Convergence of RF, analogue & digital systems: New T&M solutions in demand

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Keeping the growth of the crossover products market in mind, T&M players need to come up with faster testing solutions at lower costs

Agilent offers vector signal analysis software

By Richa Chakravarty

Tuesday, March 20, 2012: The trend in the industry today, particularly in the consumer electronics market, reveals the growth of crossover products that combine multiple technologies. While the addition of each new function delivers more benefits to consumers, it creates challenges for the test engineers. Added complexity results in longer test times and cost overruns, forcing test engineers to evaluate alternative approaches.

For years, engineers wrestled with separate challenges posed by system-on-chip (SoC) and system-in-a-package (SiP) products. The traditional way of designing used separate chips for radio frequency (RF), analogue and digital signals, where boards were designed separately. Over time, there was a need for compact designs. This led to the concept of SoC, which introduced a single chip that took care of the analogue front end and the digital system. This convergence threw far greater challenges to the test engineers, requiring equipment with the flexibility to handle both architectures and a fresh approach to testing. Let’s take a close look at the challenges faced by the T&M industry.

Testing challenges posed by convergence

Basic design: The first major test challenge relates to the very basic design phase of these systems.

Sadaf Arif Siddiqui, technical marketing specialist, Agilent Technologies India Pvt Ltd

While analogue and digital systems primarily require time domain systems, RF works more on frequency domain platforms and toolsets. Very tight test integration is required across the time domain and frequency domain platforms for such designs. Informs Naresh Narasimhan, marketing manager, Tektronix India, “The complexity of T&M instruments to measure analogue and digital data at the same time and be able to trigger on either digital or the analogue data, and yet be able to correlate the two, is one big challenge faced by engineers. Due to such close proximity of signals there is a lot of interference across the two architectures, which can lead to undesired effects. Thus, this tight integration is quite challenging.”

High performance:

The demand for increased functionality, apart from higher reliability and performance within the ever shrinking form factors, has placed new demands on designers of high performance designs. “The convergence of RF, analogue and digital systems within the same design and package now requires engineers to consider coupling effects that were heretofore negligible. One typical example of this convergence can be seen in mobile handsets. As these designs become increasingly complex, the challenges of validation and testing become more difficult. To further complicate the situation, advantages such as lower costs, wider bandwidth and extended battery life are pushing digital technologies deeper into the RF portion of every handset,” says Sadaf Arif Siddiqui, technical marketing specialist, Agilent Technologies India Pvt Ltd.

Naresh Narasimhan, marketing manager, Tektronix India

 

Scalability and flexibility:

A common challenge while developing a test system strategy is how to address long term scalability and flexibility because the desired test system lifecycle is often longer than the lifecycle of a single generation of a device. Opines Tarun Gupta, business development manager, Telecom and Defence, National Instruments India, “Software defined test systems help overcome this challenge because they are inherently modular and scalable, and engineers can quickly perform lifecycle service on individual parts of the testers, such as upgrading the PC with a new processor and/or by adding new modular instruments with increased resolution, sample rate, channel count and functionality.”

EMI/EMC issues:

Other test challenges caused due to convergence are electromagnetic interference and electromagnetic compatibility (EMI/EMC) issues. Electromagnetic interference is a disturbance that affects electrical circuits either due to electromagnetic induction or the radiation emitted from an external source. This disturbance can interrupt, obstruct or even degrade the effective performance of the circuit. It can even result in a total loss of data.

Shorter design cycles: The most critical test challenge posed by this convergence is to come up with the most accurate design while reducing the design cycle. Engineers today not only look for flexibility but also want a single, yet more robust test platform to test multiple parameters of the device with a single connection.

Tarun Gupta, business development manager, Telecom and Defence, National Instruments India

 

High bandwidth:

In the next generation wireless communications standards, trends of spatial streams, wider channel bandwidths and compact designs have been observed. At present, the challenge is to be able to push the bandwidths of these instruments to handle higher frequencies.

Testing capabilities:

The traditional engineering response to testing a new RF standard, especially one that involves converging systems, often requires selecting a box instrument with the closest specifications. For automated test systems with multiple test requirements, this approach usually results in a different box for each measurement requirement in the system. When the test requirements are uniform and non-changing, this method may be sufficient, but it becomes cumbersome, slow and ultimately more expensive when testing today’s complex devices, which often use multiple wireless standards.

Issues in creating prototypes:

Another challenge faced by design engineers at various stages of design is the need for quick prototyping. Adds Tarun Gupta, “The graphical system design approach includes both software and hardware as part of the exploration and implementation platform. Often engineers have excellent high level software tools, but when they get to the real implementation of prototypes or end systems, the tool chain starts slowing down development. Models break down at boundary conditions, do not behave as expected in the real world, or there are difficulties to implementing the software to hardware.”

N1 offers software defined modular instrumentation with GPS, WLAN, RFSO and WiMAX toolkits

Along with this, the evolution of new wireless technology such as Bluetooth, Wi-Fi, and WiMAX being integrated in the embedded systems has raised other testing challenges such as logic timing, algorithm errors, analogue-to-digital converter (ADC) overflows, frequency hops, un-deterministic timing due to network conditions, dynamic power levels, time correlation, etc.

