Transverse Filters Research Articles

Over-Moded Transverse Magnetic Cavity Filters for Narrowband Millimeter-Wave Applications

A new version of transverse magnetic (TM) cavity filters for high-frequency applications is presented in this letter. The basic building block of these filters is the over-moded transverse magnetic cavity (OTMC). The OTMC supports a pair of high-order resonant modes, namely TM320 and TM230, as well as various nonresonating modes that can be exploited to provide an additional input-to-output path (the propagating TM11 is the one primarily employed in the particular configuration here presented). Besides the possibility of realizing elliptic responses having the maximum number of transmission zeroes, a higher ${Q}$ -factor as well as a significantly reduced sensitivity to manufacturing imperfections is the main benefit making these structures especially suitable for the practical realization of very narrowband millimeter-wave filters. The experimental results of an elliptic fourth-order OTMC filter with 0.2% fractional bandwidth at 41.415 GHz validate the feasibility of these new transverse magnetic filters.

Miniaturized dielectric waveguide filters

ABSTRACTDesign techniques for a new class of integrated monolithic high-permittivity ceramic waveguide filters are presented. These filters enable a size reduction of 50% compared to air-filled transverse electromagnetic filters with the same unloaded Q-factor. Designs for Chebyshev and asymmetric generalised Chebyshev filter and a diplexer are presented with experimental results for an 1800 MHz Chebyshev filter and a 1700 MHz generalised Chebyshev filter showing excellent agreement with theory.

A NMR reverse diffusion filter for the simplification of spectra of complex mixtures and the study of drug receptor interactions

A reverse diffusion filter NMR experiment (Drev) is proposed for the study of small molecules in binding with macromolecules. The filtering efficiency of Drev to eliminate the signals of the macromolecule is shown to be superior to conventional transverse relaxation filters at least for macromolecules containing a significant fraction of flexible residues. The Drev filter was also a useful complement for ligand-based NMR screening in combination with saturation transfer difference experiments.

An Experimental Assessment of Transverse Adaptive Fir Filters as Applied to Vibrating Structures Identification

The present work is aimed at assessing the performance of adaptive Finite Impulse Response (FIR) filters on the identification of vibrating structures. Four adaptive algorithms were used: Least Mean Squares (LMS), Normalized Least Mean Squares (NLMS), Transform‐Domain Least Mean Squares (TD – LMS) and Set‐Membership Binormalized Data‐Reusing LMS Algorithm (SM – BNDRLMS). The capability of these filters to perform the identification of vibrating structures is shown on real experiments. The first experiment consists of an aluminum cantilever beam containing piezoelectric sensors and actuators and the second one is a steel pinned‐pinned beam instrumented with accelerometers and an electromechanical shaker.

Active control of environmental noise, VIII: increasing the response to primary source changes including unpredictable noise*1

Conventional adaptive cancellation systems using traditional transverse finite impulse response (FIR) filters, together with least mean square (LMS) adaptive algorithms, well known in active noise control, are slow to adapt to primary source changes. This makes them inappropriate for cancelling rapidly changing noise, including unpredictable noise such as speech and music. Secondly, the cancelling structures require considerable computational processing effort to adapt to primary source and plant changes, particularly for multi-channel systems. This paper describes methods to increase the adaptive speed to primary source changes in large enclosed spaces and outdoor environments. A method is described that increases the response to time varying periodic noise using traditional transverse FIR filters. Here a multi-passband filter, with individual variable adaptive step sizes for each passband is automatically adjusted according to the signal level in each band. This creates a similar adaptive response for all frequencies within the total pass-band, irrespective of amplitude, minimizing the signal distortion and increasing the combined adaptive speed. Unfortunately, there is a limit to the adaptive speed using the above method as classical transverse FIR filters have a finite adaptive speed given by the stability band zero bandwidth. For rapidly changing periodic noise and unpredictable non-stationary noise, a rapid to instantaneous response is required. In this case the on-line adaptive FIR filters are dispensed with and replaced by a time domain solution that gives virtually instantaneous cancellation response (infinite adaptive speed) to primary source changes, and is computationally efficient.

Active control of environmental noise, VIII: increasing the response to primary source changes including unpredictable noise

Conventional adaptive cancellation systems using traditional transverse finite impulse response (FIR) filters, together with least mean square (LMS) adaptive algorithms, well known in active noise control, are slow to adapt to primary source changes. This makes them inappropriate for cancelling rapidly changing noise, including unpredictable noise such as speech and music. Secondly, the cancelling structures require considerable computational processing effort to adapt to primary source and plant changes, particularly for multi-channel systems. This paper describes methods to increase the adaptive speed to primary source changes in large enclosed spaces and outdoor environments. A method is described that increases the response to time varying periodic noise using traditional transverse FIR filters. Here a multi-passband filter, with individual variable adaptive step sizes for each passband is automatically adjusted according to the signal level in each band. This creates a similar adaptive response for all frequencies within the total pass-band, irrespective of amplitude, minimizing the signal distortion and increasing the combined adaptive speed. Unfortunately, there is a limit to the adaptive speed using the above method as classical transverse FIR filters have a finite adaptive speed given by the stability band zero bandwidth. For rapidly changing periodic noise and unpredictable non-stationary noise, a rapid to instantaneous response is required. In this case the on-line adaptive FIR filters are dispensed with and replaced by a time domain solution that gives virtually instantaneous cancellation response (infinite adaptive speed) to primary source changes, and is computationally efficient.

