Bandpass Transfer Functions Research Articles

Input-Reflectionless Quasi-Elliptic-Type Single- and Dual-Band Bandpass Filters Based on Passive Channelized Principles

An approach to design quasi-elliptic-type planar filters with single- and dual-band bandpass transfer functions and input-absorptive capabilities is presented. Two-branch channelized passive circuit configurations are exploited for this purpose, in which the low-order reflective-type filtering profile of their branches is converted into the desired sharp-rejection input-reflectionless filtering action in the overall circuit. This is achieved by means of fully-destructive and frequency-selective transversal signal-interference effects at the total input and output accesses of the channelized filter, respectively. The theoretical operational principles of the proposed concept of single/dual-passband input-reflectionless two-branch channelized filter are detailed, along with design considerations for their RF transmission-line-based implementation. Besides, its generalization to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\boldsymbol {N}$ </tex-math></inline-formula> -channel architectures is also analyzed. Furthermore, as the fundamental elements of the devised channelized filtering philosophy to increase selectivity, alternative solutions to realize their output phase-delay sections for a more-flexible control of the transmission zeros in the overall transfer function are discussed. For experimental-demonstration purposes, two microstrip proof-of-concept prototypes are developed and measured. They consist of 3-GHz single-band and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2.58/3.43$ </tex-math></inline-formula> -GHz dual-band designs with input-quasi-reflectionless spectral ratio above 2.5:1 and 3:1, respectively.

Silicon-on-Insulator Microwave Photonic Filter With Widely Tunable and Reconfigurable Flat-Top Bandpass Functionality

We report of a silicon photonics (SiP) flat-top bandpass microwave photonic (MWP) filter with large out-of-band power rejection (OBPR) of up to more than 40 dB and exhibiting central frequency tunability over a range as large as 70 GHz, while still guaranteeing a minimum full-span OBPR larger than 25 dB. Furthermore, the RF bandpass transfer function can be widely configured without sacrificing the filter performance. In the present realization, a continuous bandwidth tuning from 5 to 10 GHz (corresponding to a 100% of bandwidth variation) is demonstrated. The operation is based on optical-to-RF mapping the response of a tunable and bandwidth reconfigurable photonic integrated optical filter, realized with a high-order distributed feedback resonator (DFBR) waveguide Bragg grating structure. A high level of functional integration is provided in a compact footprint of less than 2 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> by embedding within the circuit a SiP phase modulator generating the modulation sideband scanning the DFBR filter, and a tunable optical splitter optimizing the MWP filter performance. Possibility of further extending system integration for monolithic on-chip operation is also investigated.

Dynamics of towed particles in a turbulent flow

We present an experimental study exploring the dynamics of inertial spheres towed at a constant mean velocity in a turbulent flow. Our work focuses on finite size particles, in the sense that their diameter is significantly larger than the dissipation scale and lies in the range of inertial scales of the background turbulence. Our experimental setup allows to register the Lagrangian velocity and acceleration of particles with different diameters, densities and free-stream velocities. The analysis of towed particles dynamics shows a clear trend of velocity and acceleration fluctuations to be reduced with increasing particle inertia, while acceleration fluctuations are found to be Gaussian, at odds of usual results for finite-size freely advected particles. Besides, the multi-scale spectral dynamics of the particle is shown to be related to that of the background turbulence by a linear second-order band-pass transfer function. We analyse this behaviour at the light of a simple model where the coupling between the particle and the flow is entirely attributed to the drag force, a usual approach for dense point-like particles freely-advected in a turbulent flow, which is known however to fail predicting the transport of freely advected finite-size particles. We show that this drag-dominated model quantitatively predicts the dynamics of finite size towed particles, simply requiring to tune the effective particle response time. This suggests that, contrary to the case of freely advected finite size inertial particles, the towing configuration efficiently emphasises the actual role of the drag force by imposing it as an unambiguous leading term in towed particle/turbulence interactions.

Theory and design of narrowband band-stop filters using slotted ground resonators

This paper reports the demonstration of design and implementation of narrow band band-stop filters using slotted ground resonators. Using coupled-mode resonator theory, the systematic implementation of BSFs are performed to achieve narrow stopband (&lt;25% FBW) with desired stopband isolation. By exchanging the band-pass transfer function polynomials, the BSF design has become straight-forward with these band-stop resonators. Designed and optimized BSFs are fabricated, characterized and analysed as a detailed report. Slotted ground resonators yield compact and scalable BSFs which are potential alternatives for the development of future microwave systems.

