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Complete solutions for characterization, debug, compliance test of HDMI designs


New Challenges

The High-Definition Multimedia Interface (HDMI) is being implemented broadly in devices from high-definition televisions to personal computers to set-top boxes. The overwhelming con­cern for developers of these products is interoperability. Interoperability starts with the physical layer where the digital content is driven from one device through media such as a cable to a receiving device. Tools to measure the parameters of these devices are required to understand if the device is in compliance, and to how close the device performance is to specification.

When insight is delivered as early as possible in the design cycle, and corrective action is taken on the design, the first condition for success in the market – product quality – is met. Keysight Technologies, Inc. test solutions can provide these insights that help make the right decisions at key moments.

The measurement challenges for HDMI continue to be difficult ones. With the prior release of the HDMI Compliance Test Specification (CTS), data rates were specified to 1.65 Gb/s on each lane, for a composite 5 Gb/s. With CTS 1.3, the highest rate has been increased to 2.25 Gb/s and 3.4 Gb/s, with the possibility of going to 4.5 Gb/s per lane.

It is safe to say that when data rates double the problems you encounter more than double. A simple way to understand this is to consider changing from 1.5 Gb/s to 3.0 Gb/s. The unit interval (UI) changes from 667 ps to 330 ps. If you had 300 ps allowed in your jitter budget for the former device and tried using the same design for the newer requirements, your jitter budget would be gone before you ever got started! The eye would be almost completely closed.

Key tasks

HDMI characterization can be segmented into four areas: source testing, sink testing, media physical layer evaluation, and protocol test. In each of these areas, the HDMI CTS has recommended procedures, methods and equipment to perform these tests. In many cases, there are multiple methods, tools or processes to get the job done. The deciding factors on which method to use may be your comfort level with a particular measurement tool, cost, and/or convenience. Keysight offers solutions in each area to meet your needs from the electrical physical layer to protocol.

Applying expertise

When it comes to quality digital measurements and signal integrity, Keysight has decades of experience in RF, microwave and protocol engineer­ing. We understand the reflections, skin effect, insertion and return loss, impedance profiles as well as jitter budget and tolerance, timing margins, compliance and other issues that digital designers and developers have to face in high data rate standards. As an active member of the HDMI Organization with consistent partici­pation in compliance workshops and specification issues, Keysight has a solid background in the physical, data link, and protocol layers of HDMI.

Thanks to its premier position as a test company, Keysight also has a long history of collaborative innovation with industry leaders. The expertise of Keysight’s Application Engineering team reflects these important experi­ences. But they also put Keysight in a position to develop tools that meet the physical challenges, are customized to the needs of the standard, and are relevant to the way designers and developers need to use them.

Complete, reliable test coverage

But what makes Keysight test solutions so compelling is that they are the best tools, in every category, to meet the challenges presented by HDMI. We developed these tools to match the application’s specific needs – real-time and sampling oscilloscopes to verify signal integrity; pattern/protocol generators to create the necessary stimulus signals, BERTs to test jitter tolerance of receivers, time-domain reflectometer (TDR) and a vector network analyzer (VNA) to characterize impedance, and automation software to speed up and simplify the measurement process. That’s why most HDMI Authorized Test Centers (ATC) utilize Keysight solutions.

Because you can rely on the quality of Keysight equipment, it is the key to easier, faster and more confident test­ing of your HDMI designs. That takes strain out of engineering and lowers development costs. Accurate results reduce the number of design cycles to help you get to market faster, and they ensure robust products that uphold your hard-won lead in the market.

HDMI Source Test

There are many tests stipulated by the CTS for HDMI Sources (see Table 1). These include measuring standard waveform parameters such as rise and fall times, over and undershoot, but also eye diagrams and jitter analysis where the clock recovery method is stipulated by the HDMI standard. Further, new specified filtering algorithms require equalizing the cable end eye and must be performed to correlate receiver performance.

Measure with confidence

Whether troubleshooting, capturing contiguous waveforms, ensuring correct operation, or proving compli­ance, a real-time oscilloscope with active differential probes and test point access fixtures are critical. Noise floor, jitter noise floor, probe accuracy and test fixture quality all affect measurement accuracy. For example, the receiver eye tests examine the minimum level for adequate receiver operation. Poor noise performance in the oscilloscope may deceive you by indicating a lesser level is setup than really is, thereby overestimating receiver performance.

Keysight’s Infiniium 80000B Series Oscilloscopes provide the lowest noise floor, jitter noise floor, and trigger jitter in the industry, enabling more accurate measurements and a better charac­terization of your device performance. In addition, the InfiniiMax active differential probes provide industry leading noise performance and probe bandwidth and accuracy. Connections to your device are simplified with the N1080A Test Point Access (TPA) plug cable and fixture board, or connect directly to IC pins via the InfiniiMax probes.


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