29​Noise Figure Mode (Option 356)

Noise figure requires these options: – Spectrum analyzer mode (Option 233—Combination Analyzers Only) – Preamplifier (Option 235) – DC variable voltage source (Option 309) – Noise source refer to https://www.keysight.com/us/en/assets/3125-1447/configuration-guides/FieldFox-Handheld-Analyzers-D-models.pdf Not required, but recommended for improved accuracy: – External preamplifier (U7227A/C/F and U7228A/C/F). Refer to https://www.keysight.com/find/usb-preamp

Noise figure mode sets the sweep to Continuous OFF to allow time for connecting a noise source, before beginning any measurements.

Figure 29-1 ​Example of Jitter Uncertainty (21 points)—with Uncertainty Bars. Learn more in “How to use Auto-Integration” on page 809.

Figure 29-2 ​Example of Jitter Uncertainty (21 points)—with Uncertainty Bars Disabled. Learn more in “How to use Auto-Integration” on page 809.

In this Chapter

:

See Also

Using Noise Figure

Noise Figure enables you to do the following:

Select Noise Figure Mode before making any setting in this chapter.

How to select Noise Figure Mode:

—​Press Mode_.

—​Then More.

—​Then Noise Figure.

Figure 29-3 ​Display Annotation—Overview

Figure 29-4 ​Dual Window Display Annotation

Figure 29-5 ​Calibration Annotation

Figure 29-6 ​ENR Status and Mode Annotation

Figure 29-7 ​Uncertainty Annotation

Figure 29-8 ​Smart Noise Source Annotations

Figure 29-9 ​Smart Noise Source – Source Menus

Figure 29-10 ​Smart Noise Source – Meas Setup > Noise Source > Noise Source Control

How to Define a Noise Figure Measurement

The Option 356 Noise Figure mode uses the Y-factor method to calculate the noise figure.

This section contains the following:

—​“Example: Typical Noise Figure Measurement Procedure” on page 767

—​“Overview of Softkey Menus” on page 768

—​“How to Use DUT Measurement Setups” on page 776

—​“Single / Continuous / Restart” on page 792

—​“Points ” on page 792

—​“Resolution Bandwidth (Res BW)” on page 793

—​“Alignments” on page 793

—​“Calculating Noise Figure Measurement Uncertainty” on page 794

—​“Using ENR Tables” on page 799

—​“Using Markers (Noise Figure)” on page 802

To learn more about Smart Noise Sources, refer to https://www.keysight.com/us/en/products/noise-figure-analyzers-noise-sources/noise-sources.html.

Example: Typical Noise Figure Measurement Procedure

This section briefly reviews the steps in setting up a noise figure measurement. If you are not familiar with this process or would like more information, refer to “Overview of Softkey Menus” on page 768 and “How to Use DUT Measurement Setups” on page 776.

1.​Set up a Noise Source ENR Table:
(Meas Setup > Noise Source > ENR Table Edit/Save/Recall).

2.​Set the resolution bandwidth: BW > Res BW

3.​Set the frequency range: Freq/Dist >

—​Start,

—​Stop,

—​Center, and

—​Span

4.​Set the number of points: Sweep > Points (minimum = 3 points, maximum = 1001 points, default = 21)

5.​Use Meas Setup > Integration Setup Integration (See also “How to use Auto-Integration” on page 809.)

—​Max. Time/Pt. (Available when Mode = Auto) or

—​Time/Pt. (available when Mode = Fixed)

6.​Perform a Receiver Calibration: (Cal > Run Receiver Cal and follow prompts).

7.​Enter DUT setup type: Meas Setup > DUT > Type

—​Amplifier (default),

—​Downconverter,

—​Upconverter, or

—​Multi-Stage Converter

8.​Run a User Calibration (i.e., If you are using an external preamp).
(Cal >Run User Cal and follow prompts).

9.​Use Measure to select the type of noise figure measurement:

—​Noise Figure,

—​Noise Factor,

—​Gain,

—​Noise Temperature, or

—​Y-Factor

10.Use Meas Setup > Uncertainty > Uncert Contributions to Enable/Disable Uncertainty Contributions:

—​Jitter Uncert OFF ON,

—​ENR Uncert OFF ON,

—​Mismatch Uncert OFF ON,

—​User Cal Uncert OFF ON (applies the current User Cal uncertainty to the current measurement’s uncertainty calculations), and

—​Then Back > Uncert Bars to ON.

Overview of Softkey Menus

This sections describes the Noise Figure’s Measure, Measure Setup softkeys, and related sub-menu softkeys.

1.​Define a measurement type.

a.​Select a Measure—choose:

—​Noise Figure Specify Noise Figure (default) or

—​Noise Factor Specify a Noise Factor or

—​Gain Specify Gain or

—​Noise Temperature Specify Noise Temperature or

—​YFactor Specify Y-Factor

b.​Then modify the settings based on the selected noise figure type

2.​Select Measure Setup—choose:

—​Noise Source or “DUT or” on page 772, “Integration or” on page 773, or “Uncertainty” on page 773.

Opens a menu of softkeys to define the Noise Figure’s ENR Mode Smart (Smart Source), Spot, and Table and uncertainty values.

To learn more, refer to Figure 29-8 on page 764, Figure 29-9 on page 765, and Figure 29-10 on page 766.

