CN-0311 Datasheet, PDF (1/4 Pages) Analog Devices – Broadband, Low Error Vector Magnitude (EVM) Direct Conversion Transmitter Using LO Divide-by-2 Modulator

Circuit Note
CN-0311
Circuits from the Lab™ reference circuits are engineered and
tested for quick and easy system integration to help solve today’s
analog, mixed-signal, and RF design challenges. For more
information and/or support, visit www.analog.com/CN0311.
Devices Connected/Referenced
ADF4351 Fractional-N PLL IC with Integrated VCO
ADL5385 Wideband Transmit Modulator
ADP150
Low Noise 3.3 V LDO
ADP3334 Low Noise Adjustable LDO
Broadband, Low Error Vector Magnitude (EVM) Direct Conversion Transmitter Using
LO Divide-by-2 Modulator
EVALUATION AND DESIGN SUPPORT
Circuit Evaluation Boards
ADF4351 Evaluation Board (EVAL-ADF4351EB1Z)
ADL5385 Evaluation Board (ADL5385-EVALZ)
Design and Integration Files
Schematics, Layout Files, Bill of Materials
CIRCUIT FUNCTION AND BENEFITS
This circuit is a complete implementation of the analog portion of a
broadband direct conversion transmitter (analog baseband in, RF
out). RF frequencies from 30 MHz to 2.2 GHz are supported by
using a phase-locked loop (PLL) with a broadband integrated
voltage controlled oscillator (VCO). Unlike modulators that use a
divide-by-1 local oscillator (LO) stage (as described in CN-0285),
harmonic filtering of the LO is not required.
5.5V
1µF
ADP150
5.5V
1µF
ADP3334
V_VCO
3.3V
1µF
V_DD
I/Q SMA INPUTS
1µF
5.0V
FREF_IN
16 17 28 10 4 26 6 32
V_VCO DV_DD AV_DD CE PDB_RF V_P SDV_DD
1nF 1nF
29 REFIN
51Ω
1 CLK
RF_OUTB+ 14
RF_OUTB– 15
2 DATA
3 LE
ADF4351
RF_OUTA+ 12
V_VCO
Z_BIAS
4.7kΩ
22 R_SET
RF_OUTA– 13
Z_BIAS
1nF
V_TUNE 20
CP_OUT 7
SW 5
CP_GND SD_{GND AGND} A_{GNDVCO DGND}
8
31
9 11 18 21 27
180Ω
22nF
330nF
82Ω
10nF
IBBP
IBBN
LOIP
LOIN
1nF
QBBP
QBBN
VPS1, VPS2
ADL5385
DIVIDE-BY-2
QUADRATURE
PHASE
SPLITTER
I/Q SMA INPUTS
Figure 1. Direct Conversion Transmitter (Simplified Schematic: All Connections and Decoupling Not Shown)
RFOUT
Rev. 0
Circuits from the Lab™ circuits from Analog Devices have been designed and built by Analog Devices
engineers. Standard engineering practices have been employed in the design and construction of
each circuit, and their function and performance have been tested and verified in a lab environment at
room temperature. However, you are solely responsible for testing the circuit and determining its
suitability and applicability for your use and application. Accordingly, in no event shall Analog Devices
be liable for direct, indirect, special, incidental, consequential or punitive damages due to any cause
whatsoever connected to the use of any Circuits from the Lab circuits. (Continued on last page)
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: [phone]
www.analog.com
Fax: [phone]
©2012 Analog Devices, Inc. All rights reserved.