MAX2022ETX+D Maxim Integrated, MAX2022ETX+D Datasheet - Page 15

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

Specifications of MAX2022ETX+D

• Rohs: yes

MAX2022
The DAC outputs must be filtered by baseband filters to
remove the image frequency signal components. The
baseband signals for four-carrier operation cover DC
to 10MHz. The image frequency appears at 481MHz to
491MHz. This very large frequency spread allows the
use of very low-complexity lowpass filters, with excellent
in-band gain and phase performance. The low DAC noise
floor allows for the use of a very wideband filter, since
the filter is not necessary to meet the 3GPP noise floor
specification.
The MAX2022 quadrature modulator then upconverts the
baseband signals to the RF output frequency. The output
power of the MAX2022 will be approximately -28dBm
per carrier. The noise floor will be less than -169dBm/Hz,
with an ACLR typically greater than 65dBc. This perfor-
mance meets the 3GPP specification requirements with
substantial margins. The noise floor performance will be
maintained for large offset frequencies, eliminating the
need for subsequent RF filtering in the transmitter lineup.
The RF output from the MAX2022 is then amplified by
a combination of a low-noise amplifier followed by a
MAX2057 RF-VGA. This VGA can be used for lineup
compensation for gain variance of transmitter and power
amplifier elements. No significant degradation of the
signal or noise levels will be incurred by this additional
amplification. The MAX2057 will deliver an output power
of -6dBm per carrier, 0dBm total at an ACLR of 65dB and
noise floor of -142dBc/Hz.
External Diplexer
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 interface. Care
must be taken to match the I/Q ports to the external
circuitry. Without matching, the LO’s second-order term
(2f
where it can remix with the internal LO signal to produce
additional LO leakage at the RF output. This reflection
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.
www.maximintegrated.com
LO
) it may reflect back into the modulator’s I/Q ports
Downconversion 1500MHz to 3000MHz
Figure 3. Diplexer Network Recommended for UMTS
Transmitter Applications
As demonstrated in
on each of the I+, I-, Q+, Q- ports reduces the amount of
LO leakage present at the RF port under varying tempera-
ture, LO frequency, and baseband termination conditions.
See the
that the resistor value is chosen to be 50Ω with a corner
frequency 1 / (2�RC) selected to adequately filter the f
and 2f
baseband response at the highest baseband frequency.
The common-mode f
Q+/Q- effectively see the RC networks and thus become
terminated in 25Ω (R/2). The RC network provides a path
for absorbing the 2f
tor provides high impedance at f
diplexing process.
Q
I
Quadrature Modulator/Demodulator
LO
Typical Operating Characteristics
High-Dynamic-Range, Direct Up/
L = 11nH
L = 11nH
leakage, yet not affecting the flatness of the
C = 2.2pF
C = 2.2pF
C = 2.2pF
LO
Figure
LO
and f
and 2f
50Ω
50Ω
50Ω
50Ω
LO
3, providing an RC termination
LO
RF MODULATOR
leakage, while the induc-
LO
LO
0°
MAX2022
90°
and 2f
signals at I+/I- and
Maxim Integrated │ 15
∑
for details. Note
LO
to help the
RF
LO