ltc5590 Linear Technology Corporation, ltc5590 Datasheet - Page 14

• Manufacturer Part Number: ltc5590
• Description: Dual 600mhz To 1.7ghz High Dynamic Range Downconverting Mixer
• Manufacturer: Linear Technology Corporation

LTC5590
APPLICATIONS INFORMATION
The RF input impedance and input reflection coefficient,
versus RF frequency, are listed in Table 1. The reference
plane for this data is Pin 1 of the IC, with no external
matching, and the LO is driven at 1.09GHz.
Table 1. RF Input Impedance and S11
(at Pin 1, No External Matching, f
LO Input
The LO input, shown in Figure 5, is connected to the
primary winding of an integrated transformer. A 50Ω
impedance match is realized at the LO port by adding
an external series capacitor, C2. This capacitor is also
needed for DC blocking if the LO source has DC voltage
present, since the primary side of the LO transformer is
DC-grounded internally. The DC resistance of the primary
is approximately 4.5Ω.
14
FREQUENCY
(GHz)
0.6
0.7
0.8
0.9
1.0
1.1
1.2
1.3
1.4
1.5
1.6
1.7
MIXER A
MIXER B
TO
TO
LTC5590
Figure 5. LO Input Schematic
IMPEDANCE
34.2 + j24.5
41.3 + j22.4
48.5 + j18.1
54.3 + j10.1
54.2 – j4.6
29.3 – j9.4
27.7 – j4.5
27.4 – j1.6
27.8 – j0.1
29.4 + j0.2
RF INPUT
38.4 – j16
31.2 –j0.5
BIAS
BIAS
LO
= 1.09GHz)
MAG
0.33
0.26
0.18
0.10
0.06
0.22
0.29
0.29
0.29
0.28
0.26
0.23
ENA
ENB
I
SEL
S11
LO
5590 F05
14
18
17
16
ANGLE
C2
–116
–149
–165
–175
–180
–178
107
–45
179
97
84
61
LO
The secondary of the transformer drives a pair of high
speed limiting differential amplifiers for channels A and B.
The LTC5590’s LO amplifiers are optimized for the 700MHz
to 1.5GHz LO frequency range; however, LO frequencies
outside this frequency range may be used with degraded
performance.
The LO port is always 50Ω matched when V
even when one or both of the channels is disabled. This
helps to reduce frequency pulling of the LO source when
the mixer is switched between different operating states.
Figure 6 illustrates the LO port return loss for the different
operating modes.
The nominal LO input level is 0dBm, though the limiting
amplifiers will deliver excellent performance over a ±6dBm
input power range. Table 2 lists the LO input impedance
and input reflection coefficient versus frequency.
Table 2. LO Input Impedance vs Frequency
(at Pin 16, No External Matching, ENA = ENB = High)
FREQUENCY
(GHz)
0.7
0.8
0.9
1.0
1.1
1.2
1.3
1.4
1.5
–10
–20
–25
–15
–5
0
700
Figure 6. LO Input Return Loss
800
IMPEDANCE
29.7 + j34.7
39.9 + j34.1
48.7 + j26.6
50.8 + j15.1
46.5 + j6.2
39.9 + j2.5
34.0 + j1.4
29.2 + j2.1
25.6 + j3.8
INPUT
900 1000 1100
FREQUENCY (MHz)
BOTH CHANNELS ON
ONE CHANNEL ON
BOTH CHANNELS OFF
1200
MAG
0.46
0.37
0.26
0.15
0.07
0.12
0.19
0.26
0.33
1300 1400 1500
5590 F06
S11
CC
is applied,
ANGLE
116
165
174
173
168
97
86
78
78
5590f