Theory and Design of a Flexible Two-Stage Wideband Wilkinson Power Divider

This article presents the design scheme of a wideband Wilkinson Power Divider (WPD) with two-stage architecture utilizing quarter-wave transmission lines and short-circuit stubs. The bandwidth of the proposed WPD is flexible and can be controlled using the design parameters. The proposed design achieves excellent isolation between output ports in addition good in-band performance. The analysis of the proposed circuit results in a simplified transfer function which is then equated with a standard band-pass transfer function to determine the parameters of transmission lines, stub’s impedances, and the value of the isolation resistors. Furthermore, it is also demonstrated that a simple alteration in the proposed circuit enables the design of a wideband DC isolated WPD that maintains a good in-band and isolation performance. A number of case studies have been included to highlight the flexibility of the proposed design. Two distinct prototypes are developed on different boards to demonstrate the wideband performance of the proposed design. An excellent agreement between the experimental and measured results for both the designs over a wide band including very good isolation between ports validate the proposed design.

Voltage-Mode Multifunction Biquad Filter and Its Application as Fully-Uncoupled Quadrature Oscillator Based on Current-Feedback Operational Amplifiers

This research introduces a new multifunction biquad filter based on voltage mode (VM) current-feedback operational amplifier (CFOA) and a fully uncoupled quadrature oscillator (QO) based on the proposed VM multifunction biquad filter. The proposed VM multifunction biquad filter has high impedance to the input voltage signal, and uses three CFOAs as active components, while using four resistors and two grounded capacitors as passive components. The VM CFOA-based multifunction biquad filter realizes band-reject, band-pass, and low-pass transfer functions at high-input impedance node simultaneously, which has the feature of easy cascading in VM operation without the need for additional voltage buffers. Additionally, the filter control factor parameter pole frequency (ωo) and quality factor (Q) of the proposed VM multifunction biquad filter can be independently set by varying different resistors. By slightly modifying the VM multifunction biquad filter topology, a VM fully-uncoupled QO is easily obtained. The difference from the previous VM CFOA-based multifunction biquad filter is that the proposed VM CFOA-based multifunction biquad filter can be independently controlled by the filter control factor parameters, ωo and Q. The proposed VM CFOA-based multifunction biquad filter can be transformed into a VM QO with fully-uncoupled adjustable of the oscillation condition and the oscillation frequency. The oscillation condition and the oscillation frequency can be fully-uncoupled and controlled by varying two sets of completely different resistors. The proposed VM fully-uncoupled QO solves the amplitude instability. The constant amplitude ratio of two quadrature sinusoidal waveforms can be realized when tuning FO. PSpice simulation and experimental results prove the performances of the proposed VM multifunction filter and VM fully-uncoupled QO. Simulation and experimental results confirm the theoretical analysis of the proposed circuits.

A Discrete-Time MOS Parametric Amplifier-Based Chopped Signal Demodulator

This article presents a discrete-time parametric amplifier (DTPA) as the signal demodulator for chopper amplifier. Unlike the conventional chopper, the DTPA demodulator features noise-efficient gain augmentation while demodulating the chopped signal. The demodulator also enables low-frequency noise cancellation during the inherent track-and-hold (T/H) process of the charge parametrization. The positive feedback loop and the dc servo loop are implemented for applications requiring larger input impedance and dc input offset cancellation using a bandpass transfer function. Design considerations for the DTPA-based demodulator circuit and the merits and demerits of the chopper-DTPA amplifier are discussed as well. The proposed design has been fabricated in a standard 180-nm CMOS technology node. The complete design occupies 0.127 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> of the die area and consumes 2.4-μW power from a 1.5 V of VDD. The measurement results show that the DTPA demodulator provides 8-dB gain enhancement while improving on the prior art of T/Hbased demodulator and the amplifier achieves input referred noise voltage of 2 μV <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rms</sub> in 143-Hz bandwidth.

A 6-nW 0.0013-mm² ILO Bandpass Filter for Time-Based Feature Extraction

Event-driven wake-up sensing methods are emerging functions necessary to increase the autonomy of power-hungry multisensors Internet-of-Things applications. To decrease the power consumption of feature extraction function essential for event-based wake-up, this letter introduces a novel injection-locked oscillator (ILO) filter architecture, to be used in a time-based filter bank for feature extraction. After reviewing the phase shifter property and dynamic behavior of a switched-capacitor injected relaxation ILO, ILO high-pass and bandpass filter designs and transfer functions are presented, resulting in the implementation of a four-channel ILO filter bank in a 65-nm CMOS technological node. Experimental measurements demonstrate the ILO bandpass filtering function works at a power consumption of 6 nW, an active area of 0.0013 mm2 and an output dynamic range of 46 dB. The filter bank average power consumption reaches 3 nW/channel for a total bandwidth from 130 Hz to 5.5 kHz.

