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M
Adjustable, High-Linearity,
SiGe Dual-Band LNA/Mixer ICs
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15
Detailed Description
Low-Noise Amplifier
Within its operating bands, each device in the
MAX2320 family (except the MAX2327) has three
modes of LNA operation: high gain, high linearity
(HGHL); high gain, low linearity (HGLL); and low gain,
high linearity (LGHL). The logic inputs control the LNA
mode as described in the
AC Electrical Characteristics
.
Use HGHL mode when extra-high LNA linearity is
required for cross-modulation suppression. Use HGLL
mode when the transmitter is off and cross-modulation
is not a concern. When the LNA changes modes, the
input VSWR change is minimal. Use LGHL mode for
receiving large signals and when high sensitivity is not
required. The MAX2327 LNA has only an HGLL mode.
Adjust the HGHL mode LNA linearity by changing
R
RLNA
, and adjust linearity of the other modes by
changing R
RBIAS
.
Downconverter
The downconverters in these devices are double-bal-
anced mixers. The PCS-band mixer and digital cellular-
band mixer share the same IF output ports. The cellular
band FM mixer has its own IF output to feed a different
filter. Adjust the downconverter linearity and current by
changing R
RBIAS
(see
Typical Operating Character-
istics
). When the linearity requirement is high, the mode
control inputs increase the current in the downconvert-
er. When the linearity requirement is not high, the cur-
rent is lower.
LO Output Buffers
The BUFFEN logic input turns the open-collector LO
output buffers on and off. This feature saves current if
the buffers are not required.
Operational Modes
Each device has logic input pins that control the differ-
ent operational modes listed in Tables 1–5.
MAX2320/MAX2321/MAX2326 Operation
The MAX2320/MAX2321/MAX2326 are dual-band, triple-
mode receivers that amplify and downconvert cellular-
and PCS-band signals. They consist of cellular and PCS
LNAs; cellular digital, cellular FM, and PCS digital mix-
ers; and cellular and PCS LO buffers. The MAX2321 has
an LO frequency doubler on-chip, so a single cellular-
band VCO can be used for both the cellular- and PCS-
band mixers. Selecting the PCS path activates the LO
frequency doubler. The MAX2326 has an LO divide-by-
two circuit, so a single PCS-band VCO can be used for
both the cellular and PCS mixers. Selecting the cellular
path activates the LO divide-by-two circuit. Three logic
input pins—
BAND
, GAIN, and LIN—control eight opera-
tional modes of the LNAs and mixers. The modes are
summarized in Table 1.
Table 1. MAX2320/MAX2321/MAX2326 Operational Modes
Note:
L = Logic Low; H = Logic High
BAND
Shutdown. The entire part is shut down except for the LO buffer, which is con-
trolled by BUFFEN.
L
DESCRIPTION
GAIN
L
LIN
L
Low-Gain, High-Linearity (LGHL) PCS Mode. The PCS LNA and mixer are in
LGHL mode.
L
L
H
High-Gain, Low-Linearity (HGLL) PCS Mode. The LNA and mixer are in HGLL
mode.
L
H
L
High-Gain, High-Linearity (HGHL) PCS Mode. The LNA and mixer are in
HGHL mode.
L
H
H
High-Gain, Low-Linearity (HGLL) Cellular FM Mode. The cellular LNA is in
HGLL mode. The FM mixer and associated LO buffer are selected.
H
L
L
Low-Gain, High-Linearity (LGHL) Cellular Digital Mode. The cellular LNA and
mixer are in LGHL mode.
H
L
H
High-Gain, Low-Linearity (HGLL) Cellular Digital Mode. The cellular LNA and
mixer are in HGLL mode.
H
H
L
High-Gain, High-Linearity (HGHL ) Cellular Digital Mode. The cellular LNA
and mixer are in HGHL mode.
H
H
H