19-0579; Rev 0; 10/06
MAX2021 Evaluation Kit
General Description
The MAX2021 evaluation kit (EV kit) simplifies the evalu-
ation of the MAX2021 direct upconversion (downconver-
sion) quadrature modulator (demodulator) designed for
RFID handheld and portal readers, as well as single and
multicarrier 750MHz to 1200MHz GSM/EDGE,
cdma2000
®
, WCDMA and iDEN
®
base-station applica-
tions. It is fully assembled and tested at the factory.
Standard 50Ω SMA connectors are included on the EV
kit’s input and output ports to allow quick and easy eval-
uation on the test bench using RF test equipment.
This document provides a list of test equipment required
to evaluate the device, a straight-forward test procedure
to verify functionality, a description of the EV kit circuit,
the circuit schematic, a bill of materials (BOM) for the kit,
and artwork for each layer of the PCB.
cdma2000 is a registered trademark of Telecommunications
Industry Association.
iDEN is a registered trademark of Motorola, Inc.
Features
o
Fully Assembled and Tested
o
50Ω SMA Connectors on Input and Output Ports
o
750MHz to 1200MHz RF Range
o
High-Linearity and Low-Noise Performance
o
Broadband Baseband Input/Output
o
DC-Coupled Input Provides for Direct DAC/ADC
Interface
Evaluates: MAX2021
Ordering Information
PART
MAX2021EVKIT
TEMP RANGE
-40°C to +85°C
IC PACKAGE
36 QFN-EP*
*EP
= Exposed paddle.
Component List
DESIGNATION
C1, C6, C7,
C10, C13
QTY
5
DESCRIPTION
33pF ±5%, 50V C0G ceramic
capacitors (0402)
Murata GRM1555C1H330J
0.1µF ±10%, 16V X7R ceramic
capacitors (0603)
Murata GRM188R71C104K
82pF ±5%, 50V C0G ceramic
capacitor (0402)
Murata GRM1555C1H820J
8.2pF ±0.25pF, 50V C0G ceramic
capacitor (0402)
Murata GRM1555C1H8R2C
Not installed
PCB edge-mounted SMA RF
connectors
(flat-tab launch)
Johnson 142-0741-856
Headers 1 x 3 (0.100 spacing
0.062in thick board)
Not installed
432Ω ±1% resistor (0402)
Any
DESIGNATION
R2
R3
R4–R11
TP1
QTY
1
1
0
1
DESCRIPTION
619Ω ±1% resistor (0402)
Any
332Ω ±1% resistor (0402)
Any
Not installed
Large test point for 0.062in PCB
(red)
Mouser 151-107-RC
Large test point for 0.062in PCB
(black)
Mouser 151-103-RC
Large test point for 0.062in PCB
(white)
Mouser 151-101-RC
Mod/Demod IC (6mm x 6mm,
36-pin QFN exposed paddle)
Maxim MAX2021ETX+
Note: U1 has an exposed paddle
conductor that requires it to be
solder attached to a grounded
pad on the circuit board to
ensure a proper
electrical/thermal design.
C2, C5, C8,
C11, C12
5
C3
1
TP2
1
C9
C14–C25
1
0
TP3, TP4
2
J1–J6
6
J7, J8
L1–L4
R1
2
0
1
U1
1
________________________________________________________________
Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
MAX2021 Evaluation Kit
Evaluates: MAX2021
Component Suppliers
SUPPLIER
Johnson
M/A-Com
Murata
PHONE
507-833-8822
800-366-2266
770-436-1300
WEBSITE
www.johnsoncomponents.com
www.macom.com
www.murata.com
1) Calibrate the power meter. For safety margin, use a
power sensor rated to at least +20dBm, or use
padding to protect the power head as necessary.
2) Connect a 3dB pad to the DUT end of the RF signal
generators’ SMA cable. This padding improves
VSWR and reduces the errors due to mismatch.
3) Use the power meter to set the RF signal generators
according to the following:
LO signal source: 0dBm into DUT at 900MHz (this
will be approximately 3dBm before the 3dB pad).
Use an oscilloscope to calibrate the baseband I/Q
differential inputs to the following:
•
Use a signal source where I+, I-, Q+, and Q-
are all 50Ω single-ended outputs. Load the I+/I-
ports and Q+/Q- ports with 50Ω differential
loads. Set the voltage across the 50Ω differen-
tial loads to be 1.4V
P-P
differential. Remove the
50Ω differential loads. Note that the DUT’s I+/I-
and Q+/Q- port impedances will provide the
differential loading in Step 10.
•
Note:
Indicate that you are using the MAX2021 when contacting
these component suppliers.
Quick Start
The MAX2021 EV kit is fully assembled and factory test-
ed. Follow the instructions in the
Connections and
Setup
section for proper device evaluation as an
upconverter.
Test Equipment Required
This section lists the recommended test equipment to
verify the operation of the MAX2021 as an upconverter.
It is intended as a guide only, and substitutions may be
possible.
