Technical data

5-4

Operating Concepts

Output Power

Understanding the Power Ranges

The built-in synthesized source contains a programmable step attenuator that allows you to directly and

accurately set power levels in twelve different power ranges. Each range has a total span of 20 dB. The

twelve ranges cover the instrument's full operating range. In addition, some amount of overrange and

underrange is permitted beyond the stated limits. Performance outside of the range limits varies from one

analyzer to another and is not specified. A power range can be selected either manually or automatically.

Automatic mode

If you select PWR RANGE AUTO, you can enter any power level within the total operating range of the

instrument and the source attenuator will automatically switch to the corresponding range.

Each range overlaps its adjacent ranges by 15 dB, therefore, certain power levels are designated to cause

the attenuator to switch to the next range so that optimum (leveled) performance is maintained. These

transition points exist at

−10 dB from the top of a range and at +5 dB from the bottom of a range. This

leaves 10 dB of operating range. By turning the analyzer front panel knob with PORT POWER, being the

active function, you can hear the attenuator switch as these transitions occur. See Chapter 1,

“Specifications and Regulatory Information” for the analyzer’s power limits.

Manual mode

If you select PWR RANGE MAN, you must first enter the power ranges menu and manually select the

power range that corresponds to the power level you want to use. This is accomplished by pressing the

POWER RANGES, softkey and then selecting one of the 12 available ranges. The active power will always

be reset to be within this range. In this mode, you will be able to select power levels above or below the

range limits. The factory limits on setting power level are +6 dB above the maximum range power and

−12

dB below the minimum range power. Typical performance for power overrange is 2 dB above the maximum

(more at lower frequencies and less at higher frequencies) and typical under range is 12 dB. An

under-range condition may cause a phase lock lost message to be displayed.

When a calibration is active, the power range selection is switched from auto to manual mode, and PRm

appears on the display. This feature is necessary to maintain accuracy once a measurement calibration is

activated.

NOTE After measurement calibration, you can change the power within a range and still maintain

nearly full accuracy. In some cases better accuracy can be achieved by changing the power

within a range. It can be useful to set different power levels for calibration and

measurement to minimize the effects of sampler compression or noise floor. If you decide to

switch power ranges, the calibration accuracy is degraded and accuracy is no longer

specified. However, the analyzer leaves the correction on. The annotation C

∆ will be

displayed whenever you change the power after calibration.

Power Coupling Options

There are two methods you can use to couple and uncouple power levels with the analyzer:

• channel coupling