[discussion]a resonator and a well matched poor radiator

[DrunkBear]

i believe there are a lot of people working on resonators here. i'm curious on what would the S parameter of a good resonator be like(suppose the resonator is excited by a single port, thus S11 could be the focus)?
i raised the question because often i have the following situation. We may have a well matched antenna. In the S parameter diagram, we do get an ideal match at a specific frequency, however, the efficiency the simulation tools predict is rather poor. This may be resonable, since a well matched component is not necessarily a good radiator, due to its working mechanism. but how could this happed since the energy supplied from the source goes into the component(S11 is good means small reflection) but cannot radiated toward the free space--from a energy conservation point of view?
i've had this problem in my mind for a long time. could anyone help give a good explanation?

 

[Abhishekabs]

[discussion]a good resonator and a well matched antenna

I am curious to know what do you mean by good resonator & bad resonator?
Also you match your antenna to avoid redlections that is avoid power loss.
Are you confused between resonator & resonator being used as an antenna?
I have seen people using Patch antenna as a resonator.
This concept is used in Oscillator designs.

 

[radiohead]

Re: [discussion]a good resonator and a well matched antenna

I agree that it must be losses in the matching circuit or in the radiator itself. However it would be strange that these losses only occur at one single frequency, they should occur accross the full band although to different extent.

Using a patch antenna as a resonator for an oscillator is not a good idea. If you want good radiation efficiency for the antenna, it should absorb all power, right? This means that at resonance it will represent a certain radiation resistance R0, which will lead to a bad unloaded Q and therefore bad phase noise. Unless you don't care about that.

 

[DrunkBear]

Re: [discussion]a good resonator and a well matched antenna

Thank u for ur both replies!

to Abhishekabs:i referred "good" resonator just to emphasize the resonator is working normally. that's not the key of this question. i'm sorry i made u confused. yes, maybe the case u mentioned when a patch antenna is used as a resonator is exactly what i came across. could u pls give some examples of these literature. it's also nice if you show some key words that i could look up these papers by myself. many thx!

to radiohead:i don't think the poor radiation efficiency is caused by the losses. the reason is as the following. as u know, for a simple patch antenna working at fundamental mode, the maximum radiation in the broadside direction is achieved as two equivalent magnetic current sources are excited with the same magnitude and reversed phase and could be viewed as a two-unit array. however, in my case, for some reason, the reversed phase condition cannot be satisfied. thus, even if a low loss material (or even vaccum) is used as substrate and PEC is applied as conducting patch and GND in the simulation, low efficiency is still expected(but at a specific frequency, the S11 is below, let's say, -10dB. so it seems, for me, like a resonator.). that also explains ur doubt on the loss versus frequency band because loss is not the key reason for the poor radiation.