ADL5385(Rev0) 데이터 시트보기 (PDF) - Analog Devices
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ADL5385 Datasheet PDF : 24 Pages
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ADL5385
When an offset of +VIOS is applied to the I-channel inputs,
VIOPP = 500 mV + VIOS/2, while
VIOPN = 500 mV − VIOS/2, such that
VIOPP − VIOPN = VIOS
The same applies to the Q channel.
It is often desirable to perform a one-time carrier null
calibration. This is usually performed at a single frequency.
Figure 29 shows how carrier feedthrough varies with LO
frequency over a range of ±50 MHz on either side of a null at
350 MHz.
–25
–30
–35
–40
–45
–50
–55
–60
–65
–70
–75
–80
–85
300 310 320 330 340 350 360 370 380 390 400
OUTPUT FREQUENCY (MHz)
Figure 29. Carrier Feedthrough vs. Frequency After Nulling at 350 MHz
Sideband Suppression Optimization
Sideband suppression results from relative gain and relative
phase offsets between the I and Q channels and can be
suppressed through adjustments to those two parameters.
Figure 30 illustrates how sideband suppression is affected by the
gain and phase imbalances.
0
–10
2.5dB
–20 1.25dB
–30 0.5dB
0.25dB
–40 0.125dB
–50 0.05dB
0.025dB
–60 0.0125dB
–70
0dB
–80
–90
0.01
0.1
1
10
100
PHASE ERROR (Degrees)
Figure 30. Sideband Suppression vs. Quadrature Phase Error for Various
Quadrature Amplitude Offsets
Figure 30 underscores the fact that adjusting one parameter
improves the sideband suppression only to a point; the other
parameter must also be adjusted. For example, if the amplitude
offset is 0.25 dB, improving the phase imbalance better than 1°
does not yield any improvement in the sideband suppression.
For optimum sideband suppression, an iterative adjustment
between phase and amplitude is required.
The sideband suppression nulling can be performed either through
adjusting the gain for each channel or through the modification
of the phase and gain of the digital data coming from the digital
signal processor.
Rev. 0 | Page 14 of 24
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