AD7011
TERMINOLOGY
Error Vector Magnitude
Signal to (Noise + Distortion) Ratio
This is a measure of the rms error vector introduced by the
AD7011 where signal error vector is defined as the rms devia-
tion of a transmitted symbol from its ideal position when filtered
by an Ideal RRC Receive filter, as illustrated in Figure 8.
Gain Matching Between Channels
The is the gain matching between the I and Q outputs, measured
when transmitting all zeros.
Offset Vector Magnitude
This is the measured ratio of signal to (noise + distortion) at the
output of the transmit I and Q DACs. The signal is the rms
amplitude of the fundamental. Noise is the rms sum of all non-
fundamental signals up to half the sampling frequency (f
S
/2),
excluding dc. The ratio is dependent upon the number of
quantization levels in the digitization process; the more levels,
the smaller the quantization noise. The theoretical signal to
(noise distortion) ratio for a sine wave is given by:
SNR = (6.02N
+ 1.76)
dB
where
N
is the number of bits. Thus for an ideal 10-bit con-
verter, SNR = 61.96 dB.
Q
ERROR VECTOR
This is a measure of the offset vector introduced by the AD7011
as illustrated in Figure 8. The offset vector is calculated so as to
minimize the rms error vector for each of the constellation
points.
Output Signal Range and Different Output Range
The output signal range is the output voltage swing and dc bias
level for each of the analog outputs. The different output range
is the difference between ITx and
ITx
for the I channel and the
difference between QTx and
QTx
for the Q Channel.
IS-54 Spurious Power
SIGNAL VECTOR
This is the rms sum of the spurious power measured at multiples
of 30 kHz, in a root raised cosine window of
±
16.4 kHz, relative
to twice the rms power in a RRC window in the 0 to 16.4 kHz
band.
Signal Vector Magnitude
OFFSET
VECTOR
0,0
I
This is the radius of the IQ constellation diagram as illustrated
in Figure 8.
Figure 8.
–8–
REV. B
AD [ ANALOG DEVICES ]
