Noiseless Damping?

[JosephKK]

There is a loop receive antenna. It is the LC circuit with the Q at
the order of 100. It has a high resonant peak. The frequency and the
amplitude of the peak are sensitive to the component values,
temperature, particular parts, etc. I would like to damp the Q down to
something like 10, so the parameters would be much more stable and
predictable. This can be done by adding a series or a parallel resistor
to LC.

However the SNR of the antenna drops approx. proportionally to sqrt(Q)
due to the thermal noise of the damping resistor. I wonder if it could
be possible to implement the noiseless damping. Cooling down the
resistor is not an option.

One idea is to switch the damping resistor on-off with a high frequency
and a low duty ratio. Or to switch or vary the value of the capacitor so
the resonance peak will be dithered. It has many side effects, though.

Any ideas, suggestions?


Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
http://www.abvolt.com

My quickest thoughts were using a PIN diode to limit the "Q" or a
quiet JFET to reduce "Q" as needed. Both could be dynamically
adjustable.

 

[[email protected]]

Thermodynamics proves that the universe is cruel.

John

Wait a minute. Does this mean you can't cut taxes, build up the
military and balance the budget at the same time?

 

[Vladimir Vassilevsky]

On Mar 14, 12:23 pm, John Larkin


Wait a minute. Does this mean you can't cut taxes, build up the
military and balance the budget at the same time?

Of couse you can. Just make debts and print money. What an interesting
time! I lived through the disintegration of the USSR, now I experience
the demolishion of the USA, I wonder if I will see the demise of China!

VLV

 

[John Larkin]

Of couse you can. Just make debts and print money. What an interesting
time! I lived through the disintegration of the USSR, now I experience
the demolishion of the USA, I wonder if I will see the demise of China!

VLV

The US has one of these stock market bubble-meltdowns about every 20
years on average, although modern technology may allow them to get
closer together, as in the dot-com bust and the latest mortgage thing;
both, as it turns out, being Clinton legacies. The relaxation time
constant seems to be about equal to the greed/fear decay time of
amateur investors. Some money changes hands, some people get hurt,
lots of press gets generated, Congress makes a lot of speeches and a
few new laws, and life goes on. The US still has pretty good basics:
lots of land and food, a young and vigorous population, a good
environment for science and technology and business.

John

 

[Michael A. Terrell]

Of couse you can. Just make debts and print money. What an interesting
time! I lived through the disintegration of the USSR, now I experience
the demolishion of the USA, I wonder if I will see the demise of China!

VLV

Then beat the rush and haul your ass to Africa.


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[[email protected]]

The US has one of these stock market bubble-meltdowns about every 20
years on average, although modern technology may allow them to get
closer together, as in the dot-com bust and the latest mortgage thing;
both, as it turns out, being Clinton legacies. The relaxation time
constant seems to be about equal to the greed/fear decay time of
amateur investors. Some money changes hands, some people get hurt,
lots of press gets generated, Congress makes a lot of speeches and a
few new laws, and life goes on. The US still has pretty good basics:
lots of land and food, a young and vigorous population, a good
environment for science and technology and business.

John

Do you think there will be a meltdown when the powers that be realize
nobody is looking at their stupid adverts? Yahoo spends $850 million
for something like Facebook. Hell, I wouldn't spend a nickel on
MySpace, Facebook, or number 3 in the same genre. Everytime I see a
Myspace page I think what a bunch of f-ing arseholes.

I'm looking at the Google "sponsored" ads at the side of the page as I
type. They are all from Taiwan. Only question marks appear since I
guess I don't have Asian fonts loaded. Oh, but these fools will get a
bill for their advert being "displayed"

 

[Michael A. Terrell]

Do you think there will be a meltdown when the powers that be realize
nobody is looking at their stupid adverts? Yahoo spends $850 million
for something like Facebook. Hell, I wouldn't spend a nickel on
MySpace, Facebook, or number 3 in the same genre. Everytime I see a
Myspace page I think what a bunch of f-ing arseholes.

I'm looking at the Google "sponsored" ads at the side of the page as I
type. They are all from Taiwan. Only question marks appear since I
guess I don't have Asian fonts loaded. Oh, but these fools will get a
bill for their advert being "displayed"

Yahoo bought Geocities a few years ago, then limited the websites to
20 MB of traffic per 24 hours, which was stupid because the more people
seeing a website with their ads means more revenue.

Yahoo bought Broadcast.com, and shut it down. It was home to a lot
of radio stations online, and had very good audio quality. It went down
without notice to the people who used it to hear their favorite
stations.


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