SiGe, High-Linearity, 2300MHz to 4000MHz
Upconversion/Downconversion Mixer with LO Buffer
MAX2044
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Detailed Description
The MAX2044 is a high-linearity passive mixer targeting
2.5GHz and 3.5GHz wireless infrastructure applications.
With an ultra-wide 2600MHz to 4300MHz LO frequency
range, the MAX2044 can be used in either low-side or
high-side LO injection architectures for virtually all WiMAX,
LTE, and MMDS receive and transmit applications.
When used as a low-side LO injection downconverting
mixer in the 3000MHz to 4000MHz band, the MAX2044
provides +32.5dBm of input IP3, with typical conversion
loss and noise figure values of only 7.7dB and 8.5dB,
respectively. The integrated baluns and matching cir-
cuitry allow for 50I single-ended interfaces to the RF
and the LO port. The integrated LO buffer provides
a high drive level to the mixer core, reducing the LO
drive required at the MAX2044’s input to a -3dBm to
+3dBm range. The IF port incorporates a differential
output, which is ideal for providing enhanced 2RF - 2LO
or 2LO - 2RF performance.
Specifications are guaranteed over broad frequency ranges
to allow for use in WiMAX, LTE, and MMDS base stations.
The MAX2044 is specified to operate over a 2300MHz
to 4000MHz RF input range, a 2600MHz to 4300MHz
LO range, and a 50MHz to 500MHz IF range. Operation
beyond these ranges is possible (see the Typical Operating
Characteristics for additional information).
RF Input and Balun
The MAX2044 RF input provides a 50I match when
combined with a series DC-blocking capacitor. This
DC-blocking capacitor is required as the input is inter-
nally DC shorted to ground through the on-chip balun.
When using an 8.2pF DC-blocking capacitor, the RF
port input return loss is typically better than 13dB over
the 3300MHz to 3900MHz RF frequency range. A return
loss of 15dB over the 2400MHz to 2700MHz range is
achievable by changing the input matching components
per Tables 1 and 2. Other combinations of C1 and C12
can be used to optimize RF return loss in the 2300MHz
to 4000MHz band.
LO Inputs, Buffer, and Balun
With a broadband LO drive circuit spanning 2600MHz to
4300MHz, the MAX2044 can be used in either low-side
or high-side LO injection architectures for virtually all
2.5GHz and 3.5GHz applications. The LO input is inter-
nally matched to 50I, requiring only a 2pF DC-blocking
capacitor. A two-stage internal LO buffer allows for a
-3dBm to +3dBm LO input power range. The on-chip
low-loss balun, along with an LO buffer, drives the
double-balanced mixer. All interfacing and matching
components from the LO inputs to the IF outputs are
integrated on-chip.
High-Linearity Mixer
The core of the MAX2044 is a double-balanced, high-
performance passive mixer. Exceptional linearity is pro-
vided by the large LO swing from the on-chip LO buffer.
IIP3, 2RF - 2LO rejection, and noise figure performance
are typically +32.5dBm, 68dBc, and 8.5dB, respectively.
Differential IF Output
The MAX2044 has a 50MHz to 500MHz IF frequency
range, where the low-end frequency depends on the
frequency response of the external IF components.
The MAX2044’s differential ports are ideal for provid-
ing enhanced 2RF - 2LO and 2LO - 2RF performance.
Single-ended IF applications require a 1:1 (impedance
ratio) balun to transform the 50I differential IF imped-
ance to a 50I single-ended system. An MABAES0029
1:1 transformer is used to characterize the part and its
loss is included in the data presented in this data sheet.
The user can connect a differential IF amplifier or SAW
filter to the mixer IF port, but a DC block is required on
both IF+/IF- ports to keep external DC from entering the
IF ports of the mixer. Capacitors C4 and C7 are required
DC blocks since the IF+ and IF- terminals are internally
biased to VCC/2.
Applications Information
Input and Output Matching
The RF input provides a 50I match when combined with
a series DC-blocking capacitor. Use an 8.2pF capaci-
tor value for RF frequencies ranging from 3000MHz to
4000MHz. See Tables 1 and 2 for alternative compo-
nents that provide an excellent match over the 2300MHz
to 3000MHz band. The LO input is internally matched to
50I; use a 2pF DC-blocking capacitor to cover opera-
tions spanning the 2600MHz to 4300MHz range. The
IF output impedance is 50I (differential). For evalua-
tion, an external low-loss 1:1 (impedance ratio) balun
transforms this impedance down to a 50I single-ended
output (see the Typical Application Circuit).