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test&measurementZONE Products for the week of January 5, 2009
Agilent Technologies Says…
Industry-First End-to-End DigRF V4 Measurement Solution for Mobile Handset Design
Test Solution Spans Digital and RF Domains to Accelerate Development of LTE and WiMAX Wireless Devices
Agilent Technologies Inc. announced the industry's first Digital Radio Frequency (DigRF) V4 test solution. It enables comprehensive stimulus and analysis for developers of radio-frequency integrated circuits (RF-IC) and baseband ICs (BB-IC) as well as integrators of wireless handsets.
DigRF V4, driven by the MIPI (Mobile Industry Processor Interface) Alliance, is a high-speed digital serial bus between mobile baseband and RF chips that is a key enabling technology for LTE and WiMAX.
"Cross-domain" test, such as DigRF V4, offers new insights that reach from individual digital bits all the way through to IQ-modulated RF signals. Agilent's test solution allows engineers to work in the domain (digital or RF) and abstraction level (physical or protocol layers) of their choice to quickly characterize RF-ICs and rapidly solve cross-domain integration problems.
The Agilent digital wireless test solution integrates DigRF V4 stimulus and protocol analysis tools into Agilent's popular portfolio of digital, RF and wireless instruments. The new Agilent RDX (Radio Digital Cross-Domain) tester consists of two new modules, the Agilent N5343A exerciser module and the N5344A analysis module, which are housed in small, modular Agilent N2X mainframes. The modular structure is built to accommodate future MIMO designs.
The Agilent E5345A and E5346A active probing solutions with ultralow capacitive loading (less than 0.15 pF) and high sensitivity provide system insight with minimum disturbance at the gigabit speeds used in DigRF V4 testing. Design engineers can choose between Agilent's new N5345A Midbus Probe with Soft Touch technology for fast probing on prototype boards, and B5346A flying leads probing solutions, which enable effortless monitoring of DigRF V4 links in space-constrained designs.
This solution also protects one's investment by supporting both DigRF V4 and V3 specifications. The test software environment includes protocol generation and analysis, and interoperates with industry-leading Agilent Signal Studio software and 89600 vector signal analysis software. RF engineers save time by using familiar vector signal generation and analysis software, which supports the DigRF exerciser and analysis modules, as well as signal analyzers and signal sources.
"This DigRF V4 solution allows RFIC engineers and system integrators to develop their 4G mobile products with the fastest insight in cross domains," said Siegfried Gross, vice president and general manager of Agilent's Digital Test Division. "Agilent's offering for digital, serial protocol and wireless test allows customers to transform mobile device architectures to digital technologies with a new set of tools that are well integrated into the wireless use model."
"As WiMAX and LTE technologies advance, the need to integrate the digital and wireless worlds--while driving interoperability through test standards--is becoming essential," says Ron Nersesian, vice president and general manager of Agilent's Wireless Business Unit. "We have expertise in both domains and offer a complete solution for unifying the two worlds to help build the greatest confidence into mobile handset design from turn-on through integration."
EN-Genius Says…
The high-speed DigRF spec addressed by this test system (actually an assemblage of products from Agilent Technologies) is emerging as a standard serial interface between baseband chips and RFICs to be used in next-generation nomadic devices.
The industry group that's driving DigRF is the MIPI (Mobile Industry Processor Interface) Alliance. As you might expect, MIPI is comprised of the companies making RFICs, as well as those offering the associated baseband chips. Naturally, wireless communications OEMs are part of the mix, too. MIPI's goal is to achieve interoperability between the disparate RFICs and baseband devices – recognizing that they may be from different suppliers.
In the leading-edge high-bandwidth LTE and WiMAX air-interface portables, crucial circuitry is allocated between the two types of chips: one handles baseband processing and the other RF. DigRF's purpose is to smooth the inter-chip communication between the two.
Beyond all-important interoperability, DigRF also promises reduced cost, as a result of lower pin-counts (up to six wires), and extended battery life enabled by trading off speed with low-power and sleep modes.
High Bandwidth
The 4G standards (the DigRF V4 standard also encompasses 2.5G, 3GPP, and 4G standards) have 8B/10B encoded downlink speeds of over 300 Mbit/s in MIMO (multiple input, multiple output) configurations. At the chip level, LTE's full bandwidth requires 1.2 Gbit/s net bandwidth (with control overhead) on the link between a baseband IC and an associated RFIC.
