Roll-off Rate Research Articles

A compact low-profile substrate integrated waveguide wearable filtenna for 5G communication

We have proposed the design and synthesis of a compact, low-profile, flexible substrate integrated waveguide (SIW) wearable filtering antenna (filtenna) for 5 G communication, along with two parasitic resonator patches. We initially used a half-mode rectangular-shaped substrate-integrated (HMRSI) cavity as a resonating patch to minimize circuit size. The HMRSI cavity is located in close proximity to two parasitic truncated corner patches that serve as both the radiator and the final stage resonators, thereby optimizing filtering performance and expanding the operating bandwidth. The interaction of the parasitic patches with the HMRSI cavity produces one radiation null at the upper band-edges, while the corner truncation and notching on the parasitic patches with defected ground creates the other, enhancing the roll-off rate. Typical filter synthesis technology guides the design of the antenna. We have manufactured and measured an optimized prototype. The proposed flexible filtenna demonstrates excellent out-of-band selectivity, and its measurement aligns well with simulated ones, achieving an 8.2% fractional bandwidth (FBW), a maximum realized gain of 6.1 dBi, and a flat passband gain response. The proposed filtenna has also studied the human body and achieved a low specific absorption rate (SAR), which enables it to be an on-body wearable filtenna.

Numerical Analysis in Double-Sided Polishing: Mechanism Exploration of Edge Roll-Off

Understanding the mechanism of stress concentration effects on the surface of semiconductor substrate materials—silicon wafers—in Double-Sided Polishing (DSP) is particularly important for improving polishing quality. In this study, a two-dimensional finite element model is established to study the effect of contact state and stress concentration during polishing on edge roll-off (ERO) and polishing rate uniformity. The variation in this contact state is influenced by changes in wafer thickness and the gap between it and the carrier. The model is validated by experiments and helps to further analyze and interpret the experimental results, identifying six stages of contact states during the polishing process. The research indicates that the phenomenon of stress concentration at the edge of a wafer is caused by the pads creating a large amount of compression at the edge of the wafer. Additionally, there appears to be a threshold value during the polishing process, below which the stress concentration on the wafer changes, thereby altering the magnitude of edge roll-off and, ultimately, affecting overall flatness. This study provides a basis for optimizing the process design.

A high-selectivity filtering DDPA with raised DDPs and metal vias

ABSTRACT A high-selectivity filtering dense dielectric patch (DDP) antenna (DDPA) with raised DDPs and metal vias is proposed in this paper. The proposed filtering DDPA has three resonant modes, the first two modes are TE 11 mode and the third mode is TE 12 mode. The first TE 11 mode is generated because of the centrally raised small DDP. The second TE 11 mode and the TE 12 mode are the modes of DDP itself. The proposed filtering DDPA has two radiation nulls (RNs). The low-frequency radiation null (LFRN) is generated by loading equal length parallel slots on the ground. DDP itself has a non-radiative high-frequency radiation null (HFRN). By loading symmetrical same metal vias on the DDP, the radiative TE 12 mode and the non-radiative TE 12 mode move to the low-frequency at the same time. That results in a wider passband and excellent high-frequency response. The proposed filtering DDPA is manufactured and measured for verification. The impedance bandwidth is 8.2% from 3.75 GHz to 4.07 GHz. The average gain is 7.7 dBi, and the average roll-off rate is 177 dB/GHz. The measured results prove that the proposed filtering DDPA has good radiation performance and high-selectivity.

A Modified High-Selective Frequency Selective Surface Designed by Multilevel Green’s Function Interpolation Method

A compact high-selective band-pass frequency selective surface (FSS) with the unit cell less than λ/7 is presented. For the simulation of the structure, the multilevel Green’s function interpolation method (MLGFIM) using Floquet theory is adopted to accelerate the calculation of the complex unit cell. The radial basis function (RBF)-QR method is used in the interpolation, which makes the shape parameter in the RBF function not required to be retested for different periodicity. In this design, with an aperture coupling structure between the top and bottom layers patterned by triangular patches and meander lines, the FSS has two transmission zeros (TZs) on both sides of the pass-band and achieves a steep roll-off rate of 192 dB/GHz. Consequently, the FSS has high selectivity and out-of-band suppression, besides profiting from the low profile and symmetric geometry, this FSS exhibits good angular and polarization stabilities. The prototype of the proposed FSS is fabricated and good performance is obtained.

