Intellectual Merit: This BRIGE research project aims to demonstrate a new class of ultra wideband software defined radio transmitters using a novel mixer-less direct digital-to-RF digital-to-analog converter. The linchpin of the proposed direct RF modulator is a multi-path and multi-phase digital-to-analog converter architecture, designed to cancel ? in the digital domain ? sampling image frequencies and non-linearity spurs, and yet operate at the Nyquist-rate of the RF signal. Specifically, the transmitter comprises a wholly-digital baseband to RF modulation scheme that will enable unparalleled degree of programmability and achieve very high dynamic range spurious free operation. Furthermore, in light of various mismatches in the parallel digital-to-analog converter paths, self-healing algorithms will be investigated to enable built-in test and tune of the circuit parameters.
Broader Impacts: The proposed modulator will eliminate the need for heterodyne mixing following the digital-to-analog conversion, a technology deemed critical to meet the Software Defined Radio forum?s definition of the ?ideal software radio?. This technology could be transitioned to a wide range of rapidly evolving commercial and military communication systems such as cognitive radios and software defined radars. Additionally, the new architecture can serve as a catalyst for upgrading the current radio-transmitter handheld to a common radio architecture supporting all different standards and technologies. Beyond its technological and commercial potential, this research will further strengthen a multidisciplinary teaching and research track in radio circuits and systems. If awarded, this project will directly support a female Ph.D. student and two undergraduate students during summer. The PI will also establish close collaboration with North Carolina A&T University, one of the leading national institutions graduating minority engineers, through funding of a minority graduate student for a summer research program in the proposed topic.
The Wireless Innovation and Infrastructure Initiative (Wi3) announced in Feb 2011 aims to provide high-speed wireless in America, and deploy a nationwide interoperable wireless network for public safety. To meet such lavish goals, cognitive radios (CRs) and software defined radios (SDRs), both considered as a disruptive technology, have been touted as the holy-grail that will enable the future wireless world. Cognitive radios are fully programmable wireless devices that can sense their environment and dynamically adapt their transmission waveform, channel access method, spectrum use, and networking protocols as needed by the network. It is anticipated that cognitive radio technology will soon emerge from early stage laboratory trials and vertical applications to become a general-purpose programmable radio, much like microprocessors have served a similar role for computation. Towards this goal, this leapfrog research aims to demonstrate a new class of robust and low power SDR transmitters based on a novel mixer-less direct digital-to-RF (DDRF) technology. The research offers an unconventional approach to designing Digital to Analog converters that operate up to 10GHz speed and thus moving the digital hardware closer to the radio antenna. The linchpin of this research is a multi-path and multi-phase RF digital to analog converter (DAC) architecture, designed to cancel nonlinearity (distortion) and sampling image spurious, and yet operate at the Nyquist-rate of the RF signal. The success of this research effort will ultimately lead to the large-scale deployment of cognitive radio networks that dynamically optimize spectrum use. Paralleling this effort, the research has also opened up avenues to explore the design of self-healing circuits and systems to calibrate and fine tune the performance of Direct to Digital transmitters at GHz speeds.
