CN-0245 Datasheet, PDF (4/5 Pages) Analog Devices – Wideband LO PLL Synthesizer with Simple Interface to Quadrature Demodulators

CN-0245
Circuit Note
Table 1. ADF4350 RF Output Filter Component Value (DNI = Do Not Insert)
Frequency Range
(MHz)
ZBIAS
L1
L2
C1a
C1c
C2a
C2c
C3a
C3c
(nH) (nH) (pF)
(pF)
(pF)
(pF)
(pF)
(pF)
a. 500–1300
27 nH|| 50 Ω
3.9
3.9
DNI
4.7
DNI
5.6
DNI
3.3
b. 850–2450
19 nH || (100 Ω in position C1c) 2.7
2.7
3.3
100 Ω 4.7
DNI
3.3
DNI
c. 1250–2800
50 Ω
0Ω
3.6
DNI
DNI
2.2
DNI
1.5
DNI
d. 2800–4400
3.9 nH
0Ω
0Ω
DNI
DNI
DNI
DNI
DNI
DNI
120pF
3.3V
0.1µF
120pF
RF_OUTA+ 12
RF_OUTA– 13
Z_BIAS
C1a
L1
Z_BIAS
C1c
L1
C2a
L2
C2c
L2
C3a
1nF
3 LOIP
C3c
1nF
4 LOIN
ADF4350
C1a
C2a
C3a
ADL5380
Figure 8. ADF4350 RF Output Filter Schematic
COMMON VARIATIONS
The interface discussed above is applicable to any PLL with
differential LO outputs and to any 1 × LO or 2 × LO-based I/Q
demodulator. The ADL5382 is a 1 × LO-based I/Q demodulator
that operates from 700 MHz to 2700 MHz and provides slightly
higher IP3 than the ADL5380. TheAD8347 (1 × LO) and
AD8348 (2 × LO) are lower power I/Q demodulators that
integrate front-end variable gain amplifiers and fixed-gain
baseband amplifiers.
CIRCUIT EVALUATION AND TEST
The circuits shown in Figure 4 and Figure 6 were implemented
using the CN-0134 evaluation board (CFTL-0134EVALZ) and
the ADL5387 or ADL5380 evaluation boards. The CN-0134
evaluation platform includes the ADF4350, pads for an LO
filter, and differential LO outputs to SMA connectors.
The ADF4350 must be programmed, and the software is
contained on the CD that accompanies the evaluation board.
Table 2 provides the ordering guide for the various evaluation
boards.
The CN-0134 evaluation board is configured by default to an
850 MHz to 2450 MHz filter design as specified in Table 1. To
implement an alternative filter, the appropriate components
must be swapped out.
Table 2. Evaluation Board Information
Evaluation Board
ADL5387
ADL5387-EVALZ
ADL5380
Low Band (400 MHz to 3 GHz) ADL5380-30A-EVALZ
Mid Band (3 GHz to 4 GHz)
ADL5380-29A-EVALZ
CN-0134
CFTL-0134-EVALZ
Equipment Needed
• Windows XP, Windows Vista (32-bit), or Windows 7
(32-bit) PC with USB port
• Evaluation boards as listed in Table 2
• RF source (Rohde & Schwarz SMT06 or equivalent)
• Spectrum analyzer (Rohde & Schwarz FSEA30 or
equivalent)
• Power supplies:
• ADL5387-EVALZ: +5 V
• ADL5380-30A-EVALZ: +5 V
• CFTL-0134-EVALZ: +5.5 V
Test
The CN-0134 evaluation platform allows easy evaluation and
has an integrated crystal oscillator on board. A PC with the
ADF4350 software is required to program the synthesizer to the
desired LO frequency. The ADL5387/ADL5380 quadrature
demodulator will downconvert the RF frequency to baseband.
The differential I and Q baseband outputs are applied to the
FSEA spectrum analyzer in the FFT mode, and image rejection
is measured.
Additional documentation can be found in the following design
support packages for CN-0245, CN-0134, and CN-0144:
CN-0245 Design Support Package:
www.analog.com/CN0245-DesignSupport
CN-0134 Design Support Package:
www.analog.com/CN0134-DesignSupport
CN-0144 Deign Support Package:
www.analog.com/CN0144-DesignSupport
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