lt5519 Linear Technology Corporation, lt5519 Datasheet - Page 9

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

APPLICATIO S I FOR ATIO
Table 4. Input Capacitor Values vs Frequency
The performance was evaluated with the input tuned for
each of these frequencies and the results are summarized
in Figures 6-8. The same IF input balun transformer was
used for all measurements. In each case, the LO input
Figure 6. Conversion Gain and Single Sideband Noise Figure
vs Tuned IF Input Frequency
FREQUENCY
(MHz)
Figure 7. IIP3 and IIP2 vs Tuned IF Input Frequency
140
240
300
350
440
44
70
–1
–2
–3
–4
27
25
23
21
19
17
15
13
6
5
4
3
2
1
0
0
0
INPUT TUNED FOR EACH TEST FREQUENCY
INPUT TUNED FOR EACH TEST FREQUENCY
V
P
T
V
P
CC
LO
A
CC
LO
IIP3
= 25 C
= 5V, T
= –5dBm
= 5V
= –5dBm
CAPACITANCE (C1, C2)
GAIN
LOW SIDE
100
100
U
INPUT FREQUENCY (MHz)
INPUT FREQUENCY (MHz)
HIGH SIDE LO
A
HIGH SIDE
HIGH SIDE LO
LOW SIDE
= 25 C
2200
200
200
(pF)
820
220
68
39
27
18
U
300
300
LOW SIDE
HIGH SIDE LO
LOW SIDE
SSB NF
W
400
400
IIP2
CAPACITANCE (C3)
5519 F07
5519 F06
500
500
70
20
18
16
14
12
10
8
6
4
2
0
60
50
40
30
20
10
0
(pF)
6.8
6.8
6.8
33
33
33
15
U
frequency was adjusted to maintain an RF output fre-
quency of 1000MHz.
Low Frequency Matching of the RF Output Port
Without any external components on the RF output, the
internal transformer of the LT5519 provides a good 50
impedance match for RF frequencies above approximately
850MHz. Below this frequency, the return loss drops
below 10dB and degrades the conversion gain. The addi-
tion of a single 10pF capacitor in series with the RF output
improves the match at lower RF frequencies, shifting the
10dB return loss point to about 700MHz, as demonstrated
in Figure 9. This change also results in an improvement of
the conversion gain.
Figure 9. Conversion Gain and Return Loss vs Output Frequency
Figure 8. LO to RF Leakage vs Tuned IF Input Frequency
–40
–50
–60
–10
–20
–30
–4
–5
–6
–1
–2
–3
–7
0
0
700
1
INPUT TUNED FOR EACH TEST FREQUENCY
V
P
T
C
CC
LO
A
OUT
= 25 C
800
= 5V
= –5dBm
100
= 10pF
RF OUTPUT FREQUENCY (MHz)
C
INPUT FREQUENCY (MHz)
OUT
900
NO C
NO C
= 10pF
200
1000
OUT
OUT
LOW SIDE LO
1100
300
HIGH SIDE LO
1200
RETURN LOSS
400
1300 1400
GAIN
5519 F09
5519 F08
500
LT5519
0
–5
–10
–15
–20
–25
–30
–35
9
5519f