Residual FM

Residual FM measures the unwanted frequency variation in the CW signal of the DUT.

This test supports two equipment setups:

Phase Noise System Test Procedure

A Phase Noise System is used to measure the Residual FM by taking a single sideband phase noise measurement of the DUT. The area under the phase noise plot between 300 Hz and 3 kHz is the Residual FM.

Required Test Equipment

Test Equipment

Critical Specifications for This Test

Recommended Models

Alternate Models

Phase Noise System

 

N5511A Options 540, CH21

  1. CH2 is not required but recommended for future capability.

E5505A
E5501A/B
E5502A/B
E5503A/B
E5504A/B

Reference Source1

 

E8257D2 Opt UNR or UNX or UNY

8664A Opt 004,
8665A Opt 004,
8665B Opt 004,
E8247C Opt UNR,
E8257C Opt UNR,
E8267C Opt UNR,
E8267D Opt UNR , or UNX, or UNY
E8663B
E8663D Opt UNX or UNY

Cable

 

8120-4921 APC 3.5 (m) to (m)

 

Cable

 

11500C Type-N (m) to (m)

 

Cable

 

8120-1840 BNC (m) to (m)
10503A BNC (m) to (m)

 

Adapter

 

E9625A BNC Tee (m) (f) (f)

 

Adapter

 

11901D 2.4 mm (f) to APC 3.5 (m)

 

Adapter

 

1250-1749 APC 3.5 (f) to (f)

 
  1. The reference source must have a frequency high enough based on the test points being tested. Note that test points are not the same as the frequency range of the DUT. Therefore, some alternative models may not be sufficient for all DUTs. The E8257D recommended model is sufficient for all DUT configurations.
  2. Option 1EA or 1EU is not required providing that the LO in use has leveled output power at each test frequency.

Connections and Setup Procedures

  • All test equipment requires a 30 minute warmup period to ensure accurate performance.

  • In the following test setup, cables are designated as solid lines and direct connections are designated as dashed lines.

 

There are two sets of procedures depending on the model of the phase noise test system used:

Select from the links below according to the phase noise test system being used.

N5511A PNTS, .

 

 

  1. Connect all test equipment as shown.

  2. Connect GPIB cables to all GPIB-controlled test equipment.

  3. Preset all test equipment and the DUT.

  4. Change the following parameters in the N5510A PNTS user interface:

    1. Select the View pull-down menu.

    2. Select Display Preferences and un-check the Spurs box.

    3. Select OK to close Display Preferences.

    4. Select the System pull-down menu and select Server Hardware Connections.

    5. Select or ensure the following:

      1. Test Set has Keysight M9550A selected.

      2. FFT Analyzer has Keysight M9551A selected.

    6. Select Close to close Server Hardware Connections.

    7. Select the Define pull-down menu, select Measurement, and select the following settings:
       

Parameter

Setting

 

 

Type and Range Tab

Measurement Type

Absolute phase noise (using a phase locked loop)

Measurement Method

Fast

Start Offset Resolution Expansion

10

Channel Setup

Single

Start Offset Frequency

290 Hz (must be < 300 Hz)

Stop Offset Frequency

3.1 kHz (must be > 3 kHz)

FFT Analyzer Minimum Number of Trace Averages

4

RBW %

0.24 (8192 point FFT)

FFT Overlap %

75

FFT Window Type

Flat Top

 

 

Sources Tab

Carrier Source Frequency

Obtain tested frequencies from the TME data entry form.

Carrier Source Power

+10 dBm

Detector Input Frequency

Same as Carrier Source Frequency

Reference Source Power

+15 dBm to 3 GHz

+10 dBm > 3 GHz

VCO Nominal Tune Constant

0.1 ppm x carrier source frequency

VCO Tune Range

1 Volt

VCO Input Resistance

50 Ω

Center Voltage

0 V

 

 

Cal Tab

Phase Detector Constant

Derive detector constant from measured beat note

VCO Tune Constant

Measure VCO Tune Constant

Verify calculated phase lock loop suppression

Blank

 

 

Block Diagram Tab

Carrier Source

Manual

Reference Source

Model number of reference source

Phase Detector

Automatic Detector Selection

Test Set Tune Voltage Output

Front Panel

Test Set Tune Voltage Destination

Reference Source

VCO Tune Mode

DCFM

 

 

Test Set Tab

LNA Low Pass Filter

Internal — Selected

Auto — Checked

LNA Gain

Auto Gain — Selected

Minimum Auto Gain — 14 dB

PLL Integrator Attenuation

0 dB

Use Channel #2

Unchecked

 

 

Graph Tab

Title

User specified

Graph Type

Spectral Density of Phase Fluctuations (dB/Hz)

