Can antenna with zero gain resonate?

[kae_jolie]

so can you have an antenna which is perfectly matched at 800 MHz have zero or negative gain at 800 MHz?

in other words, any link between return loss and gain?

Isn't efficiency the link between return loss and gain? If an antenna is matched, it is efficient. Gain = directivity x efficiency, so gain should be higher unless directivity is super low.


Please save me the textbook definitions of gain and return loss as I am fully aware of them...I would really appreciate a straight-forward reply to my questions with explanation.

 

[vfone]

There is no real link between return loss and antenna gain or antenna radiation. Of course if you reflect more RF input power then the antenna will radiate less RF power, but this is not practically a relation.
The main thing that will make the antenna to radiate more power (higher gain) is its Radiation Resistance, which depends mainly by the antenna shape related to the wavelength.

https://en.wikipedia.org/wiki/Radiation_resistance

 

[kae_jolie]

Is it the higher the radiation resistance the higher the gain? Or the higher the radiation resistance the lower the gain? And why?

 

[vfone]

The Antenna Efficiency is the ratio of power radiated from the antenna to the power dissipated in the antenna structure.

Antenna_Efficiency(%) = 100*[Rr / (Rr+Rd)]
where Rr is Radiation Resistance (wanted) and Rd is Radiated Dissipation (unwanted).

So, higher the Radiation Resistance, higher the antenna efficiency.
Usually antennas smaller than λ/4 have small radiated resistance.

 

[kae_jolie]

Could you send me a link to this equation:

Antenna_Efficiency(%) = 100*[Rr / (Rr+Rd)]
where Rr is Radiation Resistance (wanted) and Rd is Radiated Dissipation (unwanted)

I only found this equation: R = Rloss + Rrad, which says electrical resistance = Loss (ohmic) resistance + radiation resistance.

I can't find it anywhere. Also, Antenna efficiency is the ratio of power radiated to power accepted into antenna, not power dissipated in antenna. Could you also send me a link to your definition for antenna efficiency?

Thanks.

 

[kae_jolie]

I found the equation....never mind.

Thanks.