Design of Modified $4\times6$ Filtering Butler Matrix Based on All-Resonator Structures

In this paper, two novel 4 × 6 filtering Butler matrices with uniform and nonuniform power distribution are proposed. The matrices, consisting of a network of coupled resonators and two phase shifters, provide power division and phase shift together with a bandpass transfer function. The analytical synthesis procedures for the 4 × 6 filtering Butler matrices are presented. To verify the concept experimentally, two 4 × 6 filtering Butler matrices, operating at 2.4 GHz, with uniform and nonuniform power distribution are designed, fabricated, and measured. Simulated and measured results are found to be in good agreement with each other. Multibeam antenna arrays are realized by using the Butler matrix, and the theoretical analysis has been confirmed by measurements of multibeam antenna arrays, which show reduced sidelobe level (SLL).

A New Low-Voltage Low-Power Dual-Mode VCII-Based SIMO Universal Filter

In this paper, a new low-voltage low-power dual-mode universal filter is presented. The proposed circuit is implemented using inverting current buffer (I-CB) and second-generation voltage conveyors (VCIIs) as active building blocks and five resistors and three capacitors as passive elements. The circuit is in single-input multiple-output (SIMO) structure and can produce second-order high-pass (HP), band-pass (BP), low-pass (LP), all-pass (AP), and band-stop (BS) transfer functions. The outputs are available as voltage signals at low impedance Z ports of the VCII. The HP, BP, AP, and BS outputs are also produced in the form of current signals at high impedance X ports of the VCIIs. In addition, the AP and BS outputs are also available in inverting type. The proposed circuit enjoys a dual-mode operation and, based on the application, the input signal can be either current or voltage. It is worth mentioning that the proposed filter does not require any component matching constraint and all sensitivities are low, moreover it can be easily cascadable. The simulation results using 0.18 μm CMOS technology parameters at a supply voltage of ±0.9 V are provided to support the presented theory.

Multifunctional Electronically Reconfigurable and Tunable Fractional-Order Filter

In this paper the authors present a multifunctional reconfigurable fractional-order filter performing a low-pass, high-pass, band-pass and band-reject transfer function. The filter is based on two types of active elements, OTA (Operational Transconductance Amplifier) and ACA (Adjustable Current Amplifier). It provides pole frequency control, depending on the values of the transconductance of the OTA elements. The quality factor is also electronically controlled, depending on the amplification of the ACA element. The order of the filter can be changed by switching the fractional-order capacitor having various values of the order. The circuit was implemented as a PCB (Printed Circuit Board) and measured in laboratory conditions. Measurement results are compared with the simulation results. The behavioural models were used for the purpose of the simulation.DOI: 10.5755/j01.eie.25.1.22732

High performance voltage output filter realizations using second generation voltage conveyor

In this article, new voltage-output filter realizations based on second generation voltage conveyor (VCII) as basic building block are presented. The results of this study show that VCII is a suitable candidate for applications requiring a voltage as filter output signal, considering that the availability of a low impedance voltage output terminal in VCII makes unnecessary the use of extra voltage buffers at the filter output, resulting in filter implementations with simpler structure, reduced power consumption, and chip area. New configurations of VCII based filters with first order low-pass (LP), second order LP, and second order bandpass (BP) transfer functions are shown. The proposed circuits enjoy a very simple structure employing only one active element and four passive components. Simulation results for a VCII transistor implementation in a 0.35 μm standard CMOS technology and a supply voltage of ±1.65 V approve the presented theory.

Novel Filtering 180° Hybrid Coupler and Its Application to $2 \times4$ Filtering Butler Matrix

In this paper, a novel filtering 180° hybrid coupler is proposed and used to design a $2 \times 4$ filtering Butler matrix. The filtering 180° hybrid coupler can provide power division and phase shift together with a second-order bandpass transfer function, and is based only on coupled resonators. The $2 \times 4$ filtering Butler matrix is easily realized by utilizing several hybrid couplers. The analytical synthesis procedures for the hybrid coupler and Butler matrix are presented in this paper. Finally, broadside and end-fire arrays are realized by using the Butler matrix. To illustrate the concept experimentally, a filtering 180° microstrip hybrid coupler and a $2 \times 4$ filtering microstrip Butler matrix are designed, fabricated, and measured. Simulation and measured results are found to be in good agreement with each other.

