1
Relationship of VSWR to Return Loss:
VSWR and return loss are related quantities. Note that the reflection coefficient written in terms of the VWSR as:
can be
VSWR – 1
VSWR + 1
ρ
ρ =
VSWR
1 + | Γ |
1 | Γ
Which provides the relationship we started with. The return loss can then be cast in terms of VSWR as,
RL(DB) = -20log
10
VSWR – 1
VSWR + 1
Conversely,
VSWR =
10
RL(dB)
+ 1.0
20.0
RL(dB)
10
20.0
- 1.0
So if either of the two quantities is known the other can be calculated from it. A table showing conversions is shown below for convenience
________________________________________________________________________
Signal Processing Group Inc., technical memorandum. Signal Processing Group Inc, designs, develops and manufactures, Analog and RF/Wireless ASICs and RF/Wireless modules using state of the art semiconductor, PCB and assembly technologies. Please contact us from our website at http://www.signalpro.biz
, or email us directly at spg@signalpro.biz.

2
23.1
23.7
24.3
24.9
25.7
26.4
27.3
18
19
20
20.8
21.7
22.6
6
7
8
9
10
11
12
13
14
15
16
17
2
3
4
5
Return loss ( db)
0
1
VSWR
Infinite
17.39
8.724
5.848
4.419
3.569
3.009
2.614
2.322
2.099
1.924
1.784
1.670
1.576
1.498
1.432
1.376
1.328
1.288
1.252
1.222
1.195
1.179
1.16
1.15
1.139
1.129
1.120
1.109
1.100
1.109
________________________________________________________________________
Signal Processing Group Inc., technical memorandum. Signal Processing Group Inc, designs, develops and manufactures, Analog and RF/Wireless ASICs and RF/Wireless modules using state of the art semiconductor, PCB and assembly technologies. Please contact us from our website at http://www.signalpro.biz
, or email us directly at spg@signalpro.biz.
0.069
0.065
0.060
0.056
0.051
0.047
0.043
0.125
0.112
0.100
0.089
0.082
0.074
0.501
0.446
0.398
0.354
0.316
0.281
0.251
0.223
0.199
0.177
0.158
0.141
Reflection coefficient
1.0
0.891
0.794
0.707
0.630
0.562

3
28.3
29.4
30.7
32.3
34.1
36.6
40.1
46.1
1.079
1.07
1.06
1.049
1.04
1.03
1.019
1.009
0.038
0.033
0.029
0.024
0.019
0.014
0.009
0.004
It is instructive to examine a graphical view of the relationship between VSWR and the return loss presented below.
Note the slow variation of the return loss as the VSWR reaches between 1.0 to 2.0.
Conversely for a VSWR of 7 or 8 the return loss is large. If the return loss is greater than
10dB the VSWR is less than 2.0.
________________________________________________________________________
Signal Processing Group Inc., technical memorandum. Signal Processing Group Inc, designs, develops and manufactures, Analog and RF/Wireless ASICs and RF/Wireless modules using state of the art semiconductor, PCB and assembly technologies. Please contact us from our website at http://www.signalpro.biz
, or email us directly at spg@signalpro.biz.