Detailed Description
The MAX2043 can operate as either a downconverter
or an upconverter mixer that provides 7.5dB of conver-
sion loss with a typical 7.8dB noise figure. IIP3 is
+31dBm for both upconversion and downconversion.
The integrated baluns and matching circuitry allow for
50Ω single-ended interfaces to the RF port and two LO
ports. The RF port can be used as an input for down-
conversion or an output for upconversion. A single-
pole, double-throw (SPDT) switch provides 50ns
switching time between the two LO inputs with 43dB of
LO-to-LO isolation and -52dBm of LO leakage.
Furthermore, the integrated LO buffer provides a high
drive level to the mixer core, reducing the LO drive
required at the MAX2043’s inputs to a -3dBm to +6dBm
range. The IF port incorporates a differential output for
downconversion, which is ideal for providing enhanced
IIP2 performance. For upconversion, the IF port is a dif-
ferential input.
Specifications are guaranteed over broad frequency
ranges to allow for use in UMTS/WCDMA and
2G/2.5G/3G DCS 1800, PCS 1900, cdma2000, and
WiMAX base stations. The MAX2043 is specified to
operate over a 1700MHz to 3000MHz RF input range, a
1900MHz to 3000MHz LO range, and an IF range of
near 0MHz to 350MHz. The external IF component sets
the lower frequency range.
RF Port and Balun
For using the MAX2043 as a downconverter, the RF
input is internally matched to 50Ω, requiring no external
matching components. A DC-blocking capacitor is
required because the input is internally DC shorted to
ground through the on-chip balun. The RF return loss is
typically 15dB over the entire 1700MHz to 3000MHz RF
frequency range. For upconverter operation, the RF
port is a single-ended output similarly matched to 50Ω.
An optional L-C BPF can be installed at the RF port to
improve some upconverter performance.
LO Inputs, Buffer, and Balun
The MAX2043 is optimized for a 1900MHz to 3000MHz
LO range. As an added feature, the MAX2043 includes
an internal LO SPDT switch that can be used for fre-
quency-hopping applications. The switch selects one
of the two single-ended LO ports, allowing the external
oscillator to settle on a particular frequency before it is
switched in. LO switching time is typically less than
50ns, which is more than adequate for typical GSM
applications. If frequency-hopping is not employed,
simply set the switch to either of the LO inputs. The
switch is controlled by a digital input (LOSEL): logic-
high selects LO1, logic-low selects LO2. LO1 and LO2
inputs are internally matched to 50Ω, requiring only a
22pF DC-blocking capacitor. To avoid damage to the