Then choose:

—​ENR Mode [Table] then choose from:

——Spot You can enter ENR data for the noise source you are using as a single spot value.

The single spot value is used either for measurements at a single frequency, or for measurements across a range of frequencies that is narrow enough such that the ENR value does not change significantly across that range. (Default == Spot).

——Smart (Auto) The FieldFox checks for a valid USB noise source and automatically loads any ENR and calibration values. And, automatically loads a T Cold value from the USB Noise Source, measured in Kelvin.

——Table You can enter ENR data for the noise source you are using as a table of values. The values held in the table can be used for measurements at a range of frequencies as well as at a fixed frequency.

—​ENR Spot Values Opens a menu to enter a spot value either for measurements at a single frequency or for measurements across a range of frequencies that is narrow enough such that the ENR value does not change significantly across that range (Active when ENR Mode set to Spot).

Then choose:

——ENR sets the ENR spot value in dB (default is 15 dB).

——ENR Uncert. sets the ENR spot uncertainty value in dB (default is 0.000 dB).

——On | G| sets the On value (hot) of the ENR spot value’s 50W match, G (0.000 to 1.000).

——Off | G| sets the Off value (cold) of the ENR spot value’s 50W match, G (0.000 to 1.000).

——ENR Uncert. Cov. [2s] Opens a menu to set the value of the ENR uncertainty coverage.

Then choose: 1s, 2s (default), or 3s.

——More opens additional ENR Spot Value softkey menu choices

——G Spec. Style [Fixed] Opens a menu of softkeys to set the G specification style.

Then choose Maximum, 95th %ile (default), 80th %ile, Median, Mean, or Fixed (Default == Fixed).

——G Distribution [Rayleigh] Opens a menu of softkeys to set the type of G distribution.

Then select Rayleigh (default), Fixed, or Uniform in Circle.

—​ENR Table Edit/Save/Recall Opens the ENR table menu to edit, save, or recall noise source values (Active when ENR Mode set to Table).

Then choose:

——Edit ENR Table Opens the currently selected table of noise source values (generic default noise source values are populated for quick check). Enter your noise source’s values for more accurate measurements.

——New ENR Table opens a new ENR table for entering and saving additional noise source values.

——Save ENR Table Opens a menu of softkeys to enable you to enter a unique noise source filename.

——Recall ENR Table Opens a menu of file recall softkeys and displays a list of stored noise source files.

——Storage Device [Internal] Opens a menu of softkeys to set the storage location for your files.

Then choose Internal (default), SD Card, or USB.

——Back to return to previous menu.

—​T Cold Default When making measurements at different ambient temperatures, you can set the T_cold value in Kelvin (K) manually (User). When set to Default, the T_cold value is set to the 296.5 K (Default == Default).

—​Noise Source Control Opens a menu of ENR noise source control softkey choices. (Active only when ENR Mode == Smart (Auto)).

Then choose:

——Reconnect Automatically reconnects the FieldFox to a noise source. If one is not found, the FieldFox displays "Noise Source is NOT CONNECTED". Allow 10 to 20 seconds for the instrument to detect the noise source.

——Auto Load ENR OFF ON When Auto Load is enabled the FieldFox automatically searches for a compatible USB noise source and reloads the stored calibration and temperature data. When disabled no existing search is made for USB noise source data to be loaded. (Default == ON)

When Auto Load == ON and compatible USB noise source is detected (e.g., U1832/U1833A/B/C/D) the FieldFox briefly displays:

"Recalled \temp\U1832A.enr"

When Auto Load == OFF, but a valid USB noise source is discovered, the following message is displayed:

"Noise Source Found;ENR file NOT auto loaded."

——Reload ENR Data Manually reloads any existing USB noise figure sensor data. This softkey is inactive/grayed out when a Noise Source is not detected. When a USB noise source is detected and this softkey is pressed, the data from the noise source is loaded into the ENR table overwriting any previous ENR table data.

——Source Output Norm OFF ON Controls the automatic noise source control (Default == Normal). This softkey is inactive/grayed out when a Noise Source is not detected.

When set to Normal, the noise source ON/OFF is automatically controlled by the noise source application.

When set to ON or OFF Re-Run Receiver Cal and Run User Cal softkeys are inactive/grayed out. No valid results is provided by the noise source application.

——ENR Table OFF ON Enables/disables the ENR Table data for use in the current measurement (Default == OFF).

If the ENR Table is set to ON, when Auto Load ENR is set to ON and a noise source is connected to the analyzer, the ENR table data is overwritten.

If the Auto Load ENR is set to OFF, no data is loaded into the ENR table.

——Refresh T Cold] When the noise source is set to Smart (Auto) and a U1832/U1833A/B/C/D noise source is detected the T Cold value can be read from the noise source. This softkey is inactive/grayed out when a compatible Noise Source is not detected.

—​Back to return to previous menu.

—​DUT or

Opens a menu of softkeys to define your DUT Type (Amplifier, Downconverter, Upconverter, or Multi-Stage Converter), frequency context, and loss compensation. Refer to “How to Use DUT Measurement Setups” on page 776.

—​Integration or

Opens a menu of softkeys to define the Integration’s Mode Auto or Fixed and Jitter values.

