lt5527euf-trpbf Linear Technology Corporation, lt5527euf-trpbf Datasheet - Page 13

• Manufacturer Part Number: lt5527euf-trpbf
• Description: 400mhz To 3.7ghz High Signal Level Downconverting Mixer
• Manufacturer: Linear Technology Corporation

APPLICATIO S I FOR ATIO
Compared to the lowpass/4:1 transformer matching tech-
nique, this network delivers approximately 0.8dB higher
conversion gain (since the IF transformer loss is elimi-
nated) and comparable noise figure and IIP3. At a ±15%
offset from the IF center frequency, conversion gain and
noise figure degrade about 1dB. Beyond ±15%, conver-
sion gain decreases gradually but noise figure increases
rapidly. IIP3 is less sensitive to bandwidth. Other than IF
bandwidth, the most significant difference is LO-IF leak-
age, which degrades to approximately – 38dBm compared
to the superior performance realized with the lowpass/4:1
transformer matching.
Discrete IF balun element values for four common IF
frequencies are listed in Table 5. The corresponding
measured IF output return losses are shown in Figure 11.
The values listed in Table 5 differ from the calculated
values slightly due to circuit board and component
parasitics. Typical conversion gain, IIP3 and LO-IF leak-
age, versus RF input frequency, for all four IF frequency
examples is shown in Figure 12. Typical conversion gain,
IIP3 and noise figure versus IF output frequency for the
same circuits are shown in Figure 13.
Table 5. Discrete IF Balun Element Values (R
For fully differential IF architectures, the IF transformer
can be eliminated. An example is shown in Figure 14,
where the mixer’s IF output is matched directly into a SAW
filter. Supply voltage to the mixer’s IF pins is applied
L L
L
C C
IF FREQUENCY
1 2
3
6 7
,
,
=
(MHz)
190
240
380
450
ω
X
=
=
IF
IF
ω
R
IF
IF
ω
•
•
IF
R
U
R
OUT
1
IF
•
L1, L2
(nH)
120
100
R
56
47
U
OUT
W
OUT
C6, C7
(pF)
6.8
4.7
2.7
3
= 50Ω)
U
(nH)
220
220
L3
68
47
Figure 11. IF Output Return Losses with Discrete Balun Matching
Figure 12. Conversion Gain, IIP3 and LO-IF Leakage vs RF Input
Frequency Using Discrete IF Balun Matching
Figure 13. Conversion Gain, IIP3 and SSB NF vs IF Output
Frequency Using Discrete IF Balun Matching
–10
–15
–20
–25
–30
–5
26
24
22
20
18
16
10
14
12
26
24
22
20
18
16
14
12
10
6
4
0
8
2
1700
8
6
4
2
0
150
50
IIP3
SSB NF
G
IIP3
G
C
100
C
190MHz
200
1900
150
190IF
240IF
380IF
450IF
IF OUTPUT FREQUENCY (MHz)
240MHz
RF INPUT FREQUENCY (MHz)
250
200
IF FREQUENCY (MHz)
300
2100
250
300
350
380MHz
LOW SIDE LO (–3dBm)
T
LOW SIDE LO (–3dBm)
T
A
A
= 25°C
2300
= 25°C
350
400
400
450
450MHz
2500
450
LO-IF
500
190IF
240IF
380IF
450IF
500
5527 F13
5527 F11
5527 F12
2700
550
550
0
–10
–20
–40
–50
–60
–30
LT5527
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