Contact Inquiries: Michele Durant, 310-317-5321

October 20, 2004
For Immediate Release

Malibu Lab Reveals Breakthrough Technologies for the Direct Sampling of Multi-GHz Signals in Analog-To-Digital Conversion

LOS ANGELES, October 20, 2004—HRL Laboratories, LLC today announced a breakthrough combination of photonic and indium phosphide (InP) heterojunction bipolar transistor (HBT) technologies to accomplish the direct sampling of multi-gigahertz signals for analog-to-digital conversion.  Analog-to-digital conversion of very high frequency signals (> 10 GHz) is a key signal processing step for digital receivers used in many advanced radars and satellite communication hardware.   

Using photonic sampling, HRL has demonstrated that high resolution A/D conversion of very high frequency signals can be accomplished without using mixer-cascades.  In HRL�s direct sampling approach, a train of 10-GHz low-jitter picosecond optical pulses -- generated by a highly stable mode-locked laser -- are used in conjunction with an optical modulator to sample the analog input.  A notable feature of optical sampling is immunity from signal-induced jitter.  Furthermore, the higher harmonics of the picosecond pulses can downsample the high frequency analog input, creating low frequency signals that one can now digitize with high resolution (for example, using a  bandpass  delta-sigma analog-to-digital converter). 

Presently, the A/D conversion of these high frequency signals is achieved by downconverting them to intermediate frequencies (IF), using cascades of well-matched mixers, RF-filters, and high quality local oscillators (LO).  After frequency downconversion, the analog signal can be digitized with high resolution via the adoption of oversampling and noise-shaping approaches, as in delta-sigma analog-to-digital converters (ADCs).  In addition, the IF-signal becomes less prone to the degradation of A/D resolution induced by the ADC�s sampling-jitter.  However, the aforementioned mixer approach is typically hardware cumbersome and power consumptive.

Using InP-HBT processing technologies, HRL has fabricated, on a 3 millimeter by 2 millimeter chip, optoelectronic circuits that integrate photodetectors (for detecting the optically sampled signal) and continuous-time delta-sigma A/D electronics that possess a bandpass frequency located at ~1.8 GHz. Specifically, HRL demonstrated the photonic A/D of 12 GHz signals with ~10 bits of resolution (over a noise bandwidth of 1 MHz).  Although the experiment was carried out only for analog inputs lying in the X-band, the same technology can be extended easily to digitize 12– to 50-GHz analog signals.

This work was supported by the Defense Advanced Research Projects Agency (DARPA) and the Air Force Research Laboratory, Sensors Directorate (Rome, New York site)

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HRL Laboratories, LLC is a corporate R&D laboratory owned by Boeing, General Motors, and Raytheon. HRL performs R&D services for its three owners, for the U.S. government, and for other commercial entities.

 

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