positive values in returnLoss

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Shahar ben ezra
Shahar ben ezra 2020년 10월 31일
댓글: Shahar ben ezra 2020년 11월 4일
When I create an RL graph I get the positive graph
but it need to be negative
Why is my graph upside down?
my code:
C = 3*10^8;
F = 30*10^6 %hz
Z0 = 50
Lamda =C/F %m
ant_Half = dipole('Length', Lamda/2 );
figure(5) ; returnLoss(ant_Half,F-3e6:F/100:F+3e6,Z0)
my fig

답변 (1개)

Dushyant Marathe
Dushyant Marathe 2020년 11월 4일
Hi Shahar,
It is my understanding that you are able to plot return loss in dB for dipole antenna. However, you are uncertain about sign of the values. The magnitude of s-parameter S11 for passive device like antenna is expected to be a negative number in dB. However, return loss |Tin| as defined below is always a positive number for passive device.
RL = −20 log |Tin|
For a matched load (|Tin| = 0) has a return loss of ∞ dB (no reflected power), while a total reflection (|Tin| = 1) has a return loss of 0 dB (all incident power is reflected). Note that return loss is a non-negative number for reflection from a passive network or device.
Example :
If |Tin| = 0.452
return loss is RL = −20 log |Tin|=−20 log (0.452) = 6.9 dB
Please, refer to the return loss documentation for more information. From above link, its seen that return loss for loopCircular antenna is positive.
  댓글 수: 1
Shahar ben ezra
Shahar ben ezra 2020년 11월 4일
I can understand what you're saying
But that I do by Antenna designer
I get the right result (What I expect to get)
Look at the formula

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