Pole Filter Research Articles

An edge-coupled magnetostatic bandpass filter

The further development of 5G and 6G communication systems introduced new frequency allocations beyond 6 GHz, necessitating the development of compact bandpass filters that can operate over wide gigahertz frequency ranges. Herein, we report on the design, fabrication, and characterization of an edge-coupled magnetostatic forward volume wave bandpass filter (MSFVW). Using micromachining techniques, we fabricate both 2-pole and 4-pole filters from a yttrium iron garnet (YIG) film grown on a gadolinium gallium garnet (GGG) substrate with inductive transducers. By adjusting an out-of-plane magnetic field, we demonstrate linear center frequency tuning for a 4th-order filter from 4.5 GHz to 10.1 GHz while retaining a fractional bandwidth of 0.3%, an insertion loss of 6.94 dB, and a − 35 dB rejection level. We characterize the filter nonlinearity in the passband and stopband with IIP3 measurements of − 4.85 dBm and 25.84 dBm, respectively. In this work, we demonstrate a compact octave tunable narrowband channel-select filter with a significant degree of design flexibility and performance comparable to the state-of-the-art.

Fish Swarmed Kalman Filter for State Observer Feedback of Two-Wheeled Mobile Robot Stabilization

Over the past few decades, there have been significant technological advancements in the field of robots, particularly in the area of mobile robots. The performance standards of speed, accuracy, and stability have become key indicators of progress in robotic technology. Self-balancing robots are designed to maintain an upright position without toppling over. By continuously adjusting their center of mass, they can maintain stability even when disturbed by external forces. This research aims to achieving and maintaining balance is a complex task. Self-balancing robots must accurately sense their orientation, calculate corrective actions, and execute precise movements to stay upright. Eliminating disturbances and measurement noise in self-balancing robot can enhance the accuracy of their output. One common technique for achieving this is by using Kalman filters, which are effective in addressing non-stationary linear plants with unknown input signal strengths that can be optimized through filter poles and process covariances. Additionally, advanced Kalman filter methods have been developed to account for white measurement noise. In this research, state estimation was conducted using the Fish Swarm Optimization Algorithm (FSOA) to provide feedback to the controller to overcome the effects of disturbances and noise in the measurements through the designed filter. FSOA mimics the social interactions and coordinated movements observed in fish groups to solve optimization problems. FSOA is primarily used for optimization tasks where finding the global optimal solution is desired. The results show that the use of an optimized Kalman filter with FSOA on a two-wheeled mobile robot to handle system stability reduces noise values by 38.37%, and the system reaches a steady state value of 3.8 s with a steady error of 0.2%. In addition, by using the proposed method, filtering disturbances and measurement noise in self-balancing robot can help improve the accuracy of the self balancing robot’s output. System response becomes faster towards stability compared to other methods which are also applied to two-wheeled mobile robots.

Novel Active Damping Design Based on a Biquad Filter for an LLCL Grid-Tied Inverter

LLCL filters for grid-tied inverters have been adopted to get better performance for the harmonics near the switching frequency than commonly used LCL filters. However, the resonant peak caused by a pair of unstable resonance poles of the LLCL filters is introduced and makes the system become unstable. In this paper, a biquad filter composed of a notch filter and a resonator is introduced to restrain the resonant peak. In this method, the resonance point and the notch point of the biquad filter are placed at the appointed frequency, and the resonant peak is transferred to the stable area by phase transformation, so that the system does not cross −180° at the resonant peak. This method makes the system have higher control bandwidth and stronger robustness even in a weak power grid. Meanwhile, a proportional-integral multiresonant repetitive controller is used to restrain low-frequency current harmonics and improve the steady-state and dynamic performance of the control system. Furthermore, based on the active damping of the biquad filter, the stability criterion of the control system under a weak power grid is given. Finally, the accuracy of the analysis and the effectiveness of the method is verified by simulations.