X Scale minimum

Same as start offset frequency

X Scale maximum

Same as stop offset frequency

Y Scale maximum

0 dB/Hz

Y Scale minimum

–170 dB/Hz

Normalize Trace Data

1 Hz bandwidth

Making the Measurement

  1. Set the DUT frequency to the first carrier frequency in the TME data entry form.

  2. Set the DUT RF Output to On.

  3. Perform a phase noise measurement.

  4. Click on the Analyze pull-down menu and select Trace Integration.

  5. Use the following settings:

    Parameter

    Actual Offset

    Data Type

    Snu(f) (Spectral density of frequency fluctuations)

    CCIT Weighting

    checked

    Start Offset

    300 Hz

    Stop Offset

    3 kHz

    Data to Integrate

    Noise

     

  6. Click on the Integrate button and read the Residual FM value from under the Value of definite integral.

  7. Enter the Residual FM value into the TME user interface for Residual FM and compare it to the specification.

  8. Repeat steps 1 through 8 for each frequency test point through 3 GHz.

  9. For test points > 3 GHz, a connection change is required.

    1. Connect the UUT RF Output to the 1.2 GHz to 40 GHz Sig/RF Input of the M9550A Phase Detector module in the N5511A PNTS.

    2. Connect the Reference Source Output to the 1.2 GHz to 40 GHz Ref/LO Input of the M9550A Phase Detector module in the N5511A PNTS.

    3. Repeat steps 1 through 8 for each frequency test point > 3 GHz.

  10. If testing an E4438C without Option UNJ:

    1. Turn off Phase Noise Mode 1.
    2. Turn on Phase Noise Mode 2.

    3. Repeat steps 1 through 8 for each frequency test point in the table below.

      Frequency (MHz)

      100

      250.1

      500

      1000

      2000

      3000

      4000

      6000

 

For E550xA legacy phase noise test systems, .

Setup with a carrier frequency of 500 MHz

  1. Connect all test equipment as shown.

  2. Connect GPIB cables to all GPIB-controlled test equipment.

  3. Preset all test equipment and the signal generator.

  4. Connect the E8257D RF output to the N5500A reference input.

  5. Connect the N5500A Tune Voltage Output to the E8257D Ext 1 input.

 

Table 1: E4438C and E4428C Carrier Test Frequencies and Power

Frequency (MHz)

DUT Power (dBm)

Reference Power (dBm)

100

14

12

250.1

14

12

500

14

12

1000

14

12

2000

10

5

3000

10

5

4000

10

5

6000

10

5

 

  1. In the Keysight N5500A Phase Noise System user interface, change the following parameters:

    1. Select the View pull down menu.

    2. Select Display Preferences and clear the Spurs box.

    3. Select OK to close Display Preferences.

    4. From the System pull down menu, select Server Hardware Connections.

    5. Ensure the correct FFT Analyzer is selected, either the 11 PCI20428W-1 or the 89410A.

    6. Connect the signal generator's RF OUTPUT to the N5500A signal input.

    7. From the Define pull down menu, select Measurement, and set the following:

Parameter

Setting

 

 

Type and Range Tab

Measurement Type

Absolute phase noise using phase lock loop

Start Offset Frequency

300 Hz

Stop Offset Frequency

3 kHz

FFT Averages

4

FFT Quality

Normal

Swept Quality

Normal

 

 

Sources Tab

Carrier Source Connected

Test Set

Carrier Source Frequency

See Table 1.

Carrier Source Power

See Table 1.

Detector Input Frequency

See Table 1.

Reference Source Power

See Table 1.

Nominal Tune Constant

1,000 Hz/Volt

Tune Range

5 volts for PSG

 Input Resistance

50 ohms for PSG (600 ohms for 8665B)

 

 

Cal Tab

Measure Phase Detector Constant

Checkmark

Measure VCO Tune Constant

Checkmark

Verify calculated phase lock loop suppression

Blank

Phase Lock Loop Suppression

Use theoretical value.

 

 

Block Diagram Tab

Carrier Source

Manual

Down Converter

None

Reference Source

E8257D (or as configured)

Phase Detector Mode

Automatic Detector Selection

Test Set Tune Voltage Destination

Reference Source

VCO Tune Mode

DCFM

 

 

Test Set Tab

Input Attenuation

0 dB

LNA Low Pass Filter

Auto

LNA Gain

Auto Gain

PLL Integrator Attenuation

0 dB

 

 

Downconverter Tab

Input Attenuation

Auto

IF Gain

Auto

Microwave/Millimeter Band

Microwave (0 – 26.5 GHz)

Reference Chain Reference

10 MHz

External Tune Enable

Checkmark

 

 

