MAX2022ETX+D Maxim Integrated, MAX2022ETX+D Datasheet - Page 13

• Manufacturer Part Number: MAX2022ETX+D
• Description: Modulator / Demodulator 1.5-2.5GHz Quadratr Modulator
• Manufacturer: Maxim Integrated

Specifications of MAX2022ETX+D

• Rohs: yes

MAX2022
Modulator Baseband I/Q Input Drive
The MAX2022 I and Q baseband inputs should be driven
differentially for best performance. The baseband inputs
have a 50Ω differential input impedance. The optimum
source impedance for the I and Q inputs is 100Ω differen-
tial. This source impedance will achieve the optimal signal
transfer to the I and Q inputs, and the optimum output RF
impedance match. The MAX2022 can accept input power
levels of up to +12dBm on the I and Q inputs. Operation
with complex waveforms, such as CDMA or WCDMA
carriers, utilize input power levels that are far lower. This
lower power operation is made necessary by the high
peak-to-average ratios of these complex waveforms. The
peak signals must be kept below the compression level of
the MAX2022. The input common-mode voltage should
be confined to the -2V to +1.5V DC range.
The MAX2022 is designed to interface directly with Maxim
high-speed DACs. This generates an ideal total transmit-
ter lineup, with minimal ancillary circuit elements. Such
DACs include the MAX5875 series of dual DACs, and
the MAX5895 dual interpolating DAC. These DACs have
ground-referenced differential current outputs. Typical
termination of each DAC output into a 50Ω load resistor
to ground, and a 10mA nominal DC output current results
in a 0.5V common-mode DC level into the modulator I/Q
inputs. The nominal signal level provided by the DACs will
Figure 1. MAX5895 DAC Interfaced with MAX2022
www.maximintegrated.com
BBQ
BBI
DUAL 16-BIT INTERP DAC
OFFSET ADJUST
I/Q GAIN AND
MAX5895
FREQ
FREQ
50Ω
50Ω
50Ω
50Ω
LO
Downconversion 1500MHz to 3000MHz
be in the -12dBm range for a single CDMA or WCDMA
carrier, reducing to -18dBm per carrier for a four-carrier
application.
The I/Q input bandwidth is greater than 50MHz at -0.1dB
response. The direct connection of the DAC to the
MAX2022 insures the maximum signal fidelity, with no
performance-limiting baseband amplifiers required. The
DAC output can be passed through a lowpass filter to
remove the image frequencies from the DAC’s output
response. The MAX5895 dual interpolating DAC can be
operated at interpolation rates up to x8. This has the ben-
efit of moving the DAC image frequencies to a very high,
remote frequency, easing the design of the baseband
filters. The DAC’s output noise floor and interpolation
filter stopband attenuation are sufficiently good to insure
that the 3GPP noise floor requirement is met for large
frequency offsets, 60MHz for example, with no filtering
required on the RF output of the modulator.
Figure 1
ing the MAX2022 with a Maxim DAC, in this case the
MAX5895 dual 16-bit interpolating-modulating DAC.
The MAX5895 DAC has programmable gain and dif-
ferential offset controls built in. These can be used to
optimize the LO leakage and sideband suppression of the
MAX2022 quadrature modulator.
50Ω
50Ω
Quadrature Modulator/Demodulator
0°
High-Dynamic-Range, Direct Up/
illustrates the ease and efficiency of interfac-
90°
RF MODULATOR
MAX2022
∑
RF
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