Can anyone tell me the formula for creating a tuned passive network that will create a ringing, or damped, wave from a squarewave?
For clarity, an example of the above procedure using 10KHz would be appreciated.
What affects the persistence of the ring? Is it possible to create a ringing wave using a sinewave instead of square?
Thank you,
Steve C.
The network should be a RLC series circuit tuned to the fundamental or one of the harmonics.
The Q determines the decay or damping rate.
A sinewave has no harmonics, so a gated variable gain amplifier would have to be used instead.
Full details and example photos in my Active Filter Cookbook.
-- Many thanks, Don Lancaster voice phone: (928)428-4073 Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552 rss: http://www.tinaja.com/whtnu.xml email: don@tinaja.com Please visit my GURU\'s LAIR web site at http://www.tinaja.com
Ringing is what a tunes circuit does when you hit it with an impulse or edge.
The general formula that relates the values of inductance and capacitance to their resonant frequency is:
1/(2*pi*f)= sqrt(L*C) with f in hertz, L in henries and c in farads.Does 10kHz refer to the square wave, or the ringing frequency produced by the edges of a much lower frequency square wave?
It is called Q or quality factor, and it is the ratio of energy stored in a tuned circuit (resonator) divided by the energy lost each cycle. The higher the Q, the slower the energy loss, so the more cycles the resonator rings before the ringing energy falls by half.
Not easily, since the sine wave contains energy only at one frequency. You would first have to distort it in some way, to generate harmonic frequencies for the ringing resonator to feed on.
Oops. Come to think of it, tuning to the squarewave fundamental will only return a continuous sinewave. You would have to tune to a desired high odd harmonic instead.
You also would end up with two damped sinewaves of opposite polarity, one on each leading edge and one on each trailing edge.
-- Many thanks, Don Lancaster voice phone: (928)428-4073 Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552 rss: http://www.tinaja.com/whtnu.xml email: don@tinaja.com Please visit my GURU\'s LAIR web site at http://www.tinaja.com
Just set the sinewave to the resonant frequency of the tank. If you then remove the sinewave, you can measure the Q of the tank as the energy dissipates. It's called ringdown.
Here's an example of an optical resonator with a Q of 1e7-1e8 measured with ringdown:
Here's some applications:
Heavy Water Detection - Detecting a single species in a mixture of chemically similar molecules:
Ultra-sensitive (label-free, single-molecule) detection:
Publications:
The same technique can be used to measure the Q of a tank. See
It can also be used to measure extremely small concentrations of substances in liquids and gasses using lasers in resonant cavities. Many examples available on the web. Search for "ringdown".
Regards,
Mike Monett
Thank you John for asking. It was meant to refer to the squarewave to be fed into the network, not the resultant ringing.
Would you be so kind as to apply the formula below, using the 10KHz example, so I can be sure I understand? Math is not one of my strong points.
BTW is it also possible to produce ringing with a tuned RC network?
Best regards,
Steve Crocker
Me neither. That's why I use a calculator. By the way, if
10kHz is the square wave frequency, what ringing frequency do you want it to excite?
Not without some gain element added. RC filters have a very low Q, so they don't ring more than about a quarter of a cycle.
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