Number Of Passbands Research Articles

High Performance Multiple Passband Substrate Integrated Plasmonic Filters

We proposed a new variety of substrate integrated plasmonic filters (SIPFs) with multiple passband characteristics based on the concept of spoof surface plasmon polaritons (SSPPs). By etching a periodic interdigital structure array on the top metal layer of substrate integrated waveguide (SIW), we can achieve high-efficiency microwave SSPP transmission with an insertion loss of 1 dB in the passband of 7.4-12.5 GHz, and a high rejection level of 27 dB in the rejection bands. By introducing antisymmetric C-ring resonators (ASCRs) in the filter structure, the passband number and bandwidth of the filter can be flexibly manipulated. To validate the proposed design, four SSPP filters prototypes are fabricated and tested, showing good filtering performances with a high transmission coefficient ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{S}21\mathbf {&gt;}-$ </tex-math></inline-formula> 1 dB) and low reflection coefficient ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{S}11\,\,\mathbf { &lt; } - $ </tex-math></inline-formula> 12 dB) in their passbands, and a high rejection level over 15 dB between them. By changing the geometric parameters of ASCR, the number of passbands can be increased from 1 to 3, and the passband center frequency and bandwidth can be engineered accordingly. The proposed SSPP filters with good multiple passband characteristics may have great potential applications in microwave wireless integrated plasmonic circuits and communication systems.

A Multiband Microwave Photonic Filter Based on a Strongly Coupled Microring Resonator With Adjustable Bandwidth

A bandwidth-tunable multiband microwave photonic filter (MPF) using a strongly coupled microring resonator (MRR) with optical phase modulation is demonstrated theoretically and experimentally. Two notches of the MRR adjacent to the optical carrier break the intrinsic balance of the phase-modulated signal and then two sub-MPFs are formed thanks to the conversion from phase modulation to intensity modulation (PM-IM). The frequency responses of the two sub-MPFs are superimposed to form a passband with a fixed center frequency. Due to the periodicity of the MRR transmission spectrum, multiple passbands separated by a certain spacing appear in the frequency domain and combine to form a multiband MPF, whose bandwidth can be adjusted by tuning the wavelength of the carrier. The tunable bandwidth and shape factors ranging from 0.73 GHz to 2.73 GHz and 5.06 to 1.38 are experimentally performed. The number of passbands can be reconfigured. The proposed multiband MPF has the potential to be employed in modern multi-standard wireless communication systems.

ON THE ACCURACY OF THE DIFFERENTIAL EMISSION MEASURE DIAGNOSTICS OF SOLAR PLASMAS. APPLICATION TO SDO /AIA. II. MULTITHERMAL PLASMAS

The Differential Emission Measure (DEM) analysis is one of the most used diagnostic tools for solar and stellar coronae. Being an inverse problem, it has limitations due to the presence of random and systematic errors. We present in theses series of papers an analysis of the robustness of the inversion in the case of AIA/SDO observations. We completely characterize the DEM inversion and its statistical properties, providing all the solutions consistent with the data along with their associated probabilities, and a test of the suitability of the assumed DEM model. While Paper I focused on isothermal conditions, we now consider multi-thermal plasmas and investigate both isothermal and multithermal solutions. We demonstrate how the ambiguity between noises and multi-thermality fundamentally limits the temperature resolution of the inversion. We show that if the observed plasma is multi-thermal, isothermal solutions tend to cluster on a constant temperature whatever the number of passbands or spectral lines. The multi-thermal solutions are also found to be biased toward near isothermal solutions around 1 MK. This is true even if the residuals support the chosen DEM model, possibly leading to erroneous conclusions on the observed plasma. We propose tools to identify and quantify the possible degeneracy of solutions, thus helping the interpretation of DEM inversion.

Narrow band filter using 1D periodic structure with defects for DWDM systems

A 1D binary periodic structure with defect has been analysed using Transfer Matrix Method. For a particular nine layered structure of SiO2 and InP, a number of full stop bands (in other words, zero passbands or forbidden bands) at different regions of the spectrum under investigation are observed. Introducing a central spatial defect in the system by adjusting the layer width, it is possible to achieve an extremely narrow passband centred on 1554.9nm in the 7th forbidden band. Moreover by varying the defect width, the number of passbands can be increased. These passbands have flat and 100% stopband and hence can be better candidate to drop single or multiple frequencies in WDM systems. It is further observed that with increase in the number of layers and/or defect width, the number of mini pass bands outside the original forbidden band also increases. Also by FDTD simulation it is seen that the field is localised within the defect for the passband frequency.

Investigation on two dimensional photonic crystal resonant cavity based bandpass filter

In this paper, different cavities, namely quasi square, tri-quarter square, square, hexagonal, circular, elliptical, diamond and annular ring based photonic crystal bandpass filters (PCBPFs) are proposed and investigated by exploiting coupling between two in-line quasi waveguides and a resonant cavity. The resonant wavelength, output efficiency and bandwidth of designed PCBPFs are studied by varying the size of the cavity. The normalized transmission spectra of PCBPF are observed using 2D finite difference time domain (FDTD) method. The photonic band gap (PBG) is calculated by plane wave expansion (PWE) method. The circular cavity based PCBPF gives better performance than others because of its circular resonating modes. The number of passbands is increased linearly while increasing the size of the cavity. The overall size of the PCBPF chip is about 11.4μm×11.4μm, which is more suitable for photonic integrated circuits (PIC), wavelength division multiplexing (WDM) systems and sensing applications.

