To explore novel RF circuit topologies designed in the time rather than in the frequency domain for achieving very high impedance transformations (>200:1) over ultra wide bandwidths (DC-9GHz). The proposed approach will result in circuits that will be instrumental in communication and characterization systems focused on high-impedance RF components including nanoscale FETs and nanomechanical resonators.
Intellectual Merit: For over half a century the design of nearly all wireless commercial communication systems has been following two major design conventions: 1) the RF system impedance is set to 50 with a realizable impedance transformation ratio of less than 10:1 due to technological limitations; 2) the bandwidth of the transmitted data is limited to a small fraction of the center frequency, typically less than 10%. Although higher bandwidths are possible, they come at the expense of extra loss and real estate on the chip. Until recently, these limitations have not hindered the implementation of high-performance wireless communication systems because conventional RF devices and the developed predominantly frequency-domain design techniques are well suited for 50 narrowband systems.
The advent of nanotechnology, however, has enabled microwave engineers to produce RF devices with drastically different properties that often conflict with conventional design rules. As both active (transistors) and passive (nanomechanical resonators) RF devices are reducing in size by three orders of magnitude from micrometers to nanometers in order to satisfy speed and frequency requirements, their impedances are getting increasing higher and they now reach 1-50k. Moreover, ultra-wideband (UWB) architectures have been relatively recently legalized by the FCC allowing designers to develop significantly simpler receiver architectures. However, the practical difficulties of realizing low-loss and compact ultra-wideband matching networks as well as electronic circuits that produce pulses wider than 5GHz, is currently limiting this technology to the lower UWB band (3.1 -4.8 GHz), leaving the more interesting allowable part of the spectrum (5 -10.6 GHz) unexplored The complete lack of solutions in these areas has made the integration of nanoscale devices to RF systems practically impossible. The exploratory proposed effort is focused on developing revolutionary design techniques to alleviate the above described problems. In particular, we propose to explore novel RF circuit topologies designed in the time rather than in the frequency domain. These topologies are based on time-variant circuits that can be reconfigured and matched to the desired bandwidths. Our preliminary results clearly demonstrate that these concepts results in extremely simple and compact circuits with impedance transformation ratios in excess of 200:1 over a 9GHz bandwidth.
Broader Impacts: To the best of the investigators' knowledge this is the first attempt to utilize time variant circuits for wideband RF nanoelectronics. This area is particularly interesting because it brings the promise of significantly faster RF communication systems with major cost and battery-life benefits. Due to their very high impedances, though, RF nanoelectronics have not been utilized in any system architectures so far. The impedance mismatch between them and traditional 50 systems (200:1 to 1000:1) is so high that renders these devices unusable. This exploratory research proposes for the first time a viable solution to this serious problem. If successful, system-level researchers will be capable for the first time to bring the promise of RF nanoelectronics to reality because they will be able to implement nano- amplifiers, mixers, filters and eventually RF front-ends.
