3.5GHz Downconverter Mixers
with Selectable LO Doubler
Table 4. MAX2683 IFOUT Port S-Parameters (V
= +5V, T = +25°C)
CC
A
R
BIAS
= 820Ω
R
BIAS
= 1.2kΩ
R
BIAS
= 1.2kΩ
RF
FREQUENCY
(MHz)
S11 PHASE
(degrees)
S11 PHASE
(degrees)
S11 PHASE
(degrees)
S11 MAG
S11 MAG
S11 MAG
150
200
250
300
350
0.915
0.907
0.904
0.899
0.894
-11.3
0.914
0.905
0.905
0.900
0.893
-11.2
0.930
0.920
0.917
0.911
0.907
-10.9
-14.8
-14.7
-14.2
-17.7
-17.8
-17.2
-21.3
-21.3
-20.3
-24.5
-24.5
-23.5
Table 5. MAX2684 IFOUT Port S-Parameters (V
= +5V, T = +25°C)
CC
A
R
BIAS
= 820Ω
R
BIAS
= 1.2kΩ
R
BIAS
= 1.2kΩ
RF
FREQUENCY
(MHz)
S11 PHASE
(degrees)
S11 PHASE
(degrees)
S11 PHASE
(degrees)
S11 MAG
S11 MAG
S11 MAG
860
880
900
920
940
960
0.955
0.952
0.950
0.946
0.943
0.941
-49.4
0.955
0.952
0.948
0.944
0.940
0.936
-49.6
0.955
0.950
0.946
0.941
0.937
0.935
-49.7
-50.6
-51.4
-52.3
-53.3
-53.8
-50.3
-50.5
-51.1
-51.4
-52.0
-52.3
-53.0
-53.1
-53.6
-54.0
as well as an output matching network for optimum per-
formance. See Typical Operating Circuit for recommend-
ed component values. See Tables 4 and 5 for IFOUT
port S-parameters.
___________Applications Information
Layout Considerations
A properly designed PC board is an essential part of
any RF/microwave circuit. Keep RF signal lines as short
as possible to reduce losses, radiation, and induc-
tance. Use separate, low-inductance vias to the ground
plane for each ground pin. For best performance, sol-
der the exposed pad on the bottom of the device pack-
age evenly to the board ground plane.
Bias Circuitry
The linearity and supply current of the MAX2683/
MAX2684 are externally programmable with a single
resistor, R
, from BIAS to GND. A nominal resistor
BIAS
value of 1.2kΩ will set an IIP3 of +9dBm and a supply
current of 55mA. Decreasing the resistor value
improves linearity at the cost of increased supply cur-
rent. Increasing the resistor value decreases supply
current while degrading linearity. Use resistor values in
the range of 820kΩ to 2kΩ.
Power-Supply and ENX2 Bypassing
Proper voltage-supply bypassing is essential for high-
frequency circuit stability. Bypass V
with a 10µF
CC
capacitor in parallel with a 100pF capacitor located as
close to the V pin as possible.
CC
Bypass ENX2 with a 100pF capacitor to ground to mini-
mize noise injected into the LO doubler cell. Use a
series resistor (typically 1.2kΩ) to further reduce cou-
pling of high-frequency signals into the ENX2 pin.
______________________________________________________________________________________ 15