dB Loss Research Articles

Series of split silencers for ventilation systems

The paper is devoted to the prospects of noise reduction in ventilation systems with large cross-section main air ducts. The design schemes of a split silencer for various systems obtained as a result of calculations and experiments are proposed. For a silencer whose split ducts are formed by successive narrowings and expansions the parameters ensuring minimum noise reduction of 7.5 dB and pressure loss of up to 120 Pa are shown and the recommendations for usage in systems where two-phase flows propagate are given. For a silencer whose split ducts contain internal elements the parameters that provide a minimum noise reduction of 10 dB and pressure loss of up to 90 Pa are identified and the recommendation for usage in supply ventilation systems with the required disinfection is presented. For a silencer that combines two sections with oppositely oriented split ducts its applicability in systems without aerodynamic restrictions and with increased acoustic requirements was noted. For additional silencer section composed from Helmholtz split resonators the parameters that ensure even noise reduction are shown and the recommendation for usage in systems without restrictions on the length of the main duct and with increased low-frequency noise reducing requirements is given.

MEMS Slow-Wave CPW Phase Shifter for mm-Wave Applications

MEMS-based phase shifters show the best performance in terms of figure of merit, but their footprints are usually large and it is difficult to achieve several bits. This paper demonstrates a miniaturized phase shifter based on slow-wave CPW and MEMS that occupy 0.47 mm2. A total phase shift of 152° was obtained with a maximum insertion loss of 3 dB, resulting in a figure of merit of 50°/dB at 60 GHz. The 3-bit device showed an insertion loss variation of 1.3 dB and return loss better than 13 dB. The pull-in and pull-out voltages were measured to be 17 V and 10 V, respectively. The presented device is well suited for mm-wave phased array applications. Thanks to the proposed concept, more bits could be easily achieved and much higher frequencies could be addressed.

A 112 Gb/s PAM-4 RX Front-End With Unclocked Decision Feedback Equalizer

The implementation of an unclocked DFE (UC-DFE) architecture for high-speed PAM-4 signals is investigated in this brief. Instead of clocked slicers and flip-flops, data-decision and feedback delay control are performed by saturated analog delay chains. As a result, the UC-DFE, previously exploited for NRZ signals, saves power consumption and silicon area while the simple implementation allows operation at high data-rate. A receiver front-end comprising a linear equalizer and the proposed 2-tap UC-DFE scheme is designed in 7 nm FinFET technology. From post-layout simulations, the receiver recovers a PAM-4 signal at 112 Gb/s after an 18 dB loss channel with a power efficiency of 0.47 pJ/bit. The receiver also works with NRZ signals at half the bit-rate equalizing 24 dB channel loss with a power efficiency of 0.70 pJ/bit.

Flexible Coaxial Ribbon Cable for High-Density Superconducting Microwave Device Arrays

Superconducting electronics often require high-density microwave interconnects capable of transporting signals between temperature stages with minimal loss, cross talk, and heat conduction. We report the design and fabrication of superconducting 53 wt% Nb-47 wt% Ti (Nb47Ti) FLexible coAXial ribbon cables (FLAX). The ten traces each consist of a 0.076 mm O.D. NbTi inner conductor insulated with PFA (0.28 mm O.D.) and sheathed in a shared 0.025 mm thick Nb47Ti outer conductor. The cable is terminated with G3PO coaxial push-on connectors via stainless steel capillary tubing (1.6 mm O.D., 0.13 mm thick) soldered to a coplanar wave guide transition board. The 30 cm long cable has 1 dB of loss at 8 GHz with -60 dB nearest-neighbor forward cross talk. The loss is 0.5 dB more than commercially available superconducting coax likely due to impedance mismatches caused by manufacturing imperfections in the cable. The reported cross talk is 30 dB lower than previously developed laminated NbTi-onKapton microstrip cables. We estimate the heat load from 1 K to 90 mK to be 20 nW per trace, approximately half the computed load from the smallest commercially available superconducting coax from CryoCoax

HMSIW based highly selective filter for radar applications

PurposeThis paper aims to present, design and implement a novel half-mode substrate integrated waveguide (HMSIW)-based narrow bandpass filter, which offers advantages like low insertion loss, compact size and high selectivity. Proposed filter will be used in the K-band automotive radar application.Design/methodology/approachThe filtering response in the proposed design is achieved by inserting inductive posts in the HMSIW cavity. Ansoft high frequency structure Simulator (HFSS) is used for the simulation of the proposed structure, which is a three-dimensional full-wave solver using the finite element method (FEM). The proposed filter is fabricated on the dielectric material RT duroid 5,880 with the dielectric constant ɛr = 2.2, dissipation factor t and = 4 × 10–4 and height h = 0.508 mm.FindingsFrequency tuning is also carried out by changing the lateral distance between two inductive posts. Moreover, a comparison of the proposed structure with the previously published work is presented. Proposed method provides the unique advantages such as low insertion loss, high selectivity and compact in size.Originality/valueIndigenous method has been used for the development of the filter. Proposed filter will be used in transmitter subsystem of the K-band radar system operating at the center frequency of 11.2 GHz. Measurement results are well-matched with the simulated one. Obtained measured result shows return loss of 20.39 dB and insertion loss of 1.59 dB with 3 dB fractional bandwidth (FBW) of 2.58% at the center frequency of 11.2 GHz.

Design and test of a broadband rectangular waveguide TE 10 –TE 20 mode converter

A broadband rectangular waveguide TE 10 –TE 20 mode converter with high mode purity and conversion efficiency is designed, fabricated and measured in this Letter. Based on the broadband characteristic of ridged twist waveguide and its characteristic of polarisation direction torsion of electromagnetic wave, this mode converter achieves broadband and high-efficiency TE 10 –TE 20 mode conversion. Simulation results reveal that the return loss of the proposed mode converter is >20 dB and insertion loss is <0.04 dB in whole Ka-band. Two prototype TE 20 mode converters were fabricated. Back-to-back millimeter-wave measurements by vector network analyser were performed to verify the design. The measured performances show return loss of the proposed mode converter is >20 dB and insertion loss is 97.7%.

Fully Metallic Anisotropic Lens Crossover-in-Antenna Based on Parallel Plate Waveguide Loaded With Uniform Posts

This article presents a Ka-band fully metallic crossover-in-antenna based on an anisotropic lens. The crossover-in-antenna is a multifunction device simultaneously acting as a waveguide crossover and a multibeam antenna. The anisotropic lens performs like a Maxwell fish-eye (MFE) lens and a Luneburg lens in different incident directions, supporting the transmission and radiation, respectively. The lens consists of a parallel plate waveguide (PPW) with gradient spacing loaded with periodic uniform cuboid posts, which can be treated as an array of anisotropic subwavelength unit cells with gradient equivalent refractive indices. The WR28 waveguides are employed as the input-output ports. A flare is added to improve the radiation and impedance matching of antenna channels. According to the experimental results, a waveguide crossover is well realized with the reflection coefficients lower than -15 dB and insertion losses mostly lower than 1.4 dB from 28.7 to 38.2 GHz. Meanwhile, a multibeam antenna with four independent beams is obtained in the whole Ka-band, showing the gains higher than 12.5 dBi and the radiation efficiencies higher than 87.8%. The results indicate that the proposed crossover-in-antenna has application potential in the high-density multifunction integration of millimeter-wave (mmW) systems.

Low-loss tunable dielectrics for millimeter-wave phase shifter: from material modelling to device prototyping

Passively controllable millimeter-wave phase shifters based on continuously tunable dielectrics offer promising alternatives to conventional switch-based topologies (e.g. active semiconductor devices and MEMS) with digital resolution. However, only a handful of tunable dielectrics have thus far been identified with high tunability and low loss, among them, liquid crystal (LC) in the nematic phase is of research and development interest. This work presents the modelling of LC materials at 66 GHz based on a novel shielded coplanar device structure in place of traditional waveguides. Phase shifters of 0-π tunability are fabricated and measured, with an insertion loss of -4 dB and return loss lower than -15 dB demonstrated.

A uniquely shaped MIMO antenna on FR4 material to enhance isolation and bandwidth for wireless applications

This paper presents a CPW fed wideband four element multiple input multiple output (MIMO) antenna. The MIMO structure is developed from the analysis of a single wideband CPW fed antenna with −10 dB bandwidth of 1700 MHz. After which a two antenna element structure is analyzed having the same bandwidth range with isolation below −50 dB. Finally, the proposed four element MIMO structure is designed with isolation less than 30 dB between the antenna elements with an Envelope Correlation Coefficient (ECC) below 0.003, measured gain between 2.4 dBi & 5.9 dBi and the radiation efficiency is well above 90% over the entire operating range. The targeted applications lie between 4.3 and 6.0 GHz under the C band spectrum for WLAN and Wi-Fi. The proposed design is printed on a uniquely shaped FR4 substrate to achieve low insertion loss and greater isolation between the antenna elements. The edge-to-edge distance between the adjacent antenna elements is 15 mm keeping which the antenna elements are placed on the arms of the substrate pattern. This also further helps in increasing the number of antenna elements just by extending the armed pattern with constant edge-to-edge distance. The important parameters of the MIMO system such as ECC with a value as low as 0.0002, Diversity Gain (DG) of 9.998 dB, Total Active Reflection Coefficient (TARC), Mean Effective Gain (MEG) measuring the ratio < 3 dB and Channel Capacity Loss (CCL) of 0.0635 bits/s/Hz are observed at the center frequency of 5 GHz. All the necessary simulations are carried out in Ansys HFSS.

