lt5519 Linear Technology Corporation, lt5519 Datasheet - Page 8

• Manufacturer Part Number: lt5519
• Description: 0.7ghz To 1.4ghz High Linearity Upconverting Mixer
• Manufacturer: Linear Technology Corporation

LT5519
APPLICATIO S I FOR ATIO
Though the LO input is internally matched to 50 , there
may be some cases, particularly at higher frequencies or
with different source impedances, where a further opti-
mized match is desired. Table 2 includes the single-ended
input impedance and reflection coefficient vs frequency
for the LO input for use in such cases.
Table 2. Single-Ended LO Input Impedance
RF Output Port
An internal RF transformer, shown in Figure 5, reduces the
mixer-core impedance to provide an impedance of 50
across the RF
tested with the outputs configured for single-ended opera-
tion, as shown in the Figure 5; however, the outputs can be
used differentially as well. A center tap in the transformer
provides the DC connection to the mixer core and the
transformer provides DC isolation at the RF output. The
8
FREQUENCY
(MHz)
1000
1200
1400
1600
1800
200
400
600
800
LO
50
IN
+
and RF
14
15
V
LT5519
Figure 4. LO Input Circuit
CC
LO
LO
62.8 – j12.0
61.6 – j14.2
U
IMPEDANCE
72.3 – j16.1
63.3 – j11.3
63.2 – j7.4
63.3 – j9.5
+
61.6 – j7.5
61.9 – j6.0
62.7 – j6.1
–
INPUT
–
pins. The LT5519 is designed and
U
85
5pF
5pF
W
0.223
0.153
0.124
0.119
0.125
0.134
0.144
0.155
0.163
MAG
220
220
S11
5519 F04
U
ANGLE
– 29.2
– 23.6
–28.4
–34.7
–22.7
–25.5
–30.8
–37.1
–43.4
RF
secondary windings of the transformer; thus a DC voltage
should not be applied across these pins.
The impedance data for the RF output, listed in Table 3, can
be used to develop matching networks for different load
impedances.
Table 3. Single-Ended RF Output Impedance
Operation at Different Input Frequencies
On the evaluation board shown in Figure 10, the input of
the LT5519 can be easily matched for different frequencies
by changing the capacitors, C1, C2 and C3. Capacitors C1
and C2 set the input matching frequency while C3 im-
proves the LO to RF leakage performance. Decreasing the
value of C3 at higher input frequencies reduces its impact
on conversion gain. Table 4 lists some actual values used
at selected frequencies.
FREQUENCY
+
(MHz)
and RF
1000
1100
1200
1300
1400
700
800
900
–
pins are connected together through the
Figure 5. RF Output Circuit
V
IMPEDANCE
27.6 + j32.0
50.9 + j23.5
53.5 + j10.3
39.7 + j32.1
42.0 – j3.1
36.6 – j3.4
33.0 – j2.0
8
CC3
48.3 + j1.3
LT5519
OUTPUT
10pF
RF
RF
V
5519 F05
CC
+
–
0.465
0.354
0.227
0.105
0.022
0.093
0.159
0.207
MAG
11
10
S11
RF
50
OUT
ANGLE
–157
–164
–172
88.1
74.7
65.5
103
143
5519f