Multiple Passbands Research Articles

Planar UWB Filter with Multiple Notched Band and Stopband with Improved Rejection Level

AbstractAnalysis and realization of a microstrip-based planar ultra-wideband (UWB) filter with integrated multiple notch elimination property and simultaneously extended upper stopband is proposed. Initially, a UWB filter based on back-to-back microstrip-to-CPW technology is designed. Later, multiple spiral defected ground structures (DGS) are embedded to obtain multiple passband notches. Further, double equilateral U (DEU)-type DGS are used to improve upon the rejection level in upper stopband. The multiple passband notches are results of embedded spiral-shaped DGS (SDGS), while extended upper stopband is the outcome of suppressed higher-order spurious harmonics. The flexible dual-attenuation poles of DEU-shaped DGS suppress the stopband harmonics and widen the stopband. An approximate lumped equivalent circuit model of the proposed filter is modelled. The filter is compact and its layout measures 25.26 mm × 11.01 mm. The measured result is in good agreement with the full-wave electromagnetic (EM) simulation and circuit simulation.

SIX-YEAR OPTICAL MONITORING OF THE BL LACERTAE OBJECT 1ES 0806+52.4

We present the results of the first systematic long-term multi-color optical monitoring of the BL Lacertae object 1ES 0806+52.4. The monitoring was performed in multiple passbands with a 60/90 cm Schmidt telescope from December 2005 to February 2011. The overall brightness of this object decreased from 2005 December to 2008 December, and regained after that. A sharp outburst probably occurred around the end of our monitoring program. Overlapped on the long-term trend are some short-term small-amplitude oscillations. No intra-night variability was found in the object, which is in accord with the historical observations before 2005. By investigating the color behavior, we found strong bluer-when-brighter chromatism for the long-term variability of 1ES 0806+52.4. The total amplitudes at the c, i and o bands are 1.18, 1.12, and 1.02 mags, respectively. The amplitudes tend to increase toward shorter wavelength, which may be the major cause of bluer-when-brighter. Such bluer-when-brighter is also found in other blazars like S5 0716+714, OJ 287, etc. The hard X-ray data collected from the Swift/BAT archive was correlated with our optical data. No positive result was found, the reason of which may be that the hard X-ray flux is a combination of the synchrotron and inverse Compton emission but with different timescales and cadences under the leptonic Synchrotron-Self-Compton (SSC) model.

VERIFICATION OF CORONAL LOOP DIAGNOSTICS USING REALISTIC THREE-DIMENSIONAL HYDRODYNAMIC MODELS

Many different techniques have been used to characterize the plasma in the solar corona: density-sensitive spectral line ratios are used to infer the density, the evolution of coronal structures in different passbands is used to infer the temperature evolution, and the simultaneous intensities measured in multiple passbands are used to determine the emission measure distributions. All these analysis techniques assume that the intensity of the structures can be isolated through background subtraction. In this paper, we use simulated observations from a three-dimensional hydrodynamic simulation of a coronal active region to verify these diagnostics. The density and temperature from the simulation are used to generate images in several passbands and spectral lines. We identify loop structures in the simulated images and calculate the background. We then determine the density, temperature, and emission measure distribution as a function of time from the observations and compare these with the true temperature and density of the loop. We find that the overall characteristics of the temperature, density, and emission measure are recovered by the analysis methods, but the details are not. For instance, the emission measure curves calculated from the simulated observations are much broader than the true emission measure distribution, though the average temperature evolution is similar. These differences are due, in part, to a limitation of the analysis methods, but also to inadequate background subtraction.

1P1-V01 Coarse-to-fine法を取り入れた生体模倣型実時間両眼視差検出システム(ロボットビジョン)

We developed an algorithm and architecture for calculating the optimal binocular disparity efficiently based on the binocular disparity energy model with a coarse-to-fine strategy. Because the model requires a lot of spatial filtering whose computational cost is very high, we designed hardware architecture so that it executes the required spatial computation in real time by using a resistive network and a field programmable gate array (FPGA). The resistive network enables fast multiple band pass filtering required for implementing the disparity model. The algorithm takes advantages of the hardware architecture to calculate the optimal disparity from multiple band-passed images. The optimal disparities calculated from band-passed images with a low and high frequency offer a wide detectable disparity range and high precision, respectively. We evaluated the algorithm by using a software simulation. The results showed that the algorithm offers both a wide disparity range and high precision.

