User`s guide

AM Noise Measurement Fundamentals 11
Agilent E5505A User’s Guide 289
AM detector specifications
Detector type low barrier Schottky diode
Carrier frequency range 10 MHz to 26.5 GHz
Maximum input power +23 dBm
Minimum input power 0 dBm
Output bandwidth 1 Hz to 40 MHz
AM detector considerations
• The AM detector consists of an Agilent 33330C Low-Barrier Schottky Diode
Detector and an AM detector filter (Agilent 70429A K21).
• The detector, for example, is an 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.
• The AM detector output blocking capacitor in the 70429A Option K21,
N5500A Option 001, or N5507A 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.
• 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 46 shows carrier frequencies with corresponding
offset frequencies.
CAUTION
The 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 70429A Option K21 is designed
specifically for this purpose or the internal DC blocking filter in either the N5500A
or N5507A may be used.
Table 46 Maximum carrier offset frequency
Carrier Frequency Offset Frequency
≥250 κΗz100 MHz
≥50 MHz 20 MHz
≥5 MHz 2 MHz
≥500 kHz 200 kHz