Then choose:

—​Mode Auto Fixed Select Auto (default) to let the FieldFox select the optimum coupled instrument settings. Changes can be made to the Jitter Goal and Max Time/Pt. values. When integration Mode is set to Fixed, the Time/Pt. softkey is active and can be modified.

—​JItter Goal Sets the maximum peak-to-peak jitter value. Values greater than this value triggers the Jitter Warning (i.e., if Jitter Warning = ON). (Only active when
Mode = Auto.) (Default is 0.5 dB.)

—​Max Time/Pt. Sets the maximum amount of time the jitter is measured at a given point to attempt to reach the Jitter Goal value (i.e., the measurement time per point is automatically adjusted to the minimum time required, but will never exceed the displayed Max Time/Pt.). After this time, values in excess of the jitter Goal value trigger the Jitter Warning.

—​Jitter Warning Enables/Disables the Jitter Warning. The Jitter Warning displays when the Jitter value exceeds the Jitter Goal value. (Default = ON.)

—​Time/Pt. Sets the Time/Pt. when Mode is set to Fixed. (Only active when Mode = Fixed.)

—​Back to return to previous menu.

—​Uncertainty 

Opens a menu of uncertainty softkeys for setting the DUT, Preamp, and Uncert. Contributions.

Then choose:

—​DUT Sets the DUT Mode to either Spot (default) or Table.

Then choose:

——DUT Mode Set to Spot (default) or to Table

For DUT MODE Spot choose:

——DUT Spot Values (Only active when DUT Mode = Spot).

Then choose:

——Input |G| Sets the input Gvalue.

——Output |G| Sets the output Gvalue.

——G Spec. Style [Fixed] Opens a menu of softkeys to set the G specification style.

Then choose Maximum, 95th %ile, 80th %ile, Median, Mean, or Fixed (default).

——G Distribution [Fixed] Opens a menu of softkeys to set the type of G distribution.

Then select Rayleigh, Fixed (default), or Uniform in Circle.

——Back to return to previous menu.

——DUT Table Edit/Save/Recall (Only active when DUT Mode = Table).

Then choose:

——Import DUT Data Opens a menu of softkeys where you can select a DUT *.csv or *.snp data file to import into your table.

Then choose Recall File, Sort by File Name, Sort by Date, Next Page, Previous Page, or Cancel.

——Edit DUT Data Opens a menu of softkeys where you can edit the current selected DUT table data file (e.g., serial number, model number, G Spec. Style, G Distribution, Input |G|, Output |G|, and frequencies).

Then choose Edit, Next Page, Previous Page, Add Row (only active for Frequency), Delete/Clear (only active for Frequency), or Done.

——New DUT Table Opens a menu of softkeys to choose a new DUT table.

——Save DUT Table Opens a Create a filename menu of softkeys to enter a DUT table filename and then to save the file.

——Recall DUT Table Opens a Select a file menu of softkeys to enter a DUT table filename to recall.

——Storage Device [Internal] Opens a set of softkeys to select where your DUT table is saved.

Then choose Internal, SD Card, or USB.

—​Back to return to previous menu.

—​Preamp Sets the DUT Mode to either Spot (default) or Table.

Then choose:

——Preamp Mode Set to Spot (default) or to Table.

For Preamp MODE Spot choose:

——Preamp Spot Values (Only active when DUT Mode = Spot).

Refer to similar “DUT Spot Values (Only active when DUT Mode = Spot).” on page 774.

——Back to return to previous menu.

——Preamp Table Edit/Save/Recall (Only active when Preamp Mode = Table).

Refer to similar “DUT Table Edit/Save/Recall (Only active when DUT Mode = Table).” on page 774.

——Back to return to previous menu.

—​Uncert Contributions Opens a menu of uncertainty contribution softkeys.

Then choose:

——Jitter Uncert. Enable/disable the Jitter Uncertainty.

——ENR Uncert. Enable/disable the ENR Uncertainty.

——Mismatch Uncert. Enable/disable the Mismatch Uncertainty.

——User Cal Uncert. Enable/disable the User Cal Uncertainty.

——Back to return to previous menu.

—​Uncert Cover Sets the uncertainty coverage value for the current settings.

Then choose: 1s, 2s (default), or 3s.

—​Uncert Bars Enables/disables the uncertainty calculator uncertainty bars values for the current settings.

—​Back to return to previous menu.

How to Use DUT Measurement Setups

Noise figure Option 356 has four predefined measurement setups:

—​Amplifier

—​Downconverter

—​Upconverter

—​Multi-Stage Converter

Refer to “Using Measure Setup to Choose DUT Type” on page 776.

Each of the four measurements has frequency context and loss compensation softkeys that can used to optimize the DUT’s noise figure measurement. Refer to “DUT Type and Frequency Context” on page 785 and to “DUT Type Loss Compensation” on page 790.

Using Measure Setup to Choose DUT Type

This section contains the following:

—​Setting DUT > Type [Amplifier], see Figure 29-11 on page 777 and for Smart Noise Source, see Figure 29-15 on page 781.

—​Setting DUT > Type [Downconverter], see Figure 29-12 on page 778 and for Smart Noise Source, see Figure 29-16 on page 782.

—​Setting DUT > Type [Upconverter], see Figure 29-13 on page 779 and for Smart Noise Source, see Figure 29-17 on page 783.

