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R3131 Spectrum Analyzer Operation Manual

APPENDIX 2 GLOSSARY

Resolution Bandwidth

The spectrum analyzer uses the bandpass filter (BPF) to analyze the frequency components contained in the

input signal. The 3dB bandwidth of the BPF is called the resolution bandwidth (See Figure A2-1(a) below).

BPF characteristics should be set according to the sweep width and the sweep speed used for the trace. This

spectrum analyzer sets the optimal value for the sweep width. In general, smaller bandwidths improve reso-

lution so the resolution of the spectrum analyzer should be expressed using the narrowest resolution band-

width (See Figure A2-1(b) below).

RBW = resolution bandwidth

23 dB

Resolution bandwidth

(a)

RBW RBW

[ignal spacing

rnIT

Resolution

(b)

Figure A2-1 Resolution Bandwidth

RBW Signal spacing

Reference Level Display Accuracy

When reading the absolute level of an input signal on the spectrum analyzer, the level is determined by the

distance in dB from the uppermost scale on the screen. The level set for this uppermost scale is called the

reference level.

The reference level is modified by the IF GAIN key and the input attenuator, and is displayed in dBm or dBi.t.

The absolute accuracy of this display is the reference level accuracy.

Reference level

Figure A2-2 Reference Level

A2-1

ADVANTEST R3131 Series User Manual

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