N6820VRXE Virtual Receiver Feature

Introduction

Keysight’s N6820VRXE Virtual Receiver (VRx) feature is a software platform that includes drivers, libraries, tools, and applications to process RF spectral and time-series data streams that originate in files. This feature can operate standalone or interact with products like the Surveyor 4D software. The VRx feature acts like a receiver “proxy” and provides functions and capabilities found in hardware receivers such as creating frequency domain data (spectrum) with arbitrary averaging, resolution bandwidth, overlap, and windowing. It also performs digital down conversion (DDC) for processing narrowband IQ data streams with arbitrary sampling rates and center frequency.

VRx places endpoints into the Surveyor 4D code to process spectral data and time domain data (from DDCs) using spectral search and signal classification tools to analyze and provide a report of the contents of very large IQ time-series recordings. When used together, Surveyor 4D becomes a softwarebased spectrum search and analytic tool eliminating the need for additional hardware.

VRx player

The VRX player enables Surveyor 4D software to connect to IQ wideband recordings and “play” those files as though the data were coming from a live receiver.

The player includes a file manager and preview display that loads the selected file from a list for manual viewing. The file preview includes both spectrum and spectrogram views, markers, a slide bar, and color options for use when viewing.

VRX also facilitates playback of wideband recorded data streams into the Surveyor 4D software. With choices for spectrum search settings, VRx can define overlap processing of the spectral data, resolution bandwidth, average type, and number of averages, like the Search Setup menu in Surveyor 4D. The VRx resampler will convert the recording during playback into a sample rate compatible with USD spectral shape detectors or search settings that rely on a specific frequency bin size. The screenshot below shows the VRx user interface (UI) with a file preview on the left and file playback, into Surveyor 4D, on the right.

Surveyor 4D with VRx endpoints

The VRx player connects to one or more instances of Surveyor 4D using an endpoint defined by the Surveyor 4D VRx configuration file as (highlighted text is an example):

platformCfg: endpointAddr=A00D-C0EE-C001-USD1 library=vrxSearchDrv.dll

This string replaces the hardware definition that would normally appear in the configuration file. To run multiple instances connected to the VRx player, each instance will need a unique endpoint address. The VRx player discovers available connections and binds to them when you select the “Connect” button. An example of the benefits of the capability is when you are searching for two very different signal types, requiring different resolutions to classify them properly, or using different instances to search various frequency ranges within the recording bandwidth. 

Surveyor 4D combined with VRX starts like other instances of Surveyor with a few exceptions: 

   • No Search Setup menu. VRx will define the search setup.

   • No IQ Snapshot controls (camera icon) since the wideband IQ data is already present.

   • No ModRec window. Narrowband confirmers in USD perform Modulation recognition.