• One DC supply capable of delivering +5.0V and
350mA
•
One low-noise RF signal generator capable of deliv-
ering 10dBm of output power in the 1GHz to 3GHz
frequency range (i.e., HP 8648)
One I/Q generator capable of producing two differ-
ential 1MHz sine waves, 90° out-of-phase with each
other, with a 1.4V
P-P
differential amplitude
One quad-channel oscilloscope with a 100MHz
minimum bandwidth
Low-capacitance oscilloscope probes
One RF spectrum analyzer with a 100kHz to 3GHz
frequency range (HP 8561E)
One RF power meter (HP 437B)
One power sensor (HP 8482A)
4) Disable the signal generator outputs.
5) Connect the I/Q source to the differential I/Q ports.
6) Connect the LO source to the EV kit LO input.
7) Measure the loss in the 3dB pad and cable that will be
connected to the RF port. Losses are frequency
dependent, so test this at 900MHz (the RF frequency).
Use this loss as an offset in all output power/gain
calculations.
8) Connect this 3dB pad to the EV kit’s RF port con-
nector and connect a cable from the pad to the
spectrum analyzer.
9) Set DC supply to +5.0V, and set a current limit
around 350mA, if possible. Disable the output volt-
age and connect the supply to the EV kit (through
an ammeter, if desired). Enable the supply.
Readjust the supply to get +5.0V at the EV kit. A
voltage drop occurs across the ammeter when the
device is drawing current.
10) Enable the LO and the I/Q sources.
•
•
•
•
•
•
Connections and Setup
This section provides a step-by-step guide to testing the
basic functionality of the EV kit as an upconverter. As a
general precaution to prevent damaging the outputs by
driving high VSWR loads, do not turn on DC power or
RF signal generators until all connections are made.
This upconverter procedure is general to operation with
an I/Q baseband input signal at 1MHz. Choose the test
frequency based on the particular system’s frequency
plan and adjust the following procedure accordingly.
See Figure 2 for the test setup diagram.
Testing the Direct Upconverter
Adjust the center and span of the spectrum analyzer to
900MHz and 5MHz, respectively. The LO leakage
appears at 900MHz and there are two sidebands at
899MHz and 901MHz (LSB and USB). One of the side-
bands is the selected RF signal, while the second is the
image. Depending on whether the Q channel is 90
degrees advanced or 90 degrees delayed from the
I channel determines which sideband is selected and
2
_______________________________________________________________________________________
MAX2021 Evaluation Kit
which is rejected. Note that the sideband suppression is
about 40dB typical down from the desired sideband. The
desired sideband power level should be approximately
-2.3dBm (0.7dBm output power including 3dB pad loss).
Phase and amplitude differences at the I and Q inputs
result in degradation of the sideband suppression. Note
that the spectrum analyzer’s uncalibrated absolute mag-
nitude accuracy is typically no better than ±1dB.
LO Bias
The bias current for the integrated LO buffer is set with
resistor R1 (432Ω ±1%). Resistors R2 (619Ω ±1%) and
R3 (332Ω ±1%) set the bias currents for the LO driver
amplifiers. Increasing the value of R1, R2, and R3
reduces the current, but the device operates at reduced
performance levels. Doubling the values of R1, R2, and
R3 reduces the total current to approximately 166mA, but
the OIP3 degrades by approximately 4.5dB. Refer to the
MAX2021 data sheet for more details.
Evaluates: MAX2021
Detailed Description
The MAX2021 is designed for upconverting (downcon-
verting) to (from) a 750MHz to 1200MHz RF from (to)
baseband. Applications include RFID handheld and por-
tal readers, as well as single and multicarrier 750MHz to
1200MHz GSM/EDGE, cdma2000, WCDMA, and iDEN
base stations. Direct upconversion (downconversion)
architectures are advantageous since they significantly
reduce transmitter (receiver) cost, part count, and power
consumption compared to traditional heterodyne conver-
sion systems.
The MAX2021 integrates internal baluns, an LO buffer, a
phase splitter, two LO driver amplifiers, two matched
double-balanced passive mixers, and a wideband quad-
rature combiner. The MAX2021’s high-linearity mixers, in
conjunction with the part’s precise in-phase and quadra-
ture channel matching, enable the device to possess
excellent dynamic range, ACLR, 1dB compression point,
and LO and sideband suppression characteristics. These
features make the MAX2021 ideal for four-carrier
WCDMA operation.
The MAX2021 EV kit circuit allows for thorough analysis
and a simple design-in.
IF Bias
LO leakage nulling is usually accomplished by adjust-
ing the external driving DACs to produce an offset in
the common-mode voltage to compensate for any
imbalance from I+ to I- and from Q+ to Q-.
