Datasheet

AD8366
Rev. A | Page 19 of 28
LOW FREQUENCY IMD3 PERFORMANCE
To measure the IMD3 data at low frequencies, wideband
transformer baluns from North Hills Signal Processing Corp.
were used, specifically the 0301BB and the 0520BB. Figure 55
shows the IMD3 performance vs. frequency for a 2 V p-p
composite output. The IMD3 performance was also measured
for the combined ADL5380 and AD8366 system, as shown in
Figure 56, with an FFT spectrum analyzer. An FFT spectrum
analyzer works very similar to a typical ADC, the input signal
is digitized at a high sampling rate that is then passed through an
antialiasing filter. The resulting signal is transformed to the
frequency domain using fast Fourier transforms (FFT).
The single-ended RF signal from the source generator is converted
to a differential signal using a balun that gets demodulated and
down converted to differential IF signals through the ADL5380.
This differential IF signal drives the AD8366, thus eliminating
the need for low frequency baluns. Figure 54 shows the IMD3
performance vs. frequency over the 500 kHz to 5 MHz range
for minimum and maximum gain code setting on the AD8366.
During the measurements, the output was set to 2 V p-p composite.
–90
–80
–70
–60
–50
–40
–30
–
20
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
IMD3 (dBc)
FREQUENCY (MHz)
GC63
GC0
07584-018
Figure 54. System IMD3 vs. Frequency, 2 V p-p Composite at
the Output of the AD8366
–100
–90
–80
–70
–60
–50
–40
–30
–20
–10
0
0
5
10
15
20
25
30
35
40
45
50
0 5 10 15 20 25 30 35 40 45 50 55 60
IMD3 (dBc)
OIP3 (dBm)
GAIN CODE
FREQUENCY = 1MHz
FREQUENCY = 3MHz
07584-035
Figure 55. OIP3 on Low Frequency, 2 V p-p Composite