LTM9004
16
9004fa
For more information
www.linear.com/LTM9004
applicaTions inForMaTion
RF INPUT
Figure 3 shows the mixer’s RF input which consists of an
integrated transformer and high linearity transconduc-
tance amplifiers. The primary side of the transformer is
connected to the RF input pin. The secondary side of the
transformer is connected to the differential inputs of the
transconductance amplifiers. Under no circumstances
should an external DC voltage be applied to the RF input
pin. DC current flowing into the primary side of the trans-
former may cause damage to the integrated transformer.
A series blocking capacitor should be used to AC-couple
the RF input port to the RF signal source.
at lower frequencies, however, the input return loss can be
improved with the matching network shown in Figure 3.
Shunt capacitor C10 and series capacitor C11 can be
selected for optimum input impedance matching at the
desired frequency as illustrated in Figure 4. For lower fre-
quency band operation, the external matching component
C11 can serve as a series DC blocking capacitor.
The RF input impedance and S11 parameters (without
external matching components) are listed in Table 1.
Table 1. RF Input Impedance
FREQUENCY
(MHz)
MAGNITUDE
PHASE (°)
R (Ω)
X (Ω)
500
0.78
–139.7
16.1
–10.7
600
0.69
–166.6
10.1
–3.8
700
0.60
163.7
14.0
3.8
800
0.52
132.6
25.8
6.9
900
0.48
102.7
41.9
3.4
1000
0.45
77.4
58.8
–4.3
1100
0.42
56.6
74.9
–11.4
1200
0.38
40.1
86.4
–12.4
1300
0.31
25.7
87.6
–7.1
1400
0.22
10.9
76.8
–1.4
1500
0.10
–14.5
60.9
0.3
1600
0.06
–132.9
45.9
–0.2
1700
0.19
–170.7
34.6
–0.4
1800
0.30
–177.7
26.8
0.2
1900
0.40
–172.1
21.8
1.1
2000
0.47
–169.4
18.7
1.9
2100
0.51
–168.6
16.7
2.2
2200
0.54
–169.3
15.4
2.3
2300
0.55
–172.0
14.7
1.7
2400
0.55
–176.0
14.4
0.9
2500
0.54
–178.7
14.9
–0.3
2600
0.52
–172.3
15.9
–1.6
2700
0.50
–164.3
17.6
–3.0
2800
0.49
–155.0
19.9
–4.3
2900
0.48
–144.7
22.9
–5.4
3000
0.48
–134.8
26.4
–6.0
LO Input Port
The mixer’s LO input interface is shown in Figure 5. The
input consists of an integrated transformer and a preci-
sion quadrature phase shifter which generates 0° and
The RF input port is internally matched over a wide fre-
quency range from 1.5GHz to 2.7GHz with input return loss
typically better than 10dB. No external matching network is
needed for this frequency range. When the part is operated
Figure 3. RF Input Interface
TO I MIXER
RF
EXTERNAL
MATCHING
NETWORK FOR
LOW BAND AND
MID BAND
C10
9004 F05
C11
TO Q MIXER
RF
INPUT
E2
E3
–30
–25
–20
–15
–10
–5
0
100
1000
10000
FREQUENCY (MHz)
RETURN LOSS (dB)
9004 F04
NO
MATCHING
ELEMENTS
1.95GHz
MATCH
(2.7nH +
1.8pF)
700MHz
MATCH
(18pF +
8.2pF)
Figure 4. RF Port Return Loss vs Frequency
