Keysight x-series User Manual

3 Spectrum Analyzer Mode
3.7 Burst Power Measurement
µW Preselector Bypass
Toggles the preselector bypass switch for band 1 and higher. When the microwave
presel is on, the signal path is preselected. When the microwave preselector is off,
the signal path is not preselected. The preselected path is the normal path for the
instrument.
The preselector is a tunable bandpass filter which prevents signals away from the
frequency of interest from combining in the mixer to generate in-band spurious
signals (images). The consequences of using a preselector filter are its limited
bandwidth, the amplitude and phase ripple in its passband, and any amplitude and
phase instability due to center frequency drift.
Option MPB or pre-selector bypass provides an unpreselected input mixer path for
certain X-Series signal analyzers with frequency ranges above 3.6GHz. This signal
path allows a wider bandwidth and less amplitude variability, which is an advantage
when doing modulation analysis and broadband signal analysis. The disadvantage is
that, without the preselector, image signals will be displayed. Another disadvantage
of bypassing the preselector is increased LO emission levels at the front panel input
port.
Image responses are separated from the real signal by twice the 1st IF. For IF Paths
of 10MHz and 25MHz, the 1st IF is 322.5MHz, so the image response and the real
signal will be separated by 645MHz. The 1
st
IF will be different for other IF Path
settings. When viewing a real signal and its corresponding image response in
internal mixing, the image response will be to the left of the real signal.
Also, the image response and the real signal typically have the same amplitude and
exhibit the same shape factor.
However, if Option FS1 (Fast Sweep Capability) is enabled, the image response in
the Swept SA measurement appears lower in amplitude and has a much wider
shape factor compared to the real signal.
Full Bypass Enable
With Full Bypass Enable selected, the microwave preselector is bypassed. In
addition, the low band/high band switch and microwave preamp are bypassed
whenever all the following are true:
–
The instrument is not in the Low Band, meaning:
–
the start frequency is above 3.5 GHz and
–
the stop frequency is above 3.6 GHz.
–
the internal preamp is not installed or if installed, is set to Off or Low Band
Note that this means that, when any part of a sweep is done in Low Band, the Low
Noise Path is not used, whether or not the Full Bypass Enable is selected in the user
Spectrum Analyzer Mode User's &Programmer's Reference 1285

Keysight x-series Specifications

General

Analysis Bandwidth	Up to 1 GHz (depending on model)
Real-Time Bandwidth	Up to 1 GHz (depending on model)
Form Factor	Benchtop
Connectivity	LAN, USB, GPIB
Resolution Bandwidth	1 Hz to 10 MHz (depending on model)