IQ Capture/Streaming Measurement

Remote Spectrum Monitor™ MS27201A User Guide : IQ Capture/Streaming (Option 124/125 and 126/127) : IQ Capture/Streaming Measurement

IQ Capture/Streaming Measurement

Setting up an IQ capture/streaming measurement begins with setting up the basic measurement parameters:

• For spectrum monitor measurement setup, refer to Spectrum Monitor Measurements

• For optimal dynamic range, noise floor, and residual spurs, set the reference level to just above the peak signal level when performing 16-,10-, or 8-bit captures. Otherwise, high level spurs may be present.

• Turn on the preamp when the reference level is set to –40 dBm or lower. With signal levels at –40 dBm and preamp off, spurs may be –15 dB from the signal level with 8-bit captures.

Note	When capturing IQ data, the monitor stops sweeping to start the capture. When the span is wider than the capture bandwidth or the RBW is very narrow, the LO will have to be tuned to the center frequency before the capture starts.

Once your basic measurement is configured, access the IQ Capture menu from the main MEASURE menu.

IQ CAPTURE Menu

IQ CAPTURE Menu
	START/STOP CAPTURE Click this button to execute an IQ capture. When a capture is initiated, this button changes to STOP CAPTURE and can be clicked to stop the continuous captures. Note that the captured data will still be saved unless the CANCEL SAVE button below is clicked. Check the IQ status table at the bottom of the display. CANCEL SAVE This button appears after a capture has been initiated. Click this button to present a dialog that allows you the choice to cancel the IQ capture save and discard the captured data, or to continue with the capture and save the data. CAPTURE MODE Selects the IQ capture mode: • Single for a one-time capture to internal or external (USB) storage • Continuous for capture to internal or external (USB) storage. Automatically initiates a new capture once the previous capture is saved. • Streaming for continuous IQ data streaming out of the Ethernet, USB, or Data Out port (refer to IQ STREAMING Menu). CAPTURE BW IQ capture bandwidth is the frequency range of data to be collected for the duration of the IQ length. IQ capture bandwidth and sampling rate are linked and are selected from the same dialog. SAMPLE RATE Sets the IQ sampling rate of data to be collected for the duration of the IQ length. IQ sampling rate and capture bandwidth are linked and are selected from the same dialog. CAPTURE LENGTH Sets the duration of the waveform data capture. The maximum allowable capture period is dependent on available space on the selected storage device. TIMESTAMPS Toggles data collection timestamps on or off (see IQ Timestamps. IQ TRIGGER Opens the IQ TRIGGER Menu. SAMPLE FORMAT Sets the sampling bit format (32-bit floating decimal, 32-, 16-, 10-, or 8-bit integers). SAVE TO FILE Toggles automatic or manual file saving. When set to manual, click the SAVE CAPTURE button to save the next completed IQ capture. SAVE CAPTURE Saves captured data to a file when SAVE TO FILE is set to Manual. STORAGE DEVICE Sets the capture file save location. You can select Internal or one of the available USB ports when storage media is detected. FILE NAME PREFIX Sets the file name prefix of the capture file. Files are stored a “Captures” folder internally or to USB storage media. File naming contains the following: prefix_year-month-day-time-##_capturetime in ns_number in scientific notation.dgz or .dgzm

IQ STREAMING Menu

IQ STREAMING Menu
	START STREAM Click this button to start IQ data streaming from the selected output port. When streaming is initiated, this button changes to STOP STREAM and can be clicked to stop the stream. CAPTURE MODE Selects the IQ capture mode: • Single for a one-time capture to internal or external (USB) storage (refer to IQ CAPTURE Menu) • Continuous for capture to internal or external (USB) storage (refer to IQ CAPTURE Menu) • Streaming for continuous IQ data streaming out of the Ethernet, USB, or Data Out port. CAPTURE BW IQ capture bandwidth is the frequency range of data to be collected for the duration of the IQ length. IQ capture bandwidth and sampling rate are linked and are selected from the same dialog. SAMPLE RATE Sets the IQ sampling rate of data to be collected for the duration of the IQ length. IQ sampling rate and capture bandwidth are linked and are selected from the same dialog. TIMESTAMPS Toggles data collection timestamps on or off (see IQ Timestamps. SAMPLE FORMAT Sets the sampling bit format (32-bit floating decimal, 32-, 16-, 10-, or 8-bit integers). OUTPUT PORT Selects the output port to stream the IQ data. DATA OUTPUT FORMAT Selects the data out format of IQC or PCIe. IQC is the default format and is intended for use with the MA25424A IQ Data Converter (refer to Setting Up the Data Out Port and MA25424A. PCIe is intended for use with the MA25101A IQ Streaming PCIe kit (refer to the MA25101A user guide, 10580-00476). Note that changing to PCIe will require the application to reload and the monitor will be unresponsive during that time. COMBINE FILES IQ streams are captured in individual files that are combined once the stream stops. When this toggle is on, files will be concatenated by the instrument at the end of the stream into one file. This can be time consuming depending on the stream time. You can also save the streams as individual files and use the IQ Streaming Tools to combine the files.

