Juuso T. Olkkonen

Efficient lifting wavelet transform for microprocessor and VLSI applications

Recently, wavelet analysis has gained an established role in signal and image processing applications. In this paper, we present a discrete wavelet transform algorithm based on the lifting scheme. The Haar wavelet transformed and decimated signals are lifted by the ladder-type network. A unique lifting filter is designed for in-place computation. The present algorithm is especially suitable for microprocessor and VLSI applications since it can be implemented by integer arithmetics using only register shifts and summations.

Hilbert transform assisted complex wavelet transform for neuroelectric signal analysis

In this work, we present a new approach for shift invariant complex wavelet analysis of neuroelectric signals. A key idea is to preprocess the signal with the Hilbert transformer to yield an analytic signal, which is then wavelet transformed using the linear phase complex scaling and wavelet filters. In different scales, the total energy of the wavelet transform coefficients is shift invariant. The decimated analytic wavelet coefficients suffer no aliasing effects, which are predominant in conventional wavelet analysis. We show the usefulness of the present method in multi-scale analysis of the neuroelectric signal waveforms.

Measurement and Reconstruction of Impulse Train by Parallel Exponential Filters

In many areas of science and technology, the measurement of impulse trains is an important sampling scheme. For example, wireless data transmission has grown enormously due to the recent developments in ultra wide band technology, where the information is represented as impulse trains. In this letter, we present a new approach for sampling of the impulse train using parallel exponential filters (EFs), whose outputs are measured simultaneously. We show that with parallel EFs, it is possible to reconstruct impulses with different amplitudes and appearance times within one sampling period. The reconstruction algorithm is manageable on microprocessor and VLSI circuits. Several applications of the parallel EF network are outlined.

Fractional Delay Filter Based on the B-Spline Transform

Fractional delay filters (FDFs) have a key role in communication systems. FDFs produce a delay that is a fraction of the sampling period. In this letter, we introduce a framework based on the B-spline interpolation and decimation procedure for design of the FDFs. The method generates precise fractional delays and is easy to implement in microprocessor and VLSI environments

Sampling and Reconstruction of Transient Signals by Parallel Exponential Filters

This brief introduces a new method for sampling of transient analog waveforms based on the parallel exponential filters. The signal is fed to the parallel network consisting of resistor-capacitor (RC) circuits, outputs of which are simultaneously sampled. We show that N previous samples of the input signal can be reconstructed from single output samples of N parallel RC circuits. The parallel sampling method increases the sampling rate of the data acquisition system by a factor of N. In particular, the method is useful in increasing the sampling rate of the Flash-type analog-to-digital VLSI circuits. We present the parallel RC network, develop the reconstruction algorithm, and briefly describe a variety of applications such as measurement and reconstruction of pulses produced by ultrawideband transmitters, radiation detectors, and pulse lasers.

Fractional Time-Shift B-Spline Filter

The fractional time-shift operators are essential devices in processing and adjustment of signals in modern communication systems. This letter introduces the fractional time-shift B-spline filter. The filter produces a time-shift Delta isin [0,1], which is an arbitrary fraction of the sampling period. We describe the construction and parallel implementation of the fractional time-shift filter. We give several of its applications (differentiator, integrator, and correlator) in numerical and statistical signal processing and in adaptive time-shift adjustments.

Printed electronic switch on flexible substrates using printed microcapsules

Printed electronics, the manufacturing of electronic components on large, flexible, and low-cost substrates by printing techniques, can facilitate widespread, very low-cost electronics for consumer applications and disposable devices. New technologies are needed to create functional components in this field. This paper introduces a new method to create an all-additive printed switch on flexible substrate materials, such as polymer foils and paper substrates. The active layer of the switch component consists of neutral polyaniline (PANI), which can be doped by acid to induce a shift from a non-conductive to a conductive oxidation state. Monodisperse core–shell microcapsules containing an acidic aqueous core liquid were produced by a novel inkjet-based encapsulation technology. It was shown that unfavorable water evaporation from the microcapsules could be reduced by the addition of calcium chloride to the core liquid. A switch component was prepared, consisting of inkjet-printed interdigitated silver electrodes, PANI active layer and printed microcapsules. If an external pressure was applied, for instance with a finger, then the switch component changed its state from non-conductive to conductive with a simultaneous distinct color change. The results clearly demonstrate the feasibility of the presented approach to create either a visual or electronic signal for use in printed electronic applications.

Computation of Hilbert Transform via Discrete Cosine Transform

Hilbert transform (HT) is an important tool in constructing analytic signals for various purposes, such as envelope and instantaneous frequency analysis, amplitude modulation, shift invariant wavelet analysis and Hilbert-Huang decomposition. In this work we introduce a method for computation of HT based on the discrete cosine transform (DCT). We show that the Hilbert transformed signal can be obtained by replacing the cosine kernel in inverse DCT by the sine kernel. We describe a FFT-based method for the computation of HT and the analytic signal. We show the usefulness of the proposed method in mechanical vibration and ultrasonic echo and transmission measurements.

Discrete Lattice Wavelet Transform

The discrete wavelet transform (DWT) has gained a wide acceptance in denoising and compression coding of images and signals. In this work we introduce a discrete lattice wavelet transform (DLWT). In the analysis part, the lattice structure contains two parallel transmission channels, which exchange information via two crossed lattice filters. For the synthesis part we show that the similar lattice structure yields a perfect reconstruction (PR) property. The PR condition can be used to design half-band filters, which effectively eliminate aliasing in decimated tree structured wavelet transform. The DLWT can be implemented directly to any of the existing DWT algorithms

Light transmission through a high index dielectric hole in a metal film surrounded by surface corrugations.

We analyze transmission of a normally incident plane wave through a 100nm diameter hole in a silver film that is filled with a high index dielectric and is surrounded by 300nm wide surface grooves. Specifically, we study the dependency of the transmission efficiency on the number of grooves, groove depth, and the horizontal distance between the groove and the central hole. We observe that the investigated structure exhibits over five orders of magnitude larger transmission efficiency versus a single hole without the dielectric filling.