Frequency Bandpass Filter Research Articles

Design of a tunable center frequency and small size cavity bandpass filter by separating capacitor-loaded resonators

This paper presents a tunable center frequency and small size cavity bandpass filter design method. In this method, a capacitor-loaded open terminal coaxial resonator is employed to reduce the size of cavity filters. The resonator is designed and fabricated separately into two parts to achieve the flexible operating frequency purpose. The first part is called the base of the resonator which is simply a pillar and directly fabricated integrally with the cavity housing. The second part called the hat of the resonator is the main part causing the load capacitance in cavity filters. By using different heights of the base part or/and different shapes and sizes of the hat, the operating frequency of cavity filters can be changed flexibly. This method not only reduces the difficulty and cost of cavity filter processing but also makes cavity filters reconfigurable. To demonstrate the effectiveness of the method, a cavity filter sample with a center frequency of 3.45 GHz and a bandwidth of 80 MHz was designed, fabricated, and measured. The measured results show that the insertion loss was smaller than 1.33 dB in the whole bandwidth, one zero-point at 3.350 GHz reaching -68 dB, the rejection at 3.550 GHz was -41 dB, unloaded Q was 5,898, and the dimension of the filter was 128 mm×86 mm×23 mm.

Optimization of the matching layer for high-frequency underwater acoustic transducers

A theoretical model has been established to investigate the dependence of matching layer functional mechanism of matching layer on excitation signal types, i.e., short pulse and long pulse. The results indicate that the matching layer acts as a bandpass frequency filter under both two excitation signal types. In the short pulse case, the matching layer can improve bandwidth and sensitivity simultaneously, whereas for the case of long pulse excitation, the increased bandwidth is at the expense of sensitivity. Besides, the thickness design principle of matching layer for underwater acoustic transducer was modified according to the frequency-dependent acoustic radiation impedance.

Automatic Modulation Recognition Based on Deep-Learning Features Fusion of Signal and Constellation Diagram

In signal communication based on a non-cooperative communication system, the receiver is an unlicensed third-party communication terminal, and the modulation parameters of the transmitter signal cannot be predicted in advance. After the RF signal passes through the RF band-pass filter, low noise amplifier, and image rejection filter, the intermediate frequency signal is obtained by down-conversion, and then the IQ signal is obtained in the baseband by using the intermediate frequency band-pass filter and down-conversion. In this process, noise and signal frequency offset are inevitably introduced. As the basis of subsequent analysis and interpretation, modulation recognition has important research value in this environment. The introduction of deep learning also brings new feature mining tools. Based on this, this paper proposes a signal modulation recognition method based on multi-feature fusion and constructs a deep learning network with a double-branch structure to extract the features of IQ signal and multi-channel constellation, respectively. It is found that through the complementary characteristics of different forms of signals, a more complete signal feature representation can be constructed. At the same time, it can better alleviate the influence of noise and frequency offset on recognition performance, and effectively improve the classification accuracy of modulation recognition.

In-Cabin MIMO Radar System for Human Dysfunctional Breathing Detection

The integration of wireless sensors into the automotive industry is making vehicles increasingly safe and autonomous. At present, vehicles are equipped with external sensors that facilitate maneuverability and braking and internal sensors that detect presence, seat belt state, and occupant vital signs. Early detection of dysfunctional breathing patterns can reduce the risk of accidents caused by drowsiness or fatigue. In this regard, this work presents an MIMO FMCW Radar System able to distinguish dysfunctional breathing patterns from human torso motion. The torso has been divided into six regions, and the amplitude of the elongation and the frequency of motion of each region have been measured during breathing. An elongation map is then constructed in order to graphically show the dysfunctional breathing patterns. The signal processing includes a peak search algorithm to detect elongation amplitude and a bandpass frequency filter to minimize dc components, random driver motion, and vehicle vibration. A torso elongation emulator phantom has been assembled with materials of skin-like relative permittivity and dc motors for calibration and validation of basic breathing patterns. Finally, the signal of the system is compared with that of a commercial respiration belt, and then the system is tested by performing measurements on people. The MIMO radar system is able to measure, differentiate, and classify patterns associated with dysfunctional breathing such as hyperventilation syndrome and thoracic dominant breathing.

