Bandpass Filter Characteristics Research Articles

Enhanced optical characteristics of terahertz bandpass filters based on plasmonic nanoparticles

Plasmonic nanostructures enable considerable control and manipulation of light at the subwavelength scale and are promising for demonstration of optical metamaterials with enhanced spectral response. In this paper, we introduce a generation of terahertz bandpass filters that exploit the characteristics of subwavelength plasmonic nanoparticles. The design procedure is discussed based on a well-known complementary split ring resonator with a resonant feature at the THz region (∼1.5 THz), and it has been shown that device design based on plasmonic nanoparticles can conquer the poor off-resonance selectivity limit of common THz filters and exhibit higher transmission response, faster roll-off, and almost ripple-free operation. A much larger coupling capacitance for nanoparticles in the touching condition can modify the resonance wavelength, and localized hot spots enhance the device sensitivity for special applications. The effect of plasmonic nanoparticle size on the filtering characteristics is also discussed. A simple fabrication procedure based on discontinuous islandized surface morphology of thin metallic films on a dielectric has been proposed for demonstration of the THz filters introduced here.

FILTERED POWER SPLITTER USING MICROSTRIP SQUARE OPEN LOOP RESONATORS

A microstrip power splitter with band-pass responses is presented in this paper. The design is based on square open loop resonator topology. This filtered power splitter does not require quarter wavelength transformers and will result in a smaller size than a conventional Wilkinson power divider with integrated band-pass filter. It is a two-way equal power splitter with fifth order band-pass filter characteristics. The power splitter is designed to have Chebyshev band-pass response function. A theoretical analytical circuit model will be presented. From the theoretical model, a microstrip filtered power splitter will be designed and simulated. The proposed filtered power splitter is small in size and reduces circuit complexity. The power splitter is simulated and measured, and the results are presented.

Development of prototype polychromator system for KSTAR Thomson scattering diagnostic

A polychromator is widely used by the Thomson scattering system for measuring the electron temperature and density. This type of spectrometer includes optic elements such as band-pass filters, focusing lens, collimating lens, and avalanche photodiodes (APDs). The characteristics of band-pass filters in the polychromator are determined by the measuring range of the Thomson system. KSTAR edge polychromators were developed by co-works at NIFS in Japan, and the KSTAR core polychromators were developed by NFRI in Korea. The power supply system of these polychromators is connected only to one power supply module and can manually control the APD's voltage at the front side of the power supply by using a potentiometer. In this paper, a prototype polychromator is introduced at the KSTAR. The prototype polychromator system has a built-in power supply unit that includes high voltage for the APD and ± 5 V for an op-amp IC. The high voltage for the APD is finely controlled and monitored using a PC with the LabView software. One out of the six band pass-filters has a center wavelength of 523.5 nm with 2-nm bandwidth, which can measure Zeff, and the other five band-pass filters can simultaneously measure the Thomson signal. In addition, we will show the test result of this prototype polychromator system during the KSTAR experiment campaign (2015).

Experimental study of the band-pass filter and slow-wave effect in a MDM channel based on a magnetic plasmonic analogue of EIT

In connection with an analogue of electromagnetically-induced transparency (EIT), this paper studied experimentally the tunable band-pass filter and tunable slow-wave effect of MDM (μ-negative materials/double positive materials/μ-negative materials) magnetic plasmonic channel. The results of simulations and experiments show that an evident electromagnetically-induced transparency phenomenon appears in this channel with double-side resonators, which can be used to realize simultaneous the band-pass filter and the slow-wave effect. The band-pass filter’s center frequency is founded to be determined by the size of the side resonator, the resonator direction and the effective permeability of μ-negative (MNG) metamaterials. The bandwidth can be adjusted by detuning of the two resonator frequencies, the band size of the band-pass filter depends on the number of the resonators, Thus, the band-pass filter characteristics of the MDM waveguide can be tuned by changing the resonator parameters, the resonator direction and the effective permeability of the MNG materials. Moreover, the MDM structure can also be utilized to obtain a tunable slow-wave effect (such as an adjustable frequency, a slow-down factor, and even a muti-band slow wave) based on EIT. The experimental results are in good agreement with the simulation results.

