Specifications

FIG 6-3

FIG 6-4

f) Filter the IF signal (ie, the DUT output)

if necessary.

Keep the LO outside of the frequency range of the

instrument if possible. LO power will almost certainly

leak through to the IF port of the mixer. Assume that

LO to IF isolation will be insufficient. If this leakage is

within the band of the measurement, it will add to the

noise figure measured. If it is outside the band of the

measurement but within (or close to) the overall

frequency range of the instrument, it could cause the

instrument to autorange itself to use more attenuation,

which would increase the uncertainty of the measurement.

Filter the output of the mixer to remove this LO

leakage and any LO harmonics created in the mixer

without appreciably attenuating the wanted mixer

output signal.

g) Document a frequency plan to evaluate

which of the above precautions are

necessary.

A frequency plan will help identify which of the

precautions above are the most important before the

measurement is made.

Noise

Figure

Analyzer

Noise source

IF Amplifier

Mixer

MEAS

Measurement System

Noise

Source

Drive

(DUT)

Noise Power

Freq

LSB

USB

filter response