Tracking extraterrestrial signals using the Super SID and Radio JOVE kits

A 20.1MHz dipole radio telescope was assembled, characterized and tested to detect extraterrestrial signals from planet Jupiter. Two element dipole arrays were built for the detection of 20.1MHz radio emission from the Jupiter-Io interaction, strong solar burst, the galactic background and the transit of the galactic center. Using the specifications and the layout, the dipole array was constructed. The block diagram, the schematic diagram built for NASA was used to solder together the radio frequency band pass filter, audio Preamplifier and audio amplifier to make the radio JOVE receiver. This was characterized, tested and tuned by setting the tuning knob to 20.0MHz. The dipole antenna was connected to the receiver and a variety of radio frequency emissions were detected. These signals were captured on a personal computer via the radio Jupiter Pro 3.8.3 and radio skypipe 2.6.5 software compatible with windows 7 OS and has python programme which converts data from the sod format to ASCII format to conveniently analyzed them. The data locally captured was correlated with other stations of the world. Specifically the analyzed chart of 14th July 2022 shows a lot of similarities with that captured by radio telescope UNIVERSUM shared with the global web repository.

Multi‐functional control strategy for power quality improvement of three‐phase grid using solar PV fed unified power quality conditioner

This article presents a generalised integrator with a band-pass filter frequency locked loop (GI-BPF-FLL) control algorithm for the solar photovoltaic (SPV)-integrated unified power quality conditioner (SPVUPQC) system. This control algorithm extracts fundamental components (FC) of the distorted and deformed input signals, and it has the competence of eliminating DC-offset. The key objective is to decrease the number of sensors used in the control algorithm of the SPVUPQC system while enabling the power quality enhancement features in the distribution grid. The effectiveness of the presented GI-BPF-FLL control algorithm and its performance comparison with the conventional control algorithm are discussed in both the time domain as well as frequency domain analysis. The SPVUPQC system consisting of a distribution static compensator (DSTATCOM) and a dynamic voltage restorer (DVR), to compensate simultaneously both the voltage distortions, sag/swell etc. as well as current harmonics, reactive power and load currents unbalances etc. The model of the SPVUPQC system is developed in the MATLAB/Simulink environment, and its results are presented to demonstrate its capabilities. The system's validation is also done on the hardware prototype, and it performs effectively for the voltage and current power quality enhancement simultaneously. The load side voltages magnitudes, grid side voltages and the grid currents total harmonic distortions are found within the boundaries specified in the IEEE standard 1159 and the IEEE standard 519.

Low-cost electronic circuitry for photoacoustic gas sensing

The circuitry comprises a sine wave generator based on direct digital synthesis, a laser diode driver module, a band-pass frequency filter, a synchronous detector with phase adjustment circuitry and a low pass filter to form an analog lock-in amplifier, and an analog-to-digital converter. A 32-bit ARM microcontroller programmed with the open source Mecrisp dialect of the Forth interpreter language is used to set the frequency, and read the data from the analog-to-digital converter. The circuitry is tethered via a serial interface to a personal computer. A graphical user interface written in Phython allows easy interaction with the microcontroller by sending the appropriate Forth commands. The data acquired is visualized and stored on the personal computer for further processing. The circuitry is easy to build as it is based on through-hole devices, except for two necessary surface mount items, which, however, still can be soldered with a fine tipped soldering iron. The performance of the circuitry was demonstrated by the photoacoustic detection of NO2 using a laser diode with a wavelength of 450 nm.

Range Ambiguous Clutter Suppression Approach With Elevation Time Diverse Array

When range ambiguity and range dependence coexist in forward-looking ground moving target indication radar, the traditional space-time adaptive processing (STAP) approaches may fail to work. To cope with this issue, a range-ambiguous clutter suppression approach based on elevation time diverse array (TDA) radar system and azimuth phase coding technique is presented in this article. Due to the advantages of frequency scanning, the elevation TDA radar is able to cover all directions by transmitting a single time-shifted waveform. Therefore, a frequency bandpass filter is devised for each single range bin to achieve the mainlobe echo extraction procedure. In the sequel, the azimuth phase decoding and Doppler filtering are performed to deal with the residual sidelobe ambiguous energy. With two-dimensional filtering, one can extract the unambiguous signals for each range region independently. Then, the traditional clutter compensation and STAP methods are employed to suppress the ground clutter. Finally, the effectiveness of the proposed framework in resolving range ambiguity is verified by the numerical simulation experiments.

