CN-0243 Datasheet, PDF (6/8 Pages) Analog Devices – High Dynamic Range RF Transmitter Signal Chain Using Single External Frequency Reference for DAC Sample Clock and IQ Modulator LO Generation

CN-0243
Circuit Note
1961MHz RF OUTPUT (LO = 1940MHz)
REFERENCE GENERATOR
SPECTRUM ANALYZER
Figure 11. EVAL-CN0243-EB1Z Evaluation Board
Figure 10. Spectrum Analyzer Noise Floor, Reference Phase Noise, and RF
Output Phase Noise
COMMON VARIATIONS
As described in the last section, PLL performance can be
adjusted by varying the bandwidth of the loop filters. There is a
trade-off between loop filter bandwidth and frequency settling
time that must be taken into account. If a DAC such as the
AD9122 is used, the DAC NCO can also be used for fine
frequency hopping, although there is a limit to the hopping
speed since the NCO requires programming via an SPI port.
Newer clock synthesis and distribution devices such as the
AD9520 and AD9523 may provide improvements in phase
noise.
CIRCUIT EVALUATION AND TEST
The EVAL-CN0243-EB1Z evaluation board requires the
following equipment and software for signal generation and
basic measurement:
Equipment Needed
• 5 V power supply
• Low phase noise reference source (10 MHz to 200 MHz
range @ +3 dBm), Rohde & Schwarz SMA100, low noise
option, or equivalent
• DPG2 Digital Pattern Generator from Analog Devices
• High dynamic range spectrum analyzer, Agilent E4440A or
equivalent
• Analog Devices EVAL-ADF4XXXZ USB Adapter
Software
• DPG2 Software (included with DPG)
• ADRF6702 software available at www.analog.com/ADRF6702
Figure 12. Bench Test Setup
Setup and Test
The following steps are required to properly run the
EVAL-CN0243-EB1Z evaluation board:
1. Before powering up, connect all instruments, USB
adapters, and cables, as shown in Figure 13.
2. There is only a single 5 V power supply required. This
should be connected to the female banana plugs on the
EVAL-CN0243-EB1Z board. Make sure this supply is
connected, then turn on the +5 V supply. The total
current at this point should be 850 mA to 900 mA.
3. The DPG2 software contains a GUI to program the
AD9122. Program the AD9122 for the correct
interpolations rate and NCO (if desired).
4. Turn on the DPG2 software itself. If all cables and
software are working correctly, the software should
recognize the DAC input data rate and display it in the
lower right hand corner of the DPG GUI. Note that this
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