The Fly's Eye Camera System: An instrument design for large étendue time‐domain survey

AbstractIn this paper we briefly summarize the design concepts of the Fly's Eye Camera System, a proposed high resolution allsky monitoring device which intends to perform high cadence time domain astronomy in multiple optical passbands while still accomplish a high étendue. Fundings have already been accepted by the Hungarian Academy of Sciences in order to design and build a Fly's Eye device unit. Beyond the technical details and the actual scientific goals, this paper also discusses the possibilities and yields of a network operation involving ∼10 sites distributed geographically in a nearly homogeneous manner. Currently, we expect to finalize the mount assembly – that performs the sidereal tracking during the exposures – until the end of 2012 and to have a working prototype with a reduced number of individual cameras sometimes in the spring or summer of 2013. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Multi-band optical metamaterials based on random dendritic cells

Optical metamaterials (OMs) at visible wavelengths have been extensively developed. OMs reported recently are all composed of periodic structure, and fabricated by top-down approaches. Here demonstrated are the colored visible light frequency metamaterials composed of double layer array disordered and geometrical variational dendritic cells as well as fabricated by a novel bottom-up approach. The experiment demonstrates that the OMs composed of random silver dendritic cells caused the appearance of multiple transmission passbands at red and yellow light frequencies. Moreover, the slab focusing experiment reveals a clear point image in the range of half-wavelength with an intensity of 5 % higher than that of the light source. The proposed OMs will create a new way to prepare the cloak and the perfect lens suitable for optical frequency.

High-Q filters with complete transmission by quasi-periodic dielectric multilayers

A multiple narrow bandpass filter with both high Q factor and complete transmission using quasi-periodic Thue-Morse dielectric multilayers is proposed. The Q factor of the system increases exponentially with the generation order. Even though the Q factor of resonances increases as the generation order of the multilayers increases, these resonances are still complete resonances. The number of resonance peaks for the bandpass filter of the system also increases as the generation order increases. These resonance peaks have a multifractal distribution throughout the frequency range, which is different from that in traditional periodical multilayers.

Multiple frequency bands of square split resonant rings and metal wire metamaterial

This work presents experimental measurements of two square split resonant ring and metal wire (SSRR-MW) samples with different cell sizes at microwave frequencies. The geometrical sizes of the metamaterial cells are found to play an important role in the resonant frequency. Cells with different geometrical sizes are chosen to stack into a two-layer or three-layer metamaterial unit to realize the multiple negative passbands. The effective parameters of three separate SSRR-MW models (a one-layer unit, a two-layer unit, and a three-layer unit) are retrieved from the simulation data. The composed models exhibit two or three negative bands by overlapping the passbands of original cells and broadening the overall bandwidth. The recovered parameters show good agreement with the theoretical analysis.

Metamaterial composed of different cells exhibiting a negative refraction property over multiple frequency bands

Experimental measurements are presented of the SSRR-MW (square split resonant ring and metal wire) and CSRR-MW (C split resonant ring and metal wire) samples at microwave frequencies. The geometrical shapes of the metamaterial samples are found to play an important role in determining the resonant frequency. Different cells are chosen to stack into a two-layer or a three-layer metamaterial unit to realize multiple negative passbands. The effective parameters of three one-layer models, a two-layer unit, and a three-layer unit are retrieved from the simulation data. The composed models exhibit two or more negative bands by overlapping the passbands of the original cells, and broaden the negative refraction. The recovered parameters show good agreement with theoretical analysis.

A Reconfigurable Compact Coupled Line Multiple-Band Bandpass Filter

This study proposes a circuit structure with reconfigurable multiple bands bandpass filter. This circuit can provide a triple-band or dual-band bandpass facility by adjusting two open stubs (L6 and L7) location. The circuit design used three sections of transmission line in series, the two sets of the coupled lines connected to the gap in each transmission line, and two open stubs in the appropriate locations. The design and manufacturing of the circuit structure is innovative and simple. The center frequencies of the triple-band bandpass filter are set at 2.4, 4.2, and 6.5 GHz, respectively, while the center frequencies of the dual-band bandpass filter are the two lower pass band of the triple-band bandpass filter at 2.4 and 4.2GHz. The filters were simulated using the full-wave electromagnetic simulator, IE3D, and measured by Anritsu-37269D. The simulated and measured results show good agreement in the frequency of interest.

