LT5518 데이터 시트보기 (PDF) - Linear Technology
부품명
상세내역
일치하는 목록
LT5518 Datasheet PDF : 16 Pages
| |||
LT5518
APPLICATIO S I FOR ATIO
Table 1. LO Port Input Impedance vs Frequency for EN = High
Frequency
MHz
1000
Input Impedance
Ω
44.5 + j18.2
S11
Mag
Angle
0.197
95
1400
60.3 + j6.8
0.112
30
1600
62.8 – j0.6
0.113
– 2.4
1800
62.4 – j9.0
0.136
– 32
2000
56.7 – j15.6
0.157
– 58
2200
50.9 – j16.5
0.161
– 77
2400
46.6 – j15.2
0.159
– 94
2600
42.9 – j13.9
0.165
– 109
The input impedance of the LO port is different if the part
is in shut-down mode. The LO input impedance for EN =
Low is given in Table 2.
Table 2. LO Port Input Impedance vs Frequency for EN = Low
Frequency
MHz
Input Impedance
Ω
S11
Mag
Angle
1000
42.1 + j43.7
0.439
75
1400
121 + j34.9
0.454
15
1600
134 – j31.6
0.483
– 11
1800
91.3 – j68.5
0.510
– 33
2000
56.4 – j66.3
0.532
– 53
2200
37.7 – j54.9
0.544
– 70
2400
27.9 – j43.6
0.550
– 87
2600
22.1 – j33.9
0.553
– 104
RF Section
After up-conversion, the RF outputs of the I and Q mixers are
combined. An on-chip balun performs internal differential
to single-ended output conversion, while transforming the
output signal impedance to 50Ω. Table 3 shows the RF
port output impedance vs frequency.
Table 3. RF Port Output Impedance vs Frequency for EN = High
and PLO = 0dBm
Frequency
MHz
Input Impedance
Ω
S22
Mag
Angle
1000
21.3 + j9.7
0.421
153
1400
29.8 + j20.3
0.348
121
1600
39.1 + j23.5
0.280
100
1800
50.8 + j18.4
0.180
77.1
2000
52.1 + j5.4
0.057
65.5
2200
43.2 – j0.1
0.073
– 179
2400
36.0 + j2.0
0.164
171
2600
32.1 + j5.6
0.228
159
The RF output S22 with no LO power applied is given in
Table 4.
Table 4. RF Port Output Impedance vs Frequency for EN = High
and No LO Power Applied
Frequency
MHz
Input Impedance
Ω
S22
Mag
Angle
1000
21.7 + j9.9
0.416
153
1400
32.3 + j19.5
0.312
119
1600
42.2 + j18.5
0.214
102
1800
46.8 + j9.6
0.104
103
2000
41.8 + j3.7
0.098
154
2200
36.1 + j4.3
0.170
160
2400
32.8 + j7.4
0.226
152
2600
31.2 + j10.5
0.264
144
For EN = Low the S22 is given in Table 5.
Table 5. RF Port Output Impedance vs Frequency for EN = Low
Frequency
MHz
Input Impedance
Ω
S22
Mag
Angle
1000
20.9+j9.6
0.428
154
1400
28.5 + j20.2
0.365
123
1600
36.7 + j24.5
0.311
103
1800
48.7 + j23.1
0.229
80.2
2000
55.7 + j11.0
0.116
56.7
2200
48.9 + j0.6
0.013
158.9
2400
39.8 – j0.02
0.115
–179
2600
34.2 + j3.2
0.193
167
To improve S22 for lower frequencies, a shunt capacitor
can be added to the RF output. At higher frequencies, a
shunt inductor can improve the S22. Figure 6 shows the
equivalent circuit schematic of the RF output.
VCC
20pF
52.5Ω
21pF 3nH
RF
OUTPUT
5518 F06
Figure 6. Equivalent Circuit Schematic of the RF Output
Note that an ESD diode is connected internally from
the RF output to ground. For strong output RF signal
levels (higher than 3dBm) this ESD diode can degrade
the linearity performance if the 50Ω termination imped-
ance is connected directly to ground. To prevent this, a
5518f
11
Share Link: 