08 | Keysight N1911A/N1912A P-Series Power Meters and N1921A/N1922A Wideband Power Sensors - Data Sheet

Characteristic Peak Flatness

The peak flatness is the flatness of a peak-to-average ratio measurement for various tone-separations for an equal magnitude two-

tone RF input. Figure 2 refers to the relative error in peak-to-average ratio measurements as the tone separation is varied. The mea-

surements were performed at –10 dBm with power sensors with 1.5 m cable lengths.

Figure 2. N192XA Error in peak-to-average measurements for a two-tone input (High, Medium, Low and Off filters)

-3.5

-3.0

-2.5

-2.0

-1.5

-1.0

-0.5

0.0

0.5

0

5

10

15

20

25

30

Input tone separation frequency (MHz)

High

Medium

Low

(< 500 MHz)

Off

(> 500 MHz)

Off

Noise and drift

Sensor model

Zeroing

Zero set

Noise per sample

< 500 MHz

> 500 MHz

N1921A /N1922A

No RF on input

200 nW

200 nW

100 nW

2 μW

50 nW

RF present

550 nW

200 nW

Measurement average setting

1

2

4

8

16

32

64

128

256

512

1024

Free run noise multiplier

1

0.9

0.8

0.7

0.6

0.5

0.45

0.4

0.3

0.25

0.2

Video BW setting

Low 5 MHz

Medium 15 MHz

High 30 MHz

Off

Noise per sample multiplier

< 500 MHz

≥ 500 MHz

0.5

0.45

1

0.75

2

1.1

1

1

1. Within 1 hour after a zero, at a constant temperature, after 24 hour warm-up of the power meter. This component can be disregarded with Auto-zero mode

set to ON.

2. Measured over a one-minute interval, at a constant temperature, two standard deviations, with averaging set to 1.

Effect of video bandwidth setting

The noise per sample is reduced by applying the meter video bandwidth filter setting (High, Medium or Low). If averaging is implement-

ed, this will dominate any effect of changing the video bandwidth.

Effect of time-gating on measurement noise

The measurement noise on a time-gated measurement will depend on the time gate length. 100 averages are carried out every 1 us of

gate length. The Noise-per-Sample contribution in this mode can approximately be reduced by √(gate length/10 ns) to a limit of 50 nW.