Performance Evaluation
57
CG635 Synthesized Clock Generator
CG635 Configuration
Use the following procedure to configure the CG635 for the phase noise test:
1.
Press ‘SHIFT’, ‘INIT’, ‘Hz’ to return the CG635 to default settings.
2.
Press the Q/Q
¯
ź
button to 7 dBm output level for the Q/Q
¯ outputs.
3.
Use the numeric key pads to enter the test frequency and press the appropriate
units key to complete the entry.
HP 89440A Configuration
First press the ‘Preset’ key to force the unit to default settings. Then enter the settings
detailed in Table 29.
Table 29: HP 89440A configuration for phase noise tests
Key Menu
2
nd
Menu
Setting
Instrument Mode
Inst Mode
Demodulation
Demodulation Setup
Ch1 Result
PM
Auto
carrier
On
PM auto type
Phase
Range
Ch1 range
10 dBm
Measurement Data
Meas Data
PSD
Average Average
On
Num
averages
100
Frequency
Center
622.08 MHz *
Span
400 Hz *
Marker
Enter marker position
100 Hz *
The settings marked with a * will change at each test point as specified in Table 30
below.
Phase Noise Test Procedure
At each test point identified in Table 30, set the CG635 to the given frequency. Then set
the HP 89440A to the given center frequency, span, and marker position. Record S(f)
reported by the HP 89440A at the marker position in units of dBradrms
2
/Hz. Calculate
the phase noise from S(f) using the equation L(f) = S(f) – 3dB. For example, if the HP
reports that the noise at 100Hz offset is –91 dBradrms
2
/Hz, then S(100) = –91
dBradrms
2
/Hz. L(100) = S(100) – 3dB = –94 dB
c
/Hz. The measured phase noise should
be lower than the maximum phase noise specified in Table 30.
Table 30: Phase noise measurements
Frequency
Span
Marker
S(f)
L(f) = S(f) – 3dB
Max L(f) (dBc/Hz)
622.08 MHz
400 Hz
100 Hz
–90
4 kHz
1 kHz
–100
40 kHz
10 kHz
–100
400 kHz
100 kHz
–110
620.80 MHz
400 Hz
100 Hz
–90
4 kHz
1 kHz
–100
40 kHz
10 kHz
–100
400 kHz
100 kHz
–110
