lt5522 Linear Technology Corporation, lt5522 Datasheet - Page 12

• Manufacturer Part Number: lt5522
• Description: 600mhz To 2.7ghz High Signal Level Downconverting Mixer
• Manufacturer: Linear Technology Corporation

APPLICATIO S I FOR ATIO
LT5522
Table 2. LO Port Input Impedance vs Frequency
12
IF Output Port
The IF outputs, IF
collectors of the mixer switching transistors (see Fig-
ure 10). Both pins must be biased at the supply voltage,
which can be applied through the center-tap of a trans-
former or through matching inductors. Each IF pin draws
15mA of supply current (30mA total). For optimum
single-ended performance, these differential outputs
should be combined externally through an IF trans-
former. Both evaluation boards include IF transformers
for impedance transformation and differential to single-
ended transformation.
The IF output impedance can be modeled as 400Ω in
parallel with 1pF. An equivalent small-signal model (in-
cluding bondwire inductance) is shown in Figure 11. For
most applications, the bondwire inductance can be
ignored.
FREQUENCY
(MHZ)
1000
1500
2000
2500
3000
100
250
500
–10
–20
–30
–15
–25
–5
0
1E8
Figure 9. LO Input Return Loss
+
200.5 – j181.0
and IF
U
IMPEDANCE
55.9 – j61.6
44.6 – j27.7
37.9 – j7.8
33.6 – j1.8
31.0 – j0.3
30.6 – j0.4
31.8 – j1.0
LO FREQUENCY (Hz)
INPUT
–
U
, are internally connected to the
1E9
W
0.763
0.505
0.286
0.163
0.197
0.234
0.240
0.223
MAG
5522 F09
5E9
S11
U
ANGLE
–142.1
–172.3
–178.9
–178.4
–176.0
–14.3
–54.4
–84.8
For IF frequencies below 140MHz, an 8:1 transformer
connected across the IF pins will perform impedance
transformation and provide a single-ended 50Ω output.
No other matching is required. Measured performance
using this technique is shown in Figure 12. Output return
loss is shown in Figure 13.
Figure 12. Typical Conversion Gain and IIP3
Using an 8:1 IF Transformer
Figure 10. IF Output with External Matching
–1
Figure 11. IF Output Small-Signal Model
8
6
5
4
3
1
7
2
0
0
0.5pF
460Ω
LT5522
LT5522
20
RF = 1800MHz
RF = 1800MHz
RF = 900MHz
RF = 900MHz
V
40
IF FREQUENCY (MHz)
CC
R
400Ω
S
60
80
1pF
IF
IF
+
–
11
10
0.7nH
0.7nH
LOW SIDE LO
P
100
5522 F10
LO
IIP3
G
= –5dBm
C
IF
IF
120
C4
15mA
15mA
+
–
5522 F12
11
10
L1
L2
5522 F11
V
140
CC
16
14
10
24
22
20
18
12
6
8
4:1
IF OUT
5522fa