CN-0243

Circuit Note

Rev. 0 | Page 6 of 8

SPECTRUM ANALYZER

REFERENCE GENERATOR

1961MHz RF OUTPUT (LO = 1940MHz)

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 11. EVAL-CN0243-EB1Z Evaluation Board

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