An Innovative Push-To-Talk (PTT) Synchronization Scheme for Distributed SAR

Bistatic/multistatic synthetic aperture radar (Bi-/M-SAR) has extensive applications, including cross- and along-track interferometry, multiangle imaging, and so on. However, these applications are affected by several factors, especially the time and frequency synchronization that this article focuses on. Here, the new insights about the focus are described, based on which an innovative push-to-talk (PTT) scheme is first put forward to solve the time and frequency synchronization problems of distributed SAR. It realizes unidirectional and long-distance synchronization through the two-segment frequency rate (TSFR) waveform composed of the two linear frequency modulation (LFM) signals with different frequency rates and achieves radar imaging and synchronization with a high rate ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${f}_{\mathrm{ syn}}$ </tex-math></inline-formula> ) at the same time by the frequency diversity (FD) waveforms and bandpass filters. To clarify the PTT scheme, its system framework and synchronization error models are detailed. Besides, the channel impulse response, multiple errors, the signal-to-noise ratio (SNR) of synchronous links, and time synchronization accuracy are analyzed. In addition, some simulations are carried out to evaluate its performance. Those results demonstrate that the PTT scheme can perform the long-distance synchronization with high <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$f_{\mathrm{ syn}}$ </tex-math></inline-formula> , its synchronization accuracy increases with the improvement of SNR and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$f_{\mathrm{ syn}}$ </tex-math></inline-formula> , and it can measure the time and frequency deviations in different ranges accurately. In a word, the PTT scheme has the potential to be used in future distributed SAR missions.

Sensory Adaptation in the Whisker-Mediated Tactile System: Physiology, Theory, and Function.

In the natural environment, organisms are constantly exposed to a continuous stream of sensory input. The dynamics of sensory input changes with organism's behaviour and environmental context. The contextual variations may induce >100-fold change in the parameters of the stimulation that an animal experiences. Thus, it is vital for the organism to adapt to the new diet of stimulation. The response properties of neurons, in turn, dynamically adjust to the prevailing properties of sensory stimulation, a process known as “neuronal adaptation.” Neuronal adaptation is a ubiquitous phenomenon across all sensory modalities and occurs at different stages of processing from periphery to cortex. In spite of the wealth of research on contextual modulation and neuronal adaptation in visual and auditory systems, the neuronal and computational basis of sensory adaptation in somatosensory system is less understood. Here, we summarise the recent finding and views about the neuronal adaptation in the rodent whisker-mediated tactile system and further summarise the functional effect of neuronal adaptation on the response dynamics and encoding efficiency of neurons at single cell and population levels along the whisker-mediated touch system in rodents. Based on direct and indirect pieces of evidence presented here, we suggest sensory adaptation provides context-dependent functional mechanisms for noise reduction in sensory processing, salience processing and deviant stimulus detection, shift between integration and coincidence detection, band-pass frequency filtering, adjusting neuronal receptive fields, enhancing neural coding and improving discriminability around adapting stimuli, energy conservation, and disambiguating encoding of principal features of tactile stimuli.

QZSS L5 Bandwidth Frequency Filter Design for QZSS Receiver

The purpose of this study was to design QZSS L5 Bandwidth Frequency Filter for QZSS Receiver. We presented the configuration of the Butterworth bandpass filter by using PSpice as the tool for the simulation. Bandpass filter frequency of the QZSS L5 with bandwidth is designed in 25 MHz using the Butterworth filter which is presented in this article. These designed circuits are composed of the 3rd order. Moreover, the combination between low pass filter and high pass filter is performed as a bandpass filter. In conclusion, this designed filter on the frequency of QZSS L5 is to be useful by using the Butterworth bandpass filter.

Machine-Learning-Enabled Automatic Sonic Shear Processing

Flexural-dipole sonic logging has been widely used as the primary method to measure formation shear slowness because it can be applied in both fast and slow formations and can resolve azimuthal anisotropy. The flexural-dipole waveforms are dispersive borehole-guided waves that are sensitive to borehole geometry, mud, and formation properties, and therefore the processing techniques need to honor the physical dispersive signatures to obtain an accurate estimation of shear slowness. Traditional processing techniques are based on either a model-dependent method, in which an isotropic model is used as a reference to compensate for the dispersion effect, or a model-independent method, which optimizes nonphysical parameters to fit a simplified model to the field dispersion data extracted in the slowness-frequency domain. Many methods often require inputs, such as mud slowness, frequency bandpass filter, or an initial guess of formation shear. Consequently, these methods often fail to interpret the dispersion signature properly when those inputs are inaccurate or when the waveform quality is poor due to downhole logging noises. The users must manually tune the processing parameters and/or choose different methods as a workaround, which causes extra time and effort to obtain the result, hence imposes a significant challenge for automating sonic shear processing. We developed a physics-driven, machine-learning-based method for enhancing the interpretation of borehole sonic dipole data for wireline logging in an openhole scenario. A synthetic database is generated from an anisotropic root-finding, mode-search routine and used to train a neural network model as an accurate and efficient proxy. This neural network model can be used for real-time sensitivity analysis and performing inversion to the measured sonic dipole dispersion data to estimate relevant model parameters with associated uncertainties. We introduce how this trained model can be used to enhance the labeling and extraction of the dipole dispersion mode. We developed a new method that outperforms previous model-dependent and model-independent approaches because the new method introduces a mechanism to constrain the solution with physics that also has the capability to incorporate more complicated physical dispersion signatures. This new method does not rely on a good initial guess on mud slowness and formation shear slowness, nor any tuning parameter. This leads to significant progress toward fully automated sonic interpretation. The algorithm has been tested on field data for challenging borehole and geological conditions.