Once the IQ Capture menu is accessed, the IQ CAPTURE table is displayed at the bottom of the screen.

IQ CAPTURE Table

The IQ CAPTURE table provides the following:

• STATUS: Current status of the IQ Capture. When a capture is in process, “Saving (xx%)” will be shown with an X to stop the current capture. When streaming is in process, the status will show “Streaming.”

• TRIGGER TYPE: Indicates the currently selected IQ trigger type.

• WAITING FOR TRIGGER: Indicates the capture has been started but is waiting for a trigger to initiate.

• MAX LENGTH: Indicates how long a capture can be with the current settings and available storage.

• AVAILABLE MEMORY: Indicates how much storage space is available on the target device (internal or external).

IQ TRIGGER Menu

Note	Trigger commands are shared between IQ capture and zero span, so these two functions are mutually exclusive.

IQ TRIGGER Menu
	TIMESTAMPS toggles data collection timestamps on or off (see IQ Timestamps. SOURCE The SOURCE button offers several triggering options depending on which view mode the instrument is set: • Free Run: When trigger is free run (or manual), a trigger is only initiated when the START CAPTURE button is clicked or when a remote command is sent. • Video: Sets the video trigger level. When RF energy is detected above that level, a capture is initiated. Note that the user must first click START CAPTURE before the monitor will begin looking for the trigger. LEVEL Used when the trigger source is set to Video. Sets the video trigger level threshold that initiates a capture. The level crossing applies to rising, falling, or both edges. Use the hysteresis setting below to adjust the sensitivity of the trigger level. DELAY Sets the IQ trigger delay when the trigger source is not set to Free Run. IQ trigger delay can be set to positive and negative values. A negative value includes data from the specified time before the trigger event. TIME INTERVAL Used to set a periodic trigger event. The monitor waits the user defined amount of time between trigger events. SLOPE Used when the trigger source is set to External or Video. Sets the trigger slope to rising, falling, or both. When slope is set to Both, the monitor triggers on both the rising and falling edges. Triggering on both rising and falling edges is not available in zero span. HYSTERESIS Hysteresis is used to address noisy trigger signals. The hysteresis setting adjusts the sensitivity of the trigger system (the difference between the firing level and the arming level as shown in Figure: Trigger Levels and Hysteresis). A low hysteresis value sets the arming and firing levels close to each other, meaning a small signal change will cause a trigger. A large hysteresis value sets the arming and firing levels far apart, meaning a large signal change will be required to cause a trigger. IQ CAPTURE Returns to the IQ CAPTURE Menu.

Trigger Levels and Hysteresis

IQ Streaming Tools

The IQ STREAMING menu allows you to concatenate an existing IQ metadata file (.dgzm) with a session of IQ data files (.dgz) that were streamed to a USB device after the stream operation is complete. The data files must all come from the same stream session.

1. Access the System menu (3-line icon in the upper left corner).

2. Click TOOLS to access the instrument tools menu, then select IQ STREAMING.

IQ Streaming

1. Click IQ METADATA FILE and then select the metadata file that you wish to concatenate with IQ data streams. All of the data stream files in the selected directory will be concatenated with the metadata file.

2. Click the OUTPUT DIRECTORY and select the destination for the concatenated files. If desired, select Delete Source Files.

3. Click START to begin the concatenation. The progress bar will indicate relative progress.

Note	Concatenating files can be time consuming depending on the streaming parameters and time. The process can be much faster if performed on a PC using the MS2720xA PC application. Refer to MS27201A PC Software for details on using this application.