LTC5505 LINER [Linear Technology], LTC5505 Datasheet - Page 13

• Manufacturer Part Number: LTC5505
• Description: 800MHz to 2.7GHz High Linearity Direct Conversion Quadrature Demodulator
• Manufacturer: LINER [Linear Technology]

APPLICATIONS INFORMATION
The LO input impedance and S11 parameters (without
external matching components) are listed in Table 2.
Table 2. LO Input Impedance
FREQUENCY
(GHz)
0.8
0.9
1.0
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
2.0
2.1
2.2
2.3
2.4
2.5
2.6
2.7
IMPEDANCE (
24.1 +j 31.7
31.2 +j 31.4
37.5 +j 28.9
41.9 +j 24.6
42.9 +j 16.4
41.2 +j 14.1
39.5 +j 13.1
37.8 +j 13.1
36.6 +j 13.6
35.6 +j 14.6
35.1 +j 15.7
34.9 +j 17.1
35.1 +j 18.5
35.5 +j 19.9
36.3 +j 21.2
37.2 +j 22.5
9.6 +j 23.7
13 +j 27.1
17.9 +j 30
43.4 +j 20
INPUT
V
CC
Ω
)
5pF
65Ω
0.731
0.669
0.592
0.508
0.421
0.341
0.272
0.221
0.189
0.186
0.201
0.217
0.236
0.264
0.272
0.281
0.284
0.287
MAG
0.18
0.25
65Ω
Figure 8. I/Q Output Equivalent Circuit
S11
ANGLE (°)
5pF
127.9
120.4
113.2
106.1
103.5
113.1
120.3
124.5
125.6
123.1
120.1
116.6
105.1
99.8
95.1
93.4
96.2
125
113
109
5pF
65Ω
I-Channel and Q-Channel Outputs
Each of the I-channel and Q-channel outputs is internally
connected to V
bias voltage is V
or AC-coupled to the external loads. Each single-ended
output has an impedance of 65Ω in parallel with a 5pF
internal capacitor, forming a low-pass fi lter with a –3dB
corner frequency at 490MHz. The loading resistance
on each output, R
than 300Ω to assure full gain. The gain is reduced by
20 • log
terminated by R
by 7.23dB when each output pin is connected to a
50Ω load (or 100Ω differentially). The output should be
taken differentially (or by using differential-to-single-
ended conversion) for best RF performance, including
NF and IM2.
The phase relationship between the I-channel output signal
and the Q-channel output signal is fi xed. When the LO
input frequency is larger (or smaller) than the RF input
frequency, the Q-channel outputs (Q
lag) the I-channel outputs (I
When AC output coupling is used, the resulting high-
pass fi lter’s –3dB roll-off frequency is defi ned by the RC
constant of the blocking capacitor and R
R
LOAD
65Ω
>> 65Ω.
10
(1 + 65Ω/R
5pF
CC
CC
LOAD
through a 65Ω resistor. The output DC
– 1.1V. The outputs can be DC-coupled
LOAD
LOAD
. For instance, the gain is reduced
(single-ended), should be larger
) in dB when the output port is
OUT
Q
Q
I
I
OUT
OUT
OUT
OUT
5575 F08
+
+
–
+
–
, I
16
15
14
13
OUT
OUT
–
+
) by 90°.
, Q
LOAD
LT5575
OUT
, assuming
–
) lead (or
13
5575f