Design of two-dimensional FIR digital filters used for broadband digital beamforming by combination of spectral transformation and window method

Cintra

et al. 2012

Meas. Sci. Technol.

Multi-beamforming is an important requirement for broadband space imaging applications based on dense aperture arrays (AAs). Usually, the discrete Fourier transform is the transform of choice for AA electromagnetic imaging. Here, the discrete cosine transform (DCT) is proposed as an alternative, enabling the use of emerging fast algorithms that offer greatly reduced complexity in digital arithmetic circuits. We propose two novel high-speed digital architectures for recently proposed fast algorithms (Bouguezel, Ahmad and Swamy 2008 Electron. Lett. 44 1249–50) (BAS-2008) and (Cintra and Bayer 2011 IEEE Signal Process. Lett. 18 579–82) (CB-2011) that provide good approximations to the DCT at zero multiplicative complexity. Further, we propose a novel DCT approximation having zero multiplicative complexity that is shown to be better for multi-beamforming AAs when compared to BAS-2008 and CB-2011. The far-field array pattern of ideal DCT, BAS-2008, CB-2011 and proposed approximation are investigated with error analysis. Extensive hardware realizations, implementation details and performance metrics are provided for synchronous field programmable gate array (FPGA) technology from Xilinx. The resource consumption and speed metrics of BAS-2008, CB-2011 and the proposed approximation are investigated as functions of system word size. The 8-bit versions are mapped to emerging asynchronous FPGAs leading to significantly increased real-time throughput with clock rates at up to 925.6 MHz implying the fastest DCT approximations using reconfigurable logic devices in the literature.

Section: Overview Of Digital Multi-beamforming For Space Imaging Sciencementioning

confidence: 99%

Multiplier-free DCT approximations for RF multi-beam digital aperture-array space imaging and directional sensing

Potluri

Cintra

et al. 2012

Meas. Sci. Technol.

“…were computed using the BSIM4 Cadence simulated data under PVT variations, using (25) where each is an element of the matrix of functions such that, where is the uniformly distributed random integer and . The random selection of is decided at the start of the experiment.…”

Section: Monte-carlo Analysis Of the Fan Filter Response Under Pvtmentioning

confidence: 99%

RF Analog Beamforming Fan Filters Using CMOS All-Pass Time Delay Approximations

Wijenayake

IEEE Trans. Circuits Syst. I

et al. 2012

A continuous-time (CT) radio frequency (RF) antenna array beamformer and analog circuit based on a discrete-space-continuous-time (DSCT) 2-D fan-filter having transfer function is derived. The proposed transfer function is based on a 2-D FIR discrete domain fan filter. The discrete domain prototype is converted to the proposed mixed-domain DSCT analog filter by replacing unit sampled delays with CT analog first-order all-pass networks corresponding to the bilinear transform. First-order all-pass network is a poor approximation to a CT delay . To address this, a novel broadband pre-warping method is proposed to exactly compensate for such "bilinear warping". A 65 nm CMOS VLSI circuit for is proposed and an example fan filter with axis oriented at , half-fan-angle and maximum frequency is simulated employing closed-form expressions, an ABCD parameter based model and 65 nm CMOS simulations in Cadence. A stop-band interference rejection of 38 dB is verified by BSIM4 based simulations. The proposed circuit for operates at 3.7 mA from a 1.2 V supply. The beamfomer is shown to operate correctly in the presence of PVT variations of .Index Terms-Analog beamforming, CMOS, delay approximation, fan filter, VLSI.

“…True time delays for each antenna are found for a particular beam direction and inter antenna spacing and are realized as tapped delay lines [74,75]. In finite impulse response (FIR) beamforming [60,61,76,77], the time delays are implemented as FIR digital filters. This method has high computational intensity compared to the proposed IIR technique.…”

Section: Review: Beam Filter Designmentioning

confidence: 99%

Digital Architectures for UWB Beamforming Using 2D IIR Spatio-Temporal Frequency-Planar Filters

Kondapalli

International Journal of Antennas and Propagation

Bruton

2012

A design method and an FPGA-based prototype implementation of massively parallel systolic-array VLSI architectures for 2nd-order and 3rd-order frequency-planar beam plane-wave filters are proposed. Frequency-planar beamforming enables highly-directional UWB RF beams at low computational complexity compared to digital phased-array feed techniques. The array factors of the proposed realizations are simulated and both high-directional selectivity and UWB performance are demonstrated. The proposed architectures operate using 2's complement finite precision digital arithmetic. The real-time throughput is maximized using look-ahead optimization applied locally to each processor in the proposed massively-parallel realization of the filter. From sensitivity theory, it is shown that 15 and 19-bit precision for filter coefficients results in better than 3% error for 2nd- and 3rd-order beam filters. Folding together with Ktimes multiplexing is applied to the proposed beam architectures such that throughput can be traded forK-fold lower complexity for realizing the 2-D fan filter banks. Prototype FPGA circuit implementations of these filters are proposed using a Virtex 6 xc6vsx475t-2ff1759 device. The FPGA-prototyped architectures are evaluated using area (A), critical path delay (T), and metricsATandAT2. TheL2error energy is used as a metric for evaluating fixed-point noise levels and the accuracy of the finite precision digital arithmetic circuits.