MAX2678 Evaluation Kit
Evaluates: MAX2678
General Description
The MAX2678 evaluation kit (EV kit) is an easy-to-use
platform that enables straightforward evaluation of the
MAX2678 two-stage high-performance GPS LNA, which
is designed for use in demanding automotive applica-
tions and provides 35dB gain. The EV kit includes all
functionality that would typically be found in a typical
remote antenna module, with the exception of a 12V
regulator. Optimal matching and coupling circuits are
included on the EV kit, enabling “plug and play” operation.
In many applications, an interstage SAW filter is used to
maximize immunity to out-of-band interferers. A pair of
common SAW filter footprints are available to enable evalu-
ation in this configuration. Resistor options are provided to
enable stand-alone testing of either gain stage or cascade
testing of the two gain stages and optional SAW filter.
Interfacing the MAX2678 EV kit to RF test equipment is
streamlined using industry-standard SMA connectors.
Benefits and Features
● Flexible Evaluation of the MAX2678 IC
•
Stand-Alone AMP 1 or AMP 2 Configuration
•
Cascade Configuration with Interstage SAW Filter*
● Optimal Matching and Coupling Eliminates Tuning
● All Ports Matched to 50Ω and Accessible through
SMA Connectors for Simple Interfacing
● Proven PCB Layout
● Fully Assembled and Tested
*SAW
filter not included.
Ordering Information
appears at end of data sheet.
MAX2678 EV Kit Board Photo
19-8719; Rev 0; 11/16
MAX2678 Evaluation Kit
Evaluates: MAX2678
Quick Start
Required Equipment
●
MAX2678 EV kit
● Linear DC power supply capable of sourcing at least
100mA between 3V and 5.25V
●
Network analyzer
●
Noise figure meter
● Two RF signal generators with maximum RF power
level of at least 0dBm
●
Spectrum analyzer
●
Power meter
Measure IP3 of AMP 1 (AMP 2 Can be Measured in
a Similar Manner)
This procedure details how to conduct a two-tone test for
IP3. Note that two signal generators are required. Always
be aware of the possibility of interaction between the signal
generators, although the power levels used in this case are
modest, so this is only a moderate concern. Regardless,
it is a good idea to use attenuators or isolators to ensure
sufficient isolation and to be prepared for some trouble-
shooting and a few iterations of testing.
1)
2)
3)
Disable RF generators and connect them together
through a hybrid combiner.
Set RF frequencies of generators to 1575MHz and
1576MHz, respectively.
Connect output of combiner to power meter.
Enable generators one at a time and adjust the output
level such that each generator is delivering -35dBm
to the power meter (depending on the power meter,
the level may need to be calibrated at a higher level
and then backed off to achieve the desired -35dBm
value).
4)
5)
Disable signal generators, connect combiner output
to spectrum analyzer, and then enable generators.
Adjust spectrum analyzer and confirm that IM3
products cannot be observed at 1574MHz or 1577MHz.
If IM tones are observed, adjust spectrum-analyzer
attenuation level to confirm whether the IM is
generated in the spectrum analyzer or generators. If
the IM is created by the signal generators, add addi-
tional isolation and recalibrate the level as needed.
Disable generators and then connect output of
combiner to the AMP 1 input (IN1, J5).
Connect output of AMP 1 (OUT1, J7) to spectrum
analyzer and increase spectrum-analyzer attenua-
tion by approximately 15dB (this helps to eliminate
uncertainty whether any distortion is generated in the
spectrum analyzer).
Confirm 5V power supply connection to EV kit
connector JU1 and then enable the supply output.
Enable signal-generator outputs.
Procedure
The EV kit is fully assembled and tested and can be tested
directly out of the box. The following procedures provide
examples of how to measure common specifications of the
MAX2678.
Measure the Stand-Alone Gain of Each Gain Stage
Follow the steps below to measure the stand-alone gain
of each of the two gain stages. Full 2-port S parameters
can be measured using this procedure, but be aware that
the observed angle will not be referenced to the device’s
pins. Detailed discussion of calibrating S parameter
measurements is beyond the scope of this document.
1)
2)
3)
4)
5)
6)
7)
8)
9)
Configure the network analyzer with -35dBm RF power
level and 800MHz to 2000MHz frequency span.
Perform 2-port calibration of the network analyzer.
Disable power-supply output, adjust output level to
5V, and set current limit to at least 100mA.
Connect supply leads to connector JU1 on the EV kit.
Connect network analyzer to AMP 1 (Port 1 = J5,
Port 2 = J7).
Enable power supply.
Measure |S21| of AMP 1.
Disable power supply.
Connect network analyzer to AMP 2 (Port 1 = J4,
Port 2 = J6).
8)
9)
6)
7)
10) Enable power supply.
11) Measure |S21| of AMP 2. By default, AMP 2 is in high-
gain mode (component R7 open).
10) Measure IM3 using spectrum analyzer and calculate
IP3 assuming input power level of -35dBm/tone.
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Maxim Integrated
│
2
MAX2678 Evaluation Kit
Evaluates: MAX2678
Measure P
1dB
of AMP 1 (AMP 2 Can be Measured
in a Similar Manner)
This procedure can be used to measure gain compression.
Note that this is a single-tone test.
1)
2)
3)
4)
5)
6)
Disable RF generator output and configure with
1575MHz RF frequency and -30dBm power level.
Connect generator to AMP 1 input (IN1, J5).
Connect spectrum analyzer to AMP 1 output
(OUT1, J7).
Confirm 5V power-supply connection to EV kit
connector JU1 and then enable the supply output.
Enable signal generator.
