Maxim Integrated 71M6533-DB - Manual (Page 37)

71M6533- DB Demo Board User’s Manual
Page: 37 of 75 ` REV 3
Finally, we calculate the new calibration current gain coefficient, including compensation for a slight gain
increase in the phase calibration circuit.
2 9
0
9
0
9 20 20
) 2 1 ( ) 2 cos( ) 2 1 ( 2 1
)) 2 cos( ) 2 1 ( 2 2 2 ( 2
1
1 _
_
 
  
   
  


T f
T f PHADJ PHADJ
A
I CAL
I CAL
XI
NEW


2.1.2 CALIBRATION WITH FIVE MEASUREMENTS
The five measurement method provides more orthogonality between the gain and phase error derivations. This
method involves measuring E
V
, E
0
, E
180
, E
60
, and E
300
. Again, set all calibration factors to nominal, i.e. CAL_IA =
16384, CAL_VA = 16384, PHADJA = 0.
First, calculate A
XV
from E
V
:
1. 1
 
V XV
E A
Calculate A
XI
from E
0
and E
180
:
2. 1 ) cos( 1
) 0 cos(
) 0 cos(
0
  


S XI XV
S XI XV A A
IV
A A IV
E


3. 1 ) cos( 1
) 180 cos(
) 180 cos(
180
  


S XI XV
S XI XV A A
IV
A A IV
E


4. 2 ) cos( 2
180 0
  
S XI XV
A A E E

5.
) cos( 2
2
180 0
S
XI XV
E E
A A

 

6.
) cos(
1 2 ) (
180 0
S XV
XI
A
E E
A

 

Use above results along with E
60
and E
300
to calculate

S
.
7. 1
) 60 cos(
) 60 cos(
60



IV
A A IV
E S XI XV

1 ) sin( ) 60 tan( ) cos(
  
S XI XV S XI XV
A A A A
 
8. 1
) 60 cos(
) 60 cos(
300


 

IV
A A IV
E S XI XV

1 ) sin( ) 60 tan( ) cos(
  
S XI XV S XI XV
A A A A
 
Subtract 8 from 7
9. ) sin( ) 60 tan( 2
300 60 S XI XV
A A E E
  
use equation 5:
10. ) sin( ) 60 tan(
) cos(
2
180 0
300 60 S
S
E E
E E


 
 
11. ) tan( ) 60 tan( ) 2 (
180 0 300 60 S
E E E E
    