lt5579 Linear Technology Corporation, lt5579 Datasheet - Page 16

• Manufacturer Part Number: lt5579
• Description: 1.5ghz To 3.8ghz High Linearity Upconverting Mixer
• Manufacturer: Linear Technology Corporation

LT5579
TYPICAL APPLICATIONS
The following examples illustrate the implementation
and performance of the LT5579 in different frequency
confi gurations. These circuits were evaluated using the
circuit board shown in Figure 12.
1650MHz Application
In this case, the LT5579 was evaluated while tuned for an
IF of 70MHz and an RF output of 1650MHz. The matching
confi guration is shown in Figure 8.
Input capacitors are used only as DC blocks in this ap-
plication. The 4.7nH inductors and the 120pF capacitor
transform the input impedance of the IC up to approximately
16
70MHz
IF
MABAES0061
4:1
1nF
1nF
Figure 8. IF Input Tuned for 70MHz
120pF
4.7nH
4.7nH
9.1Ω
9.1Ω
47pF
47pF
12.5Ω. The relatively low input frequency demanded the
use of 4.7nH chip inductors instead of short transmission
lines.
Closer to the IC input, 47pF capacitors were used instead
of a single differential capacitor (C3 in Figure 1), because it
was found that the addition of common mode capacitance
improved the high side LO performance in this applica-
tion. The value of these 47pF capacitors was selected to
resonate with the 100nH inductors at 70MHz. Note that
adding common mode capacitance does not improve
performance with all frequency confi gurations.
100nH
100nH
LO
1.5pF
6.8nH
1650MHz
RF
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