keysight technologies speed pxi test solutions with...

Keysight TechnologiesSpeed PXI Test Solutions with Effective Software Selection

Application Note

Introduction

Software tool selection plays a very large role in the development of an RF test system. Indeed, the implementation of the software portion of the test solution may be the largest engineering decision in RF testing. This is particularly true when choosing PXI modular hardware for test. Selecting hardware options such as frequency range, analysis bandwidth, sensitivity, accuracy, dynamic range and performance are not the only factors necessary for success in testing. Engineers must design solutions to handle complex signals, address a variety of standards and optimize productivity.

Whether the emphasis is on rapid deployment of complex RF tests or the creation of maximum throughput solutions, it is likely that no single software package will meet the demands of all types of testing. Instead, a layered approach that takes advantage of both off-the-shelf solutions and the measurements built into the modular hardware drivers will be more efficient and reliable, and pose the least risk to the development schedule and budget.

This application note will help you match your major RF test priorities with the most efficient software tools available, from instrument drivers to standard-specific measurement applications, to advanced modulation analysis and resource optimization tools.

Table of ContentsIntroduction ....................................................................................................................................... 02

Balancing speed of test system development against speed of test execution ........................ 03

Limitations of a single software tool approach .............................................................................. 04

Key characteristics of RF test solutions .................................................................................... 04

Benefits of a multiple software tool approach .............................................................................. 04

Choosing a test execution and software baseline solution ......................................................... 05

Architectural considerations beyond the baseline solution ......................................................... 06

Choosing a text executive for the multiple software approach .............................................. 06

Running in-process and out-of-process applications ............................................................. 06

Benefits of using a resource manager ...................................................................................... 08

Complex test system scenario ........................................................................................................ 09

Conclusion ......................................................................................................................................... 10

03 | Keysight | Speed PXI Test Solutions with Effective Software Selection - Application Note

Balancing Speed of Test Development Against Speed of Test Execution

RF test engineers are likely to have multiple — often competing — priorities in any given test situation. However the balance of these priorities generally tilts in one of two directions, as summarized below in Figure 1. Though they may not fall at the extremes of this continuum, most RF test systems place a higher priority on either efficient development of complex tests for systems and subsystems or achieving the highest throughput for simpler testing of components such as power amplifiers and front end modules.

Efficient-Test Development

Fast TestThroughput

Efficient test development

When testing products and subsystems the emphasis is often on the most efficient path to a complete test solution and reliable results. Signals and standards are complex, and there is great benefit in using measurement applications that perform complete, standards-compliant tests. Rapid development and deployment of test solutions, with confidence in the validity of results, is more important than optimizing test throughput.

Examples of these tests include modulation quality, protocol verification, and evaluation of the functionality of multi-channel operation, beamforming and multi-user schemes. These tests are frequently performed on new and emerging standards.

Fast test throughput

Testing of components such as simple power amplifiers and front end modules is less extensive than that of complete products and subsystems, and must be performed much more rapidly to be economical. These simpler tests must be optimized for speed to a great degree, requiring software tools that enable the most efficient use of RF test hardware resources.

Examples of these tests include channel power, adjacent channel power, and power spectrum measures such as spurious or harmonic distortion.

For this testing, incremental improvements in test time are worth considerable investment in test hardware and software optimization.

Figure 1. Trade-offs to consider when developing a test system.


Limitations of a Single Software Tool Approach

It is conceptually simple to implement a single tool approach where one program calls a succession of measurement modules and hardware drivers. However this approach may be complex in its execution and limit measurement throughput, for a number of reasons:

– Keeping up with complex and rapidly evolving standards. Modern communication standards are comprised of detailed, multi-layered specifications, and are frequently revised. Standard-specific measurement applications rather than individual mea-surement modules can provide direct, verified measurements which are conveniently updated as standards evolve.

