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Entry  Mon Jan 18 23:44:19 2010, kiwamu, Update, Electronics, triple resonant circuit for EOM whole_circuit.pngdesigned_circuit.png
    Reply  Tue Jan 19 00:10:44 2010, rana, Update, Electronics, triple resonant circuit for EOM 
    Reply  Tue Jan 19 02:40:38 2010, Koji, Update, Electronics, triple resonant circuit for EOM 
       Reply  Tue Jan 19 03:04:14 2010, Koji, Update, Electronics, triple resonant circuit for EOM 
       Reply  Tue Jan 19 03:27:47 2010, kiwamu, Update, Electronics, Re: triple resonant circuit for EOM 
          Reply  Tue Jan 19 23:26:07 2010, kiwamu, Update, Electronics, Re:Re: triple resonant circuit for EOM matching_edit.pngeq1.pngdesigned_response.png
Message ID: 2529     Entry time: Tue Jan 19 03:27:47 2010     In reply to: 2526     Reply to this: 2533
Author: kiwamu 
Type: Update 
Category: Electronics 
Subject: Re: triple resonant circuit for EOM 

1. You are right, the gain for the single resonant circuit was about 9.3 in my measurement.

But the reason why the triple is better than the single resonant circuit comes from the transformer.

The impedance can be degraded by a loss of the transformer, because it got worse after applying the transformer in the past measurement.

Also I definitely confirmed that the circuit had the impedance of 7.2 kOhm at the resonance of 52.9MHz without the transformer.

So it shall give the gain of 12, but did not after applying the transformer.

 

2.  Yes, I think we need some variable components just in case.

 

5.  For the impedance matching, I will select a transformer so that 55MHz is matched. In contrast I will leave two lower resonances as they are.

This is because 11MHz and 29.5MHz usually tend to have higher impedance than 55MHz. In this case, even if the impedance is mismatched, the gain for these can be kept higher than 11.

I will post the detail for this mismatched case tomorrow.

 

Quote:

The design looks very good. I have some questions.

1. As far as I remember, you've got the gain of slightly worse than 10 for a 55MHz single resonant case. Why your expectation of the gain (G=11) for the highest resonance better than this?

Supposing the loss exists only on the EOM, the other part of the LC network for the triple work as an inductor at the resonant frequency. This is just equivalent as the single resonant case. So the expected gain at 55MHz should coincides with what we already have. Probably, the resistance of 4 Ohm that is used here had too rough precision???

2. How can you adjust the resonances precisely?

Do we need any variable components for Cs and Ls, that may have worse quality than the fixed one, generally speaking.
I myself has no experience that I had to tune the commercial EOM because of a drift or whatever. I hope if you can adjust the resonance with a fixed component it should be fine.

3. Changing Cp. What does it mean?

Do you put additional cap for Cp?

4. The resonances for the lower two look very narrow. Is that fine?

This will show up in a better shape if we look at the transfer function for the gain. Is this right?

If we have BW>100kHz, it is sufficient.

5. Impedance matching for the lower two resonances.

Yep. You know this problem already.

 

 

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