—​Setting DUT > Type [Multi-Stage Converter], see Figure 29-14 on page 780 and for Smart Noise Source, see Figure 29-18 on page 784.

Figure 29-11 ​DUT – Measurement Setup – Type [Amplifier] Screen

Figure 29-12 ​DUT Measurement Setup – Type [Downconverter] Screen

Figure 29-13 ​DUT Measurement Setup – Type [Upconverter] Screen

Figure 29-14 ​DUT Measurement Setup – Type [Multi-Stage Converter] Screen

ENR Mode: Smart (Auto) – Calibration Wizard (DUT)

Figure 29-15 ​DUT – Measurement Setup – Type [Amplifier] Screen –
ENR Mode: Smart (Auto)

Figure 29-16 ​DUT – Measurement Setup – Type [Downconverter] Screen –
ENR Mode: Smart (Auto)

Figure 29-17 ​DUT – Measurement Setup – Type [Upconverter] Screen –
ENR Mode: Smart (Auto)

Figure 29-18 ​DUT – Measurement Setup – Type [Multi-Stage Conv] Screen –
ENR Mode: Smart (Auto)

DUT Type and Frequency Context

Noise figure enables you to define the frequency context for your noise figure measurements:

—​ RF (DUT In):

—​Start

—​Stop

—​Center

—​Span

—​Freq Context—(Inactive for Amplifier):

—​RF

—​IF

—​LO—(Inactive for Amplifier)

—​IF (DUT Out)—(Inactive for Amplifier)

—​Start

—​Stop

—​Center

—​Span

This section contains the following:

—​Setting Meas Setup > DUT > Next > RF (OUT in), see Figure 29-19 on page 786

—​Setting Meas Setup > DUT > Next > IF (DUT Out), see Figure 29-20 on page 787

—​Setting Meas Setup > DUT > Freq Context [IF], see Figure 29-21 on page 788

Frequency Context – RF (DUT In)

The RF (DUT In) softkey can be used to define the DUT Type’s RF Start, Stop, Center, and Span frequencies. Refer to “Frequency Range and Frequency Context” on page 789.

Figure 29-19 ​DUT >Type [Amplifier] and [Multi-Stage Converter] > RF (DUT In)—Frequency Context

Frequency Context – IF (DUT Out) – Inactive for Type [Amplifier]

The IF (DUT Out) softkey can be used to define the DUT Type’s IF Start, Stop, Center, and Span frequencies. Refer to “Frequency Range and Frequency Context” on page 789.

Figure 29-20 ​DUT >Type [Downconverter], [Upconverter], and [Multi-Stage Converter] > IF (DUT Out)—Frequency Context (Inactive for Type [Amplifier]

DUT Type—Freq Context (IF or RF)—(Inactive for DUT Type [Amplifier])

Frequency context can be used to define the DUT Type’s RF Context IF (default) and RF values. Refer to “Frequency Range and Frequency Context” on page 789.

Figure 29-21 ​DUT >Type [Downconverter], [Upconverter], and [Multi-Stage Converter] > Freq Context [IF] or [RF]—(Inactive for Type [Amplifier])

Frequency Range and Frequency Context

Set the range of frequencies over which you would like to make DUT type measurements and frequency context for noise measurements.

When the frequency range is changed after a calibration is performed, the cal becomes interpolated. Learn more in “Interpolation *” on page 149.

How to set Frequency Range and Frequency Context

—​Press Freq/Dist (Measurement) or

for Frequency Context:

—​Press Meas Setup > DUT) > RF (DUT In) and IF (DUT Out)

—​Then Freq/Dist and choose from the following

—​Start and Stop frequencies - beginning and end of the sweep.

—​Center and Span frequencies – the center frequency and span of frequencies (half on either side of center).

—​Freq Annotation and one of the following:

—​Follow each setting by entering a value using the numeric keypad, arrows, or the rotary knob.

—​After using the keypad, select a multiplier key. Learn about multiplier abbreviations in Chapter 1, “Overview.” 

—​After use the arrows or the rotary knob, press Enter.

Figure 29-22 ​

DUT Type Loss Compensation

For all of the DUT Types (Amplifier, Downconverter, Upconverter, and Multi-Stage Converter) the loss compensation, before the DUT (BeforeDUT) and after the DUT (AfterDUT) can be enabled or disabled for loss and for temperature.

Loss compensation can be used to compensate for double sidebands (DSB). Loss compensation can be used in the case of DSB measurements to compensate for the doubling of the measured noise level (i.e., 3.01 dB increase). For all sideband cases you can enable or disable Loss (device loss) and Temperature (device temperature). Refer to Figure 29-23 on page 791.

This section contains the following:

—​Setting Meas Setup > DUT > Loss Compensation > Before DUT and After DUT, see Figure 29-23 on page 791.

Setting DUT Loss Compensation

Figure 29-23 ​DUT Loss Compensation

Single / Continuous / Restart

This setting determines whether the FieldFox measures continuously or only once each time the Single or Run / Hold +/- button is pressed. Use Hold / Single or to conserve battery power or to allow you to save or analyze a specific trace.

How to set Single or Continuous

—​Press Sweep 3.

