Design Con 2015

Stars of DesignCon: Analog art unravels high-speed digital woes

January 24, 2013

R_Colin_Johnson-January 24, 2013

Analog engineering is coming to the aid of high-speed digital designers, now that digital interfaces run at radio frequencies. RF designs for television, microwave, and radar systems can now be applied to solve design problems with multi-GHz digital interfaces such as DDR3, PCIe, SATA and Ethernet.

Taking that challenge into the real world, rngineersfrom Signal Integrity Software Inc. (Sisoft), and Cray  will present a case study at DesignCon. They'll detail how they solved a supercomputer clock jitter problem with a RF filter which added no extra parts to the design, but merely reformed the transmission lines on the circuit board.

[Click here to register for DesignCon 2013, Jan. 28-31 at the Santa Clara Convention Center. Options range from an All-Access Pass to Free Expo Admission, which includes the option to attend a dozen tech training sessions.].

The paper, Applying Microwave Techniques to Digital Systems: A Simple Case Study, will be presented at DesignCon on Tuesday, January 29. It's part of the track on Analog, Mixed-Signal, and RF Design and Verification.

"Analog and RF circuit design expertise can help you out of a lot of unusual problems with your high-speed digital circuits," said said Michael Steinberger, Lead Architect at SiSoft. "What we hope to do in our presentation is bridge the gap in terminology and fabrication techniques for digital engineers."

Analog engineers have already perfected as wide variety of RF transmission lines that process signals, including waveguides, resonators, power dividers, antennas and other three-dimensional structures that routinely perform useful signal processing functions. In  their presentation, a microwave filter will be used to solve a digital design problem, but the authors also present a roundup other RF transmission-line solutions that could be useful to digital engineers.

"There is a very direct connection between our abstract design and its implementation as a microwave filter--which is very much like a menu of options," said Michael Steinberger, Lead Architect at SiSoft. "Engineers can select from these coupled transmission lines to solve their own problems in a very straight-forward way."

A microwave filter was implemented as buried stripline on the circuit board where ground planes will contain the fields and impedance and routing length can be tightly controlled.

The authors show how to to translate a long-established microwave filter design into a solution for a very current problem in high-speed digital design: the conditioning of a processorÕs clock source to obtain high duty-cycle accuracy. In doing so, they show how to bridge the gap in terminology and methodology between the digital and analog worlds.

The problem was a clock doubling circuit at Cray that produced an unacceptable amount of "jitter." The solution was a microwave transmission line for correcting "phase noise" by passing odd harmonics, but suppressing even harmonics, thus preventing duty-cycle distortion. The resulting four-pole Chebyshev filter was implemented with coupled transmission lines in buried copper stripline segments in the circuit board.

Info Redux:

Session: Applying Microwave Techniques to Digital Systems: A Simple Case Study

DesignCon Registration (direct to registration page link):  Click here to register for DesignCon 2013, Jan. 28-31 at the Santa Clara Convention Center. Options range from an All-Access Pass to Free Expo Admission, which includes the option to attend a dozen tech training sessions.

And Don't Miss:  DesignCon Free Education & Training
(Host: Agilent Technologies; Corporate Sponsore: Rambus; Diamond Sponsor: SiSoft; Diamond Sponsor: Teledyne LeCroy: Platinum Sponsor: Rohde & Schwarz)

Monday, January 28:
•    Challenges and Solutions in Characterizing a 10Gb Device  (Agilent)
•    PCI Express 3.0 Characterization,Compliance, and Debug for Signal Integrity Engineers (Teledyne LeCroy)
    
Tuesday, January 29:
•    Synchronous Time and Frequency Domain Measurements Using a Digital Oscilloscope (Rohde &  Schwarz)
•    Ensuring Validation & Analysis of Complex Serial Bus Link Models  (Tektronix)
•    USB 2.0 Compliance Testing (Rohde & Schwarz)
•    Phase Noise and Jitter Measurements (Rohde & Schwarz)
•    True Differential S-parameter Measurements / Rohde & Schwarz
•    Synchronous Time and Frequency Domain Measurements Using a Digital Oscilloscope (Rohde & Schwarz)
•    USB 2.0 Compliance Testing (Rohde & Schwarz)
•    Phase Noise and Jitter Measurements (Rohde & Schwarz)
•    True Differential S-parameter Measurements (Rohde & Schwarz)
•    Ensuring Validation & Analysis of Complex Serial Bus Link Models (Tektronix)
•    Advances in 3D SI Simulations of Interconnects for Chip/Package/PCB  (CST of America Inc.)

Wednesday, January 30:
•    Making DDR4 Work For You (Agilent)
•    Debugging to Find the Root Cause of Compliance, Limit or Mask Test Violations (Teledyne LeCroy)

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