Identification of potential mineral exploration targets from the interpretation of aeromagnetic data covering the Sirwa region (Central Anti-Atlas, Morocco)

Situated at the junction between the Moroccan High Atlas and the Anti-Atlas, the Sirwa Massif has always been a perfect target for mining exploration for its unique geological characteristics that provide an economically valuable concentrations of metals. It corresponds to a crustal uplift at an elevation above 2000 m that were slightly folded and lifted during the Hercynian and Alpine orogeny. The structural settings of this area are very complicated due to the acute shortage of surface and subsurface structural data. The aeromagnetic data represents a powerful tool for the identification and the delineation of the poorly exposed faults, that could promote the development of new ore deposits.The processing of the residual magnetic map was carried out to locate anomalies, define the trends and boundaries of the buried structures and identify the magnetic contacts that might represent faults, fractures or lithologic boundaries. This is done by the reduction to the north pole (RTP) filter and several edge detectors processes (i.e., total horizontal derivative, the tilt angle derivative and the 3D-Euler deconvolution). The orientations of lineaments extracted from the total horizontal derivative and Tilt derivative maps predominantly suggest NE-SW to ENE-WSW trending structures, in agreement with the post-Pan-African rifting event. However, we have identified a few NW-SE and NNW-SSE trending lineaments probably related to the recent Variscan movements. The 3D Euler deconvolution (ED) suggests a depth solution that ranges from 600 m to 3400 m. The deepest lineaments have an ENE-WSW direction, and the shallowest with a depth of about 600 m, shows a NE-SW/NW-SE direction. These results reveal new tectonic features that can be useful for future mine exploration

The topography of zeros and poles of a third order IIR digital filter with finite word length in the z-plane

Earlier it was found that the zeros and poles of IIR digital filters with finite word length are elements of the set of algebraic numbers. Therefore, not every point of the unit circle of the z-plane can be a zero and / or a pole of such digital filters. The position of admissible positions for zeros and poles depends on the degree of algebraic numbers and the length of the fractional part of the coefficients of the equivalent canonical structure of the corresponding order. The formation of the corresponding configurations is considered as a z-plane discretization due to the quantization of the filter coefficients. The z-plane discretization for second-order filters has been well studied. The geometric locus of the corresponding algebraic numbers is a system of concentric circles, that is, plane algebraic curves of the second degree. This paper presents the results of studying the geometrical place of the third order IIR filter zeros and poles.

Structure‐induced low‐sensitivity design of sampled data and digital ladder filters using delta discrete‐time operator

AbstractThe concept of the delta discrete‐time operator‐based doubly terminated two‐pair (ladder) is discussed here for use in sampled‐data and digital filter design. The two‐pair filter utilizes traditional backward Euler and forward Euler integrators, is lossless under scaling (LUS), and possesses good magnitude sensitivity which is induced intrinsically due to the filter structure. This paper is an overview and consolidation of results published by the authors over the years in various conferences (Khoo et al., 1998, 1999, 2001, 2008, 2008a, 2008b) in a unifying and tutorial fashion. To achieve the low magnitude sensitivity, the well‐known Feldtkeller equation corresponding to the delta‐operator formulation is derived to establish the theoretical basis for the realization. One significant advantage of the design procedure presented here using the delta operator is that it overcomes the numerical problem at the spectral factorization stage of the conventional z‐domain lossless‐discrete‐time integrator (LDI) synthesis method when the filter poles are clustered around z = 1. Furthermore, the entire operation involves only rational polynomials, as opposed to fractional power polynomials as in the LDI and other methods in z‐domain. The method presented can realize three distinct forms of transfer functions with varied transmission zeros.

Non-Intrusive Contact Respiratory Sensor for Vehicles.