Design and comparison of amplitude-type and phase-only transverse super-resolving pupil filters

An optimization procedure for designing super-resolving filters is presented, which is to design amplitude-type and phase-only transverse super-resolving Toraldo filters by nonlinear programming at the special Strehl ratio (the ratio of the maximum intensity of the central core of the super-resolving pattern to that of the Airy pattern). Results of comparisons between the performance of our filters and those of the references indicate that the former is superior to the latter. The super-resolving characters of the two types of filters are also discussed and compared.

Transverse or axial superresolution in a 4Pi-confocal microscope by phase-only filters.

A novel procedure to design axial and transverse superresolving pupil filters for the 4Pi-confocal microscope is presented. The method is based on the use of a series of figures of merit developed to describe the effect of inserting two identical filters in the two arms of the illumination path of the microscope. As a practical implementation, we have applied our method to obtain superresolving continuous phase-only filters. Different resolution-improving phase functions are shown for the transverse and the axial direction. These filters provided axial gain up to 1.3 and transverse gain up to 1.4 without an increase in sidelobes.

Role of the cytoplasmic tyrosines of beta 1A integrins in transformation by v-src.

GD25 cells lacking beta 1 integrins or expressing beta 1A with mutations of conserved cytoplasmic tyrosines (Y783, Y795) to phenylalanine have poor directed migration to platelet-derived growth factor or lysophosphatidic acid when compared with GD25 cells expressing wild-type beta 1A. We studied the effects of v-src on these cells. Transformation with v-src caused tyrosine and serine phosphorylation of wild-type beta1 A but not of Y783/795F doubly mutated beta 1A. v-src-transformed cells had rounded and/or fusiform morphology and poor assembly of fibronectin matrix. Adhesion to fibronectin or laminin and coupling of focal contacts to actin-containing cytoskeleton were preserved in transformed Y783/795F cells but lost on transformation when beta 1A was wild type. Transformed Y783/795F cells also retained ability, albeit limited, to migrate across filters, whereas transformed cells with wild-type beta 1A were unable to transverse filters. Studies of single tyrosine mutants showed that the more important tyrosine for retaining ability to adhere, assemble focal contacts, and migrate is Y783. These results suggest that overactive phosphorylation of cytoplasmic residues of beta 1A, particularly Y783, accounts in part for the phenotype of v-src-transformed cells.

Modulation of beta1A integrin functions by tyrosine residues in the beta1 cytoplasmic domain.

beta1A integrin subunits with point mutations of the cytoplasmic domain were expressed in fibroblasts derived from beta1-null stem cells. beta1A in which one or both of the tyrosines of the two NPXY motifs (Y783, Y795) were changed to phenylalanines formed active alpha5 beta1 and alpha6 beta1 integrins that mediated cell adhesion and supported assembly of fibronectin. Mutation of the proline in either motif (P781, P793) to an alanine or of a threonine in the inter-motif sequence (T788) to a proline resulted in poorly expressed, inactive beta1A. Y783,795F cells developed numerous fine focal contacts and exhibited motility on a surface. When compared with cells expressing wild-type beta1A or beta1A with the D759A activating mutation of a conserved membrane-proximal aspartate, Y783, 795F cells had impaired ability to transverse filters in chemotaxis assays. Analysis of cells expressing beta1A with single Tyr to Phe substitutions indicated that both Y783 and Y795 are important for directed migration. Actin-containing microfilaments of Y783,795F cells were shorter and more peripheral than microfilaments of cells expressing wild-type beta1A. These results indicate that change of the phenol side chains in the NPXY motifs to phenyl groups (which cannot be phosphorylated) has major effects on the organization of focal contacts and cytoskeleton and on directed cell motility.

The design of transverse filters and their use in visual electrograms

The subject under study is a digital filtering method which combines the advantages of both theoretical precision and great flexibility of use. This method has enabled us to develop transverse filters which respect the principle of causality and offer a fast and simple solution in the filtering of electrophysiological potentials. Here we present both the design of transverse filters and their application to visual electrophysiological signals.

The (comparative) performance of HGMS -- Filters with a strictly ordered wire matrix in the axial and transverse configuration

We present experimental data on the initial efficiencies of axial and transverse HGMS-filters with a periodically ordered wire matrix. The efficiencies were determined for particles in narrow size ranges by a photo-sedimentation analysis. We also compare the experimental data with the predictions of our recently developed multiwire theories for the performance of axial and transverse filters.

A New Class of Distributed Prototype Filters with Applications to Mixed Lumped/Distributed Component Design

The distributed prototype filter consists of a cascade of shunt stubs of equal length alternating with uniform transmission lines, each of twice the stub length. If the stubs are open circuited, they may be replaced by lumped capacitors to synthesize a mixed lumped/distributed (L/D) filter having near optimum Chebyshev or Zolotarev characteristics. The rate of cutoff and the general character of the stopband region is predictable. The use of Zolotarev prototypes enables the impedance level within the filter to be controlled and gives greater selectivity. Designs suitable for either transverse electromagnetic (TEM) line or waveguide low-pass filters are presented. If the stubs are short-circuited, the prototype may be used to design quasi-high-pass or bandpass filters of very large bandwidth. An example is given of an inductive-iris-type filter of approximately 100-percent bandwidth for which previous theories have been unsuitable. The theory is capable of extension to more complicated mixed L/D structures containing both series and shunt elements.

Erratum: Conductor admittance in transverse TEM filters and slow-wave structures

Erratum: Conductor admittance in transverse TEM filters and slow-wave structures

Conductor admittance in transverse TEM filters and slow-wave structures

The admittance Y(φ) of a single rectangular conductor in a transverse TEM filter or slow-wave structure can be expressed in a series of mutual interaction terms with the neighbouring conductors and with the surrounding ground planes. The first four interaction terms are computed numerically and yield Y(φ) with about 1% accuracy.