residual FM

The inherent short-term frequency instability of an oscillator in the absence of any other modulation. In the case of analyzers, we usually expand the definition to include the case where the local oscillator is swept. Residual FM is usually specified in peak-to-peak values, because they are most easily measured on the display, if they are visible at all.

residual responses

These are discrete responses seen on an analyzer display although no input signal is applied.

resolution

Refer to frequency resolution

resolution bandwidth

The ability of an analyzer to display adjacent responses discretely (hertz, hertz decibel down). This term is used to identify the width of the resolution bandwidth filter of an analyzer at some level below the minimum insertion-loss point (maximum deflection point on the display). The 3 dB resolution bandwidth is specified; for others, it is the 6 dB resolution bandwidth.

rose-n-fell

For digital displays, this is the display detection mode in which the value displayed at each point on a trace is based upon whether or not the video signal both rose and fell during the frequency or time interval represented by the point. If the video signal only rose or only fell, the maximum value is displayed. If the video signal both rose and fell, the maximum value during the interval is displayed by odd-numbered points, and the minimum value by even-numbered points. To prevent the loss of a signal occurring during an even-numbered interval, the maximum value of the signal during this interval is preserved. At the next (odd-numbered) interval, the value displayed is the greater value carried over, or the maximum, that occurs during the current interval.

sample

The instantaneous value of an incoming signal. On digital displays, each displayed point of the signal indicates the instantaneous value of the signal for that part of the frequency span or time interval represented by the point.

Glossary-22