Orientation-based solar noise impact on underwater and free-space optical wireless communication systems: experimental investigations

Solar noise, when it interferes with the received signal at the system receiver (Rx) of an optical wireless communication (OWC) system, degrades the system’s performance. The detrimental effect of solar noise on OWC systems has been well established in the literature. This work experimentally demonstrates solar noise interference in the OWC system by pointing the system Rx in various orientations in air and water mediums, e.g., 0° (Rx pointing horizontally leftward), 45°, 90° (Rx pointing vertically downward), 135°, 180° (Rx pointing horizontally rightward), 225°, 270° (Rx pointing vertically upward), and 315°. The experimental outcomes depict the signal’s noise content, spectral leakage, and roll-off rate variation at multiple Rx orientations. We also demonstrate the solar noise interference in transmitting an image through the outdoor underwater OWC link by pointing the system Rx in various orientations. Experimental demonstration confirms that the same OWC system never behaves identically in the presence of solar noise if the system Rx keeps changing its orientation during the maneuver.

Bandpass frequency selective surfaces with fast roll-off characteristics

We propose a bandpass frequency selective surface (FSS) with fast cut-off characteristics and low insertion loss. It consists of a compact high-frequency hybrid compression board with five metal layers, two Rogers RO4003C layers, and two F4B layers. The hierarchical fitting of equivalent circuits is utilized to analyze the FSS, which maintains angular stability for dual-polarized electromagnetic waves at incidence angles of less than 20 degrees. Under normal incidence, transmission amplitudes in the K-band exceed −0.87 dB. Furthermore, the proposed FSS achieves a roll-off rate of 87.6 dB GHz−1, which can be applied in dual-frequency observing systems for millimeter astronomy.

Microstrip Quasi-Elliptic Absorptive Bandpass Filter with Ultra-Wide Reflectionless Range and Compact Size

Absorptive bandpass filters (ABPFs) are highly attractive in modern microwave communication systems due to their ability to internally absorb the harmful stopband RF-power reflections. This paper reports an approach to designing quasi-elliptic ABPFs with ultra-wide reflectionless range, enhanced selectivity, and compact size. The method is realized based on a fourth-order quasi-elliptic absorptive lowpass filter (ALPF) prototype with a simplified structure. This ALPF prototype exhibits both good impedance-matching over the whole normalized frequency domain and an adjustable transmission zero close to the passband. By applying an equivalent impedance transformer model, a coupled-line-based ABPF scheme is devised from the ALPF prototype, which eliminates conventional dispersive transmission line inverters, resulting in an ultra-wide reflectionless range and a compact size. Closed-form equations are derived to support the filter synthesis. A 2.45 GHz microstrip ABPF with 30% fractional bandwidth is designed for verification. The measured minimum in-band insertion loss is 0.83 dB and the reflectionless range of return loss better than 10 dB is from DC to 12.88 GHz. Both the upper and lower stopband suppression exceed 20 dB, with the upper stopband extending up to 6.80 GHz. The upper and lower out-of-band roll-off rates are 93.9 and 121.4 dB/GHz, respectively. The overall circuit size is 0.12 λg2.

Design of a Microwave Quadrature Hybrid Coupler with Harmonic Suppression Using Artificial Neural Networks

In this paper, a compact and simple structure of an elliptic microstrip lowpass filter (LPF) is designed for harmonic suppression in microwave quadrature hybrid coupler (QHC) applications. A radial resonator and a rectangular resonator are used to produce an elliptic LPF. The proposed LPF is used on the outer sides of the branch line coupler, which has improved the coupler harmonic suppression. Furthermore, artificial neural networks (ANNs) are incorporated to improve the LPF design process. The LPF best structure is obtained using the proposed ANN model. The proposed LPF has a compact size, which only occupies 16.4 mm × 7.3 mm equals to 0.164 λg × 0.073 λg, has a cut frequency of 2.2 GHz, and shows a sharp transmission band with a roll-off rate of 158.3 dB/GHz. Finally, the deigned QHC operates correctly at 1 GHz, which shows high harmonic suppression ability. The proposed QHC provides wide suppression band from 2.25 GHz up to more than 14 GHz, which can effectively suppress 3rd, to 14th harmonics. The proposed coupler features desirable parameters of S11, S21, S31, and S41, with magnitude of −21 dB, −3.4 dB, −3.3 dB, and −22.5 dB, at the operating frequency. The proposed approach mitigates the complexity of the circuit fabrication, compared with the previous methods while achieved desirable performances for the proposed QHC.

