S-Parameter and VSWR
S-parameters describe the input-output power relationship between 2 ports in an electrical system.
Notation : for example , Port 1 and Port 2, S12 represents the power transferred from Port 2 to Port 1.
What is the physical meaning of S21 = - 10dB ?
It means if we have 0dB power is delivered to Port 1, then we only have -10dB of power is received at Port 2.
What is the physical meaning of return loss/reflection coefficient ?
We denote the return loss as S11 , which represent how much power is reflected from the Port 1/Antenna 1.
For example S11 = 0dB means that all the power is reflected, nothing is radiated.
Base on the former description, we can easily observe from a frequency response plot of |S11| to decide which frequency will be efficient, say in 2.5 GHz in the figure above.
What is the meaning of VSWR ?
Impedance mismatch will induce return loss, and this cause a "reflected voltage wave" , which creates standing wave along the transmission line. Thus we called it voltage standing wave ratio (VSWR).
Large VSWR implies a lot of return loss/more impedance mismatch.
Notation : for example , Port 1 and Port 2, S12 represents the power transferred from Port 2 to Port 1.
What is the physical meaning of S21 = - 10dB ?
It means if we have 0dB power is delivered to Port 1, then we only have -10dB of power is received at Port 2.
What is the physical meaning of return loss/reflection coefficient ?
We denote the return loss as S11 , which represent how much power is reflected from the Port 1/Antenna 1.
For example S11 = 0dB means that all the power is reflected, nothing is radiated.
Base on the former description, we can easily observe from a frequency response plot of |S11| to decide which frequency will be efficient, say in 2.5 GHz in the figure above.
What is the meaning of VSWR ?
Impedance mismatch will induce return loss, and this cause a "reflected voltage wave" , which creates standing wave along the transmission line. Thus we called it voltage standing wave ratio (VSWR).
Large VSWR implies a lot of return loss/more impedance mismatch.
|
VSWR
|
(S11)
Linear |
Reflected
Power (%)
|
Reflected
Power (dB) |
|
1.0
|
0.000
|
0.00
|
-Infinity
|
|
1.5
|
0.200
|
4.0
|
-14.0
|
|
2.0
|
0.333
|
11.1
|
-9.55
|
|
3.0
|
0.500
|
25.0
|
-6.00
|
|
6.0
|
0.714
|
51.0
|
-2.92
|
留言
張貼留言