– Effective use of hardware resources to increase measurement throughput. A single program accessing hardware drivers makes efficient use of routines built into hardware. However, in many situations, the test plan will also require some mea-surements executed with different software tools and/or at a higher level. Efficiently coordinating access to the RF hardware in this situation may be difficult for the test engineer. Managing hardware resources to optimize both measurement and task switching speed and avoid resource contention or requestor conflicts is a job best left to designers with deep knowledge of the hardware/firmware combination.

Key characteristics of RF test solutions In most cases, RF test solution development starts with what will be called a baseline solution in this application note. The main baseline solution characteristics for the two major test priorities are compared and contrasted below.

For efficient test development – Turnkey test suites for most common

communication signal formats. – Standards-based spectrum, waveform

and modulation quality testing. – Built-in test limits and pass/fail

indicators. – Live, instrument-like displays available

as needed for monitoring and/or troubleshooting.

– SCPI command compatibility to allow reuse of tests developed with benchtop apps.

For fast test throughput – Wide choice of waveform and spec-

trum acquisition modes. – Rich API to provide necessary hooks

for optimizing measurement speed. – Supported in key software develop-

ment environments—Visual Studio, LabVIEW, MATLAB, etc.

– Advanced driver features such as list mode, hardware-based FFT, stepped spectrum, etc.

– Live soft front panels for real-time monitoring and/or troubleshooting.

Benefits of a Multiple Software Tool Approach

Accommodating the complexity of many modern DUTs and/or the requirements for test throughput will require multiple software tools with different strengths. A test architecture beginning with a baseline solution and incorporating additional software applications provides a number of practical benefits. Below is an example for RF signal analysis test systems:

– Direct access to sophisticated, standard-specific test suites and a convenient way of keeping them updated.

– Deployment of advanced software to handle emerging standards, non-standard signals, and unusual measurements.

– Consistent results in the manufacturing phase with benchtop solutions proven in R&D and system verification.

– Hardware/software resource management tools to optimize measurement through-put from multiple RF signal analyzers.

– Instrument-like displays and virtual front panel controls for monitoring and troubleshooting


Choosing a Test Executive and Software Baseline Solution

It’s logical to consider the test executive first, since it’s the program that controls the testing itself. When the measurements are handled by a single program, this allows flexibility in the choice of test executive. But when testing complex DUTs, it is often optimal to use multiple software tools – and software compatibility considerations will direct and constrain the choice of test executive.

Using the RF signal analysis test system as an example, below are typical choices for baseline solutions which incorporate multiple software tools.

For efficient development

M90XA X-Series Measurement Applications for Modular InstrumentsThe X-Series Measurement Applications are Keysight’s family of PC-hosted, RF test applications. They are derived from their benchtop analyzer counterparts and use the same industry-proven measure-ment science, which insures excellent measurement continuity across platforms. They can be deployed with little or no software expertise, and use the same SCPI command sets as the benchtop versions, allowing maximum leverage of legacy test systems.

For fast test throughput

Driver-Based ProgrammingThis approach allows users to trade off turnkey simplicity for very high flexibility.Raw spectrum and/or waveform data is acquired via fast, efficient programmatic calls to the PXI hardware drivers, with the results post-processed in the user’s test routines. The driver’s API exposes a broad range of key acquisition parameters, allowing them to be freely adjusted for most efficient operation. Advanced driver-level functions provide even more opportunity for optimization.


Architectural Considerations Beyond the Baseline Solution

For some users, choosing a baseline solution provides sufficient functionality to address test needs. But for most, the baseline choice is just a starting point. A combination of the baseline plus additional software is required.

Along with choosing a baseline solution, there are other architectural considerations, in-cluding the choice of a test executive (Keysight VEE, TestStand, LabView, MATLAB, etc.), 32- vs. 64-bit computing platform, etc. For the user whose solution consists entirely of the baseline solution, these decisions are fairly straightforward, and can be made simply on the basis of available computing hardware and/or other user preferences. However, when solutions are built from a combination of software packages, these decisions have far-reaching implications, that must be carefully considered upfront.

