R3267 Series Spectrum Analyzer Operation Manual (Vol.1)
4.1 Input Saturation
4-1
4
PRINCIPLE OF MEASUREMENT
This chapter describes the input saturation, internal operation and Nyquist filter in ACP measurements, and
the gated sweep of the analyzer.
4.1
Input Saturation
Measurement error may increase depending on the setting of the attenuator when a relatively large input sig-
nal is input. This problem can be caused by an input saturation. This section describes input saturation.
•
Cause of input saturation
A block diagram of the analyzer input section is shown in Figure 4-1. The input signal at the input con-
nector passes through the attenuator and enters the mixer.
Figure 4-1Input Section Block Diagram
The output level of the mixer is usually proportional to the input level. The mixer output becomes satu-
rated as the input reaches a certain level, and the error increases (see Figure 4-2).
Figure 4-2Relationship between the Input and Output of the Mixer
•
Measures against input saturation
Mixer input level must be lowered by adjusting the attenuator to an optimum level once input saturation
appears.
CAUTION
If the output from the attenuator is too low, you cannot analyze the weak signal. However, internal
circuitry of the mixer, may be damaged if the output from the attenuator is too large.
Attenuator
Mixer
1st
Local oscillator
IFout
RFin
LOin
Input level RFin
Outpu
t
le
v
el IFou
t