Potential-controlled filtering in quantum star graphs

We study the scattering in a quantum star graph with a Fülöp–Tsutsui coupling in its vertex and with external potentials on the lines. We find certain special couplings for which the probability of the transmission between two given lines of the graph is strongly influenced by the potential applied on another line. On the basis of this phenomenon we design a tunable quantum band-pass spectral filter. The transmission from the input to the output line is governed by a potential added on the controlling line. The strength of the potential directly determines the passband position, which allows to control the filter in a macroscopic manner. Generalization of this concept to quantum devices with multiple controlling lines proves possible. It enables the construction of spectral filters with more controllable parameters or with more operation modes. In particular, we design a band-pass filter with independently adjustable multiple passbands. We also address the problem of the physical realization of Fülöp–Tsutsui couplings and demonstrate that the couplings needed for the construction of the proposed quantum devices can be approximated by simple graphs carrying only δ potentials.

Tunable and switchable dual-wavelength dissipative soliton generation in an all-normal-dispersion Yb-doped fiber laser with birefringence fiber filter

We report the generation of tunable single- and dual-wavelength dissipative solitons in an all-normal-dispersion mode-locked Yb-doped fiber laser, to the best of our knowledge, for the first time. Besides single-wavelength mode-locking, dual-wavelength mode-locking was achieved using an in-line birefringence fiber filter with periodic multiple passbands, which not only allows multiple wavelengths to oscillate simultaneously but also performs spectrum modulation on highly chirped dissipative pulse. Furthermore, taking advantage of the tunability of the birefringence fiber filter, wavelength tuning for both single- and dual-wavelength dissipative soliton mode-locking was realized. The dual-wavelength operation is also switchable. The all-fiber dissipative laser with flexible outputs can meet diverse application needs.

Broadband Multiple Cone-Beam 3-D IIR Digital Filters Applied to Planar Dense Aperture Arrays

A digital beamformer that can synthesize array factors (AFs) with multiple, ultrawideband (UWB), frequency-independent beams at lower computational complexity is proposed. The beamformer is based on a novel 3-D infinite impulse response (IIR) transfer function $H_{\rm MC}\left({\bf z}\right)$ having multiple cone-shaped passbands in the 3-D spatio–temporal (ST) frequency-domain $\mmb{\omega}\in\BBR^{3}$ . The magnitude frequency response and the AF of $H_{\rm MC}\left({\bf z}\right)$ are simulated for dual- and single-passband cases. An element pattern of a broadband Vivaldi antenna is simulated at 1.4 GHz and is used to obtain the total array pattern. Computational complexity of $H_{\rm MC}\left({\bf z}\right)$ for single-passband (1Cone) case and that of the conventional phased array (PA) beamformer are derived. The magnitude frequency response of the proposed beamformer for 1Cone case and that of the PA beamformer are compared using the mean square error (MSE). For the given selectivity specified by the half cone angle $\epsilon={\hbox {5}}^{\circ}$ , proposed beamformer provides around 60% lower MSE for the same complexity and around 90% lower complexity for the same MSE compared with the PA beamformer.

Highly Miniaturized Multiband Bandpass Filter Design Based on a Stacked Spiral Resonator Structure

This paper describes a stacked spiral resonator (SSR) structure for designing very compact multiband bandpass filters. The resonant frequencies of the proposed SSR structure can be determined by designing the spiral geometry and controlling the mutual coupling in a stacked structure. The multiple passband bandwidths can then be determined by the spacing of different layer patterns between two coupled SSRs. An adequately designed geometry of the input/output resonator with a tapped-line feed can achieve matching conditions for all passbands simultaneously. Moreover, multiple transmission zeros created on both sides of each passband provide high stopband roll-off rates.