—​Then choose one of the following:

—Continuous 

——ON Causes noise figure (NF) to make continuous sweeps. This is the typical setting for making measurements. Each Run / Hold +/- press causes NF to toggle between continuous sweep and Hold.

——OFF Causes NF to Hold. Each Run / Hold +/- or Single press causes NF to make ONE sweep, then Hold. The Hold annotation changes to an arrow --> while the sweep occurs.

—Single Automatically sets Continuous OFF and causes NF to make ONE sweep, then Hold.

—Restart Resets the sweep to the current defined start frequency point.

Points

Points is the number of measurements that are measured and displayed along the X-axis. The higher number of data points, the better the ability to resolve closely spaced signals and the slower the sweep speed.

How to set number of points

—​Press Sweep 3 

—​Then Points [current setting]

—​Then choose from: 03 | 05 | 11 | 21 | 51 | 101 | 201 | 401 | 601 | 801 | 1001

Resolution Bandwidth (Res BW)

In NF Mode, the Res BW settings increase the measurement speed and quality of a measured noise figure. The wider (higher) the Res BW, the faster and better the noise figure measurement. However, as the Res BW is narrowed, the sweep speed becomes slower and the measurement quality is degraded.

So: Wider Res BW = better noise measurement and faster measurement time

How to set Res BW

—​Press BW 2.

—​Then Res BW.

—​Then choose from the following:

—​300 kHz | 1 MHz | 3 MHz | 5 MHz Press the desired resolution bandwidth.

The current Res BW setting is shown at the bottom of the screen.

This setting could impact the accuracy of the measurement. See Specifications in https://www.keysight.com/us/en/assets/7018-03314/data-sheets/5990-9783.pdf.

Alignments

The Noise Figure mode requires alignment types: amplitude. Refer to the SA chapter’s “Alignments” on page 219 for information on all alignments.

Calculating Noise Figure Measurement Uncertainty

The Noise Figure mode can calculate and display the uncertainty of the noise measurement, whether it is a Noise Figure, Noise Factor, or Noise Temperature measurement.

The uncertainty calculation accounts for the following sources of uncertainty, both in the measurement and in the user calibration (Run User Cal):

—​Noise power uncertainty caused by finite sample size (Jitter)

—​Noise power uncertainty caused by mismatch

—​ENR uncertainty of the noise standard

The following are not included because they have been determined to be insignificant:

—​Linearity (i.e., due to the linear wide dynamic range receiver, the automatic gain adjustment, and the small power excursions of the hot/cold measurement)

—​Residual temperature drift of the FieldFox (i.e., due to the internal reference switch)

Other possible causes of uncertainty that are not included in the uncertainty analysis are temperature drift of the following:

—​DUT,

—​Noise source, or

—​Preamplifier

When any one of the four uncertainty values reads all “0.00” across the band, a yellow UNC? annotation is displayed on the left side of the FieldFox display.

Refer to ENR “Using ENR Tables” on page 799.

Reverse noise wave generation by the DUT or preamplifier

All amplifiers, including the DUT and preamplifiers used in the noise figure measurement, are active devices which may generate noise power from both their input and output ports. The Noise Figure mode uncertainty calculation does not account for uncertainties caused when the input generated noise reflects back into the amplifier and adds to the total measured noise power. These types of uncertainties are minimized by using well matched noise sources in the measurement and in the user calibration. And, in the case of very low power output DUTs (<15 dB gain + noise figure), by using an isolator on the input of the preamplifier.

Electromagnetic interference

DUTs, preamplifiers, noise sources, and connectors may all potentially be affected by radiated signals present in the test environment. Care should be taken to establish an appropriate test environment for the noise figure measurement.

DUT oscillations, microphonic behavior, etcetera

Any instability in the DUT will cause unaccounted noise measurement uncertainties.

Entering Uncertainty Information

In addition to information gathered during the measurement, the following information must be provided by the user in order to determine the noise measurement uncertainty:

—​DUT Reflection Coefficient

For this section, see also “Overview of Softkey Menus” on page 768 (Uncertainty > DUT on page 773).

DUT Reflection Coefficients values may be imported to a DUT table from *.snp or *.csv Files, entered by editing a DUT table, recalled as a previously saved DUT table (in a *.dut file), or set as a spot value to be applied across all frequencies.

Specified Style (Spec Style): Following the GUM method for Type B evaluation of standard uncertainty described in Reference[1]¹, the uncertainty calculation takes into account not only the entered value of the reflection coefficient, but also the nature of this value. This can either be a measured value for the DUT, or some form of specified value. This is indicated by the Spec Style setting. Specified Styles may be either a percentile value, maximum, fixed, median or mean. This value indicates the nature of the entered value relative to the population of values it represents. Refer to Table 29-1 on page 796.

Distribution: Distribution settings refer to the population distribution of the
| G| values for the device. Refer to Table 29-2 on page 796.

—​Noise Source Reflection Coefficient, ENR Uncertainties   , and ENR values:

For this section, see also “Overview of Softkey Menus” on page 768 (Noise Source on page 769) and “Using ENR Tables” on page 799.

Noise source reflection coefficients, ENR Uncertainties, and ENR values may be entered by Recalling a previously generated *.enr file, editing an ENR table, or set as a spot value to be applied across all frequencies. Note that any *.enr file which uses the standard *.enr file format may be recalled by the Noise Figure mode.

