Datasheet

MAX2023
High-Dynamic-Range, Direct Up-/Downconversion
1500MHz to 2500MHz Quadrature Mod/Demod
14
3dB PAD DC BLOCK 0°
3dB PAD DC BLOCK 180°
MINI-CIRCUITS
ZFSC-2-1W-S+
0° COMBINER
3dB PADS LOOK LIKE 160I TO GROUND
AND PROVIDES THE COMMON-MODE
DC RETURN FOR THE ON-CHIP CIRCUITRY.
I+
I-
3dB PAD DC BLOCK 0°
3dB PAD DC BLOCK
180°
MINI-CIRCUITS
ZFSCJ-2-1
MINI-CIRCUITS
ZFSCJ-2-1
Q+
Q-
90°
Figure 5. Demodulator Combining Diagram
EXTERNAL
STAGE
L
a
R
a
C
b
C
c
C
d
C
a
L
b
R
b
L
c
L
d
C
e
MAX2023
I/Q OUTPUTS
Figure 6. Baseband Port Typical Filtering and DC Return Network
downconverter is optimized for high linearity and excel-
lent noise performance, typically 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.
Demodulator Output Port Considerations
Much like in the modulator case, the four baseband
ports require some form of DC return to establish a
common mode that the on-chip circuitry drives. This
can be achieved by directly DC-coupling to the base-
band ports (staying within the ±3.5V common-mode
range), through an inductor to ground, or through a
low-value resistor to ground. Figure 6 shows a typical
network that would be used to connect to each base-
band port for demodulator operation. This network pro-
vides a common-mode DC return, implements a
high-frequency diplexer to terminate unwanted RF
terms, and also provides an impedance transformation
to a possible higher impedance baseband amplifier.
The network C
a
, R
a
, L
a
, and C
b
form a highpass/lowpass
network to terminate the high frequencies into a load
while passing the desired lower IF frequencies. Elements
L
a
, C
b
, L
b
, C
c
, L
c
, and C
d
provide a possible imped-
ance transformer. Depending on the impedance being
transformed and the desired bandwidth, a fewer number
of elements could be used. It is suggested that L
a
and
C
b
always be used since they are part of the high-fre-
quency diplexer. If power matching is not a concern,
then this would reduce the elements to just the diplexer.