Frequency and bandwidth tunable reliable MEMS bandpass filter for 24 GHz radar applications

In this work, radio frequency (RF) micro-electromechanical system (MEMS)-based frequency and bandwidth tunable bandpass filter is presented for application in 24 GHz Doppler radar transceivers. The filter is fabricated on 635 μm alumina substrate using surface micromachining process. Total area of the filter is only 2.8 mm2 excluding bias lines and pads. Functional building blocks of the proposed filter are fabricated and tested independently to ensure optimum filter responses. The proposed filter can be tuned to any frequency between 22 and 24 GHz based on electrostatic actuations. It demonstrates insertion loss of 1.67 dB and matching of 18.6 dB at 24 GHz with fractional bandwidth of 6.5%. Filter gives acceptable matching over a 5 GHz bandwidth (21.65-26.65 GHz) with an average insertion loss of 4.7 dB. Filter works satisfactorily up to 10 billion cycles with 0.1 to 1 W of RF power. To the best of our knowledge, this is the first reported tunable MEMS bandpass filter at 24 GHz with 10 billion cycles reliability and with 1 W of RF power for radar applications.

Analisa Elemen Multiarms Resonator Open Loop Pada Band-Pass Filter Mikrostrip Yang Bekerja Di Frekuensi EHF

The use of bandpass filters is commonly used but the use of specifications varies depending on needs, in this case the microstrip bandpass filter is expected to observe the multiarms characteristics of the open loop resonator on the performance of the bandpass filter for EHF frequencies. The design of this microstrip bandpass filter uses a multiarms open loop resonator design where at the beginning of the simulation stage uses only 1 arm with patch width, arm spacing, feeder line width and patch length based on trial and error. The final simulation results are obtained with a connector distance of 2 mm and a distance of 1 mm between arms with a value of S11 = -13.8 dB and S21 = -2.8 dB at a frequency of 30.8 GHz based on the simulation results. The filter has been successfully fabricated but cannot be measured because the frequency is too high and the measuring instrument cannot measure the frequency

Physics-Driven Machine-Learning-Based Borehole Sonic Interpretation in the Presence of Casing and Drillpipe

SummaryInterpretation of sonic data acquired by a logging-while-drilling (LWD) tool or wireline tool in cased holes is complicated by the presence of drillpipe or casing because those steel pipes can act as a strong waveguide. Traditional solutions, which rely on using a frequency bandpass filter or waveform arrival-time separation to filter out the unwanted pipe mode, often fail when formation and pipe signals coexist in the same frequency band or arrival-time range. We hence developed a physics-driven machine-learning-based method to overcome the challenge. In this method, two synthetic databases are generated from a general root-finding mode-search routine on the basis of two assumed models: One is defined as a cemented cased hole for a wireline scenario, and the other is defined as a steel pipe immersed in a fluid-filled borehole for the logging-while-drilling scenario. The synthetic databases are used to train neural network models, which are first used to perform global sensitivity analysis on all relevant model parameters so that the influence of each parameter on the dipole dispersion data can be well understood. A least-squares inversion scheme using the trained model was developed and tested on synthetic cases. The scheme showed good results, and a reasonable uncertainty estimate was made for each parameter. We then extended the application of the trained model to develop a method for automated labeling and extraction of the dipole flexural dispersion mode from other disturbances. The method combines the clustering technique with the neural-network-model-based inversion and an adaptive filter. Testing on field data demonstrates that the new method is superior to traditional methods because it introduces a mechanism from which unwanted pipe mode can be physically filtered out.This novel physics-driven machine-learning-based method improved the interpretation of sonic dipole dispersion data to cope with the challenge brought by the existence of steel pipes. Unlike data-driven machine learning methods, it can provide global service with just one-time offline training. Compared with traditional methods, the new method is more accurate and reliable because the processing is confined by physical laws. This method is less dependent on input parameters; hence, a fully automated solution could be achieved.