Parasitic Compensation and Hence Isolation Improvement of PIN Diode-Based Switches

This brief presents a transmission line based resonant technique to nullify the parasitic effect of a PIN diode used to design a narrowband high frequency switch. Resonant condition is obtained by using a section of transmission line in series with a single PIN diode in a shunt branch. The method guarantees isolation improvement at any design frequency lower than the series resonant frequency of a diode. It does not use any lumped component other than those required for biasing. Thus, the method greatly improves the high frequency performance of a PIN diode as a switch. A transmission line based analysis is carried out to obtain the design equations. The theoretical prediction is verified by fabrication and measurement. A single-pole-single-throw (SPST) switch using just one single PIN diode provides measured isolation of 40 dB and insertion loss of 1.5 dB at 10.55 GHz. The return loss is more than 20 dB over 10.2-10.8 GHz. A low cost NXP semiconductors BAP64-02 PIN diode with high parasitic and the manufacturer specified highest frequency as 6 GHz is used to show the competency of the proposed method. A second SPST switch using two diodes provides isolation of 72 dB, insertion loss of 1.8 dB and return loss of 35 dB at 10.55 GHz. An SP4T switch is also fabricated and tested. Measured 1 dB compression point for all the switches is higher than 23 dBm.

Fast prediction mode selection and CU partition for HEVC intra coding

Compared with the predecessor H.264/advanced video coding, high-efficiency video coding (HEVC) is a new video coding standard with nearly double coding efficiency under the same coding quality. However, the computing complexity of HEVC increases sharply. To solve this problem, a fast algorithm for intra prediction mode selection based on mode grouping is proposed by reducing the number of modes entering rough mode decision. Moreover, the dual support vector machine is proposed to efficiently select the coding unit (CU) size, which is based on texture features of CU and sub-CUs including content complexity and direction complexity. By using the new CU size selection algorithm, the encoder can confirm the split for complex CU and terminate the split for simple CU in advance, so as to reduce the computing complexity of CU size selection. The experimental results show that by employing the two fast algorithms in intra coding, it can save 42.80% encoding time, with 0.98% increment in bit rate and 0.018 dB loss of peak-signal-to-noise ratio of luminance, compared with the reference software x265-1.7.

Design and performance analysis of hybrid SPDT RF MEMS switch

This paper presents the design and simulation of Hybrid type RF MEMS switch for satellite communication application. The Hybrid switch beam is having non-uniform meanders and holes. The gold material is used as a beam and CPW. The gap between the beam and dielectric is 3 μm. The design is based on the shunt and series configuration consisting of 2 capacitive switches and 2 Ohmic switches. The performance analysis is done by using the HFSS tool. The individual Ohmic switch having 31 dB isolation and capacitive switch having 67 dB isolation. The proposed Hybrid switch having 87 dB isolation when both switches are in the OFF state. During ON state, the switch shows the low insertion loss of − 0.18 dB and return loss of − 63 dB at 16 GHz.

Ultra-compact and efficient 1 × 2 mode converters based on rotatable direct-binary-search algorithm.

In this paper, we innovatively demonstrate a rotatable direct-binary-search algorithm. Based on this unique inverse design method, the coupling region of nanophotonic device can be realized with multi-shape and multi-rotation pixels. In addition, the novel 1× 2 mode converters with multipurpose design goals on a 220 nm-thick top silicon-on-insulator platform are proposed by utilizing this enhanced algorithm, which can simultaneously achieve power splitting and mode conversion. By 3D fine difference time domain solutions, the 1 × 2 mode converter that converts TE0 mode into TE1, with a footprint of 2.7 µm × 2.4 µm, exhibits the excess loss of 0.1 - 0.2 dB (TE1 mode), crosstalk of lower than -20.6 dB (TE0 mode) and reflection loss of lower than -19.5 dB (TE0 mode) from 1500 nm to 1600 nm. The 1 × 2 mode converter that transforms TE0 into TE2 occupies the footprint of 3.6 µm × 3 µm. The excess loss is 0.3 - 0.4 dB (TE2 mode) in the wavelength range of 1500 - 1600 nm. The crosstalks are lower than -17.5 dB (TE1 mode) and -25.1 dB (TE0 mode), and the reflection loss is lower than -18.3 dB (TE0 mode). Besides, the fabrication tolerances caused by both expansion or contraction of etched pattern contour and round corner effect are also investigated.

Design of the 3.7 GHz, 1 kW CW solid state driver for LHCD system of the SST-1 tokamak

Abstract Advances in solid state device technologies have seen its use foray into areas such as microwave heating and powering the RF cavities of an accelerator. This paper explores the possibility of use of a solid state source/driver for current drive systems of tokamaks. The design of a modular solid state source to be used as a driver for klystrons in the LHCD system of SST-1 tokamak is presented. It comprises of solid state power amplifier (SSPA) units, driven by voltage controlled oscillator (VCO) and pre-driver (gain) amplifier. The paper discusses about the design methodology and simulation of these individual components. The component and system level computer simulation based on behavioural and file based model was performed using AWR Microwave Office (MWO) software. The linear and non-linear EM analysis of individual components have been carried out to ascertain its performance. The designed VCO delivers an output power of 20.2 dBm and phase noise of -91.64 dB/Hz (100 KHz offset) at 3.7 GHz. The pre-driver stage (gain amplifier) provides a large signal gain of 15.7 dB and return loss of -14 dB at 3.7 GHz. The individual power amplifier draws a continuous wave (CW) output power of 45.2 dBm for an input power of 35 dBm and efficiency of 56.68%. The system simulation results exhibit around 1 kW of output power in ideal conditions.

A SIW-Based Polarization Rotator With an Application to Linear-to-Circular Dual-Band Polarizers at $K-/Ka$ -Band

A polarization rotator based on substrate integrated waveguide (SIW) is proposed in this article. The rotator is designed as a dual-band, single-layer, frequency-selective surface (FSS) that transmits a wave rotated of 90° with respect to the incident one in one of the two bands maintaining unchanged the polarization in the other one. Other than the design and characterization of the rotator, its application to a linear-to-circular dual-band polarizer is also investigated. To this purpose, the rotator is coupled to a conventional meander line polarizer generating orthogonal circular polarizations (CP) in the two bands. This configuration is useful in SatCom applications where the required high isolation between TX and RX channels is obtained assigning orthogonal polarizations to the two bands. As a design example, a prototype is designed and experimentally validated in the SatCom K-/Ka -bands. Measured performance shows an isolation between the TX and RX channels of more than 35 dB and insertion losses which do not exceed 1.5 dB in the two operating bands.

Low-noise distributed acoustic sensing using enhanced backscattering fiber with ultra-low-loss point reflectors.

We present a low-noise distributed acoustic sensor using enhanced backscattering fiber with a series of localized reflectors. The point reflectors were inscribed in a standard telecom fiber in a fully automated system by focusing an ultra-fast laser through the fiber cladding. The inscribed reflectors provided a reflectance of -53 dB, significantly higher than the Rayleigh backscattering level of -70 dB/m, despite adding only 0.01 dB of loss per 100 reflection points. We constructed a coherent φ-OTDR system using a double-pulse architecture to probe the enhanced backscattering fiber. Using this system, we found that the point reflectors enabled an average phase noise of -91 dB (re rad2/Hz), 20 dB lower than sensors formed using Rayleigh backscattering in the same fiber. The sensors are immune to interference fading, exhibit a high degree of linearity, and demonstrate excellent non-local signal suppression (>50 dB). This work illustrates the potential for low-cost enhanced backscattering fiber to enable low-noise, long-range distributed acoustic sensing.

Development of a low stress RF MEMS double-cantilever shunt capacitive switch

In this paper, a novel RF MEMS shunt capacitive switch with application in the Ka frequency band is proposed. The spring design and the step structure added to the beam succeeded in improving the performance of the switch and reducing the stress which results in extended life-time of the switch. Also, by optimally reducing the gap between the dielectric and the beam (without problems such as self-actuation), the actuation voltage of the switch is significantly reduced. Electromechanical and scattering parameters analysis have been done by using COMSOL Multiphysics and HFSS software, respectively. The actuation voltage of the proposed device is 9.2 V. Since the aluminum has a lower mass compared to gold, an aluminum beam has been used in the switch. Desirable scattering parameters at the resonance frequency of 33.5 GHz have been obtained which include insertion loss of − 0.3 dB and return loss of − 18 dB. The high isolation of − 57 dB verifies the improved performance of the switch. Finally, as another innovation in this paper, the effect of inductor and capacitor presence in the input of transmission line is investigated. This analysis has been done by using ADS. Results of the circuit analysis presented in this paper, help the MEMS switch designers to understand the realistic switch behavior before fabrication which considerably saves cost and time.

Interleaved Subwavelength Gratings Strip Waveguide Based TM Pass Polarizer on SOI Platform

We report on an ultra-compact, low loss and broadband TM-pass polarizer, which is constructed by two interleaved subwavelength-gratings (SWGs) waveguides inserted in the center of the strip waveguide on a silicon-on-insulator (SOI) platform. The device structure is optimally engineered to support Bloch mode for fundamental TM polarization only. Therefore, the TM mode transmits along the strip waveguide with rather low propagation loss while the TE mode is completely reflected by the embedded SWGs waveguides. Simulation results show that an efficient and ultra-compact TM-pass polarizer of 5.2 μm in length is realized with extinction ratio (ER) of 31.63 dB and insertion loss (IL) of 0.18 dB at the operating wavelength of 1550 nm. The operation bandwidth for ER over 20 dB and IL below 0.32 dB is 155 nm (from 1465 to 1620 nm). By increasing the period number, the ER performance and bandwidth can be further improved. Furthermore, the fabrication of the present polarizer only requires mono-lithography and single etch process, which will greatly reduce the fabrication difficulty.

Experimental Verification of LG WAVE and Ansoft HFSS Simulation Software Using a 2 x 2 Antenna Array with EBG Structure

In this paper we are presenting the validation of the LG RF Simulation tool (WAVE) and HFSS simulation software’s through measurement results of the fabricated design, simulated in WAVE and HFSS simulation software’s. A 2 x 2 antenna array with Electromagnetic Band Gap (EBG) structure in the ground plane is simulated using WAVE and HFSS ver. 17.The prototype antenna was fabricated and characterization is carried out at CHRIST (Deemed to be University) Bangalore to know the performance of the antenna array. Return Loss and VSWR of the fabricated antenna are measured using Anritsu S820E Microwave Site Master Network Analyzer. Two - dimensional radiation patterns were plotted and compared with the simulated results obtained from WAVE and HFSS Software’s. From the results of HFSS simulation software we observed that EBG integrated array is exhibitinggainof7.089dB and Return loss of -16.2 dBat2.4GHz.Whereas the results obtained from WAVE simulation tool for the same design gave a peak gain of 5.03 dB and return loss of -12.8dB at 2.4 GHz. Measured gain of the designed array is 7.407 dB and return loss is -7.565 dB at 2.4 GHz.

Coherent Ultra-Dense WDM-PON Enabled by Complexity-Reduced Digital Transceivers

Coherent technologies, along with digital signal processing (DSP), have revolutionized optical communication systems, significantly increasing the capacity of the fiber channel owing to transmission of advanced modulation formats and mitigation of propagation impairments. However, commercial solutions for high-capacity core networks are too complex and costly, and therefore hardly feasible, for access networks with high terminal density, where cost, power budget, and footprint are the main limiting factors. This article analyzes the key enabling techniques to implement a complexity-reduced coherent transceiver (CoTRX) by exploiting photonic integration, simplified optical modulation, low-cost DFB lasers, consumer electronics, and low-complexity DSP. Bulk optical modulators are replaced by direct amplitude-and-phase modulation of an integrated electro-absorption modulated laser (EML) with a smaller footprint, generating up to 8-ary modulation formats. Hardware-efficient DSP algorithms for the coherent transmitter and receiver, including pulse-shaping for direct phase modulation, differential detection for optical phase recovery, and digital pre-emphasis with enhanced tolerance to quantization noise, are investigated to face the challenges imposed by low-cost photonic and electronic devices, such as strong phase noise, wavelength drifts, severe bandwidth limitation, and low resolution data converters. Through numerical simulations and real-time experiments, the results indicate that this new class of CoTRX enables effective implementation of wavelength-to-the-user PON with dedicated 1.25–20 Gb/s per user, in an ultra-dense 6.25–25 GHz spaced WDM optical grid, with >30 dB loss budget, outperforming the current competing technologies for access networks.