C. Eswaran

Bio: C. Eswaran is an academic researcher from Victoria University, Australia. The author has contributed to research in topics: Network synthesis filters & Chebyshev filter. The author has an hindex of 2, co-authored 4 publications receiving 27 citations.

Realization of multidimensional GIC digital filters

Abstract: A realization method for multidimensional Nth-order infinite-impulse-response (IIR) digital filters is proposed. A systematic procedure is presented for synthesizing analog reference networks comprising generalized immittance converters, and resistors, which realize M-variable Nth-order transfer functions. Digital-filter structures are then derived from these reference networks using the wave characterization. The proposed structures are canonic with respect to the number of multipliers and constitute a new class of multidimensional wave digital filters, distinct from the class of wave digital filters derived from doubly terminated LC networks. The realization method is general and relatively simple to apply, and leads to some interesting structures including structures with multiple outputs. >

An alternative sensitivity measure for designing low-sensitivity digital biquads

Abstract: A sensitivity measure is proposed for determining the optimum set of machine-representable multiplier constants in the derivation of low-sensitivity digital biquadratic filters. A comparison of this measure with two other sensitivity measures of this class is then undertaken using four different design examples. The four sixth-order filters considered are a Butterworth low-pass, a Chebyshev high-pass, an elliptic bandstop, and an elliptic bandpass filter. It is shown that the three sensitivity measures usually give slightly different low-sensitivity designs and that the new sensitivity measure often gives the best design. >

Modified series and parallel adaptors that lead to reduced sensitivity in wave digital filters

Abstract: By replacing multipliers in conventional series and parallel adaptors by digital subnetworks comprising multipliers whose constants are as far as possible machine representable, modified series and parallel adaptors are obtained whose operation is less dependent on multiplier constants that are not machine representable. Conventional and modified adaptors are then used to design several digital filters and the effects of coefficient quantization are investigated. The results obtained show that wave digital filters implemented with the modified adaptors are significantly less sensitive than filters implemented with conventional adaptors.

Realization of complex digital filters based on the concept of the generalized-immittance converter

Abstract: A systematic method for the realization of complex digital filters based on the concept of the generalized-immittance converter is presented. The method is simple to apply and can be used to realize arbitrary one-dimensional and multidimensional complex digital filters. The method is then used to realize a fourth-order Chebyshev filter, and the sensitivity performance of the filter is compared with that of other known low-sensitivity structures.

Variable Digital Filters

Abstract: There has been a constant interest in the design and implementation of digital filters with variable characteristics for different applications. In this article an attempt is made to review and systematize all known structures and methods of design of such filters. First the basic theory of the variable digital filters is introduced. Then FIR and IIR realizations with real and complex coefficients are considered, the known results for multidimensional variable filters are discussed and finally, typical implementations are overviewed. Recommendations for applications in different situations are given and unresolved problems are pointed out. This work is basically a review, but some of our original results are also included.

2D space---time wave-digital multi-fan filter banks for signals consisting of multiple plane waves

Abstract: Two dimensional space---time fan filters may be used for the highly-selective enhancement of spatio-temporal plane-waves on the basis of their directions of arrival. Unlike uniform bandwidth beam filters, ideal fan filters transmit passband signals over a range of directions of arrival that is independent of their 1D temporal spectrum. In this work, closed-form 2D wave-digital filter design equations and corresponding hardware architectures are proposed for realizing M independent fan-shaped passbands having independently steerable directionality and selectivity. A design method based on LCR ladder networks is proposed and implemented using a 2D time-multiplexed raster-scanned architecture that is suitable for low frequency applications such as audio, multimedia, seismic and ultrasonic beamforming. The architectures are designed, simulated, physically realized and tested on FPGA-based prototypes. Examples of 2D IIR M-fan filterbanks with FPGA implementations, together with measured results from on-chip hardware verifications, show the successful design and hardware realization. The filterbanks and hardware architectures are shown to be suitable for real-time sensor-array beamforming applications using custom VLSI circuits.

Improved tuning accuracy design of parallel-allpass-structures-based variable digital filters

Abstract: The best and simplest method to realize variable IIR digital filters is to apply frequency transformations on a parallel-allpass-structures-based circuits, followed by truncated Taylor series expansion of the allpass sections coefficients. In this work an approach to minimize the two main disadvantages of this method is proposed. It is shown first, after analyzing the sensitivity of the realization, that the degradation of the stop-band characteristics could be considerably decreased by minimizing the sensitivities of the allpass sections in the parallel structure over some critical frequency ranges. Then the tuning accuracy is improved by minimizing the sensitivities of the allpass sections used to apply the frequency transformations. Appropriate first- and second-order allpass sections are proposed for the most typical cases. The effectiveness of the proposed approach is demonstrated by simulation examples.

Systolic implementation of digital filters

Abstract: A systematic method for the mapping of digital filter algorithms onto systolic hardware is presented. The method is based on thez-domain characterization of the required filter. It yields filter structures that are modular, pipelined, and hierarchical, and can be used to obtain multidimensional structures. All the structures discussed have a latency of one sampling period and some have maximum concurrency. The paper also deals with the problems of line and frame wrap-around that are inherent in raster-scanned images and ways are suggested for their elimination.