Evaluation of (1 + α) Fractional-Order Approximated Butterworth High-Pass and Band-Pass Filter Transfer Functions

This paper summarizes multiple cases of high-pass (HP) and band-pass (BP) analogue filter transfer functions with fractional order 1 &lt; (1 + α) &lt; 2. All HP and BP transfer functions are evaluated against the magnitude characteristics of ideal Butterworth responses when coefficients previously determined to approximate fractional-order (FO) Butterworth low-pass (LP) transfer functions are utilized. Comparisons of the simulated FO HP and BP responses against the ideal Butterworth responses are presented, with a least squares error analysis applied to determine the transfer functions that best approximate the Butterworth response for both HP and BP FO filters.DOI: http://dx.doi.org/10.5755/j01.eie.24.2.20634

Dual-Carrier Aggregation Receiver With Reconfigurable Front-End RF Signal Conditioning

A reconfigurable receiver that can support dual-carrier aggregation is demonstrated. Switched Capacitor (SC) technique is explored at the receiver front-end for direct RF signal conditioning. By changing the connections of the switches and capacitors, various filtering profiles, including bandpass and notch functions, can be synthesized. On the other hand, complex-domain signal processing enables RF selectivity with controllable offset frequency relative to the LO frequency. Therefore, multiple RF channels can be selected simultaneously by multiple complex-domain signal processors and a shared single front-end. The scheme also enables a 4th-order RF bandpass transfer function by combining two 2nd-order bandpass transfer functions with slightly different center frequencies. In this work, a combination of a reconfigurable front-end passive SC network and two concurrent complex-domain signal processors enables the receiver to handle different signal scenarios. A proof-of-concept CMOS chip fabricated in a 65 nm CMOS technology is presented that supports single-channel and dual-carrier aggregation receiving modes. The receiver covers the frequency range from 0.1 to 1 GHz. The frequency distance between two concurrent RF channels can be tuned anywhere between 0 to +100 MHz. The near-band blocker resilience is improved by 15 dB when the front-end is configured as a notch filter.

Mass and Stiffness Impact on the Middle Ear and the Cochlear Partition.

Mass and stiffness affect on the peculiar characteristics of transmission of the middle ear and the distinctive behavior of the cochlear mechanics. Applying the principle of the mass and stiffness, the band-pass characteristic transfer function of the middle ear has been explained. The greatest transfer function of the middle ear, approximately 24-29 dB, is observed at 1-2 kHz in both cat and human species. However, at lower frequencies, the transfer function was disturbed by the stiffness of the middle ear primarily due to middle ear cavity. At higher frequencies, the transfer function was disturbed by the stiffness of the middle ear primarily due to middle ear bones. Several examples, such as an acoustic reflex, otitis media, and otosclerosis are discussed. For understanding the traveling wave of the basilar membrane, different place tuning at certain stimulus frequencies, contrastingly shaped basilar membrane to the cochlear duct, and the structural and physical characteristics of the whole cochlear partition were reviewed in terms of changing width, mass, and stiffness from the base to apex. Being about ten times wider, more massive, and one hundredfold stiffer at the base than the apex, the nature of the cochlear partition to absorb high-frequency energy changes in fluid pressure declines toward the apex. Consequently, at the base of the cochlea, high frequencies stimuli are decoded while low frequencies stimuli are decoded at the apex of the cochlea. Due to these characteristics of the cochlear partition, the direction of the traveling wave was also proved to be in the fashion of base-to-apex always.

Electronically tunable inverse active filters employing OTAs and grounded capacitors

This paper introduces inverse active filters employing operational transconductance amplifiers (OTAs) and grounded capacitors. The filter circuits can realise inverse low-pass, inverse band-pass and inverse high-pass transfer functions by addition of the circuit currents. Additionally, the circuit parameters ω0, Q and H can be set orthogonally or independently by adjusting the bias currents of the OTAs. The inverse filter circuits enjoy very low sensitivities to active and passive components. The achievement examples are given together with simulation results by PSPICE.