Graph Tab

Title

User specific

Graph Type

Spectral Density of Phase Fluctuations dB/Hz

X Scale minimum

300 Hz

X Scale maximum

3 kHz

Y Scale maximum

0

Y Scale minimum

–170

Normalize Trace Data

1 Hz bandwidth

Making the Measurement

  1. Set the signal generator frequency to the first carrier frequency and power in Table 1.

  2. For the E4438C non-Option UNJ, set the Synthesizer Mode to the proper value for the test frequency being tested.

    1. Frequency --> Optimize Φ Noise --> Mode 1 Optimize < 10 kHz Offset or Mode 2 Optimize > 10 kHz Offset

  3. Set the RF Output to on.

  4. Perform a phase noise measurement.

  5. Place markers on the Sphi (f) plot at 300 Hz and 3 kHz. Enter these values into TME.

  6. Left mouse click on the Analyze pull down menu and select Trace Integration.

 

Setup

Parameter

Setting

Data Type

Snu(f) (Spectral Density of Frequency Fluctuations)

Start Offset

300 Hz

Stop Offset

3 kHz

CCITT Weighting

Checkmarked

Data to Integrate

 

Noise

Checkmarked

 

  1. Click on the Integrate field and read the Residual FM value from under the Value of definite integral.

  2. Enter the Residual FM value into the TME user interface for Residual FM and compare it to the specification.

  3. Continue to the next carrier setup and repeat the measurement. If the next carrier is > 1 GHz, then connect the reference generator signal to the 1.2 GHz to 26.5 GHz N5500A Reference input.

  4. If testing a non-Option UNJ, then turn off the DUT Phase Noise Mode 1 and turn on Phase Noise Mode 2 and repeat steps 2 through 8 for each frequency in Table 1.

Entering the Data

The measurement data must be entered into the following form displayed on-screen when the test is run.

Shown below is the input form for the E4438C without Option UNJ. (The E4428C and E4438C with Option UNJ form has fewer test points and has N/A for the Synthesizer Mode.)

Frequency and Synthesizer Mode columns:

Residual FM column

The measured Residual FM value from the phase noise test set system.

Measuring Receiver Test Procedure

The 8902A measuring receiver measures the deviation (in Hz) of the residual FM. Because the display resolution of the measuring receiver is not high enough to discern low deviations (i.e., low residual FM), the FM deviation signal from the 8902A is passed along to an audio analyzer, where the AC level is measured.

The 8902A FM deviation output level is 1 mV per Hz of deviation.

The measuring receiver has an internal LO to down-convert the RF Input to its 1.5 MHz IF. Unfortunately, this internal LO does not have optimum phase noise for a residual FM measurement. For this test, the carrier signal is externally down-converted to 1.5 MHz and injected into the I.F. input of the measuring receiver.

Test Equipment

Critical Specifications for This Test

Recommended Models

Alternate Models

Measuring Receiver

FM Demodulated Residual FM ≤ 0.1%

8902A

 

Audio Analyzer

AC Level Accuracy:
± 3% 0.3 mV to 50 mV

Display Resolution: 0.01 mV

8903B Opt 011 or 051

 

Local Oscillator

Not used for ESGs with frequency range < 3 GHz.

Frequency Range: 100 to 6000 MHz

Residual FM

E8257D Opt UNR or UNX or UNY

(Option 1EA or 1EU is not required, providing the LO in use has leveled output power at each test frequency.)

E4428C Opt 503 or 506,
E4438C Opt 502, 503, 504, or 506, and UNJ,
E8241A Opt UNJ,
E8244A Opt UNJ,
E8251A Opt UNJ,
E8254A Opt UNJ,
E8247C Opt UNR,
E8257C Opt UNR,
E8267C Opt UNR,
E8267D Opt UNR or UNX or UNY
E8663B
E8663D Opt 503 or 509
N5181B/82B Opt 503 or 506
N5171B/72B Opt 503 or 506
N5182A Opt 1EA

Mixer

RF/LO Freq. Range: 1 to 2800 MHz

IF Frequency Range: 1.5 MHz

0955-2225

M/A COM MDC-174

M/A COM MDC-1641

  1. ESGs with Option 504 or 506 will also require the M/A COM MDC-164 mixer.

Connections and Setup Procedures
  • All test equipment requires a 30 minute warmup period to ensure accurate performance.
  • In the following test setup, cables are designated as solid lines and direct connections are designated as dashed lines.
  1. Connect all test equipment as shown.
  2. Connect GPIB cables to all GPIB-controlled test equipment.
  3. While performing this test, follow all instructions on the controller display.

 

Measuring Receiver Calibration Setup


 

Residual FM Test Setup

In Case Of Difficulty

The actual Residual FM is the sum of the Residual FM in all components in the measurement system. Ensure that the local oscillator and measuring receiver are not contributing excessive Residual FM to the measurement. For example, make sure they are meeting their specifications.