Observe gain using spectrum analyzer. This is a high-
power measurement, so confirm that the front-end
attenuator is adjusted appropriately to avoid com-
pression in the spectrum analyzer.
Increase power in 1dB steps. Observe gain for each
step. Note input level at which gain is reduced from
initially observed value (step 6) by 1dB.
Detailed Description of Hardware
SAW Filter
The MAX2678 should be used in conjunction with an
interstage SAW filter for optimal immunity to out-of-band
interferers. The EV kit enables evaluation of the device
with a pair of optional industry-standard SAW filters.
Resistor jumpers are used to realize the required signal
routing. Refer to the schematic for details regarding the
resistor configuration. Only one SAW filter should be used
at a given time. Refer to the BOM information at the end
of this document for specific details regarding the SAW
filters.
RF Signal-Routing Options
7)
Measure Noise Figure of AMP 1 (AMP 2 Can be
Measured in a Similar Manner)
Measurement of noise figure is especially challenging
because of the MAX2678’s excellent noise performance.
Some experimentation may be required to obtain the best
results. As a general rule, try to avoid clutter around the
EV kit and ensure that obvious radiators of noise are not
in close proximity to the test fixture. It may be helpful to
use a shielded enclosure for this measurement.
1)
2)
3)
4)
Calibrate noise figure meter and test fixture at
operating frequency of the IC.
Connect noise figure meter to input and output ports
of AMP 1.
Confirm 5V power-supply connection to EV kit
connector JU1 and then enable supply output.
Observe noise figure.
As previously mentioned, resistor jumpers are used to
configure the signal path, depending on whether stand-
alone or cascade/SAW filter testing is desired. Only one
of the three available overlapping resistor locations in
each signal-routing junction should be populated at a
given time to avoid creating stubs. It is recommended
that 0Ω film resistors be used since they offer very low
inductance.
Gain Select
AMP 2 includes a 3.4dB gain step. This enables the gain
to be tailored to specific applications and adjusted based
on loss in the SAW filter. The gain mode is controlled by
resistor R7, which configures AMP 2 for high gain. By
default, R7 is not installed. To enable low-gain mode,
install a 0Ω resistor in location R7.
Layout Considerations
Taking full advantage of the IC’s excellent noise perfor-
mance requires careful PCB layout. The input to AMP 1 is
the most sensitive to noise pickup. Everything downstream
of AMP 1’s output is much less sensitive due to the high
gain of AMP 1. Therefore, the IC should be oriented to
optimize the interconnect between AMP 1’s input and
the antenna. In general, this interconnect should be kept
as short as possible to achieve the best possible per-
formance, and should be isolated from suspected noise
sources by a combination of shielding and proper floor
planning. Controlled impedance should be used on all RF
interconnects to avoid any unpredictable behavior, and all
matching components and decoupling capacitors should
be placed in close proximity to the IC package.
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Maxim Integrated
│
3
MAX2678 Evaluation Kit
Evaluates: MAX2678
Ordering Information
PART
MAX2678EVKIT#
#Denotes
RoHS compliant.
TYPE
EV Kit
MAX2678 EV Bill of Materials
REFERENCE
DESIGNATOR
C1, C4
QTY
VALUE
DESCRIPTION
MANUFACTURER
MFG. PART NUMBER
C0603C330K1GAC
GRM188R72A104KA35
C0603C129C1G
GRM1885C1H101JA01
SF1186B-2
B39162-B4059-U810
142-0711-821
PEC36SAAN
LQW18AN3N9C00
CR0603-16W-000RJT
2
2
1
2
0
0
4
1
1
0
2
33pF
0.1uF
1.2pF
0603 Capacitor
0603 Capacitor
0603 Capacitor
0603 Capacitor
Low Loss SAW Filter
Low Loss SAW Filter
SMA End Launch Jack
Receptacle 0.062"
Two Pin Header; 100
Mil Centers
0603 Inductor
Murata
Murata
Kemet
C5
C6
C7
FL1
FL2
J4, J5, J6, J7
100pF
1575.42 MHz
DNI
1575.42 MHz
DNI
Murata
RF Monolithics Inc
Epcos
Johnson
Sullins
Murata
Connector
1X2 Header
3.9nH
DNI
0Ω
MAX2678
—
JU1
L2
R1, R2, R5, R6, R7
R3, R4
0603 Resistor
Resistors
U1
—
1
1
GPS LNA
PCB: MAX2678 EVKIT
Maxim Integrated
Products
—
MAX2678GTB/V+
—
www.maximintegrated.com
Maxim Integrated
│
4
FL2
1575.42 MHz
GND
GND
GND
GND
GND
7
4
1
3
MAX2678 Evaluation Kit
FL1
R1
OPEN
R3
5 OUTPUT
INPUT 2
GND 3
OPEN
0
5
4
3
2
4 GND
0
OPEN
R2
6 GND
GND 1
R5
R4
1575.42 MHz
R6
OPEN
1
MAX2678 EV Kit Schematics
IN2
J4
5
8
GND
2
3
4
5
EP
5
4
OUT2
J6
C1
1
2
3
4
VCC
Evaluates: MAX2678
Maxim Integrated
│
5
JU1
5
33pF
11
C6
1.2pF
33pF
3
2
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6
OUTPUT
INPUT
2
OUT1
J7
1
RFIN2
GND
GND
EXTCAP/ALT_VCC
RFOUT2/VCC
RFIN1
6
GAIN_SELECT
7
R7
OPEN
C4
5
IN1
J5
L2
3.9nH
1
U1
MAX2678
GND
8
GND
9
RFOUT1
2
3
4
C5
0.1uF
C7
100pF
10
VCC
1
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