Joseph X. Rodrigues

New approach to the synthesis of sharp transition FIR digital filter

A model is proposed for a linear phase, sharp transition, lowpass FIR filter. The filter model is formulated using sinusoidal functions of frequency to evaluate the impulse response coefficients in closed form. Filter transfer function is evolved in frequency and time domain. This design approach is found to be closely comparable to FRM techniques in terms of arithmetic complexity with added advantage of simpler design and having closed form expressions for impulse response coefficients. Approach can be extended to design sharp transition arbitrary passband highpass, bandpass and bandstop filters.

A novel filter design for spatially interpolated beamformer

This paper proposes a novel design approach for a linear phase lowpass FIR filter for digital beamformer applications. The simple filter design has good stopband attenuation with the use of trigonometric functions and less filter complexity. Novel slope equalization technique of the filter design reduces ripple at the transition edges of the filter hence further improves its stop band attenuation. Proposed filter replaces Dolph-Chebyshev window in the design of a uniform linear array spatially interpolated beamformer. The resulting beamformer yields narrow main beamwidth and low sidelobe level with reduced complexity. The beamformer provides for precise and independent control of main beamwidth, null to null main beamwidth and sidelobe level.

A new filter design for uniform linear array

In this paper, a new design of spatial filter for uniform linear array is presented. The array factor is expressed in terms of cosine, sine and linear functions of frequency which serves as an alternative to Chebyshev polynomials. The simple filter design has good stopband attenuation with the use of trigonometric functions with less filter complexity. Novel slope equalization technique of the filter design reduces ripples at the transition edges hence further improves its stopband attenuation. Proposed filter replaces Dolph-Chebyshev window in the design of a uniform linear array beamformer.

A novel design of sharp transition FIR filter for digital beamforming

This paper proposes a new approach to the design of linear phase, equiripple response, lowpass FIR filter for digital beamforming applications. The simple filter design without optimizations has sharp transition, good stopband attenuation with less filter complexity. An uniform linear array beamformer with a narrow transition bandwidth and low side lobes is synthesized with fewer sensor elements. This is achieved by using the proposed filters as subfilters in the frequency response masking approach. Precise and independent specification of main beamwidth and side lobe level for the beamformer is possible.

Linear phase FIR filter for narrow-band filtering

This paper proposes a novel approach to the design of linear phase, sharp transition, lowpass FIR filter. The filter has narrow transition band, low passband ripple and good stopband attenuation with reduced arithmetic complexity. The frequency response model of the filter is formulated using trigonometric functions of frequency to reduce the ripples due to Gibbpsilas phenomenon and to evaluate the impulse response coefficients in closed form. FIR highpass and bandpass filters of any passband width can also be designed using the proposed approach.