Effective modelling of human expressive states from voice by adaptively tuning the neuro-fuzzy inference system

<span lang="EN-US">This paper aims to develop efficient speech-expressive models using the adaptively tuning neuro-fuzzy inference system (ANFIS). The developed models differentiate a high-arousal happiness state from a low-arousal sadness state from the benchmark Berlin (EMODB) database. The proposed low-cost flexible developed algorithms are self-tunable and can address several vivid real-world issues such as home tutoring, banking, and finance sectors, criminal investigations, psychological studies, call centers, cognitive and biomedical sciences. The work develops the proposed structures by formulating several novel feature vectors comprising both time and frequency information. The features considered are pitch (F0), the standard deviation of pitch (SDF0), autocorrelation coefficient (AC), log-energy (E), jitter, shimmer, harmonic to noise ratio (HNR), spectral centroid (SC), spectral roll-off (SR), spectral flux (SF), and zero-crossing rate (ZCR). to alleviate the issues of the curse of dimensionality associated with the frame-level extraction, the features are extracted at the utterance level. Several performance parameters have been computed to validate the individual time and frequency models. Further, the ANFIS models are tested for their efficacy in a combinational platform. The chosen features are complementary and the augmented vectors have indeed shown improved performance with more available information as revealed by our results.</span>

Compact lowpass filter with vast out-of-band rejection utilizing DGS

A unique low-profile microstrip lowpass filter (LPF) is introduced. It features a broad range of stopband and sharp roll-off. The suggested LPF is built utilizig a T-shaped configuration which includes a stub for resonance and utilizes open stubs as attenuator cells. To further improve the stopband, a double circular ring is engraved into the ground plane. The developed filter features a cut-off frequency of 3 dB at 3.4 GHz, a roll-off rate of 108 dB/GHz, and a stopband range from 3.7 to 22.8 GHz. The attenuation is less than −20 dB. The prospective LPF is designed using a lumped LC circuit model and validated using Keysight Advanced Design System (ADS) simulation and theory. The final design is realized using RT/Duroid 4003C, which boasts a small footprint of 12.4mm×8.69mm×0.8mm. The modelling findings and measurements of the suggested LPF are in fairly good agreement.

Demonstration of a terahertz integrated planar network synthesis filter

At terahertz (THz) frequencies, there are few experimental works that demonstrate the viability of all-pole network synthesis filters to obtain desired frequency characteristics (i.e., Chebyshev, Butterworth, Bessel, etc.) using planar waveguides. This capability has been proven with non-planar waveguides, but has yet to be demonstrated using planar waveguides, which are desirable due to their integration capabilities similar to printed circuit board or monolithic microwave integrated circuit structures. In this paper, we use network synthesis methods from microwave engineering to fabricate three integrated planar low-pass filters for THz applications that have the same cut-off frequency (f c = 0.8 THz) but different orders (N = 3, 4, 5). We measure their response to a THz-bandwidth excitation pulse and find that the experimental results exhibit increasing roll-off rates with increasing filter order without incurring significant pulse distortion, which is aligned with theory.

Finding the optimum Roll-Off rate of a Raised Cosine Filter at the Receiver to Achieve the Lowest Bit Error Rate for a given Modulation Order and a given [ (Energy/Bit) / Normalized Noise] Ratio.

Finding the optimum Roll-Off rate of a Raised Cosine Filter at the Receiver to Achieve the Lowest Bit Error Rate for a given Modulation Order and a given [ (Energy/Bit) / Normalized Noise] Ratio.

A filtering dense dielectric patch antenna with rectangular silver strips

The filtering dense dielectric patch (DDP) antenna (DDPA) is proposed in this paper. Two pairs of rectangular silver strips are pasted on the top and bottom surfaces of DDP along the y-axis direction. This not only introduces the TM10-like mode, but also independently adjusts the resonant frequency of the TM10-like mode. The rectangular silver strips on the bottom surface of DDP can also make the DDPA obtain a radiation null. By pasting a pair of rectangular silver strips on the top surface of DDP along the x-axis direction, the resonant frequency of TE12 mode can be independently regulated. The resonant frequencies of TM10-like and TE12 modes of DDP form a passband. The proposed filtering DDPA is fabricated and measured to verify this idea. The simulation results are in good agreement with the measured results. The relative bandwidth of the proposed filtering DDPA is 4.64% (4.21–4.41 GHz), with an average gain of 5 dBi. The steep roll-off rates of the two sidebands are 120 and 320 dB/GHz, respectively.

CASSR based metamaterial tunable low pass filter

With the need for compact, discrete, and tunable passive devices in the upcoming wireless communication techniques, metamaterials have been proven to their incredible properties and have raised a new paradigm. The article discusses the possibility to design an electrically small metamaterial low pass filter (LPF) from a Complementary Asymmetric Single Split Resonator (CASSR) with a tunable pass-band for high-performance communication systems. The proposed CASSR filter on low-cost FR4 substrate of relative permittivity 4.4 and thickness 1.6 mm for a cut-off frequency of 1.12 GHz shows a roll-off rate of 159 dB/GHz. It is electrically small with a footprint area of 0.112λ × 0.112λ mm2 with ka = 0.70.

A Broad Stopband and High Rejection HTS Lowpass Filter for Quantum Computers

This paper presents a novel approach for extending the upper stopband of lowpass filters. The proposed technique involves dividing the hairpin unit cells' coupled lines into multiple smaller components, which shifts the harmonics to higher frequencies while maintaining the cut-off frequency. Additionally, the stopband is further extended by modifying the tapping position to suppress the second harmonic. For demonstration, an improved dual-hairpin unit cell is devised, which is able to extend the stopband up to 11.3 times the cut-off frequency. Furthermore, a cascaded lowpass filter utilizing multiple improved dual-hairpin unit cells is also designed, which is divided into two sub-filters to suppress enclosure resonance. The cascaded filter is fabricated on an HTS (high-temperature superconducting) thin film deposited on a MgO substrate, demonstrating a cut-off frequency of 483 MHz, extending the stopband to 25.1 GHz (51.9 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f_c</i> ), affording a rejection level exceeding 60 dB and insertion loss below 0.04 dB. Notably, the roll-off rate exceeds 569 dB/GHz, and the size measures only 0.144 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">λ_g</i> × 0.030 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">λ_g</i> .

Metamaterial inspired electromagnetic bandgap filter for ultra-wide stopband screening devices of electromagnetic interference

Presented here is a reactively loaded microstrip transmission line that exhibit an ultra-wide bandgap. The reactive loading is periodically distributed along the transmission line, which is electromagnetically coupled. The reactive load consists of a circular shaped patch which is converted to a metamaterial structure by embedded on it two concentric slit-rings. The patch is connected to the ground plane with a via-hole. The resulting structure exhibits electromagnetic bandgap (EBG) properties. The size and gap between the slit-rings dictate the magnitude of the reactive loading. The structure was first theoretically modelled to gain insight of the characterizing parameters. The equivalent circuit was verified using a full-wave 3D electromagnetic (EM) solver. The measured results show the proposed EBG structure has a highly sharp 3-dB skirt and a very wide bandgap, which is substantially larger than any EBG structure reported to date. The bandgap rejection of the single EBG unit-cell is better than − 30 dB, and the five element EBG unit-cell is better than − 90 dB. The innovation can be used in various applications such as biomedical applications that are requiring sharp roll-off rates and high stopband rejection thus enabling efficient use of the EM spectrum. This can reduce guard band and thereby increase the channel capacity of wireless systems.

A high-performance, temperature-stable Mg1.99Ga0.01Si0.99Al0.01O4-CaTiO3 microwave dielectric ceramic and its 5 G/6 G waveguide filter

New ultra-low loss, temperature-stable composite ceramics, (1-x) Mg1.99Ga0.01Si0.99Al0.01O4-xCaTiO3, have been developed with a view to expanding the portfolio of low-cost, MW dielectrics available for 5 G/6 G telecommunications, currently dominated by 95 wt%MgTiO3-5 wt%CaTiO3, (Mg,Ca)TiO3 (relative permittivity, εr ∼ 21, quality factor, Q×f ∼ 56,000 GHz and temperature coefficient of resonant frequency, τf ∼ 0 ppm/°C). Compared with (Mg,Ca)TiO3, 89 wt%Mg1.99Ga0.01Si0.99Al0.01O4-11 wt%CaTiO3 ceramics are also temperature stable (τf = −2.72 ppm/°C) but have lower εr (∼8.55) and a higher Q×f (∼ 72,900 GHz @ 12 GHz and 80,900 GHz @ 26 GHz), better suited to the higher frequencies earmarked for 6 G millimeter-wave (mm-wave) applications. To demonstrate its potential for 5 G/6 G telecommunications, a waveguide filter with novel negative coupling structure was fabricated based on simulated results. The filter had low insertion loss (0.43 dB) at the center frequency (4.8 GHz) and high selectivity with a roll-off rate of 576/375 dB/GHz. The S-parameters matched well at 25 °C and 85 °C, demonstrating that the filter had excellent temperature stability and was therefore suitable for future 5 G/6 G microwave and mm-wave communication devices.

Design of High Selectivity Compact Dual-Band Bandpass Filter With Seven Transmission-Zeros for GPS and WiMAX Applications

A miniaturized Y-shaped dual-band bandpass filter with multiple transmission zeros/poles is presented in this work. The proposed filter configuration comprises series coupled lines, shunt cascaded coupled line and parallel open stubs, and stepped impedance resonators. Analysis of the proposed filter is executed using a circuit simulator, and the magnitude and bandwidth variations have been studied. Equations for transmission zero frequencies have been derived and verified based on lossless transmission line theory and even-odd mode analysis to validate the proposed filter configuration. A prototype operating at 1.38 GHz (GPS) and 3.4 GHz (Wi-Max) applications is fabricated and experimented. The final prototype occupies a compact area of 0.33λg × 0.20λg, where λg is the guided wavelength at the first band (1.38GHz). The experimental results show that the roll-off rate for the first and second passbands is 212.5 and 188 dB/GHz, respectively, indicating high selectivity. The insertion loss is better than 20 dB indicating good isolation between the two passbands.

Design of BPF-Integrated SPDT Switch Based on Slotline Resonators Loaded With Diodes

Slotline Stepped-impedance resonators (SIR) loaded with p-i-n diodes are used to develop bandpass filter (BPF) integrated switches in this brief. The loaded diodes are used to switch the resonant conditions of the short-ended slotline resonators. The equations for their resonant conditions under different loads at different locations are derived and discussed. With these derived equations, the switchable filters are designed and synthesized using the classical coupled-resonator filter theory. The design concept is demonstrated by a Cascaded Quadruplet (CQ) BPFintegrated single-pole single-throw (SPST) switch at center frequency f0 = 1 GHz with with 47.7 dB OFF-state suppression (OSS). Finally, two compact BPF-integrated single-pole double-throw (SPDT) switches are designed and fabricated. One of them combines source-load (S-L) coupling and introduces two additional zeros outside the desired passband to improve the frequency selectivity. The other on fractal common feeding line is developed to reduce the impact of accumulated residual admittances from OFFstate channels, which shows high roll-off rate of sidebands as well as high port-to-port isolation of 53.1 dB, and its overall circuit size is only 0.051 λg2.

Design and Modelling of a Compact Triband Passband Filter for GPS, WiMAX, and Satellite Applications with Multiple Transmission Zero’s

Designing microwave filters with high selectivity and sharp roll-off between the stop and pass bands can be challenging due to the complex nature of the R.F. signals and the requirements for achieving high performance in a limited physical space. To achieve a high selectivity and sharp roll-off rate, this paper presents a compact filter with a triple passband response. The two different passbands at 1.57 GHz and 3.5 GHz are achieved using a step impedance resonator (SIR) with metallic slots perturbation added to the lower corner of the high impedance section of the SIRs, which helps to enhance the filter’s selectivity and size reduction greatly. The embedded L-shaped structure originates a third passband at 4.23 GHz, resulting in a triband response with eight transmission zeros below and above the passbands at 1.22/1.42/1.98/3.18/3.82/3.98/4.38/4.53 GHz, respectively. The prototype has low signal attenuation of &lt;1.2 dB and high signal reflection of &gt;25 dB for the three passbands. The fractional bandwidths achieved are 2.54%, 4.2%, and 1.65% at 1.57/3.57/4.23 GHz, respectively, with rejection levels in the stopband greater than 15 dB. Lastly, the structure is fabricated on RO-4350B PCB and observed good matching between experimental and measured results. This demonstrates that the prototype can be successfully implemented in real-world applications such as GPS, WiMAX, and Satellite systems. The area occupied by the filter on a substrate or in a circuit is 0.31 λg × 0.24 λg, where λg is the guided wavelength of the material calculated at the lowest frequency.