The EV kit has an added feature to null the LO leakage
if the above method is not available. To enable this
added feature one would first need to install 8kΩ resis-
tors for R8 through R11 (see Figure 3 for schematic
details). To minimize cross coupling of the BB signals,
consider adding in the C22 through C25 bypass
capacitors. For this method to work, a DC-coupled
source impedance (typically 50Ω) needs to appear on
all four baseband inputs to form voltage-dividers with
the 8kΩ injection resistors. Use a shunt to connect pin
1 of J7 to pin 2 of J7 and a second shunt to connect
pin 1 of J8 to pin 2 of J8. Set two DC supplies to 0V
and connect one to QBIAS (TP4) and one to IBIAS
(TP3). Observe the LO leakage level out of the RF port
and slowly adjust the QBIAS positive and observe
whether the LO leakage increase or decreases. If the
LO leakage decreases, the polarity of the offset is cor-
rect. If the LO leakage increases, QBIAS can be
adjusted negative or the shunt can be moved on J8 to
connect pin 2 to pin 3. Perform the same adjustment
and method to the IBIAS (TP3) supply. Optimize the
QBIAS and IBIAS voltages to null out the LO leakage.
Supply-Decoupling Capacitors
The MAX2021 has several RF processing stages that
use the various V
CC
pins. While they have on-chip
decoupling, off-chip interaction between them can
degrade gain, linearity, carrier suppression, and output
power. Proper voltage-supply bypassing is essential for
high-frequency circuit stability.
C1, C6, C7, C10, and C13 are 33pF supply-decoupling
capacitors used to filter high-frequency noise. C2, C5,
C8, C11, and C12 are larger 0.1µF capacitors used for
filtering lower-frequency noise on the supply.
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 IF interface.
Care must be taken to match the I/Q ports to the dri-
ving DAC circuitry. Without matching, the LO’s sec-
ond-order (2f
LO
) term may leak back into the modula-
tor’s I/Q input port where it can mix with the internal LO
signal to produce additional LO leakage at the RF out-
put. This leakage effectively counteracts against the LO
DC-Blocking Capacitors
The MAX2021 has internal baluns at the RF output and
LO input. These inputs have almost 0Ω resistance at
DC, so DC-blocking capacitors C3 and C9 are used to
prevent any external bias from being shunted directly
to ground.
_______________________________________________________________________________________
3
MAX2021 Evaluation Kit
Evaluates: MAX2021
C = 6.8pF
MAX2021
RF MODULATOR
100Ω
I
L = 40nH
C = 6.8pF
C = 6.8pF
100Ω
LO
100Ω
Q
L = 40nH
C = 6.8pF
100Ω
0°
90°
∑
RF
Figure 1. Example Diplexer Network for GSM 900 Applications
nulling. In addition, the LO signal reflected at the I/Q IF
port produces a residual DC term that can disturb the
nulling condition.
As shown in Figure 1, providing an RC termination on
each of the I+, I-, Q+, Q- ports reduces the amount of
LO leakage present at the RF port under varying temp-
erature, LO frequency, and baseband drive conditions.
Note that the resistor value is chosen to be 100Ω with a
corner frequency 1 / (2πRC) selected to adequately filter
the f
LO
and 2f
LO
leakage, yet not affecting the flatness
of the baseband response at the highest baseband
frequency. The common-mode f
LO
and 2f
LO
signals at
I+/I- and Q+/Q- effectively see the RC networks and
thus become terminated in 50Ω (R/2). The RC network
provides a path for absorbing the 2f
LO
and f
LO
leakage,
while the inductor provides high impedance at f
LO
and
2f
LO
to help the diplexing process.
The MAX2021 EV kit includes flexibility for a diplexer
network to be installed if desired. See Figure 3 for
details on the EV kit schematic.
Layout Considerations
The MAX2021 evaluation board can be a guide for your
board layout. Pay close attention to thermal design and
close placement of components to the IC. The
MAX2021 package’s exposed paddle (EP) conducts
heat from the device and provides a low-impedance
electrical connection to the ground plane. The EP must
be attached to the PCB ground plane with a low ther-
mal and electrical impedance contact. Ideally, this is
achieved by soldering the backside of the package
directly to a top metal ground plane on the PCB.
Alternatively, the EP can be connected to an internal or
bottom-side ground plane using an array of plated vias
directly below the EP. The MAX2021 EV kit uses nine
evenly spaced 0.016in-diameter, plated through holes
to connect the EP to the lower ground planes.
Depending on the ground plane spacing, large sur-
face-mount pads in the IF path may need to have the
ground plane relieved under them to reduce parasitic
shunt capacitance.
4
_______________________________________________________________________________________
MAX2021 Evaluation Kit
Evaluates: MAX2021
DIFFERENTIAL I/Q GENERATOR
BENCH MULTIMETER HPIB
(HP 34401A)
POWER SUPPLY 3-OUT, HPIB
(AG E3631A)
271mA
5.0V, 350mA (max)
(AMMETER)
+
-
+
-
Q+
+ 5V
GND
Q-
MAX2021EVKIT
I+
LO
3dB
RF SIGNAL GENERATOR
(HP 8648B)
900MHz
I-
3dB
RF
RF SPECTRUM ANALYZER
(HP 8561x)
QUAD-CHANNEL OSCILLOSCOPE
RF POWER METER
(GIGA 80701A, HP 437B)
RF HIGH
POWER SENSOR
Figure 2. Test Setup Diagram
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5
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