Teridian 71M6521, User Manual

Page: 51 / 112

71M6521 Demo Board User’s Manual
Revision 2.18
© 2005-2009 TERIDIAN Semiconductor Corporation
Page: 51 of 111
And 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
π
π
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
φ
φ
3.
1 ) cos( 1
) 180 cos(
) 180 cos(
180
− = −
−
=
S XI XV
S XI XV
A A
IV
A A IV
E
φ
φ
4.
2 ) cos( 2
180 0
− = +
S XI XV
A A E E
φ
5.
) cos( 2
2
180 0
S
XI XV
E E
A A
φ
+ +
=
6.

) cos(
1 2 ) (
180 0
S XV
XI
A
E E
A
φ
+ +
=
Use above results along with E
60
and E
300
to calculate
φ
S
.
7.
1
) 60 cos(
) 60 cos(
60
−
−
=
IV
A A IV
E
S XI XV
φ
1 ) sin( ) 60 tan( ) cos(
− + =
S XI XV S XI XV
A A A A
φ φ
8.
1
) 60 cos(
) 60 cos(
300
−
−
− −
=
IV
A A IV
E
S XI XV
φ
1 ) sin( ) 60 tan( ) cos(
− − =
S XI XV S XI XV
A A A A
φ φ
Subtract 8 from 7
9.
) sin( ) 60 tan( 2
300 60 S XI XV
A A E E
φ
= −
use equation 5:
10.
) sin( ) 60 tan(
) cos(
2
180 0
300 60 S
S
E E
E E
φ
φ
+ +
= −
11.
) tan( ) 60 tan( ) 2 (
180 0 300 60 S
E E E E
φ
+ + = −