As in the case of the DUT, in addition to entering the magnitude reflection coefficient values, the uncertainty calculation takes into account the distribution and specified style for the noise source reflection coefficient value. Additionally, the ENR table requires a value for the ENR uncertainty coverage (Uncert Coverage), which states how the entered ENR uncertainty (ENR Uncert) value is related to the population of possible ENR uncertainties. This is typically set to 2s which means that 95% of the time, the actual ENR is within the range of ENR +/- ENR Uncertainty.

—​Preamplifier Reflection Coefficients (User Calibration Only):

For this section, see also “Overview of Softkey Menus” on page 768 (Uncertainty > Preamp on page 775).

When a user calibration is performed, the Preamplifier Reflection Coefficient values may be imported to a Preamp table from *.snp or *.csv files, entered by editing a preamplifier table (Preamp Table), recalled as a previously saved preamp table (in a *.amp file), or set as a spot value to be applied across all frequencies.

As in the case of the DUT, In addition to entering the magnitude reflection coefficient values, the uncertainty calculation takes into account the distribution (G Distribution) and specified style (Spec Style) for the preamplifier reflection coefficient value.

—​User Calibration Noise Source Reflection Coefficient, ENR Uncertainties and ENR values (User Calibration Only):

These are identical to the noise source values entered for the measurement, but are entered prior to performing the user calibration (Run User Cal).

—​Controlling the Uncertainty Calculation and Display

For this section, see also “Overview of Softkey Menus” on page 768 (Uncertainty > Uncert Contributions on page 775).

When enabled, uncertainty bars are displayed on the data trace, indicating the uncertainty range for the current Noise Figure, Noise Factor, or Noise Temperature measurement. By default, the displayed uncertainty range is the measured data +/- the default coverage factor of two times the calculated standard deviation (2s), which is based on all included uncertainties. Optionally, the coverage factor may be changed to 1s, 2s or 3s. Also, as an aid in determining the cause of measurement uncertainty, any of the individual contributors (user calibration (User Cal Uncert), mismatch uncertainty (Mismatch Uncert), ENR uncertainty (ENR Uncert), or jitter uncertainty (Jitter Uncert) may be excluded from the uncertainty analysis.

Using ENR Tables

ENR tables are used to define the noise source(s) used in DUT measurements, receiver, and user calibration(s). Additionally, ENR tables are used along with DUT tables, preamplifier tables, and information collected during the measurement to compute the measurement uncertainty. Refer to Figure 29-24 on page 800.

—​Both gain and noise figure measurement accuracy will be enhanced by using a noise source with as low a reflection coefficient as possible for both the noise figure measurement and the user calibration.

—​It is not necessary to use the same noise source in the user calibration as will be used in the measurement. In some cases, it might be better to use a different noise source in the user calibration than will be used in the measurement. If this is done, it is important to select the ENR table for the calibration noise source prior to the calibration. And, then to select the ENR table for the measurement noise source prior to measuring the DUT.

See also, “Calibration Wizard” on page 803.

How to Create an ENR Table

To create an ENR table:

This procedure assumes you have previously set your frequency, resolution bandwidth, and number of points. Refer to “Example: Typical Noise Figure Measurement Procedure” on page 767.

For this procedure, refer to Figure 29-24 on page 800.

1.​Press Measure > Noise Source > ENR Mode Table (default)

2.​Then ENR Table Edit/Save/Recall 

3.​Then choose:

Edit ENR Table (to modify the currently loaded ENR table)

New ENR Table (to create a new table)

Save ENR Table (to save any changes to the currently loaded ENR table)

Recall ENR Table (to recall a previously saved table)

Back (to return to previous softkey menu)

4.​Then edit the table as necessary for your devices and measurements by entering in Header, Auto-populate, ENR, ENR uncertainty, On |G|, and Off |G|. Refer to Figure 29-24 on page 800.

Figure 29-24 ​Editing ENR Tables

About ENR (*.enr), Preamplifier (*.amp), and DUT (*.dut) Files

This section contains the following:

—​“ENR (*.enr) Files” on page 800

—​“Preamplifier (*.amp) Files” on page 801

—​“DUT (*.dut) Files” on page 801

ENR (*.enr) Files

—​ENR files are saved to, and recalled from, the NoiseFigure\ENR folder. If the folder does not already exist on a USB or SD card, it is created automatically before storing the file.

—​ENR files are stored as *.enr files. Existing ENR files that are loaded into the FieldFox can be overwritten. Your edited file will NOT be overwritten when firmware is updated.

—​To DELETE a *.enr file, use the Manage Files feature. Learn more in “Manage Files” on page 922.

Preamplifier (*.amp) Files

—​Preamplifier (*.amp) files are saved to, and recalled from, the NoiseFigure\Preamp folder. If the folder does not already exist on a USB or SD card, it is created automatically before storing the file.

—​Preamplifier files are stored as *.amp files. Existing *.amp files that are loaded into the FieldFox can be overwritten. Your edited file will NOT be overwritten when firmware is updated.

—​To DELETE a *.amp file, use the Manage Files feature. Learn more in “Manage Files” on page 922.

