SIR and SNR improvement in wideband beamspace array processing

Owing to limitations of frequency resources, advanced sensor array processing techniques are needed in a growing wireless wideband communications market. A beamspace wideband processing technique is proposed and is shown to reduce both signal to interference and SNR ratios. Performances for different array processing algorithms, flexibility and complexity cost are thus improved     

Technique for design of two-channel approximately linear phase QMFfilter bank and its application to image compression

The two-channel QMF filter bank based on allpass sections is one of the best known circuits for building up a multi-channel filter bank for signal compression. An analysis-synthesis combination can satisfy two of the three perfect reconstruction (PR) conditions. The third, the phase condition, can be met to any desired accuracy. However, when applied to images, PR is possible because non-causality can be allowed in the synthesis bank. The development of explicit formulae for the coefficients of such filters is considered. The resulting QMF designs can be used in a wavelet structure for image compression problems using rectangular or diamond symmetry. Several design examples are given, including a comparison of performance with FIR filter banks for such problems     

Adaptive array sensor processing applications for mobile telephonecommunications

The mobile telephone cellular communication system is rapidly being saturated with an increase in subscribers. Although advanced coding and modulation techniques as well as different cell cluster architectures have been implemented, a great increase in the channel capacity is needed, especially in large markets. Adaptive sensor processing has been introduced as a possible remedy to increase the channel capacity by using the directional sensitivity, which leads to a reduction of the interference. Some high-resolution algorithms are evaluated for the direction of arrival (DOA) estimation for a cellular mobile radio environment whose cluster size is varied from K=7, K=4, and K=3; more signals and scattering scenarios that typically arise in urban areas are taken into account. This information is used to beamform toward the signal of interest, resulting in a decrease of the interference. Several signal estimation procedures are evaluated and compared, and it is observed that the DOAs, among other benefits, leads to even higher performance compared with the reference signal method. The computational aspects for the different signal processing, detection and estimation schemes are also discussed     

Design of doubly complementary filters with approximate linearphase

A new procedure for the design of a real doubly complementary (DC) pair of digital filters obtained from an all-pass structure is presented. The filter design is based on a zero-phase FIR filter design with multi-band frequency specifications and approximate linear-phase characteristic. The resulting complex or real all-pass filter structure is guaranteed to be stable. Some examples illustrating the design method including comparisons with conventional approximately linear phase IIR filters are also shown     

Simple design and realisation of linear phase 2D FIR filters withdiamond frequency support

A simple design method for linear-phase 2D FIR filters with diamond frequency support is proposed. The method is based on a 1D halfband linear-phase FIR filter design and offers some flexibility in the choice of specifications; the resulting realisation is efficient in terms of computational cost. A design example is also included     

Stable, causal, perfect reconstruction, IIR uniform DFT filterbanks

A simple design procedure for stable, causal and perfect reconstruction infinite impulse response parallel uniform discrete Fourier transform filter banks (DFT FBs) based on a new polyphase decomposition, the `polyphase-oversampled' FB, is presented. The proposed design results in causal and stable analysis and synthesis filters that are all derived from a single prototype filter, resulting in efficient realisations. A discussion of the FB numerical properties and some design examples are provided     

Design of stable, causal, perfect reconstruction, IIR uniform DFTfilter banks

Design procedures for stable, causal and perfect reconstruction IIR parallel uniform DFT filter banks (DFT FBs) are presented. In particular a family of IIR prototype filters is a good candidate for DFT FB, where a tradeoff between frequency selectivity and numerical properties (as measured by the Weyl-Heisenberg frames theory) could be made. Some realizations exhibiting a simple and a massively parallel and modular processing structure making a VLSI implementation very suitable are shown. In addition, some multipliers in the filters (both the analysis and synthesis) could be made; powers or sum of powers of 2, in particular for feedback loops, resulting in a good sensitivity behavior. For these reasons as well as for the use of low order IIR filters (as compared with conventional FIR filters), the overall digital filter bank structure is efficient for high data rate applications. Some design examples are provided