# Why the return loss of an antenna decreases at higher frequencies?

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#### arxlan

##### Member level 3
Why the return loss of an antenna decreases at higher frequencies?
Is there any mathematical proof for this?

#### WimRFP

Re: Return Loss Reduction

Could you provide us some more info (frequency range, size and type of antenna, etc)?

#### arxlan

##### Member level 3
@WimRFP

A dual frequency antenna, At first resonance return loss is high and for second resonance return loss is very low.
What you think is the reason behind this?

#### ashish.mw

##### Full Member level 2
have you checked the gain(dB) v/s frequency plot? What is the gain at second freq? is it +ve dB or -ve dB? Are you sure that it is a new mode? if gain is also less, then second frequency may be a harmonic.

#### rodgerwxh

##### Banned
Just curious, return loss high means big mismatch, return loss low means match well, right? So at different resonant frequencies, the input impedance is different as well. However, if the source impedance is fixed, say 50 or 75 Ohm, then the return loss should be different at different resonant frequencies, am I correct? Please help me understand.

#### D.A.(Tony)Stewart

High return loss means good match and lots of loss in the reflected signal.

#### zorro

Why the return loss of an antenna decreases at higher frequencies?
Is there any mathematical proof for this?
...
A dual frequency antenna, At first resonance return loss is high and for second resonance return loss is very low.
This is not a general rule. That can happen in your particular design, but it could be otherwise.
Regards

Z

WimRFP

### WimRFP

Points: 2

#### arxlan

##### Member level 3
Thank you all for your suggestions. Actually i'm trying to devise some mathematical proof for this condition in my design.