In this work, we propose a low-cost solution capable of collecting the driver’s respiratory signal in a robust and non-intrusive way by contact with the chest and abdomen. It consists of a microcontroller and two piezoelectric sensors with their respective 3D printed plastic housings attached to the seat belt. An iterative process was conducted to find the optimal shape of the sensor housing. The location of the sensors can be easily adapted by sliding them along the seat belt. A few participants took part in three test sessions in a driving simulator. They had to perform various activities: resting, deep breathing, manual driving, and a non-driving-related task during automated driving. The subjects’ breathing rates were calculated from raw data collected with a reference chest belt, each sensor alone, and the fusion of the two. Results indicate that respiratory rate could be assessed from a single sensor located on the chest with an average absolute error of 0.92 min−1 across all periods, dropping to 0.13 min−1 during deep breathing. Sensor fusion did not improve system performance. A 4-pole filter with a cutoff frequency of 1 Hz emerged as the best option to minimize the error during the different periods. The results suggest that such a system could be used to assess the driver’s breathing rate while performing various activities in a vehicle.

4-Pole Tunable Absorptive Bandstop Filters Using Folded Coupled-Lines With an Inductor

The ever-growing field of wireless communication requires efficient radio frequency transceivers with tunable absorptive bandstop filters that can prevent the interference of out-of-band and reflected signals. This paper presents 4-pole tunable absorptive bandstop filters using folded coupled-lines with an inductor. A 4-pole filter transfer function is achieved to obtain an absorptive bandstop filter coupling diagram with 45° electrical-length transmission-line source/load coupling. The folded-loaded coupled-lines with an inductor are proposed to obtain the control for the required coupling coefficients based on the filter transfer functions. The required quality factor extracted through the transfer function is accomplished using a distributed resonator loaded with asymmetrical varactors without auxiliary circuits, such as an impedance-matching network. Two types of filters were designed and built on a substrate with ε <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> = 3.42 and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">h</i> = 30 mil. The center frequency tuning was performed using silicon varactors. The first filter shows a return loss of 16.2–38 dB and a rejection level of 41–48 dB in the tuning range 0.83–1.09 GHz. The second filter results in a measured return loss of 14–34 dB and a rejection level of 40.1–51 dB at 1.16–1.47 GHz. 4-pole tunable absorptive bandstop filters with high attenuation and reflectionless responses were achieved which have applications in cognitive radios and carrier aggregation systems.

Wideband 1-Bit Bandpass Delta Sigma Modulator Using Elliptic Filter in Noise Transfer Function

A 1-bit band-pass delta-sigma modulator (BP-DSM), which utilizes oversampling technology, allows a modulated signal to be directly output by using a high-speed 1-bit digital pulse train, thus realizing miniaturization of transmitters. For 1-bit BP-DSM, the noise transfer function (NTF) is used to suppress quantization noise power in the transmission band and a guideline of out-of-band gain of |NTF|&#x003C; 1.5 is used to prevent oscillation. However, in previous studies, such as Butterworth and inverse Chebyshev filters, the out-of-band gain was designed indirectly by tuning the zeros and poles in the transmission band and thus, was not stabilized sufficiently. Furthermore, even though the zeros of the NTF are identical to the poles of the loop filter, there are still widely used designs in which the zeros are set on the unit circle, making stabilization quite difficult. Therefore, in this paper, we propose a feasible implementation of the NTF for 1-bit BP-DSM with an elliptic filter that can be used to set not only in-band but also out-of-band gain, in which both the zeros and poles are set inside the unit circle. As a design result, a modulation bandwidth of 400 MHz as a relative bandwidth of 11%, a noise suppression bandwidth of 800 MHz, and an adjacent channel leakage power ratio of 50 dB were achieved at a center frequency of 3.6 GHz, enabling a wider bandwidth and higher SNR than before by improving the stability.

Identification of Gold Mineralization Zones Using Magnetic Data at Gunung Gupit Area, Magelang, Central Java

Indonesia is one of the biggest gold producing countries in the world. the discovery of new gold reserves makes the passion of the gold mining industry increase. The Gunung Gupit area of Magelang Regency in Central Java has discovered new gold potential, but has not been thoroughly explored. The magnetic method is applied to identify and determine the distribution of the presence of gold mineralized zones based on the magnetic properties of rocks. A total of 1001 points on 41 magnetic line were acquired using Proton Precession Magnetometer (PPM) Geometrics model G-856 in an area of 2.5 km2. Field data is obtained as Magnetic Field Anomaly. Reduction to pole (RTP) and low-pass filter process is applied to the magnetic anomaly. The results showed the Gunung Gupit area was divided into 4 zones based on magnetic anomaly responses, i.e strong, medium, weak anomaly and igneous rock zones. The 2.5 D modeling result shows the presence of northwest-southeast normal fault and strike slip fault that is perpendicular to the normal fault. These faults control the hydrothermal alteration in Gunung Gupit and its surroundings. A strong mineralization zone lies between these two faults. The presence of gold and other metal minerals lies in this strong mineralization zone, and moderate alteration. The coverage area is quite wide and distributed along the two faults.

Optimized four-parameter PID controller for AVR systems with respect to robustness

A procedure for the optimization of the proportional-integral-derivative (PID) controller under constraints to robustness of model uncertainties and sensitivity to measurement noise for a synchronous generator (SG) automatic voltage regulator (AVR) is presented in this paper. Performance indices related to the load disturbance response such as integral error (IE) and integral absolute error (IAE) are used as key criteria for the design method. They are minimized for a given maximum modulus of sensitivity function Ms. By maximizing loop gain regarding given sensitivities Ms and Mn we optimized load disturbance response. Contrary to majority AVR PID controller procedures, along with proportional, integral and derivative gain, a noise filter time constant is included in a proposed optimization algorithm to satisfy given sensitivity to the measurement noise Mn. A simple and effective solution of the optimization problem is obtained by binding a ratio between the integral and the derivative time constant Ti/Td. The optimal Ti/Td ratio is determined subsequently. Besides this, a step response to voltage reference change is modified with a reference filter to avoid large overshoots. This is achieved by limiting the maximum modulus of the resulting close-loop transfer function sensitivity Msp. The fact that zeros and poles of the second order reference filter have the same damping factor simplifies the procedure for resolving two out of six parameters. Also, two additional conditions result in the fact that three design parameters {Ms, Mn, Msp} are sufficient to determine the required six parameters of the two-degree-of-freedom (2DOF) PID controller. Such controller outperforms recently presented AVR controllers especially regarding the load disturbance rejection. Experiment tests with no-load SG and SG connected on the grid are carried out to prove the claims stated in this work concerning robustness performance and sensitivity to measurement noise. Also, we showed practical use of the proposed controller parameter tuning procedure by experimental runs performed on a lab generator.

Wide Programmable Range Fourth-Order, Fully-Differential Sallen-Key MOSFET-C LPF for Impedance Spectroscopy Measurements and Self-X Sensory Electronics in Industry 4.0

Abstract This paper picks up the need for a wide range programmable corner frequency for anti-aliasing and antiimaging filters in on-chip impedance spectroscopy and sensor signal readout circuitry with self-X properties (selfdiagnosing/healing) for industry 4.0 applications. A fourthorder wide tunable range MOSFET-C low pass filter is designed by using XFAB 0.35 μm CMOS technology and Cadence design tools. The proposed circuit is based on fully differential Sallen-Key architecture with Butterworth approximation. It covers a frequency range from 30 Hz up to 7 MHz. Tunability is achieved using a potentially high resistance and linearized configurable MOS resistor to control the filter pole frequency. The configurable elements in the circuit serve as tuning knobs to be controlled by machine learning. The physical design area is 0.39mm2.

