Specifications

28
Using a microwave downconverter
For carrier frequencies in the microwave range,
the Agilent 70421A, 70422A, and 70427A microwave
downconverters are available to downconvert a
pulsed carrier to the RF frequency range, making
it much easier to perform pulsed absolute phase
noise measurements. In this configuration, the
microwave downconverter is used to establish
a measurement PLL.
Example 2: Absolute pulsed measurement
using a microwave downconverter—
Agilent 8644B versus 83732B
1. Connect the components as shown in Figure 3-3.
Do not connect the signal paths to the phase
noise measurement system at this step.
2. Set up DUT (83732B).
a) Carrier frequency: 1.5 GHz
b) Amplitude: Set source power level to attain
>10 dBm at the 70420A signal input port
when using an 70420A Opt. 001, or at the
downconverter input port if using an 70420A
standard or Option 201.
c) External Pulse Enable
3. Set up pulse generator.
a) Duty Cycle = 10%
b) PRF = 20 kHz
c) Amplitude = TTL level
4. Set up 8644B reference source. Since the zero-
beat process must be manually instigated, the
reference source must be operated in a manual
mode only:
a) Carrier frequency:
300 MHz (if using an 70421A or 70422A
downconverter)
900 MHz (if using an 70427A downconverter)
b) Amplitude: Set source power level for +15 dBm
at the reference input port.
Figure 3-3. Pulsed carrier absolute phase noise measurements using a microwave
downconverter
Pulse
Generator
External Pulse
Input
Input
E5500
8644B
Input
Pulse
Modulator
Reference
Input
Tune Volts
Out
PLL
Reference
Source
Microwave
Downconverter
Tune Volts
IN
Source
"DUT"
Pulse
Modulator
83732B