Estimation of the Respiratory Rate from Localised ECG at Different Auscultation Sites.

The respiratory rate (RR) is a vital physiological parameter in prediagnosis and daily monitoring. It can be obtained indirectly from Electrocardiogram (ECG) signals using ECG-derived respiration (EDR) techniques. As part of the study in designing an early cardiac screening system, this work aimed to study whether the accuracy of ECG derived RR depends on the auscultation sites. Experiments were conducted on 12 healthy subjects to obtain simultaneous ECG (at auscultation sites and Lead I as reference) and respiration signals from a microphone close to the nostril. Four EDR algorithms were tested on the data to estimate RR in both the time and frequency domain. Results reveal that: (1) The location of the ECG electrodes between auscultation sites does not impact the estimation of RR, (2) baseline wander and amplitude modulation algorithms outperformed the frequency modulation and band-pass filter algorithms, (3) using frequency domain features to estimate RR can provide more accurate RR except when using the band-pass filter algorithm. These results pave the way for ECG-based RR estimation in miniaturised integrated cardiac screening device.

Design of Microwave Photonic Subsystems Using Brillouin Scattering

With the rapid development of microwave photonic functionalities to support 5G and defence systems, there has been an increased interest in employing stimulated Brillouin scattering (SBS)-based functionalities to perform tasks that are currently difficult to achieve with conventional electronic devices. Several advances have been made using on-chip SBS to demonstrate RF frequency phase shifters, bandpass and bandstop filters, measurement systems, and delay lines. In this article, we provide an overview of some of these developments made possible by strong on-chip SBS gain. We also provide the reader with design guidelines on the selection of the appropriate waveguide geometry, subsystem design, and analog photonic link configurations to aid them in the realisation of their requisite MWP subsystem. We also focus on some of the design trade-offs that need to be considered when using integrated SBS.

A dual resonance high frequency bandpass filter

This paper presents a design of a dual resonance high-frequency bandpass filter using the Sonnet EM Simulator. The filter prototype is enhanced by adding the short stub in the center of the design. A parametric study shows the impact of choosing appropriate configuration characteristics. This is a dual resonance bandpass filter design, with center frequencies 7.8 GHz and 9.3 GHz. Performed input match S_11 at first resonance is-28.87 dB and insertion loss S_21 is -0.05 dB. The obtained results at second resonance are S_11=-8.97 dB and S_21=-2.74 dB. Due to its characteristics, this is a high-Q medium bandwidth dual resonance bandpass filter. The design is simulated and planning to be fabricated with 0.36 mm thickness and dielectric constant ?_r=1. This paper benefits from its compact size and simple geometry over the similar filters found in the literature.

GHz-range resonant ultrasound spectroscopy for a free-standing nano film studied by picosecond ultrasonics

Progress in the wireless communication requires higher frequency bandpass filters, and the bulk acoustic-wave filter is especially the key device for the GHz-range communication. Its resonance frequencies depend on the elastic constants of individual layers, but it is never straightforward to measure them. In this study, we apply resonant ultrasound spectroscopy to a GHz-range free-standing AlN/Ru/Cr resonator to simultaneously determine the elastic constant of each layer. Using picosecond ultrasonics, we measure free-vibration resonance frequencies up to ∼70 GHz and inversely determine it. The obtained values are reasonable as thin films elasticity, confirming the applicability of the proposed method.

Design of a Frequency Doubler Circuit for Suppressing Odd Harmonics

In this paper, a doubler circuit which can suppress odd harmonics is designed by using the non-linear characteristics of field effect transistor (FET) and bipolar junction transistor(BJT) devices. The frequency doubler consists of three parts: small signal full wave rectifier circuit, frequency doubler circuit and band-pass filter circuit. It realizes fundamental and third harmonics suppression by rectifying the input signal of single FET frequency doubler. Meanwhile, the output power is twice as high as that of single FET frequency doubler (3dB higher). Circuit simulation results indicate that when the input fundamental voltage amplitude is 0.5V, the output voltage amplitude of second harmonics is 0.342V, the fundamental suppression is greater than 48.85dBc, and the third harmonic suppression is greater than 34.39dBc. Compared with the traditional single FET frequency doubler, this design improves the frequency conversion efficiency.