SDR System Level Test Challenges and Measurement Solutions

SDR System Level Test Challenges and Measurement Solutions

SDR Overview SDR is a set of Hardware and Software technologies providing reconfigurable architectures for

network and wireless terminals.

The purpose is therefore to use the same Hardware for different functions, through a dynamic configuration according to the operational context.

SDR provides an efficient and comparatively inexpensive solution to the problem of building multi-mode, multi-band, multi-functional wireless devices that can be enhanced using software upgrades

Software-defined radios (SDR) utilize a combination of FPGAs, DSPs and analog/RF designs to achieve the radio’s system performance.

The mixed-signal nature of these SDR designs can introduce system integration testing complexities when the baseband hardware and RF hardware are integrated and tested together.

SDR’s overall system performance can be impacted by an accumulation of baseband, analog and RF design impairments, which can make issues difficult to isolate in the system integration testing phase.

SDR Block Diagram

SDR Test Challenges Many factors can contribute to error along the mixed-signal transmitter chain and in turn, affect

waveform quality and the SDR’s overall error vector magnitude (EVM) performance.

EVM is a measure of waveform quality and is typically used as a metric for wireless transmitter performance.

For example, the D/A converter may introduce nonlinearities and the D/A converter clock may introduce jitter.

Additionally, local oscillator (LO) phase noise, IF/RF filters, and nonlinear gain/phase distortion from the IF/RF up-converter and power amplifier may introduce waveform distortion to the SDR’s EVM performance.

Need for instrumentation capable of working across the digital and RF elements in the SDR design, and that allows for probing at every stage along the mixed-signal chain.

Need for software-defined approach to instrumentation by using coding and modulation software to generate and measure signals through modular, general-purpose RF instrumentation.

Software Defined Instruments Software Defined Instruments (SDI) perform signal analysis and measurements in the

software that are performed in the hardware traditionally using one embedded processor for each standard.

Using SDI we can perform multiple standard measurements using one hardware.

PXI platform is ideal for SDR testing as it is PC-based and SDR multimode testing can be done using single hardware.

The functionality of PXI instruments is defined in software so a single PXI RF instrument can test multiple communications standards by simply changing the software running on the system controller.

PXI controllers employing the latest dual-core and quad-core processors can easily process the most complex communications algorithms.

As communications standards continue to scale the amount of data transferred, it is important to base a communications test platform on a high-throughput bus to transfer the data.

PXI is based on the PCI and PCI Express buses, providing up to 12 GB/s of system bandwidth.

NI PXI RF Platform

With the modular nature of PXI, you can upgrade a single component of a system. For example, you can increase the performance of all of the instruments in a PXI system by upgrading to a controller with a higher-performance processor.

This type of upgrade is not possible with stand-alone instruments where the embedded processor is not user-accessible or upgradable. Moreover, because PXI is a multivendor platform, the modular components of a system can come from multiple vendors.

SDR Multimode Transmitter Testing• SDI enables user to perform measurements at various stages in SDR transmitter chain. For e.g., digital baseband IQ before

DAC and analog IQ after DAC, analog IF and RF output signals can be measured and analyzed using single instrument.

• This enables probing and debugging the complete SDR transmitter signal chain to verify the performance of the individual components.

• Modulation Accuracy Measurements– Error Vector Magnitude (EVM)

• Average and Peak EVM Results

– Frequency Offset– Clock Offset– IQ Gain Imbalance– Quadrature Skew– IQ Offset (Carrier Leakage)– Channel Frequency Response– Modulation Error Ratio (MER)– Average and Peak Power– Various Measurement Traces (EVM vs Symbols, EVM vs Subcarriers, Constellation Graph, Spectral Flatness)

• Spectral Measurements– Channel Power– Adjacent Channel Power– Spectral Emission Mask

SDR Multimode Receiver Testing• SDI enables user to perform receiver measurements at various stages in

SDR Receiver chain. For e.g., digital baseband IQ after ADC and analog IQ before ADC, analog IF and RF output signals can be given as an input to the Receiver.

• This enables probing and debugging the complete SDR Receiver signal chain to verify the performance of the individual components.

• Receiver Measurements– Receiver Sensitivity Measurements

• BER before and after channel coding• PER (Packet Error Rate) or FER (Frame Error Rate)

– Maximum Input Level– Power Control– Receiver Selectivity

MaxEye Digital Video Test and Measurement Solutions MaxEye Technologies Digital Video Test and Measurement solutions are powered by National

Instruments LabVIEW software, NI RFSG (NI PXI 5673/5673E, NI PXI 5672) and NI RFSA (NI PXI 5663/5663E, NI PXI5661)Hardware.

Enables testing of multiple digital video and audio standards testing using one NI PXI RF hardware. Ideal solution for multimode Digital Video SDRs.

The following are the digital video broadcasting toolkits currently being supported by MaxEye Technologies. • DVB-T /H• DVB-T2 • ISDB-T/Tb • CMMB • DTMB • ATSC and ATSC-M/H • DAB/DAB Plus/T-DMB• DRM/DRM Plus • DVB-S (under development)• DVB-S2 (under development)

Product Overview MaxEye Digital Video Signal generation software is an ideal test tool for generating the

test signals with different configurations to completely test the receiver during design, verification and manufacturing floor to characterize the receiver performance.

MaxEye Digital Video analysis toolkit is an ideal tool for analyzing the signal quality of the transmitted signal.

Toolkit provides various measurement traces to enable the engineers to analyze, troubleshoot and validate the transmitter signal issues.

The toolkit measurements can be used to calibrate the Digital Video Transmitter components.

The MaxEye Digital Video analysis toolkit provides standard based modulation accuracy, power measurements and spectral measurements to enable engineers for evaluating, designing, manufacturing transmitters, amplifiers, tuners, repeaters, modulators and gap-fillers.

Product Features - Generation Real time streaming of the generated waveform using NI RFSG streaming mode.

This enables testing of the receiver continuously for hours. (Typical DTG testing requires 5 minutes of video to be played in real-time)

Multi-carrier signal generation – Generation of multiple DVB carriers using single NI RFSG. This reduces the complexity of the test setup and test automation simpler.

MaxEye test and measurement solution enables user to do the following tests Receiver Design, Verification and Manufacturing Tests Receiver Functionality Tests RF Components and Transmitter Testing

Supports MPEG TS file as an input to the toolkit for testing the video and audio quality of the receiver. The TS file bitrate is adjusted according to the signal configuration.

Product Features - Analysis Supported Measurements

Modulation Accuracy MeasurementsData MER, Pilot MERData EVM, Pilot EVMPeak EVM, Peak EVM Symbol Position, Peak EVM Subcarrier PositionFrequency OffsetClock Offset IQ Gain Imbalance, Quadrature SkewCarrier SuppressionConstellation TraceEVM vs Symbols, EVM vs Subcarriers TraceChannel Frequency Response (Spectral Flatness)Average and Peak Power

Spectral MeasurementsChannel PowerAdjacent Channel PowersSpectral Emission Mask

Generation Front Panel

Analysis Front Panel

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