RF Testing using Signal Modelling (Part 1)

This part details a study & demonstration of a compile-time approach to the implementation of IEEE 1641 (in contrast to previous studies, which have adopted a run-time approach). Greater depth is added to the methods for signal description of test resources, using Rohde & Schwarz's Vector Signal Generator, Spectrum Analyser & Vector Network Analyser.

The tests implemented are gain and 1 dB compression point, for a mobile communications device. These tests are defined using the Standard's Test Signal Framework; use is made of the Standard's Signal Modelling Language to validate the behaviour of the test signals; IEEE ATML Test Station is used to describe the mapping onto the test resources; an XML document is written to describe the mapping to the test resource IVI drivers; and, an IEEE 1641 defined COM interface is used access these documents. This process effectively compiling the IEEE 1641 test program into an IVI test program, native to the test platform.

Tests

Gain

The gain of an amplifier is the ratio of output power against input power and is usually measured in dB (decibels). This basic measurement has already been implemented in a previous phase of IEEE 1641 study and, since it is a precursor to the 1 dB Compression Point measurement, the opportunity will be taken to make a comparison of the two approaches.

1 dB Compression Point

1 dB compression point is a measure of the linearity of a device. Though the concept may seem simple, its implementation can be tedious and prone to error. There are also a number of techniques for achieving this measurement. Hence, there is some value to a consistent definition of this measurement, such as might be provided through signal modelling, which can be validated independently of its implementation.

Instrumentation

Rohde & Schwarz Vector Signal Generator R&S® SMJ 100A

The R&S® SMJ 100A meets all challenges that diverse applications place on modern vector signal generators. For example, it offers the signal quality and flexibility required in research and development - not to mention a convenient graphical user interface (GUI). And this is by no means all the R&S®SMJ100A has to offer - a fact that becomes evident in production, where it excels with its flexible baseband and low setting times. The baseband meets all requirements, from providing real-time signals to replaying pre-calculated waveforms.

Rohde & Schwarz Spectrum Analyser FSG

Rohde & Schwarz Vector Network Analyser ZVB 8

The R&S®ZVB series of vector network analyzers covers the frequency ranges from 300 kHz to 4/8 GHz and from 10 MHz to 14/20 GHz. It has been designed for universal measurements on passive and active components. The R&S®ZVB series greatly simplifies vector network analysis especially for multiport measurements and measurements on balanced devices. Featuring comprehensive measurement functions, excellent specifications, high measurement and data transfer speeds and remote-control capability, the analyzers of the R&S®ZVB series are an ideal choice for both development and production applications.

IEEE 1641 Signal Modelling with newWaveX™

newWaveX is family of signal based software tools, available in two varieties for:

Signal Development - A graphical design environment for signal based test & measurement.

Platform Development - Test instrument description and control.

All newWaveX products feature:

• Full compliance with IEEE Std. 1641 Signal & Test Definition.
• Compliance with IEEE Std. 1671 ATML Test Description.
• Validation for IEEE Std. 1641 XML.
• Signals are built from a palette of BSCs (Basic Signal Components).
• High level signal components (TSFs - Test Signal Framework) can be built from BSCs to create a library of customised signals.
• Simulation of signal designs.
• Enables test methodologies that utilise a signal-based approach.

Approach™

This study and demonstration was divided into four key stages, prior to the generation of this report:

1. Creation of a benchmark practical demonstration of the test setup, including the manual implementation of all the defined tests, with results to compare the final test results obtained under IEEE1641 test conditions.

2. Generation of a TSF Library containing TSF models for the compression test stimulus & measurements. Demonstration of simulations and comparison with the benchmark results.

3. Generation of a TSF Library containing TSF models for the gain test stimulus & measurements. Demonstration of simulations, comparison with the gain test implemented in a previous phase of study and comparison with the benchmark results.

4. Generation and demonstration of an IEEE 1641 compliant test program, using the TSF models created in stages 2 & 3, through the IVI interfaces provided by the test resources.

General Architecture

Figure 1 - General Architecture