Digital Modulation Quality

This test is performed only on ESGs that have Option 001, 002, 601, or 602.

Error Vector Magnitude (EVM) is the magnitude of the vectorial difference between the measured signal and an ideal reference signal in the I-Q plane.

Global Phase Error is the magnitude of the phase difference between the measured signal and an ideal reference signal in the I-Q plane.

Shift Error is the magnitude of the frequency difference between the measured signal and an ideal reference signal in the I-Q plane. This is expressed as a % error from the desired frequency shift.

Deviation Accuracy is the magnitude of the frequency difference between the measured signal and an ideal reference signal in the I-Q plane. This is expressed as frequency difference from the desired frequency shift, in Hz.

Rho is the figure of merit for waveform quality. Waveform quality is the basic measure of the performance of a CDMA transmitter. Rho, also called the power correlation coefficient, is the percentage of transmitter power that correlates to the ideal code. Rho indicates how well the signal's power distribution matches the ideal power distribution. A value of 1.00 indicates that all of the transmitted power correlates with the ideal transmission code.

The ESG is programmed to produce many different digital modulation formats. The ESG must have Option 402 to generate TDMA signals, and Option 401 for CDMA signals.

Required Test Equipment

This test supports two different test setups using either a PXA-series signal analyzer or an 89441A VSA spectrum analyzer. The PXA is the preferred solution.

  1. The preferred solution uses a PXA-series signal analyzer with the 89600 Vector Signal Analysis Application to measure EVM.

    Test Equipment

    Critical Specifications for This Test

    Recommended Models

    Alternate Models

    Spectrum Analyzer

    EVM Accuracy

    N9030B Opt 5xx1 and MPB2

    N9030A3 Opt 5xx1 and MPB2

    Vector Signal Analysis Application4

     

    89600 VSA with these options5:

    • 89601200C, basic vector signal analysis and hardware connectivity
    • 89601AYAC, digital demodulation analysis

    • 89601B7NC, 3G modulation analysis

    None

    1. Select any option of PXA spectrum analyzer (503, 508, 513, 526, 543, 544, 550) that has a maximum frequency greater than or equal to the maximum frequency of the unit under test.

    2. Firmware version A.11.04 or greater is required.

    3. PSA spectrum analyzers (E4440A, E4443A, E4445A, E4446A, E4447A, E4448A) are not allowed for this test.

    4. Required when using the N9030A/B.

    5. If the VSA application version installed is less than version 2019 (eg. 89601B), then these options are required: 200, 300, AYA.

  2. The alternate solution uses an 89441A vector spectrum analyzer (VSA) to measure EVM and Global Phase Error. When using the VSA, additional equipment is required for downconverting the signal above 2.65 GHz.

    For test frequencies above 2.65 GHz (the upper limit of the 89441A vector signal analyzer), the digitally modulated RF signal is down-converted with an external mixer. The resultant IF signal is routed to the VSA’s input.

    Test Equipment

    Critical Specifications for This Test

    Recommended Models

    Alternate Models

    Vector Signal Analyzer

    EVM Accuracy ≥ 1%

    89441A Opt AYA, AYH, AY9, B7A, and UFG or UTH

     

     

    20 GHz Mixer

    Frequency Range:
       RF: LO Ports: 200 MHZ - 20 GHz
       IF Port: 5 MHz - 6 GHz

    0955-2225

     

    0955-1017

    Local Oscillator

    Output Power: ≥ +16 dBM

    Frequency: 2 - 6 GHz

    E8267D Opt UNR or UNX or UNY

     

    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

    E8257D Opt UNR or UNX or UNY
    E8267D Opt UNR or UNX or UNY

    E8663B
    E8663D Opt [503 or 509] and Opt [UNX or UNY]

    N5181B/82B Opt [503 or 506] and Opt [UNX or UNY]
    N5171B/72B Opt 503 or 506

    N5182A Opt 1EA

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.
  • To expand all, click the Expand All button in the toolbar (webhelp only).

 

For test setup instructions using a PXA with the Vector Signal Analysis application, .

 
  • The PXA's firewall may need to be turned off.
  • The PXA must be logged in as Administrator.

 

  1. Install the 89600 Vector Signal Analysis Application on the same PC as TME.

  2. Ensure that the PC where TME is installed is connected to the LAN.

  3. Connect the PXA to the LAN.

    1. Get the Hostname or IP address of the PXA via the PXA's front panel information system (System > Show > System).

  4. Open the Keysight Connection Expert for the Keysight IO libraries and add the PXA to a LAN interface.

    1. If a LAN interface does not exist, add it.

    2. Add the PXA as an instrument on this interface using the Hostname or IP address from step 3a.

      Using the PXA's Hostname is the preferred method to avoid the possibility of crashing the software. The Hostname can be found in the PXA's System menu. An example of a Hostname is: K-N9030B-80323, where K = Keysight, N9030B = model, 80323 = last 5 digits of the serial number.

    3. Verify that the instrument has been successfully added to the interface.

    4. Ensure the equipment is connected as shown below:

 

For test setup using an 89441A vector signal analyzer, .

 

Test Setup for ESGs with < 3 GHz maximum frequency

 

Test setup without mixer for ESGs with ≥ 3 GHz maximum frequency

 

Test setup with mixer for ESGs with ≥ 3 GHz maximum frequency

 

In Case of Difficulty

When adding the PXA as LAN device, use the PXA's Hostname rather than the IP Address to avoid the possibility of crashing the software. The Hostname can be found in the PXA's System menu. An example of a Hostname is: K-N9030B-80323, where K = Keysight, N9030B = model, 80323 = last 5 digits of the serial number.

Troubleshooting tips if using VSA software 89601B version 21.0 or greater with Keysight IO libraries:

If the VSA software freezes during the Digital Modulation Quality test, manually verify that the you are able to “Rediscover Instruments” in the VSA software.

  1. Open the VSA software and select Utilities >Hardware > Configurations…

  2. Next, click on the Discover Instruments tab and click on the Rediscover Instruments button.

If this freezes, then you may need to set the Keysight VISA as the Preferred VISA. To set the Keysight VISA as the preferred VISA:

  1. Open the Keysight Connection Expert and go to Settings > Visa Conflict Manager > General VISA Settings.

  2. Ensure Keysight VISA is set as the preferred VISA implementation as shown in the image below: