CN-0232 Datasheet, PDF (4/6 Pages) Analog Devices – Minimizing Spurious Outputs Using a Synthesizer with an Integrated VCO and an External PLL Circuit

CN-0232
CIRCUIT EVALUATION AND TEST
The CN-0232 uses the EVAL-ADF4350EB2Z board for
evaluation of the described circuit, and with some minor
modifications, allows for quick setup and evaluation. The
EVAL-ADF4350EB2Z board uses the standard ADF4350
programming software, contained on the CD that accompanies
the evaluation board. The EVAL-ADF4153EBZ1 evaluation
board comes with the software for the ADF4153 PLL.
Equipment Needed
• EVAL-ADF4350EB2Z with programming software.
• EVAL-ADF4153EBZ1 with programming software.
• 5.5 V power supply.
• R&S SMA100A signal generator or equivalent.
• R&S FSUP26 spectrum analyzer or equivalent.
• Two PCs with Windows® XP, Windows, Vista (32-bit), or
Windows 7 (32-bit), one with an USB port and the other
with a printer port. Alternatively, the EVAL-ADF4xxxX-
USB USB adaptor kit can be used instead of the printer
port, if none is available.
The SMA coaxial cable is required to connect RFOUTB+ of the
EVAL-ADF4350EB2Z to RFIN of the EVAL-ADF4153EBZ1. A
simple SMA splitter is also needed to share the reference source
between the two boards. Some flexible microcoaxial cable is
required to connect the output of the ADF4153 loop filter to the
ADF4350 VTUNE input. To minimize unwanted interference, both
sides of the cable must be grounded to suitable GND points on
each board.
Circuit Note
Functional Block Diagram
For this experiment, the EVAL-ADF4153EBZ1 and the EVAL-
ADF4350EB2Z are used. The EVAL-ADF4350EB2Z is selected
because it contains the auxiliary RFOUTB+ output stage, which is
connected via SMA cable to the EVAL-ADF4153EBZ1, as shown
in Figure 4.
Both PLLs use the same reference input (REFIN) frequency;
therefore, an SMA splitter connects the same REFIN to both
boards.
The loop filter output on the EVAL-ADF4153EBZ1 is connected
to the VTUNE pin of the ADF4350 via a shielded coaxial cable to
ensure that no extra noise or spurs appear on the pin. Both
parts are programmed separately. It may be necessary to use
different PCs for each board to ensure no conflicts occur
between hardware drivers.
Getting Started
The UG-110 user guide details the installation and use of the
EVAL-ADF4350EB2Z evaluation software. UG-110 also
contains board setup instructions and the board schematic,
layout, and bill of materials.
The UG-167 user guide contains similar information relevant to
the EVAL-ADF4153EBZ1. Necessary modifications to the board
are the removal of the VCO (Y1). To reconfigure this board as
an input, remove the R7 resistor and change R8 and R9 to 0 Ω.
The PLL loop filter on the ADF4350 board is unused and
should be removed. At this point, the microcoaxial cable can be
used to connect the output of the ADF4153 loop filter (T7) to
the VTUNE pin of the ADF4350 (T4). It is of critical importance
that the outer shielding of this cable is connected to a ground
point on both boards.
POWER
SUPPLY
PC
REFERENCE
FREQUENCY
GENERATOR
(R&S SMA100A)
USB
5.5V
J14
COM
J15
RFOUTA+
J2
ADF4350
J3
J1 _{EVALUATION BOARD}
(EVAL-ADF4350EB2Z)
J4
RFOUTA−
RFOUTB+
RFOUTB−
T4
J5
VTUNE
50Ω
TERM
50Ω
TERM
CP OUT
J5
T7
ADF4153
EVAL-
PC
ADF4xxxX-USB
EVALUATION BOARD
(EVAL-ADF4153EBZ1)
USB
PRINTER
J2
9V BATTERY
RFIN+
Figure 4. Test Setup Functional Diagram
SPECTRUM
ANALYZER
(R&S FSUP26)
Rev. 0 | Page 4 of 6