LT5579IUH-PBF LINER [Linear Technology], LT5579IUH-PBF Datasheet - Page 13

• Manufacturer Part Number: LT5579IUH-PBF
• Description: 1.5GHz to 3.8GHz High Linearity Upconverting Mixer
• Manufacturer: LINER [Linear Technology]

C9 to step the impedance up to about 12.5Ω. At lower
frequencies additional series inductance may be required
between the IF ports and C9. The position of C9 may vary
with the IF frequency due to the different series inductance
requirements. The 4:1 impedance ratio of transformer T1
completes the transformation to 50 ohms. Table 1 lists the
differential IF input impedances and refl ection coeffi cients
for several frequencies.
Table 1. IF Input Differential Impedance
APPLICATIONS INFORMATION
FREQUENCY
(MHz)
1000
140
170
190
240
380
450
750
70
IMPEDANCE
11.8+j13.8
10.0+j5.2
10.8+j9.4
IF INPUT
8.8+j1.3
8.7+j2.3
9.0+j2.8
8.9+j3.0
9.0+j4.0
9.7+j4.9
REFLECTION COEFFICIENT
MAG
0.70
0.70
0.70
0.70
0.70
0.68
0.67
0.65
0.64
Figure 3. IF Input Return Loss with 70MHz (a),
240MHz (b) and 456MHz (c) Matching
–15
–20
–25
–10
–5
0
0
ANGLE
100 200
177
175
174
173
170
168
167
158
148
a
FREQUENCY (MHz)
b
300
400
The purpose of capacitor C3 is to improve the LO-RF
leakage in some applications. This relatively small-valued
capacitor has little effect on the impedance match in most
cases. This capacitor should typically be located close to
the IC, however, there may be cases where re-positioning
the capacitor may improve performance.
The measured return loss of the IF input is shown in
Figure 3 for application frequencies of 70MHz, 240MHz
and 456MHz. Component values are listed in Table 2. (For
70MHz matching details, refer to Figure 8.)
Table 2. IF Input Component Values
Note: (1) Depends on RF , (2) T1 = M/A-Com MABAES0061
FREQUENCY
500
(MHz)
c
140
240
450
600 700
5579 F03
C1, C2
1000
(pF)
800
82
33
(pF)
120
C9
33
33
(pF)
(1)
(1)
(1)
C3
L1, L2
(nH)
100
40
40
R1, R2
(Ω)
9.1
11
11
LT5579
(at 12dB RL)
MATCH BW
<50 to 158
174 to 263
330 to 505
13
5579f