unfortunate that the scumbags of the world ruin an otherwise useful venue for people wanting to exchanged useful ideas and views. It seems that the more formal social media like Facebook pretty much dominate this kind of venue anymore anyway, so if you would like to post something on RF Cafe's Facebook page, please do.

Below are all of the forum threads, including all the responses to the original posts.


Quasar
Post subject: Laser Receiver Posted: Fri Aug 11, 2006 6:20 am

Captain

Joined: Fri Aug 11, 2006 6:07 am
Posts: 5
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.


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nubbage
Post subject: Posted: Fri Aug 11, 2006 7:55 am

General


Joined: Fri Feb 17, 2006 12:07 pm
Posts: 218
Location: London UK
My 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 likely interference?


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Quasar
Post subject: Posted: Fri Aug 11, 2006 8:15 am

Captain

Joined: Fri Aug 11, 2006 6:07 am
Posts: 5
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 that.


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Quasar
Post subject: Posted: Fri Aug 11, 2006 1:14 pm

Captain

Joined: Fri Aug 11, 2006 6:07 am
Posts: 5
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?


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IR
Post subject: Posted: Fri Aug 11, 2006 1:23 pm

Site Admin


Joined: Mon Jun 27, 2005 2:02 pm
Posts: 373
Location: Germany
Hello,

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.

_________________
Best regards,

- IR





Posted  11/12/2012
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