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So here is a question some of my EE and radio friends disagree on... Is a purely resistive matched load, like a 50 ohm dummy load, considered "resonant". In the strictest sense of the word is that a valid term here?
While it would seem odd I'm leaning towards yes, and would be the simplest example of resonance.
#EE #Electronics #Ham #HamRadio #amateurradio #adio #rf #science #physics
Your perspective is not uncommon of course. Though from that perspective the "non-vanishing" part isnt true. Any combination of capacitive reactance and inductive admittance, no matter what values are picked, will vanish at their resonant frequence. That is the textbook definition of resonance, the frequency at which the system is purely resistive without measurable reactance. A resistor just happens to satisfy that at all frequencies.
Well depends on who you ask. That is certainly one perspective you might hear, though not necessarily a universal definition.
Also just to clarify the signal is not twice the resonant frequency. It should complete once back and forth cycle for every cycle of its resonant frequency.
The problem with your definition, rather than the one I gave, is that it excludes most resonant things.. A crystal oscilator is clearly resonant and yet has no reactive components of any kind.
@freemo
You asked me, a physicist, and as such, I'm giving you the universal definition that does not depend on what other people think.
A crystal oscillator has a lot of energy stored in mechanical vibrations, even though the coupling of that energy to the electric circuit, via the piezoelectric effect, is weak.
As for "twice the resonant frequency":
Shut up and calculate!
(specifically, the energies in the electric field of a capacitor and the magnetic energy as functions of time in an inductor of an undamped LC tank circuit in resonance).
You may then proceed to grab a textbook in Theoretical Mechanics and do all the exercises about pits and pendulums, and the periodic transfer of kinetic to potential energy and back.
@Science
I asked people to offer their opinions, and i am happy you did so. lol you just told a professional Electrical engineer with an advanced degree that includes RF engineering to pick up a text book on capacitors, really... What a pompus response.
I appreciate your opinion, but I know full well what the cycle in a resonant circuit looks like, and no it does not complete a full round trip at twice the frequency. As i stated it completes one cycle, from capacitor to inductor and back to capacitor once per cycle. The fact that you are disagreeing with this fundamental fact puts your credentials in question if you are really going to hold steadfast to that.
The fact that you are defensive over being corrected, particularly over such a fundamental assertion doesnt really help your image IMO.
Just to be clear as I stated earlier I do not disagree with your definition, as i said it is common enough. But there are multiple definitions and no one official definition. so it is very much a matter of interpretation, there is not a single answer.
One could even argue that the definition involving an actual transfer between potential and kinetic energy holds true for a resistor at a molecular level. If i have a red object and shoot EM waves at it that is red then the red object absorbs more energy than if i shoot green EM at it. Because at a molecular level the molecules are resonant to one color and not the other, and thus absorbs one color more than the other. similarly if the object is black it is equally responsive at all frequencies, but the process is no different.
We can see a similar analogue in all resonant systems, whereby the system can be made to resonant to any frequency equally. We call these "universal resonators". In that sense a black body can be thought of as the universal resonator for that example. If we are talking about caviry resonance this has been demonstrated with air cavities as well where the Helmholtz resonance is universal. In my mind a resistor is really no different, it is simply the universal resonator in an electrical system (though again i agree it is unusual to refer to it as such technically speaking it is valid).
@freemo
Which part of "Shut up and calculate!" [https://events.cornell.edu/event/three_cheers_for_shut_up_and_calculate_in_fundamental_physics]
did you not understand?
@Science
Ok, so we have the same diploma (I never said you didn't by the way).. your point? You do realize the irony in asserting you have a diploma and thus some authority to someone who also has the same credentials as you right?
@freemo
So I suggested that you read a textbook on Theoretical MECHANICS,
because I'm all too aware of the blind spots of electical engineers without a first physical principles perspective.
I'm not being pompous here, I'm just right. That's a subtle difference not immediately apparent to most.
@Science
by the way notice what you just showed agrees perfectly with my statement and is not in disagreement.
> Also just to clarify the signal is not twice the resonant frequency. It should complete once back and forth cycle for every cycle of its resonant frequency.
In your graph you clearly see the signal, V(f) for the voltage signal, is at the given frequency not twice. I did **not** state the energy is at the same frequency, you did. But you decided to misread what I said and then go on a tirade and try to act like an ass and then go on about how your being right not pompass. You really need an attitude check, especially when your arguing about things someone didnt even say.
It seems you may be the one who needs to go back to a textbook. I clearly used the word signal, here is the definition of a signal, just to demonstrate that both my original assertion, and the graphs you showed, bioth agree with what I stated.
> In signal processing, a signal is a function that conveys information about a phenomenon. In electronics and telecommunications, it refers to any time varying voltage, current or electromagnetic wave that carries information.
@freemo
Looks like you're concerned about your or my image,
while I'm concerned about the defining properties of a resonator,
namely, that a resonator stores energy in two different forms, and converts this energy from one form to the other TWICE per oscillation cycle, as described by a second-order differential equation.
I don't care what you think.
Physics is NOT a Social Construct!!!
By the way, RF engineers' use of decibels, with 10dB corresponding to a factor of about three, confused the hell out of me until I understood that the important quantity that matters in information transmission is energy (or its disorganized form, entropy), not amplitude.
Turns out that textbooks are extremely bad at conveying first physical principles, but
Chetvorno - Own work, CC0, https://commons.wikimedia.org/w/index.php?curid=27408348
did a surprisingly good job, see picture.
@Science
> I don’t care what you think.
Physics is NOT a Social Construct!!!
No, of course not, what I think doesnt matter.. But it does help if you bother reading what someone says before restoring to insults, rudeness, and calling them wrong... when you very clearly misread what I said and in fact the entire rant and tirade you've went on since then continues to argue a point I never once disagreed with. In fact the point I did make (that the signal, not the energy is at the same frequency as its resonant frequency) is entierly correct and in line with all the spewing you've done since.
I already went over this and pointed out my exact quote an hour ago... clearly your not even bothering to read it as your still going on about how I am wrong and arguing over some imaginary thing you think I said and I didn't. See my earlier post:
https://qoto.org/@freemo/105353375463830513
No i am not concerned with either of our images.. I am concerned with:
1) the fact that your arguing against something I never said and still continue (I previously quoted myself to show you as much)
2) you are being rude and insulting in how you go about doing this.
As was already stated and made very clear.. I stated that the **signal** in the resonator is at the same frequency as the resonant frequency... You are arguing that the **energy** between them is at twice the rate. At no point did I state anything contrary to this.
You are literally arguing with ghosts of your own imagination of what you thought was said. Even after quoting myself and showing it to you, you still continue.
I do appreciate that you are sharing the explanation for anyone who may be reading this.. but you literally told me to go read a textbook and to shut the fuck up over somethign over something i said that turned out to be entierly correct and now have far too much pride to even admit you misread what I said and instead continue to go on as if you didnt even hear me correct you the first time.
@freemo
In case it matters, I have a Diplom in physics
AND a PhD in Electrical Engineering,
without ever having attended a regular EE program in college.
@Science