Mapping of Kedaton Archaeological Sites Using Geomagnetic Methods (Preliminary Study)

Ancient civilizations in Jombang left many historical relics in the form of temples, artifacts, and other archeological sites. Kedaton site is one of the newly discovered archeological sites. This site is buried under a few meters thick of Mount Kelud’s pyroclastic flow. Therefore, the distribution patterns of the site is needed to improve the excavation plan in order to maintain the structure of the site. One of the technical approaches that can be applied to map the site’s distribution in detail is geophysical survey. Geomagnetic method is a method commonly used in the case of archeological site investigations because of its non-destructive nature. The mapping process on Kedaton site is conducted by applying geomagnetic survey that utilizes physical parameters in the form of magnetic susceptibility. The reduce to pole filter is applied to magnetic data processing to aid interpretation, coupled with horizontal gradient method and analytic signal method further clarify the boundaries of magnetic anomaly sources. Reduce to pole filter indicates that the site’s brick detected as moderate to high magnetic anomaly values (more than 450 nT). This research succeeded in mapping clearly the boundaries of the site with an area of up to 6000 meters2 with the shape of the site resembling a building with several chambers. The main chamber is in the north which is the widest chamber, and small chambers are found on the south side.

Multi‐layered PCB distributed filter

In this paper, multi-layered print circuit board distributed resonators and filters are introduced. Here, the individual elements of the distributed resonator are made as part of a multi-layered print circuit board, commonly used in the circuitry of transceiver boards. In this way, the unused real estate available on the board is used effectively. As a demonstrator of the proposed technology, a 2-pole filter fabricated using a 5-layer substrate and consisting of a matrix of 11 × 11 elements per resonator is fabricated and its performance is measured. Due to a large number of individual elements, which perform dimensional averaging of manufacturing inaccuracies, the filter obtained in this way not only requires no post-production tuning, but it also has an extremely low profile of 5o, which is the lowest profile to be reported in the literature. The filter was made to operate at a centre frequency of 1.8 GHz with an absolute bandwidth of 65 MHz. The measured and computed results are in good agreement.

Synthesis of a New Class of Extracted Pole Filters Without the Ideal Phase Shifters

This article proposes a novel approach for extracted pole (EP) filter synthesis. The pole producing elements can be extracted without introducing phase shifters. It is made possible by extracting lowpass elements in the prototype without reducing the order of filter functions. Using the proposed elements as added redundancy, the nonideal effect in the physical model is absorbed by adjacent resonators. Those novel approaches break through the conventional framework in EP filter synthesis. The synthesized results do not introduce extra spikes caused by nonideal phase shifters in the conventional EP filters. The new theory enables the application of EP filters in broadband situations. This work also reveals the equivalence between the frequency-dependent couplings and the PPEs. The validity of the demonstrated method is illustrated via an 11-pole filter with two transmission zeros. The simulated and measured results have no extra spikes caused by the nonideal phase shifters, which verified the effectivity of the proposed theory.

Synthesis of Extracted Pole Filters With Transmission Zeros in Both Stopbands and Nonresonant Nodes of the Same Nature

Extracted pole filters alternating transmission zeros (TZs) above and below the passband are intrinsically related to the use of nonresonant nodes (NRNs) of different nature (inductive and capacitive). This work demonstrates that it is possible to synthesize an extracted pole filter showing TZs on both sides of the passband but implementing all NRNs of the same reactive nature, overcoming the limitations imposed by some technologies. The proposed feature is achieved by special consideration of the input reflection phase of the generalized Chebyshev filter function, affecting input and output resonators and placing at most two zeros at the opposite band. A third-order all-capacitive prototype filter has been synthesized and fabricated to validate the proposed statement. The concept allows us to achieve all-capacitive or all-inductive filters.

