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Document Part No. E5500-90024Ed. 1.0
Minimum input power 0 dBm
Output bandwidth 1 Hz to 40 MHz
AM Detector Considerations
G
The AM detector consists of an Agilent 33330C Low-Barrier
Schottky Diode Detector and an AM detector filter (Agilent
70429A K21).
G
The detector, for example, is an Agilent 33330C Low-Barrier
Schottky-Diode Detector. The Schottky detectors will handle
more power than the point contact detectors, and are equally as
sensitive and quiet.
G
The AM detector output blocking capacitor in the Agilent 70429A
Option K21, 70420A Option 001, or 70427A prevents the dc
voltage component of the demodulated signal from saturating the
system's low noise amplifier (LNA). The value of this capacitor
sets the lower frequency limit of the demodulated output.
G
Carrier feedthrough in the detector may be excessive for
frequencies below a few hundred megahertz. The LNA is
protected from saturation by the internal filters used to absorb
phase detector feedthrough and unwanted mixer products.
Table 12-1
shows carrier frequencies with corresponding offset
frequencies.
Table 12-1 Maximum Carrier Offset Frequency
Carrier Frequency
≥
250 kHz
≥
50 MHz
≥
5 MHz
≥
500 kHz
≥
50 kHz
G
The ac load on the detector is 50 ohms, set by the input
impedance of the LNA in the test system. The 50 ohm load
increases the detector bandwidth up to than 100 MHz.
G
The Agilent 70420A phase noise test set must be dc blocked when
using its Noise Input or internal AM detector. The test set will not
tolerate more than ± 2 mV DC Input without overloading the LNA.
A DC block must be connected in series after the AM Detector to
remove the dc component. The Agilent 70429A Option K21 is
E5500 Phase Noise Measurement System Version A.02.00
AM Noise Measurement Fundamentals
Amplitude Noise Measurement
Offset Frequency
100 MHz
20 MHz
2 MHz
200 kHz
20 kHz
12
12-5
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