HP 8590 E-Series User Manual page 343

linear input. level
The maximum input-signal level where gain compression does not occur. Refer also to gain
compression.
LO
The abbreviation for local oscillator. The local oscillator output in a superheterodyne system
is mixed with the received signal to produce a sum or difference equal to the intermediate
frequency (IF) of the receiver. Refer also to IF.
LO feedthrough
The response that occurs on a spectrum analyzer's display when the first local oscillator
frequency is equal to the first IF. The LO feedthrough is a 0 Hz marker with no error, so it
can be used to improve the frequency accuracy of spectrum analyzers with nonsynthesized
LO systems.
log display
The display mode in which vertical deflection is a logarithmic function of the input-signal
voltage. Log display is also referred to as logarithmic mode. The display calibration is
set by selecting the value of the top graticule line (reference level), and scale factor in
volts per division. On Hewlett-Packard analyzers, the bottom graticule line represents
zero volts for scale factors of 10 dB/division or more. The bottom division, therefore, is
not calibrated for those analyzers. Analyzers with microprocessors allow reference level
and marker values to be indicated in dBm, dBmV, dBpV, volts, and occasionally in watts.
Nonmicroprocessor-based analyzers usually offer only one kind of unit, typically dBm.
marker
A visual indicator we can place anywhere along the displayed trace. A marker readout
indicates the absolute value of the trace frequency and amplitude at the marked point. The
amplitude value is displayed with the currently selected units. Refer also to delta marker
and noise marker.
maximum input level
The maximum signal power that may be safely applied to the input of a spectrum analyzer.
Typically 1 W (-30 dBm) for Hewlett-Packard spectrum analyzers.
Annotation indicating an uncalibrated measurement condition exists. It appears when
instrument settings affect accuracy of measurement results to the extent that they no
longer meet specifications.
measurement bandwidth
The resolution bandwidth required for a specific EM1 measurement. For MIL-STD
measurements, the resolution bandwidth is often determined by the tester with the
approval of the contracting agency.
For commercial testing the measurement bandwidths required usually follow the
recommendations of CISPR:
Band A (10 kHz to 150 kHz): 200 Hz
Band B (150 kHz to 30 MHz): 9 kHz
Band C and D (30 MHz to 1 GHz): 120 kHz
measurement range
The ratio, expressed in dB, of the maximum signal level that can be measured (usually the
maximum safe input level) to the lowest achievable average noise level. This ratio is almost
always much greater than can be realized in a single measurement. Refer also to dynamic
range.
Glossary-9