Department Publications

The radio frequency (RF) cochlea, a biomimetic LCR transmission-line filter bank that performs O(N) broadband spectrum analysis, has been demonstrated in active CMOS and as passive microwave channelizers but has remained a one-dimensional (1-D) structure since its introduction two decades ago. We argue that the natural next step is to add a second dimension, and we explore three complementary aspects of this extension. First, we review existing 1-D RF cochlea architectures and present a 20-channel, 1 GHz constant-bandwidth passive channelizer as a representative implementation. Second, we analyze the two-dimensional (2-D) cochlear-duct geometry of Watts and Neely using finite-difference and Liouville–Green simulations: the second dimension introduces a cut-off mode whose interference with the traveling-wave mode produces an upper-skirt roll-off 1.6–1.7× steeper than the 1-D long-wave limit …

The optimal selection of approximate computing units towards low-complexity FPGA-based hardware architectures for approximate discrete cosine transform (ADCT) and approximate discrete Fourier transform (ADFT) are explored. The proposed methodology employs an existing library of FPGA based approximate adders to select Pareto-optimal 1 approximate adders for cascaded signal flow architectures found in ADCT and ADFT operations. Benefits are presented with examples from 8-point ADCT based image compression and 16-point ADFT based digital multi-beamforming applications. Examples demonstrate a nearly 25% LUT reduction in FPGA utilization compared to error-free computing, with a corresponding degradation of nearly 1 dB in terms of PSNR in image compression and 0.3 dB loss in SNR improvement in beamforming.

Low-complexity digital multi-beamforming via multiplier-less approximations for discrete spatial Fourier transform (DSFT) is explored. The proposed approach employs an approximate-DSFT (ADSFT) which - for a uniform linear array with N antennas producing N simultaneous beams, reduces the hardware multiplier requirement from 3N 2 to 0 with marginal error in the beam profiles. Importantly, the proposed approach extends the previously reported approximate discrete Fourier transform (ADFT) multi-beamforming systems having fixed beam profiles to enable configurable beam profiles, where the user can obtain N simultaneous beams within a given spatial angular region. Simulations demonstrate that the multi-beam profiles are largely accurate, and approximate selection results in deviations for 8- and 16-element ULAs, with worst-case beam angle errors of 0.3° and 0.2°, and worst-case sidelobe deviations of …

Substantial data losses occur during transmission between the sensor nodes of a wireless sensor network due to various causes such as the instability of wireless communication links and network congestion. Most of the data recovery methods proposed are computationally expensive or rely on additional data from neighboring sensors or other types of correlated data which may not always be available. In this paper, we instead propose a lightweight real-time method of missing data recovery based on chromatic derivatives (CDs), a noise robust alternative to standard derivatives that enables high-fidelity local signal approximation. Using the bandlimited nature of the measured signals, our method interpolates the missing data using CDs-based non-uniform sample reconstruction. In contrast to many state-of-the-art methods, our approach relies solely on the received data stream from the transmitting sensor for …