Integrated detection of intrinsic fluorophores in live microbial cells using an array of thin film amorphous silicon photodetectors

Two-dimensional fluorescence spectroscopy (2D FS) provides a non-invasive means to assess cell condition without the introduction of changes to the cell environment. The method relies on the measurement of the excitation–emission fluorescence intensity matrix of key intrinsic fluorophores, like aromatic amino acids, enzyme cofactors, and vitamins. Commonly used detection systems are complex, with multiple bandpass filters, and are hard to miniaturize. Here, an amorphous silicon photodetector array system integrated with amorphous silicon–carbon alloy filters designed to detect three key fluorophores – tryptophan (Trp), reduced nicotine adenine dinucleotide (NADH) and flavin adenine dinucleotide (FAD) – is demonstrated. These intrinsic fluorophores were detected in pure solutions and also in suspended yeast cells. The array system was used to monitor changes in intrinsic fluorophore concentration when a yeast cell solution was subject to a thermal shock stress.

Miniaturised multi-band substrate integrated waveguide filters using complementary split-ring resonators

A novel method for designing miniaturised multi-band filters using the complementary split-ring resonators (CSRRs) is proposed and demonstrated on the basis of substrate integrated waveguide (SIW) technology. By loading different types of CSRRs on the waveguide surface, multiple passbands propagating below the waveguide cutoff frequency can be generated separately. The proposed structures allow relatively independent control over the centre frequency and the coupling coefficient. The working principle is illustrated by the equivalent circuit and the filter coupling methodology is introduced for design purpose. Two types of dual-passband filters, a triple-band and a quadruple-band filter are designed and fabricated to validate the proposed concept. These filters are showing advantages in terms of compact size, good selectivity and stopband rejection, as well as the easy integration capability with other circuits.

Wave Transmission in Dispersive Si-Based One Dimensional Photonic Crystal

Transmission of electromagnetic waves through a Si-based one dimensional photonic crystal has been investigated. The proposed structure works as an omni-directional reflector for a certain range of wavelength for an angle of incidence up to 55?. The structure works as a narrow band TM-polarization filter for an angle of incidence more than 55?, i.e. a filter which completely blocks TE-polarized waves but allows certain wavelengths of TM-polarized waves. But at an angle of incidence of 89?, the structure works as a multiple narrow band TM-polarization filter even though no defect layer is introduced inside the structure. It is also found that this multiple narrow pass-bands of TM-polarized waves can be tuned to a desired range of wavelength by changing the temperature of the structure.

GENERALIZED SYNTHESIS AND DESIGN OF SYMMETRICAL MULTIPLE PASSBAND FILTERS

In this paper, we present a new synthesis method for a generalized symmetric multiple band bandpass fllter. By using frequency transformations on the low pass prototype, the poles and zeros of the single/dual band flltering function are obtained. These poles and zeros are combined and re-arranged to get the multiband flltering function. The coupling matrix is obtained from this multiband flltering function. A variety of fllters are synthesized in order to validate the proposed theory. A triple band and quadruple band fllters have been designed, fabricated and measured. The measured results have good agreement with the simulated results.

On the Design of a Multiple Pass-band Filter by Frequency Transformation

It is shown that the use of reactance functions for frequency transformation of a normalized low-pass filter (NLPF) to a multiple passband filter (MPBF) is straightforward and simpler than the methods using repeated low-pass to band-pass transformation or a combination of such transformations. The method gives the band edges of the MPBF corresponding to the positive and negative cutoff frequencies of the NLPF unambiguously. The transformation function is found explicitly in terms of the band edges of the MPBF and the NLPF elements are converted to those of the MPBF with ease. Furthermore, the center frequencies of the passbands are also found with ease. Dual and triple passband filters are considered for illustrating the use of the method.

A New Method to Sampling of Multiple Bandpass Signals

A traditional assumption underlying most data converters is that the signal should be sampled at a rate exceeding twice the highest frequency. In this paper, we employ a method for low-rate sampling of multi- band signals via applying periodic nonuniform sampling in shift-invariant spaces generated by m kernels with period T. To avoid the non-ideal filter in traditional method, we use reconstruction functions to recovery the sampled signal completely. Finally, we validate the method in MATLAB; the conclusion of simulation shows the frame-work presented here is feasible.