DUT (*.dut) Files

—​DUT (*.dut) files are saved to, and recalled from, the NoiseFigure\DUT folder. If the folder does not already exist on a USB or SD card, it is created automatically before storing the file.

—​DUT files are stored as *.dut files. Existing *.dut files that are loaded into the FieldFox can be overwritten. Your edited file will NOT be overwritten when firmware is updated.

—​To DELETE a *.dut file, use the Manage Files feature. Learn more in “Manage Files” on page 922.

Using Markers (Noise Figure)

In addition to the features shown here, noise figure has many of the same marker features as other FieldFox modes. See also “All about Markers” on page 819.

Figure 29-25 ​Marker Annotation

Figure 29-26 ​Marker Table Annotation

Calibration Wizard

The Noise Figure mode has two types of calibration wizard softkeys: Receiver Cal and User Cal.

To access the calibration wizards:

—​Press Cal then

—​Run Receiver Cal or

—​Run User Cal and then

—​follow the prompts

When to Calibrate

Noise Figure has two different calibrations that are important to run, depending on the type of measurement you are using:

—​Receiver calibrations (required for all measurements).

—​User calibrations (required, if the setup uses an external preamplifier).

Understanding Receiver and User Calibrations

This section contains the following:

—​“Receiver Calibration (Receiver Cal):”

—​“User Calibration (User Cal):”

—​“User Calibration (User Cal):”

—​“Optimizing Measurement Accuracy:”

 

Receiver Calibration (Receiver Cal):

The receiver calibration's purpose is to establish the true measurement bandwidth of the receiver when making noise measurements. This bandwidth information is used to calculate the gain of the DUT when there is no user calibration. But, if there is a user calibration, the gain calculation is independent of the receiver bandwidth from the receiver calibration. The receiver calibration has virtually no influence on the noise figure measurement, either with or without a user calibration. The receiver calibration only effects the gain measurement, and only when there is no user calibration.

As already stated, the receiver calibration measures the measurement bandwidth of the receiver. In most cases, this is set primarily by the digital processing of the receiver. The receiver calibration is needed, because it is influenced by the IF analog circuitry of the FieldFox. Additionally, the bandwidth is extremely stable, and does not vary significantly with time or temperature. So, once the receiver calibration has been successfully performed there is no need to repeat the receiver calibration.

Exceptions: Re-do the receiver calibration when the FieldFox receiver hardware is changed (factory repair) or in the rare case where a filter is added to the measurement system which has a narrower bandwidth than the receiver (i.e., the external bandwidth is less than the lowest resolution bandwidth (Res BW) setting of 300 kHz).

For example of Smart Noise Source Receiver Cal, refer to Figure 29-27 on page 805.

Figure 29-27 ​DUT – Measurement Setup – Receiver Calibration Screen –
ENR Mode: Smart (Auto)

User Calibration (User Cal):

In general, a user calibration should be performed whenever a preamplifier is used in the noise figure measurement. If there is no preamplifier, the user calibration is not necessary.

Although it will be interpolated if other frequencies are used, when a user calibration is performed, it should be made at the same frequencies as the measurement. The user calibration also needs to be performed with the same resolution bandwidth as is used in the measurement. The user calibration determines the noise contribution of the preamplifier, so that it can be removed from the measurement when computing the noise figure of the DUT. Also, the user calibration establishes the power gain of the receiver—preamplifier system so that the reported gain of the DUT will be the gain between input of the DUT (where the noise source is connected during the measurement) and the calibration plane (which is the point where the noise source is connected during the user calibration). Therefore, for the best gain accuracy, the noise source used in the calibration, should be connected at the same point as the DUT will be during the measurement.

For example of Smart Noise Source User Cal, refer to Figure 29-28 on page 807.

Figure 29-28 ​DUT – Measurement Setup – Run User Cal Screen –
ENR Mode: Smart (Auto)

Optimizing Measurement Accuracy:

—​Both gain and noise figure measurement accuracy will be enhanced by using a noise source with as low a reflection coefficient as possible for the user calibration.

—​When the DUT output noise power is relatively low (i.e., the gain plus noise figure of the DUT is less than 15 dB), measurement accuracy may also be improved by using a low loss isolator on the preamplifier input. Due to the output reflection coefficient of the DUT, reverse noise waves from the preamplifier, when present, will contribute a different amount of noise power during the measurement of the DUT than during the user calibration. And, this change in receiver noise power can impact the measurement accuracy.

—​It is not necessary to use the same noise source in the user calibration as will be used in the measurement. In some cases, it might be better to use a different noise source in the user calibration than will be used in the measurement. If this is done, it is important to set the ENR table for the calibration noise source prior to the calibration, and to set the measurement noise source prior to measuring the DUT.

—​Prior to starting a user calibration, it is a good practice to connect the preamplifier and noise source that will be used during the user calibration and perform a noise figure measurement of the preamplifier itself (without a user calibration). Use the same bandwidth and frequency settings that will be used in the user calibration. A successful noise figure measurement ensures that all of the connections (bias, control, and RF) have been made properly. The user calibration can be started immediately following the successful noise figure measurement of the preamplifier, with no change to the setup.

How to use Auto-Integration

This section provides an example procedure for measuring a device using noise figures’ auto integration feature. This example does not use an external preamp and was performed over a long time duration. Auto-integration is recommended to achieve greater accuracy and speed for all of your device measurements. Refer to Figure 29-30 on page 813 and Figure 29-30 on page 813.

