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An improved protocol for crystallographic refinement by simulated annealing is presented. It consists of slow cooling starting at high temperatures. Tests of refinements of aspartate aminotransferase and procin pepsin show that the slow-cooling protocol produces lower R factors and better geometry than other protocols previously published. The influence of(More)
In this paper we propose to use digital fractional sample delayers to perform high precision beam steering at the baseband sampling frequency. The major advantages of the proposed technique are that the fractional sample delayer (FSD) used has a very flat magnitude response within the baseband width allowing greater than 20-bit resolution for a 35-tap(More)
This paper presents the way of speeding up the route from the theoretical design with Simulink/Matlab, via behavioral simulation in fixed-point arithmetic to the implementation on either FPGA or custom silicon. This has been achieved by porting the netlist of the Simulink system description into the VHDL. At the first instance, the Simulink-to-VHDL(More)
Extensions of popular transformations for IIR filters are given which employ high order mapping filters. Easy control of prototype transfer function features in multiband renditions is demonstrated. A wider interpretation of transformation is also suggested which permits " less-than-N-band replication " (at a cost in dimensionality , phase fidelity and(More)
This paper reports on the establishment of the coefficient bounds for half-band fixed-point polyphase filters, having all their zeroes on the unit circle. The paper also reports on the algebraic details of the established bounds, exposing pictorially the coefficient interactions and the corresponding polo-zero-patterns (pzp) for the 5 th and 7 th order(More)
We propose a modified version of the standard homomorphic method to design a minimum-phase inverse filter for non-minimum phase impulse responses equalization. In the proposed approach some of the dominant poles of the filter transfer function are replaced by new ones before carrying out the inverse DFT. This method is useful when partial magnitude(More)
This paper presents a design technique for high fidelity multistage decimation filters based on the polyphase and decimator structures presented in [1][2], catering for powers of two sample-rate decreases. The technique is well suited for Analog-to-Digital Converter (ADC) applications in excess of 16 bit resolution. The resulting filter coefficients are(More)
This paper addresses high-order frequency transformation and extends standard Constantinides, Mullisfiranchitti transformations and the exact N-point approach we have previously reported. Using specially designed M* order allpass filters, mapping of N features of the prototype filter can be carried out independently (where N<M). The mapping filter is(More)
This paper addresses a new approach for the design of multiband filters with step like magnitude responses and extremely flat, weighted passbands down to µdBs. Our new technique can also be used for the multiband step-wise approximation of arbitrary filter magnitude responses with precise transition band control. One marked advantage of the technique is(More)
The paper addresses tlie design of tlie polyphase IIR filters based on the " '-order single-coefficient allpass sub-filters in the constraint coefficient space using the Constraint Dowdiill Simplex Algorithm. Incorporating the bit-flipping algorithm into its core engine allowed the optitilisation routine to converge to better target designs without(More)