Manual
71M6541 Demo Board REV 3.0 User’s Manual
38 Rev 4.0
3a.
[ ]
1
)60cos(
)
sin()60sin()cos()60cos(
60
−
+
=
SSXIXV
AA
E
φφ
1)sin()60tan()cos( −+=
SXIXVSXIXV
AAAA
φφ
Combining 2a and 3a:
4.
)tan()60tan()1(
0060 S
EEE
φ
++=
5.
)60tan()1(
)tan(
0
060
+
−
=
E
EE
S
φ
6.
+
−
=
−
)60tan()1(
tan
0
060
1
E
EE
S
φ
and from 2a:
7.
)cos(
1
0
SXV
XI
A
E
A
φ
+
=
Now that we know the A
XV
, A
XI
, and φ
S
errors, we calculate the new calibration voltage gain coefficient from the
previous ones:
XV
NEW
A
VCAL
VCAL
_
_ =
We calculate PHADJ from φ
S
, the desired phase lag:
[ ]
[ ]
−−−−
−−−+
=
−−
−−
)2cos()21(1)tan()2sin()21(
)2cos()21(2)21(1)tan(
2
0
9
0
9
0
929
20
TfTf
Tf
PHADJ
S
S
πφπ
πφ
And we calculate the new calibration current gain coefficient, including compensation for a slight gain increase
in the phase calibration circuit.
29
0
9
0
92020
)21()2cos()21(21
))2cos()21(222(2
1
1_
_
−−
−−−
−+−−
−−+
+
=
Tf
TfPHADJPHADJ
A
ICAL
ICAL
XI
NEW
π
π
2.2.2 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+=
VXV
EA
Calculate A
XI
from E
0
and E
180
:
2.
1)cos(1
)0cos(
)0cos(
0
−=−
−
=
SXIXV
SXIXV
AA
IV
AAIV
E
φ
φ
3.
1)cos(1
)180cos(
)180cos(
180
−=−
−
=
SXIXV
SXIXV
AA
IV
AAIV
E
φ
φ
4.
2)cos(2
1800
−=+
SXIXV
AAEE
φ