A 3.0–10.0 GHz UWB Low-Noise Amplifier with Forward Body bias Technique

ABSTRACTAn ultra-wideband (UWB) low-noise amplifier (LNA) based on cascaded common source stage with shunt–shunt resistive feedback architecture is proposed. The wideband input impedance matching is accomplished by shunt–shunt resistive branch with inductor degeneration and parallel resistor-inductor-capacitor (RLC) load, forming two parallel RLC branches having inherently two wideband band-pass filter characteristics, resonating both at lower frequency and higher frequency. The output matching is achieved via a shunt inductor and a series resistor without the use of a buffer. Additionally, both series and shunt-inductive peaking techniques are employed in the proposed UWB LNA circuit design for bandwidth extension. To reduce the supply voltage headroom consumption, the forward body bias technique is also employed in the proposed topology. The resistor-capacitor (RC)-extracted results obtained in this paper are competitive in comparison with recent reported work in appreciating good noise figure (NF) performance as well as low-voltage headroom consumption. In the post-layout simulation results, the proposed complementary-metal-oxide-semiconductor (CMOS) UWB LNA dissipates only 13 mW while achieving the S11 below −11.4 dB, S22 below −11.7 dB, a flat S21 of 11.5 ± 0.6 dB, a maximum NF of 3.48 dB, within the range of 3.04 – 3.48 dB over the 3.0–10.0 GHz band of interest. Moreover, the IIP3 is within the range of −6.3 to −7.8 dBm, P1 dB of −14.7 to −16.8 as well as the K-factor of above 1 throughout the entire bandwidth operation, attesting the fact that the resistive feedback circuit is stable. The chip area consumption is approximated to 0.997 × 0.933 mm2.

1D linear-phase band-pass multiplierless FIR Hilbert transformers and filters

ABSTRACTAn original analytical method, based on modified Christoffel–Darboux formula, is used in the paper in order to synthesise a linear-phase band-pass finite impulse response (FIR) filter function that can have an effect of Hilbert transformer. New structure of the band-pass FIR filter in recursive realisation, together with the corresponding difference equation, is presented providing the efficient filter solution without multipliers. Several examples of filter types for different parity of two real free integer parameters, including a particular solution of Hilbert transformer, are considered in terms of required number of adders and values of cut-off frequencies of the pass and stop bands. A comparison of the proposed band-pass filter characteristics with those of a classical filter solution is provided in the paper.

K‐band bandpass filter using fully micromachined substrate integrated waveguide platform with dual copper posts in glass dielectrics

A K-band bandpass filter (BPF) based on the fully micromachined substrate integrated waveguide (SIW) structure has been demonstrated. In the proposed SIW platform, borosilicate glass reflowed into the silicon trench is used as a dielectric substrate, and the vias are formed by filling the glass mould with electroplated copper after removing the embedded silicon part. The BPF's characteristics are realised by introducing dual inductive post structures into the SIW platform. The insertion loss and 3 dB bandwidth of the fabricated BPF were measured to be 2.46 dB at 29 GHz and 7.2%, respectively. The proposed BPF platform has high potential for low-loss, compact SIW-based millimetre-wave tunable filters owing to its mechanical robustness and integrity with MEMS tuning devices.

Pseudocombline bandpass filters based on half-wave resonators manufactured from sections of balanced striplines

The possibility of application of pseudocombline microwave structures with λ/2 resonators manufactured from sections of balanced striplines as bandpass filters is demonstrated. It is found that coupling coefficients of λ/2 resonators manufactured from sections of balanced striplines arranged in parallel to each other without mutual shift have nonzero values. The dependence of these coupling coefficients on the parameters of half-wave stripline resonators is studied. Frequency characteristics of some pseudocombline bandpass filters with λ/2 resonators are analyzed and experimental data are presented.

Corrections to “Compact Multi-Port Power Combination/Distribution With Inherent Bandpass Filter Characteristics” [Nov 14 2659-2672

In the paper, “Compact multi-port power combination/distribution with inherent bandpass filter characteristics,” (Rosenberg, U., et al, IEEE Trans. Microw. Theory Techn., vol. 62, no. 11, pp. 2659–2672, Nov. 2014), revisions were made to select equations that were incorrect.

Tuning of SFOAEs Evoked by Low-Frequency Tones Is Not Compatible with Localized Emission Generation.

Stimulus-frequency otoacoustic emissions (SFOAEs) appear to be well suited for assessing frequency selectivity because, at least on theoretical grounds, they originate over a restricted region of the cochlea near the characteristic place of the evoking tone. In support of this view, we previously found good agreement between SFOAE suppression tuning curves (SF-STCs) and a control measure of frequency selectivity (compound action potential suppression tuning curves (CAP-STC)) for frequencies above 3 kHz in chinchillas. For lower frequencies, however, SF-STCs and were over five times broader than the CAP-STCs and demonstrated more high-pass rather than narrow band-pass filter characteristics. Here, we test the hypothesis that the broad tuning of low-frequency SF-STCs is because emissions originate over a broad region of the cochlea extending basal to the characteristic place of the evoking tone. We removed contributions of the hypothesized basally located SFOAE sources by either pre-suppressing them with a high-frequency interference tone (IT; 4.2, 6.2, or 9.2 kHz at 75 dB sound pressure level (SPL)) or by inducing acoustic trauma at high frequencies (exposures to 8, 5, and lastly 3-kHz tones at 110-115 dB SPL). The 1-kHz SF-STCs and CAP-STCs were measured for baseline, IT present and following the acoustic trauma conditions in anesthetized chinchillas. The IT and acoustic trauma affected SF-STCs in an almost indistinguishable way. The SF-STCs changed progressively from a broad high-pass to narrow band-pass shape as the frequency of the IT was lowered and for subsequent exposures to lower-frequency tones. Both results were in agreement with the "basal sources" hypothesis. In contrast, CAP-STCs were not changed by either manipulation, indicating that neither the IT nor acoustic trauma affected the 1-kHz characteristic place. Thus, unlike CAPs, SFOAEs cannot be considered as a place-specific measure of cochlear function at low frequencies, at least in chinchillas.

Spectral characteristics of MWIR band-pass filters at cryogenic temperature

Spectral characteristics of MWIR band-pass filters at cryogenic temperature

Spurious resonance suppression for a THz single bandpass filter using lossy glass substrates

ABSTRACTNarrowband metamaterial‐based filters using an array of split ring resonator (SRR) unit cells exhibit multiband operating characteristics due to the low frequency L‐C resonance together with the high frequency dipole resonance of the SRR structure. To obtain single‐band characteristics from the metamaterial‐based terahertz (THz) band pass filter (BPF), the unwanted dipole resonance at high frequency should be suppressed. A lossy glass was used for a substrate for THz BPF that consists of a complementary split ring resonator (CSRR) to suppress the undesirable resonances at higher frequencies. The resulting CSRR filter on a glass substrate exhibited single‐band BPF characteristics with a spurious band rejection ratio over 50 dB. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:58–60, 2015

Systematical analysis for the mixed couplings of two adjacent modified split ring resonators and the application to compact microstrip bandpass filters

In this paper we synthesize a new kind of modified split ring resonator (SRR) and characterize its mixed couplings between two adjacent such SRRs with all the possible arrangements on one side of a conventional dielectric substrate. Based on the analysis of the mixed couplings, the compact microstrip bandpass filters composed of the proposed modified SRRs are systematically analyzed. We found that two designs out of all the cases have quite well bandpass filter characteristics, e.g., low insert loss within the wide passband, sharp reductions and transmission zeros out of the passband, and harmonic suppression characteristics for a wide frequency range. Both experimental demonstrations and numerical simulations are performed to verify the designed filters and the results agree well with each other. Such kind of filter design can be flexibly integrated in the miniaturized radio frequency/microwave circuits.

Technology Research of Infrasonic Signal Acquisition and Pretreatment for Identification of Nuclear Explosion

The paper designs a kind of nuclear explosion infrasonic signal acquisition equipment and brings forward a pretreatment way. Based on μC/OS and digital circuit of FPGA+ADC, the paper realizes signal acquisition, storage and transmission of infrasound, which is from 0Hz to 20Hz. And according to the characteristics of nuclear infrasonic signal, mean removal, bandpass filter and normalization are used for signal pretreatment. Experiments proved that the signal acquired from acquisition equipment can be used for identification of nuclear explosion.

Fast digital envelope detector based on generalized harmonic wavelet transform for BOTDR performance improvement

We propose a fast digital envelope detector (DED) based on the generalized harmonic wavelet transform to improve the performance of coherent heterodyne Brillouin optical time domain reflectometry. The proposed DED can obtain undistorted envelopes due to the zero phase-shift ideal bandpass filter (BPF) characteristics of the generalized harmonic wavelet (GHW). Its envelope average ability benefits from the passband designing flexibility of the GHW, and its demodulation speed can be accelerated by using a fast algorithm that only analyses signals of interest within the passband of the GHW with reduced computational complexity. The feasibility and advantage of the proposed DED are verified by simulations and experiments. With an optimized bandwidth, Brillouin frequency shift accuracy improvements of 19.4% and 11.14%, as well as envelope demodulation speed increases of 39.1% and 24.9%, are experimentally attained by the proposed DED over Hilbert transform (HT) and Morlet wavelet transform (MWT) based DEDs, respectively. Spatial resolution by the proposed DED is undegraded, which is identical to the undegraded value by HT-DED with an allpass filter characteristic and better than the degraded value by MWT-DED with a Gaussian BPF characteristic.

Efficient RF voltage transformer with bandpass filter characteristics

A microwave bandpassfilter with a large ratio between the output andthe input impedance has been designed and fabricated. Consequently,it functions both as a voltage transformer and a bandpassfilte ...

Comparative Characteristics of Bandpass Filters Based on WDR and Microstrip Resonators

The article presents the results of comparative analysis of WDR and microstrip-based resonator filters re- garding their electrical parameters and overall dimensions. For alternative WDR filters design, we use a method of intel- lectual synthesis of a band pass filter structure which is based on formalized knowledge about the physics of coupled reso- nators. The basic idea of the expert system created consists in physical analysis of signals passing through the filter, which is performed on the basis of a known solution for electrodynamic problem of scattering of fundamental electromagnetic waves in a multi-tier structure. The comparative analysis is conducted in a wide frequency range of 3 - 70 GHz. We show that the advantage of WDR filters consists in selective properties and discuss the ways of their adaptation to planar tech- nologies. It was demonstrated that electrodynamic properties of WDR filters allow creating devices ranging from narrow to ultra wide passbands. Finally, it was emphasized that a combination of superconducting materials and sapphire or quartz resonators is also very promising for developing WDR-based filters with unique selective properties.

Modulation by pregnenolone sulfate of filtering properties in the hippocampal trisynaptic circuit

Short-term synaptic plasticity alters synaptic efficacy on a timescale that is relevant to encoding information in spike trains. The dynamics of this plasticity, combined with that of the feedback and feedforward contributions of local interneurons, impose frequency-dependent properties on neuronal networks with implications for nervous system function. The trisynaptic network of the hippocampus is especially well suited to selectively filter components of frequency-dependent signals that are transmitted from the entorhinal cortex. We measured presynaptic [Ca(2+)](i) in perforant path, mossy fiber, or Schaffer collateral terminals while simultaneously measuring field potentials of principal cells of the dentate, CA3, or CA1 synaptic fields over a range of stimulus frequencies of 2 to 77 Hz. In all three synaptic fields, the average [Ca(2+)](i) during a 500 ms stimulus train rose monotonically with stimulus frequency. The average population spike amplitude during this stimulus train, however, exhibited a non-linear relationship to frequency that was distinct for each of the three synaptic fields. The dentate synaptic field exhibited the characteristics of a low pass filter, while both CA synaptic fields had bandpass filter characteristics with a gain that was greater than 1 in the passband frequencies. Importantly, alteration of the dynamic properties of this network could significantly impact information processing performed by the hippocampus. Pregnenolone sulfate (PregS), has frequency-dependent effects on paired- and multipulse plasticity in the dentate and CA1 synaptic fields of the hippocampal formation. We investigated the PregS-dependent modulation of the dynamic properties of transmission by the principal cells of the three hippocampal synaptic fields. Importantly, PregS is capable of altering the pattern separation capabilities that may underlie hippocampal information processing.

Electrical characterisation of liquid crystals at millimetre wavelengths using frequency selective surfaces

The accurate measurement of the permittivity, loss tangent and dielectric anisotropy DC bias dependence for two different liquid crystal (LC) materials in the frequency range 140–165 GHz is described. The electrical characteristics are obtained by curve fitting computed transmission coefficients to the experimental spectral response of a new class of electronically reconfigurable frequency selective surface. The periodic structure is designed to yield bandpass filter characteristics with and without an applied bias control voltage in order to measure the tunability of the LC material which is inserted in a 705 µm-thick cavity.

비분산 적외선 가스센서의 온도보상 알고리즘

본 논문에서는 써모파일을 사용한 비분산 적외선 메탄가스센서의 온도보상 알고리즘을 제시하였다. 가스측정을 위해 적외선 감지부에 내장된 써미스터의 출력전압과 분위기 온도와의 상관성을 도출하고, 협 대역통과 필터 특성과 온도 변화에 따른 센서모듈(광 공동과 적외선램프)의 출력전압 특성 및 메탄가스의 흡수계수와 광 경로에 따른 출력특성 해석을 통하여 가스센서 모듈의 온도보상 알고리즘을 도출하였다.온도보상 전 약 <TEX>$\pm$</TEX> 1,500 ppm 이상의 오차를 갖는 센서는 온도보상 알고리즘을 적용함으로써 <TEX>$20^{\circ}C$</TEX>온도변화 구간에서 최대 약 180 ppm 이하의 정밀한 센서모듈을 제작하였다. This paper describes the temperature compensation algorithm using thermopile detector for nondispersive infrared methane gas sensor. From the output voltage of thermistor that is attached onto the infrared detector, the ambient temperature was extracted. The effects of temperatures on the properties of sensor module (the characteristics of narrow bandpass filter, optical cavity and infrared lamp, and gas absorption coefficient times optical path length) have been introduced in order to implement the temperature compensation algorithm. Even though the measurement error of developed sensor module was in the range of <TEX>$\pm$</TEX> 1,500 ppm, after programming the temperature compensation algorithm, the developed sensor module shows a high accuracy less than +180 ppm error within <TEX>$20^{\circ}C$</TEX> temperature variation.