STUDY ON A SORT OF CONTROLLABLE NONLINEAR LEFT-HANDED MATERIALS

In this paper, three kinds of controllable nonlinear left-handed materials (DNLHMs) are proposed and analyzed, which are designed by introducing inductors and capacitors into the traditional nonlinear left-handed materials (NLHMs) as inhomogeneous doped elements. Due to such changes, several new transmission properties have been presented through finite-difference time-domain (FDTD) simulations. These have brought new features to our DNLHMs. On one hand, the original passband in the traditional nonlinear left-handed material is narrowed after introducing inductors. In addition, a new passband, which does not exist in doped linear LHMs, is generated. On the other hand, through introducing capacitors, the original passband of the nonlinear left-handed material can be shifted, resonance frequency can be changed, and a new passband can be generated. When capacitors and inductors are introduced simultaneously, the material properties, such as the number of passbands, the characteristic resonance frequency, and the bandwidth, can also be changed. Noting these characteristics, the values of the introduced inductors and capacitors are varied to investigate the spectrum changes of DNLHMs. Then, a series of controllable properties of the DNLHMs can be retrieved. And more importantly, the designed DNLHMs give the adjustability of suppressing high harmonics, which is not possible in the past materials.

Optimum filtration of microwave signals by a multiband spin-wave ring resonator

The optimum filtration of pulsed microwave signals by a multiband active spin-wave ring resonator has been studied for the first time. The ring resonator, which comprises a spin-wave delay line based on a ferromagnetic single crystal film of yttrium iron garnet with a microwave amplifier in the feedback chain, possesses a comblike amplitude-frequency characteristic with a large number of pass bands. It is established that the best filtration of a periodic train of rectangular microwave pulses is achieved provided that harmonics of the signal coincide with the positions of the resonator pass bands. Thus, an active spin-wave ring resonator can be used as the optimum filter for periodic pulsed microwave signals.

A Selection of Channels for a Proposed Atmospheric Temperature Sounder of ISRO

This paper presents a new assortment of temperature-sounding channels for a proposed low-Earth-orbit polar Sun-synchronous satelliteborne millimeter-wave atmospheric sounder of the Indian Space Research Organization (ISRO). The newness owes its origin to the exploration of the millimeter-wave O2 absorption spectrum in quest of optimal off-resonance frequencies that impose fewer restrictions on channel bandwidth and temperature sensitivity and yet can sound up to 40 km in the atmosphere with a 4-km vertical resolution. This is ISRO's first leap toward millimeter-wave technology. The overall receiver-noise figure for the channels in the 5-mm band (50-60 GHz) has been pessimistically estimated at 5 dB which will severely degrade the system temperature sensitivity. Therefore, channel bandwidth is at premium. The purpose of this design is to limit the number of passbands and simplify the design of frequency-selective filters by choosing center frequencies that have sufficient interleaving and also provide a scope of allotting a reasonable bandwidth. The set of temperature-sounding channels in the current design have 15 channels in 17 passbands in contrast with 15 channels in 29 passbands of the operational Advanced Microwave Sounding Unit (AMSU)-A.

Design, Fabrication, Linear and Nonlinear Optical Properties of Metal-Dielectric Photonic Bandgap Structures

The linear and the nonlinear optical properties of metallodielectric photonic bandgap (MD-PBG) structures were studied by using linear absorption spectroscopy and a femtosecond nonlinear transmission method. The MD-PBG structure consisted of three bilayers of MgF2(250 nm)/Ag(30 nm). It was prepared by evaporating MgF2 and Ag layers alternatively onto a glass plate. The optical transmission spectrum of the prepared MD-PBG structure was found to exhibit several pass bands and a broad photonic bandgap. The photonic bandgap extended throughout most of the visible region from 475 nm to 780 nm. Interestingly, there existed transmissive pass bands corresponding to the Bragg resonances: λ1 = 410 nm (T = 53.9 %), λ2 = 449 nm (T = 42.9 %), λ3 = 802 nm (T = 39.6 %) and λ4 = 878 nm (T = 16.9 %). The observed transmission spectra could be described by applying the optical transfer matrix formalism to the periodic metallodielectric multilayer. The number of pass bands was found to increase with increasing number of metal-dielectric pairs, and the band width of PBG was found to increase with increasing dielectric layer thickness. At high laser intensity, the MD-PBG structure exhibited a large nonlinear absorption. The enhanced optical nonlinearity is thought to be due to a bathochromic shift of the low-energy band edge of PBG by the saturable absorption of each metallic layer.

Synthesis of multibandpass numerical filters

The problem of low-pass to multibandpass transformation of numerical filters is considered. Properties of frequency transformations are studied and, based on these, a general design procedure is outlined which may be used for obtaining filters with any number of passbands. The procedure is illustrated by means of a ten passband example. A canonic form for realizing bandpass filters is also discussed.