MAX2023ETX+ Maxim Integrated Products, MAX2023ETX+ Datasheet - Page 11

• Manufacturer Part Number: MAX2023ETX+
• Description: Modulator / Demodulator IC MOD/DEMOD HI DYN RNG
• Manufacturer: Maxim Integrated Products

Specifications of MAX2023ETX+

• Package / Case: QFN-36
• Mounting Style: SMD/SMT
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

soidal baseband signals, a level of 89mV
on the I and the Q inputs results in a -17dBm input
power level delivered to the I and Q internal 50Ω termi-
nations. This results in an RF output power of -26.6dBm.
LO leakage at the RF port can be nulled to a level less
than -80dBm by introducing DC offsets at the I and Q
ports. However, this null at the RF port can be compro-
mised by an improperly terminated I/Q IF interface. Care
must be taken to match the I/Q ports to the driving DAC
circuitry. Without matching, the LO’s second-order (2f
term may leak back into the modulator’s I/Q input port
where it can mix with the internal LO signal to produce
additional LO leakage at the RF output. This leakage
effectively counteracts against the LO nulling. In addi-
tion, the LO signal reflected at the I/Q IF port produces a
residual DC term that can disturb the nulling condition.
As demonstrated in Figure 3, providing an RC termination
on each of the I+, I-, Q+, Q- ports reduces the amount of
LO leakage present at the RF port under varying temper-
ature, LO frequency, and baseband termination condi-
tions. See the Typical Operating Characteristics for
details. Note that the resistor value is chosen to be 50Ω
with a corner frequency 1 / (2πRC) selected to adequate-
ly filter the f
ness of the baseband response at the highest baseband
frequency. The common-mode f
I+/I- and Q+/Q- effectively see the RC networks and thus
Figure 3. Diplexer Network Recommended for DCS 1800/
PCS 1900 EDGE Transmitter Applications
High-Dynamic-Range, Direct Up-/Downconversion
Q
I
1500MHz to 2300MHz Quadrature Mod/Demod
LO
L = 11nH
L = 11nH
and 2f
________________________________________________________________________________________________
C = 2.2pF
C = 2.2pF
C = 2.2pF
LO
leakage, yet not affecting the flat-
50Ω
50Ω
50Ω
50Ω
LO
LO
External Diplexer
RF MODULATOR
0°
MAX2023
90°
and 2f
∑
P-P
LO
differential
signals at
LO
)
become terminated in 25Ω (R/2). The RC network pro-
vides a path for absorbing the 2f
while the inductor provides high impedance at f
2f
The MAX2023 can also be used as an RF demodulator,
downconverting an RF input signal directly to base-
band. The single-ended RF input accepts signals from
1500MHz to 2300MHz with power levels up to +30dBm.
The passive mixer architecture produces a conversion
loss of typically 9.5dB. The downconverter is optimized
for high linearity and excellent noise performance, typi-
cally with a +38dBm IIP3, an input P1dB of +29.7dBm,
and a 9.6dB noise figure.
A wide I/Q port bandwidth allows the port to be used as
an image-reject mixer for downconversion to a quadra-
ture IF frequency.
The RF and LO inputs are internally matched to 50Ω.
Thus, no matching components are required, and only
DC-blocking capacitors are needed for interfacing.
Bias currents for the LO buffers are optimized by fine
tuning resistors R1, R2, and R3. Maxim recommends
using ±1%-tolerant resistors; however, standard ±5%
values can be used if the ±1% components are not
readily available. The resistor values shown in the
Typical Application Circuit were chosen to provide
peak performance for the entire 1500MHz to 2300MHz
band. If desired, the current can be backed off from
this nominal value by choosing different values for R1,
R2, and R3. Contact the factory for additional details.
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. For the best performance, route the ground pin
traces directly to the exposed paddle under the pack-
age. The PC board exposed paddle MUST be connect-
ed to the ground plane of the PC board. It is suggested
that multiple vias be used to connect this paddle to the
lower level ground planes. This method provides a
good RF/thermal conduction path for the device. Solder
the exposed paddle on the bottom of the device pack-
age to the PC board. The MAX2023 evaluation kit can
be used as a reference for board layout. Gerber files
are available upon request at www.maxim-ic.com.
LO
to help the diplexing process.
Power Scaling with Changes
Layout Considerations
to the Bias Resistors
LO
RF Demodulator
and f
LO
leakage,
LO
and
11