Recovering the total magnetization direction using a novel stable reduction to the pole filter (RTP)

Interpretation of magnetic data commonly assumes that the total magnetization direction is parallel to the local geomagnetic field direction, leading to incorrect results when remanent magnetization is significant. This is a particular problem when applying interpretive filters that require knowledge of the direction of total magnetization. Here I present a novel frequency-domain, reduction-to-pole filter that is numerically stable for low latitudes and incorporates the influence of remanent magnetization. The operator is implemented through a differential algorithm that iteratively estimates the total magnetization direction. At each iteration, the code compares the ability of thirty pairs of inclination and declination values to minimize an objective function. After each comparison, the two pairs yielding the worst result are replaced by new values until the objective function is minimized. To improve results, two different methods were implemented to obtain a first guess for the inclination and declination: Helbig's integrals and comparison method. This first guess is used as reference to compose the first set of thirty pairs considered to calculate the RTP. A third possibility was also implemented, which uses thirty random pairs for the first interaction. Fisher's statistics are applied to the final population of estimated directions in order to determine the best mean direction. The new RTP filter is numerically stable and independent of a priori information about the source susceptibility, top depth, and geometry. The algorithm was tested on magnetic anomalies from several synthetic models and on real magnetic data and showed remarkable stability even in challenging settings.

Silicon Micromachined D-Band Diplexer Using Releasable Filling Structure Technique

A D-band waveguide diplexer, implemented by silicon micromachining using releasable filling structure (RFS) technique to obtain high-precision geometries, is presented here for the first time. Prototype devices using this RFS technique are compared with devices using the conventional microfabrication process. The RFS technique allows etching large waveguide structures with nearly 90° sidewall angles for the 400-μm-tall waveguides. The diplexer consists of two direct-coupled cavity six-pole bandpass filters, with the lower and the upper band at 130-134 and 141-148.5 GHz, respectively. The measured insertion loss of the two bands is 1.2 and 0.8 dB, respectively, and the measured return loss is 20 and 18 dB, respectively, across 85% of the passbands. The worst case adjacent channel rejection is better than 59 dB. The unloaded quality factors of a single cavity resonator are estimated from the measurements to reach 1400. Furthermore, for the RFS-based micromachined diplexer, an excellent agreement between measured and simulated data was observed, with a center frequency shift of only 0.8% and a bandwidth deviation of only 8%. In contrast to that, for the conventionally micromachined diplexer of this high complexity, the filter poles are not well controllable, resulting in a large center frequency shift of 3.5%, a huge bandwidth expanding of over 60%, a poor return loss of 6 and 10 dB for the lower and the upper band, respectively, and an adjacent channel rejection of only 22 dB.

Applying feature normalization based on pole filtering to short-utterance speech recognition using deep neural network

Applying feature normalization based on pole filtering to short-utterance speech recognition using deep neural network

Study of Curie point depth and heat flow from spectral analysis of aeromagnetic data for geothermal potential of Gubio, Chad Basin, Nigeria

Aeromagnetic data of Gubio area, Chad Basin, northeastern Nigeria, were interpreted quantitatively by employing spectral analysis technique with the aim to estimate the Curie point depth, geothermal gradient and heat flow in order to determine the geothermal nature of the area. Data enhancement (reduction to pole, RTP and band pass filter) was performed on the total magnetic intensity (TMI) map of the area using oasis Montaj software. The enhanced map was divided into four overlapping blocks, and each block was subjected to spectral analysis. The results gave Curie point depth values ranging from 10.63 to 20.07 km, with deepest depth at the northeast, while the shallowest depth was observed to be conspicuous in the southeastern part of the study area. The estimated geothermal gradient ranges from 28.90 to 54.57 °C km−1 with an average value of 40.26 °C km−1, with low values in the northeast direction, and increases towards southeast. The average geothermal gradient of 40.26 °C km−1 indicates the possibility of hydrocarbon generation and accumulation in Chad basin. The estimated heat flow values range from 72.24 to 136.43 mW m−2 with an average value of 100.65 mW m−2, the highest values are found around southeastern part of the study area, and the lowest values are within the northeastern part. The areas of geothermal anomalies with gradient above 50 °C km−1 may be good areas for geothermal reservoir exploration for an alternative source for power generation.