Electronically scanned RF-to-bits beam aperture arrays using 2-D IIR spatially bandpass digital filters

A beamforming system based on two-dimensional (2-D) spatially bandpass infinite impulse response (IIR) plane wave filtering is presented in a multi-dimensional signal processing perspective and the implementation details are discussed. Real-time implementation of such beamforming systems requires modeling of computational electromagnetics for the antennas, radio frequency (RF) analog design aspects for low-noise amplifiers (LNAs), mixed-signal aspects for signal quantization and sampling and finally, digital architectures for the spatially bandpass plane wave filters proposed in Joshi et al. (IEEE Trans Very Large Scale Integr Syst 20(12):2241---2254, 2012). Multi-dimensional spatio-temporal spectral properties of down-converted RF plane wave signals are reviewed and derivation of the spatially bandpass filter transfer function is presented. An example of a wideband antipodal Vivaldi antenna is simulated at 1 GHz. Potential RF receiver chains are identified including a design of a tunable combline microstrip bandpass filter with tuning range 0.8---1.1 GHz. The 1st-order sensitivity analysis of the beam filter 2-D $$\mathbf z $$ z -domain transfer function shows that for a 12-bits of fixed-point precision, the maximum percentage error in the 2-D magnitude frequency response due to quantization is as low as $$0.3\,\%$$ 0.3 % . Monte-Carlo simulations are used to study the effect of quantization on the bit error rate (BER) performance of the beamforming system. 5-bit analog to digital converter (ADC) precision with 8-bit internal arithmetic precision provides a gain of approximately 16 dB for a BER of $$10^{-3}$$ 10 - 3 with respect to the no beamforming case. ASIC Synthesis results of the beam filter in 45 nm CMOS verifies a real time operating frequency of 429 MHz.

Neurometric amplitude‐modulation detection threshold in the guinea‐pig ventral cochlear nucleus

Amplitude modulation (AM) is a pervasive feature of natural sounds. Neural detection and processing of modulation cues is behaviourally important across species. Although most ecologically relevant sounds are not fully modulated, physiological studies have usually concentrated on fully modulated (100% modulation depth) signals. Psychoacoustic experiments mainly operate at low modulation depths, around detection threshold (∼5% AM). We presented sinusoidal amplitude-modulated tones, systematically varying modulation depth between zero and 100%, at a range of modulation frequencies, to anaesthetised guinea-pigs while recording spikes from neurons in the ventral cochlear nucleus (VCN). The cochlear nucleus is the site of the first synapse in the central auditory system. At this locus significant signal processing occurs with respect to representation of AM signals. Spike trains were analysed in terms of the vector strength of spike synchrony to the amplitude envelope. Neurons showed either low-pass or band-pass temporal modulation transfer functions, with the proportion of band-pass responses increasing with increasing sound level. The proportion of units showing a band-pass response varies with unit type: sustained chopper (CS) > transient chopper (CT) > primary-like (PL). Spike synchrony increased with increasing modulation depth. At the lowest modulation depth (6%), significant spike synchrony was only observed near to the unit's best modulation frequency for all unit types tested. Modulation tuning therefore became sharper with decreasing modulation depth. AM detection threshold was calculated for each individual unit as a function of modulation frequency. Chopper units have significantly better AM detection thresholds than do primary-like units. AM detection threshold is significantly worse at 40 dB vs. 10 dB above pure-tone spike rate threshold. Mean modulation detection thresholds for sounds 10 dB above pure-tone spike rate threshold at best modulation frequency are (95% CI) 11.6% (10.0-13.1) for PL units, 9.8% (8.2-11.5) for CT units, and 10.8% (8.4-13.2) for CS units. The most sensitive guinea-pig VCN single unit AM detection thresholds are similar to human psychophysical performance (∼3% AM), while the mean neurometric thresholds approach whole animal behavioural performance (∼10% AM).

Inharmonic dispersion tunable comb filter design using modified IIR band pass transfer function

An excitation/filter system of Inharmonic sound synthesis signal is presented with an application to piano, a stiff string instrument. Specific features of the piano string important in wave propagation, dispersion due to stiffness, frequency dependent losses and presence of phantom partials are included in the proposed model. The modified narrow bandpass filter is used as a basic building block in modeling the vibrating structure. The parallel bank of narrow band pass filters is used to model the dispersion. The center frequencies of narrow bandpass filters can be tuned to follow the same relation as the partial frequencies of piano tone. Novel loss filter is designed to implement frequency dependent losses. The resulting model is called as Inharmonic Dispersion Tunable Comb filter.