Keysight’s portfolio of signal analysis products is designed to allow exactly this sort of solution building. It is important to understand that combining these elements into a single solution does require attention to architectural details, and drives some very important design choices.

Choosing a text executive for the multiple software approachWhen choosing a test executive, consider questions related to the need to coordinate and communicate among multiple applications:

– Does it support Resource Manager? Most combined application solutions will need a Resource Manager (see sidebar) in order to efficiently share the RF hardware among the different software applications. Because the Resource Manager’s API is .NET-based, users will want to understand the level of .NET support provided by the test executive they are considering.

– Does it support 64-bit applications? While many single application solutions will run satisfactorily on 32-bit PCs, most combined application solutions will require 64-bit PCs, as very large memory footprints are likely to exceed the 3 GB limit for 32-bit applications.

Running applications in-process and out-of-processThe architectural choice of running applications in-process or out-of-process offers a tradeoff between setup complexity and system performance. This is an important decision to consider upfront, because converting test architecture from one style to the other can involve a significant amount of rework. The table below highlights the key differences.

Out-of-Process Applications In-Process Applications

Advantages – Generally less complex to implement – Can run on separate/remote computers – Can mix 32- and 64-bit applications

Advantages – Able to use Resource Manager for efficient

hardware sharing – Efficient intra-process communications

Disadvantages – Lower throughput due to inefficient

hardware sharing and slow intra-process communications

– Must launch multiple applications at start-up

Disadvantages – Some applications do not support

in-process operation – May perform poorly in 32-bit environments,

due to large memory footprint

Using Keysight’s 89600 VSA Software as a Baseline Solution

The 89600 VSA software (version 18.5) was enhanced to perform efficiently in high-speed manu-facturing environments and can serve as a baseline solution or powerful add-on. Techniques and considerations for incorporating the 89600 VSA software into these solutions are provided later in this note.


In-Process versus Out-of-Process OperationWhen two applications run simultaneously in the Windows environment, they can be said to be running either in-process or out-of-process with respect to each other. The PXI test system developer who is running a test executive with other software applications will generally have a choice of running those applications in one of the two process modes. Because this choice can significantly affect performance and functionality, it’s important to have a basic understanding of the differences.

Out-of-process applications run as separate Windows processes. They are launched separately and run in separate memory spaces. In Windows Task Manager they appear as separate entries. These applications can run on the same computer or, when sup-ported, on entirely different computers. They communicate with each other through their respective external interfaces, which may require operating system resources to accomplish. Those communications are not necessarily efficient or deterministic. The image below illustrates the out-of-process operation with a test executive controlling the M90XA X-Series measurement application.

In-process applications run as a single Windows process in a single memory space, and must therefore run on the same computer. The applications communicate very efficiently because they exchange data residing in their common memory space. However, the in-process mode must be built into the application being used. In-pro-cess operations also tend to require substantial memory, potentially exceeding the 3 GB limit of 32-bit Windows processes. The image below illustrates the in-process approach.

– The test executive and M90XA application are two separate software processes. They are launched and run independently, and communicate via SCPI commands over a TCP/IP socket connection.

– The resource manager and IVI drivers ‘belong’ to the M90XA application and their API’s are not available to other applications.

– The test executive, user code, resource manager and IVI-drivers all run as a single Windows process.

– Resource manager and IVI driver API’s are fully available to other applications in the same process.

SW process #1

SCPI

Windows PC

Test Exec.(e.g. LabView)

SW process #2

M90XA Apps

IVI-Driver PXIHardware

Resource Mgr.

SW process #1

Windows PC

User Code

.NET APITest Exec.

(e.g. LabView)

IVI-Driver PXIHardware

Resource Mgr.


Benefits of Using a Resource Manager

How do you manage access to PXI measurement hardware when more than one appli-cation is depending on it for data? How do you avoid connectivity conflicts? How do you insure that the different applications aren’t overwriting each other’s hardware settings? And how do you manage all of these concerns at production speeds?