T&M devices with solutions for these challenges

To meet these variable challenges, T&M device makers are coming up with various solutions. Shares Sadaf Arif Siddiqui, “T&M solutions that provide a good integration between time and frequency domain designs/measurements can take care of these challenges. Agilent offers tools like sampling oscilloscopes with the time domain reflectometry (TDR) option and network analysers that are used to characterise transmission lines and channels. S-parameters can also be derived to characterise and remove the design inconsistencies.”

According to Tarun Gupta, a software defined approach is ideal to automate verification, validation and production tests. “Modular

Tektronix offers mixed domain oscilloscope 4104

software defined test systems lower expenses by taking advantage of commercial off-the-shelf (COTS) technologies used in high volume applications such as telecommunications and consumer electronics products. These systems also share many components—such as the chassis and power supply—across instrument modules instead of duplicating these components for every instrument function. Further, with these modular, software defined systems, one can buy the features you require for a particular application and integrate additional functionality in the future, as needed,” he added.

Agilent’s electronic engineering software (EEsof) platform (advance design system—ADS) and vector signal analysis software (VSA), which works across oscilloscopes, logic analysers and spectrum analysers (digital and RF), provides solutions to various design challenges posed by the convergence of two architectures.

The mixed domain oscilloscopes (MDO) developed by Tektronix is another revolutionary product, which has broken the barrier between the time and frequency domains. Its MDO4000 oscilloscope has analogue, digital and RF functions integrated in one instrument with the capture bandwidth of ≥1 GHz at all centre frequencies. “A T&M solution that can give a picture of all three domains in a single shot can take care of these challenges. The MDO4000 is one such device,” informs Naresh Narasimhan. Tektronix also offers real-time spectrum analysers (RSA) equipped with digital picture exchange (DPX) live RF spectrum display to effectively characterise time variant signals and solve unexpected problems.

Thus, in order to tackle these challenges, key devices should include electronic design automation (EDA) or simulation tools that can include all types of parameters during the design phase and should even incorporate instruments capable of debugging and validating RF, analogue and digital parameters. These instruments should either work in tight correlation or there should be software such as VSA that can work across all domains. Also, as the demand for higher data rates and channel capacities continues to rise, RF components with precision are essential in order to provide high quality signals. Vector network analysers (VNA) have become an indispensable tool on the design bench as well as in validation test systems as they offer exceptional accuracy and flexibility. Informs Tarun Gupta, “Unique hardware architecture allows the user to precisely characterise the device under test. A VNA allows a tester to understand the electrical contribution that each component introduces, whether in the form of an impedance mismatch or non-linear behaviour.”

Changes in T&M devices

In order to handle the challenges posed by the convergence of RF, analogue and digital features, T&M devices have been upgraded to handle different challenges. The three domains have been integrated into one screen so as to give correlated, understandable and palatable data. While regarding hardware specifications, these instruments work from DC to RF and the microwave range. “Today, users can take care of the challenges at the very design phase and simulate those in the design or EDA tools. They can then check the performance with the latest T&M instruments,” shares Sadaf Arif Siddiqui.

Engineers now have the flexibility to deploy design building blocks known as intellectual property (IP) cores, to both the device under test (DUT) and the reconfigurable instrument. This capability is called ‘IP to the pin’ because it drives user-defined software IP as close to the I/O pins of the next generation reconfigurable instruments as possible. The software IP includes functions/algorithms such as control logic, data acquisition and generation, digital protocols, encryption, math, RF and signal processing. Says Tarun Gupta, “Emerging multi-vendor IP ecosystems that feature IP cores from all major field programmable gate array (FPGA) vendors as well as their software and instrumentation partners, provide engineers with enough flexibility. National Instruments’ FPGA IPNet and the Cadence/Xilinx IP microsites are examples of these ecosystems. They contain hundreds of IP blocks and functions, including the Xilinx CORE generator, serial communication protocol cores and advanced encryption standard (AES) components, as well as peer-to-peer streaming algorithms.”

T&M devices and solutions to tackle convergence

  • Electronic design automation (EDA) tools
  • IP ecosystems—IPNet and Cadence/Xilinx
  • Mixed domain oscilloscopes
  • Real-time spectrum analysers
  • Sampling oscilloscopes
  • Software-based approaches—the EEsof platform and vector signal analysis (VSA) software, Lab view graphical programming environment
  • Vector network analysers (VNA)
  • Industry standard PXI platform and modular instrumentation

Though the T&M industry is addressing more complex testing setups, yet most of the vendors specialise in only one of the three areas due to the overall complexity of test related problems. Keeping the growth of crossover products in mind, companies require faster RF multi-site testing at a lower cost. Vendors need to understand the inter-relationship between the three vital areas and develop testing capabilities to improve throughput. If not handled correctly, the challenges and risks mentioned earlier, can negate the potential benefits of the convergence of RF, digital and analogue architectures.

Electronics Bazaar, South Asia’s No.1 Electronics B2B magazine

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