For the following example, these settings were used on the FieldFox with a Keysight 346C K01 noise source that had the following characteristics:

About Auto-Integration

With auto integration, the FieldFox Noise Figure application chooses the optimum integration time for each of the noise power measurements needed (i.e., noise source on, noise source off, and receiver reference) to compute the device's noise figure with the selected amount of measurement jitter in the shortest possible time. The auto integration feature calculates the time required to satisfy the jitter goal from the relative power levels as they are measured. One significant advantage of auto integration is that it ensures that the best possible instrument speed is used in achieving the necessary jitter requirement.

If, on the other hand, it is determined that the time required to meet the jitter goal exceeds the maximum allowed time set by the user, auto integration will divide the maximum allowed time between the power measurements in order to produce the smallest possible jitter in the noise figure measurement. In these cases, since the jitter goal has not been reached, a jitter warning marker will appear on the data trace (unless disabled by the user), indicating that the jitter goal could not be achieved within the selected time constraint.

Due to the stability of the FieldFox receiver with its internal reference switch and the design of the auto integration feature, it is possible to achieve a stable, accurate, low jitter measurement results even under challenging measurement conditions, such as when measuring low noise power output devices at high frequencies with no pre-amplifier, by setting very long maximum integration times. For example, stable measurements with 0.1 dB jitter and no discernible drift have been demonstrated measuring a low gain, low noise amplifier at 50 GHz using maximum integration times of 5000 seconds per point, in spite of ambient temperature drift of several degrees Centigrade over the course of the measurement.

While auto integration can achieve very low jitter measurements, it is a good practice to consider the contribution of the jitter uncertainty to the total measurement uncertainty when selecting a jitter goal. If the measurement uncertainty from other contributors is known to be 0.5 dB, for example, it would make little sense to set a jitter goal of 0.1 dB. Setting a jitter goal of 0.3 dB in this case would only increase the RSS uncertainty to 0.58 dB, and would potentially speed up the measurement by a factor of 9 relative to a jitter goal of 0.1 dB. Auto integration makes it possible to select the jitter level with confidence, and is therefore a valuable tool in obtaining the required level of accuracy with the fastest possible measurement time.

Auto-Integration Procedure

No user cal was performed for this measurement, because no external preamp was used.

Set the equipment up in an area where it will remain undisturbed for the determined amount of measurement time. Refer to Figure 29-29 on page 812 and Figure 29-30 on page 813. See also, Figure 29-1 on page 758 and Figure 29-1 on page 758.

1.​Enter the Measurement type:

Select Measure > Noise Figure (default)

2.​Enter the Noise Source ENR information into a table:

Select Measure Setup

Then choose:

—​Noise Source then

—​ENR Mode Table (default)

—​ENR Table Edit/Save/Recall 

—​Edit ENR Table 

—​Enter the serial number and model number of your noise source. If desired, enter other information (e.g., Options, Cal Date, etcetera).

Enter a value using the numeric keypad, the arrows, or the rotary knob.

—​Done to finish table and return to previous menu.

3.​Save the ENR table:

If you are not familiar with saving and recalling files, refer to Chapter 33, “File Management.” and then to “Saving and Recalling Files” on page 914.

Choose:

—​Save ENR Table 

Enter the filename of your noise source.

Enter a value using the numeric keypad, the arrows, or the rotary knob.

—​Done to finish table and return to previous menu.

4.​Enter the noise figure measurement’s frequency, number of points, and span settings:

—​Freq/Dist > Center > 50 GHz

—​Sweep 3 > More > 401 points

—​BW 2 > Span > 0 Hz

5.​Define the noise figure’s integration settings:

Meas Setup 4 > Integration

Then choose

—​ Mode Auto (default)

—​Jitter Goal > 0.10 dB

—​Max. Time/Pt > 300s

—​Jitter Warning ON (default)

—​Back to return to previous menu

Press Uncertainty then

—​Uncert. Bars ON

6.​Leave the setup to run for desired time.

Figure 29-29 ​Example of Jitter Uncertainty (401 points)—with Uncertainty Bars

Figure 29-30 ​Example of Jitter Uncertainty (401 points)—without the Uncertainty Bars

Figure 29-31 shows an example of a noise figure visual Jitter Warning elements that can be enabled/disabled (i.e, blue circles around points where the jitter goal was exceeded).

—​Press to toggle Jitter Warning OFF ON (default = ON)

Figure 29-31 ​Example of Jitter Uncertainty—with Jitter Uncertainty Trace

Other Features Available

—​Limit Lines - For information on using Limit Lines, refer to “All about Limit Lines” on page 834.

—​Display Lines - For information on using Limit Lines, refer to the SA chapter’s section, “Display Line” on page 226.

—​Scale Settings – For information on using Autoscale, Autoscale All, and Scale settings, “All about Scale Settings” on page 852.

Troubleshooting

Some measurements can result in invalid results (NaNs). In these cases the FieldFox’s Noise Figure Option 356 displays the following:

—​Red X on the NaN point

—​Marker readout displays: “–––”

—​SCPI will return its NaN representation (i.e., 9.91E+37)

Figure 29-32 ​Example of an invalid measurement