Comprised of separate transmit and receive differential signal pairs, DigRF V4 uses a variety of control packet and IQ (in-phase and quadrature) data packet formats. These packets are transmitted across a prescribed electrical interface.
Cross-Domain Testing
So, how do you get your hooks into the dual-domain circuitry (literally) and ensure worthwhile radio-digital cross-domain testing? How do you make measurements that require stimulus and analysis of a DUT (device under test) in both the digital (baseband) domain, and RF (analog) inputs and outputs? That's where the DigRF V4 standard meets Agilent's end-to-end DigRF V4 measurement system.
The tester uses an Agilent N5343A exerciser module and an N5344A analysis module, housed in one of the company N2X mainframes, to provide much-needed visibility. This aggregation of modules and chasses lets you evaluate device behavior by giving you the ability to closely monitor DigRF's serial bit stream.
In use, DigRF V4 control packets are decoded and displayed on a system controller to provide visibility into configuration, status, and control flow. IQ data is also extracted from DigRF V4 data packets, and analyzed using Agilent's 89600 vector signal analysis software.
For its part in the assemblage, the N5343A Exerciser (supporting both DigRF v4 and v3) is a combined stimulus and capture box. It operates to speeds to 1.5 Gbit/s, and accommodates speed and mode change tests. It provides bit-to-packet-level generation gleaned from preliminary datasheets, thereby substituting for RFIC hardware that may not be available yet from an IC house during an end-product development.
The associated N5344A Analyzer (also supporting DigRF v3 and v4) provides clock recovery, and also accommodates speed and mode change tracking. It can also simultaneous monitor Tx (transmit) and Rx (receive) signals. It's where the tester's protocol decoder and packet viewer resides.
A Common Dashboard
Significantly, you use a common dashboard for driving all the cross-domain tests, based on common vector signal generation and vector signal analysis software. This also ensures measurement consistency on both sides of the DUT.
Thus a single platform gives you insight ranging from the protocol level all the way to the RF modulation level. You can work in either digital or RF domains, and get physical layer and/or protocol layer insight.
What's neat about all this stimulus generation and transparent monitoring is that Agilent's approach lets you completely characterize components independent of associated baseband ICs. That's important in this not so fast-moving transitional world of wireless development where a preliminary baseband device may not be ready for release at the same time as a given RFIC. Similarly, it's conceivable that an RFIC maker may need to prove interoperability with a number of different baseband ICs, perhaps from different vendors as well.
RFIC transmitters are characterized by developing a digital IQ representation of the RF signal using Agilent's Signal Studio and loading it into the system controller. The exercising module packetizes the IQ data, inserts the specified control packets, and then drives the bit stream into the RFIC digital baseband input, over the DigRF V4 interface. For its part, an RFIC can convert digital signals into analog signals, processing the serial bit stream, and generating an RF signal that's captured by the Agilent MXA signal analyzer. Once that's done, you can analyze the data using Agilent 89600 VSA software.
You can then compare an RF output waveform produced by your target RFIC to the intended baseband waveform produced by the baseband IC. With that comparison, you can characterize your transmitter's behavior, including the effects of conversion of the data from digital to analog domains. You could, for example, look at any impact of RF up-conversion.
For RFIC receiver testing, a receiver can be characterized by driving a known RF signal into the RFIC's analog Rx port, using an Agilent E4438C or Agilent MXG Signal Source. The RFIC would process the RF signal and dish up digital IQ, which is packetized and output in the DigRF V4 digital serial format. Agilent 89600 VSA software, in conjunction with its MXA signal analyzer, and the DigRF exerciser and analysis modules, capture the serial bit stream and extract the relevant IQ data for analysis.
System Integration
Using the system's acquisition probe, you can also monitor transactions on the DigRF V4 interface generated by the baseband IC. In this application, control packets are displayed on the system controller, and IQ from the data packets is evaluated using the vector signal analysis package.
The receive path on the baseband can be characterized by driving the DigRF V4 interface with IQ data packets from a stimulus probe. The IQ data packets are created on the system's logic analyzer, using the digital IQ representation of the RF signal generated in Signal Studio.
Finally, it's worth reiterating what's called out in Agilent's press release with respect to the system's E5345A and E5346A active probes. These probes exhibit almost negligible capacitive loading, which is just what's needed at gigabit speeds and on densely packed ultra-high-frequency circuit boards.
The N5343A analysis and N5344A exerciser modules, including software can be ordered now, with prices starting at $15,000. The N5344A and N5345A active probes can also be ordered now with prices starting at $22,000.
Product Page DigRF V4 Testing
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