A resource manager, such as Keysight’s M9000 resource manager is an in-process service supplied with Keysight’s X-Series Measurement Applications that coordinates access to the measurement hardware. Like a fast, efficient switch, it gates the flow of commands and raw measurement data between multiple software apps and a single shared resource.

Internally, Keysight’s resource manager implements a check-out and check-in mech-anism. Applications connect to the resource manager and access is granted when the resource becomes available, asynchronously on a cooperative, first-come, first-served basis. With the resource manager, applications can be written so that hardware is checked back in as soon as acquisition is complete. This is in contrast to traditional architectures, which typically don’t release the hardware until both acquisition and measurement processing are finished. With the resource manager, the hardware can instead be switched quickly to another application while the processing of the previous measurement is still underway, implementing true multi-threaded measurements.

Figure 2. A resource manager can make more efficient use of hardware assets.

User Env. (.EXE or LV)

.NET SCPI .NET or SCPI

Hardware

IVI-DriverResource Mgr.

89600VSA

(in-proc.)

M90XAApps

(in-proc.)

UserCode

(in-proc.)

Other Benefits of Using a Resource ManagerA Resource Manager keeps track of which application used the hardware last. When an application learns that no other application has used the hardware since its last access, it is free to bypass its hardware setup steps, further speeding up the measurement. The Keysight M9000 Resource Manager, built into the X-Series Measurement Applications and 89600 VSA Software, can also be accessed from user-written code via its .NET or C API.

The Resource Manager also enables multi-threaded measurements.

Without Resource Manager: single-threaded, synchronous

Meas1, Meas2

HW utilization:less efficient

HW utilization:more efficient

Meas2

Meas1

With Resource Manager: multi-threaded, asynchronous

acquireprocess


Complex Test System Scenario

Company: A designer/manufacturer of components and subsystems for wireless

Testing task: Rapid, flexible validation and optimization of new designs

Test requirements: – Spectrum and network measurements, plus digital modulation and time domain – Verify signal processing, switching, and digital modulation quality and functionality – Determine required tests and test limits to ensure quality and improve yield and

throughput – Troubleshoot any problems found

Test challenges: – Pull together measurements from a variety of software tools and measurement

hardware. – Rapid creation of test program, to keep up with new designs from R&D – Switch between automated tests and front panel operation for troubleshooting

problems

Test solution: – Single test executive controls multiple measurement software elements, to handle

the full range of tests. – Resource manager ensures fast and efficient sharing of test hardware via “in

process” operation – Architecture easily handles combination of measurement applications and user

code – Soft front panel can be invoked for troubleshooting, without hardware or connection

changes – Rapid creation of test program, making maximum use of available software tools and

hardware

Figure 3: Elements of a multiple software tool architecture.

SW developmentenvironments

MeasurementApplication

Software

Drivers

Development Environments

Measurement Applications89600 VSA

IVI-C / IVI-COM / IVI-NET1 Drivers

SoftFront Panel

LabVIEW MATLAB WN CVIVEE Ms

ExcelCommand

ExpertVisualStudio

LabVIEWDriver

MATLABDriver

IO Libraries Suite - interface to HW

Keysight Kernel Driver

X-Apps SystemVue

OtherSignal Studio

Instrumentdrivers

I/O libraries: VISA

Kernel driver


Conclusion

The demands of testing modern wireless systems and components are complex and multi-dimensional. Whether the goal is the most efficient path to a test solution, or tuning a system for the highest throughput, the test software and architecture choices are critical. These choices have very high leverage in terms of solution efficiency, and often have large cost and time implications if architectural changes are necessary.Keysight provides both modular hardware solutions and powerful software tools to meet a wide range of RF signal test needs. Keysight solutions are also compatible with third-party software, to offer the best compatibility with the range of architectural choices that RF test engineers will make.


This information is subject to change without notice.© Keysight Technologies, 2017Published in USA, December 1, 20175992-0800ENwww.keysight.com

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