dB Variation Research Articles

Design of 0–15 GHz flat-bandwidth programmable gain amplifier based on transconductance switching technique

Gain flatness is an important technical indicator for ADC-Based SerDes in practical applications. Due to the serial interface's unknown channel characteristics, signal amplitudes at the SerDes receiver remain uncertain. Therefore, the I/O interface needs to cover a wide gain range to meet the system linearity and signal amplitude requirements. This research introduced an input-transistor switching technique for the programmable gain amplifier (PGA), which adjusts the gain by changing the input transistor's number and effective transconductance to avoid the gain-rising problem in the existing PGA structures at high frequency. The core circuit of this research adopts a inductorless structure that can save the die area. Simulation results have shown that under the TSMC CMOS 40 nm process, the use of source degeneration zero compensation technique can achieve 0–15 GHz bandwidth with +0.05 dB variation, −7.3-6.6 dB gain tuning range. The circuit voltage is 1.8V, and the power consumption is 8.208 mW.

A 5–bit CMOS attenuator with low temperature and process variations for Ka‐band phased‐array applications

AbstractA 5‐bit CMOS attenuator with low temperature and process variations is presented employing the proposed optimization and compensation technique to achieve low root mean square (RMS) attenuation error and phase variation. The proposed design technique includes optimizing ratio of transistors and attenuation resistors to reduce the temperature and process variations, and utilizing a temperature and process compensation circuitry to further minimize the chip‐to‐chip and channel‐to‐channel variations. The presented attenuator is fabricated in a 55 nm CMOS process and achieves a maximum attenuation of 15.5 dB with 0.5 dB‐per‐step resolution. Measurement results show that the maximum RMS attenuation error is 0.6 dB and phase variation is less than ±2.2°, from −45 to 85°C and between different chips or channels within frequency range from 25 to 32 GHz. The core area is 0.32 × 0.5 mm2 excluding pads.

Experimental study on the practical mitigation of passive intermodulation for time and temperature in cavity duplexer

Practical methods to mitigate level and variation of passive intermodulation with respect to time and temperature of coaxial cavity type duplexer are proposed through a variety of experimental results. From the findings derived in this study, a stable passive intermodulation response with less than 1 dB variation was shown in the environment temperature range of −10–85 °C. The duplexer with time-stable PIM response at room temperature had a stable PIM value even in the environment temperature range.

Symmetrically Direct Coupled Stacked Broadband Microstrip Antenna

ABSTRACT A technique employing the use of directly coupled stacked patches to increase impedance bandwidth with reduced cross-polarization is proposed in this paper. The top stacked multi-resonator configurations are directly excited by employing metallic shorting posts (vias) between the metallic patches. In stacked directly coupled MSA, a bandwidth of 25.8% and a gain of 8.8 dBi with a gain variation of ±0.2 dB over the band are achieved. The cross-polar levels for this configuration are less than −15 dB and −5 dB at lower and upper frequencies, respectively. To suppress the cross-polar components, a symmetrically direct-coupled stacked MSA design is proposed. In this configuration, a bandwidth of 26.1% and a gain of 9.3 dBi with ±0.3 dB variation over the entire bandwidth are achieved. The cross-polar levels are significantly suppressed up to −25 dB and −16 dB at lower and upper frequencies, respectively. The proposed antenna configurations are designed and fabricated. The experimental results agree with the simulated results.

Design and analysis of variable attenuator with simultaneous minimized flat amplitude error and insertion phase variations

This paper presents a design of an analog variable attenuator with simultaneous minimized flat amplitude error and insertion phase variation over a wide bandwidth and high attenuation range. The parasitic of PIN is compensated with series transmission lines loaded and shunt capacitors to achieve minimum flat amplitude error and insertion phase variation. Mechanism for simultaneous reduction in flat amplitude error and phase variations is obtained by developing an analytical design equation using the PIN diode equivalent circuit model. For the experimental validation, two kinds of proposed attenuators are designed and measured over 1 GHz bandwidth at a center frequency (f0) of 3.5 GHz. The measurement results are consistent with the simulation results. From the experiments, design-I provides an attenuation variation of 0.9 dB to 20 dB with a maximum flat amplitude error of 0.65 dB and insertion phase variation of 5.70° over 1 GHz bandwidth. Similarly, the design-II provides an attenuation variation of 1.06 dB to 20 dB with a maximum amplitude error of 0.49 dB and insertion phase variation of 3.19° over the same 1 GHz bandwidth.

A Broadband, mm-Wave SPST Switch With Minimum 50-dB Isolation in 45-nm SOI-CMOS

This article describes a single-pole, single-throw (SPST) CMOS switch aimed at integrated transceiver applications. The SPST switch realizes better than 50-dB isolation (ISO) across dc-to-43 GHz while maintaining an insertion loss (IL) below 3 dB. To maximize ISO, substrate coupling is compensated using bilateral RF signal cancellation in a fully differential circuit topology. Measured RF input power for 1-dB compression (IP1dB) of the IL is +19.6 dBm, and the measured input third-order intercept point is +30.4 dBm (both assuming differential inputs at 20 GHz). The prototype is fabricated in GlobalFoundries 45-nm RF-SOI CMOS technology and has an active area of 0.0058 mm2. Monte Carlo simulations predict variations due to processing of 8.3% and 2.75% in IL and ISO, respectively, ±0.2 dB variation (for both IL and ISO) from a 5% change in supply voltage, and ±0.1-dB variation (both IL and ISO) for a 0 °C–85 °C temperature sweep.

An alternative permeable topology design space for trailing-edge noise attenuation

This study focuses upon a new permeable topology design concept as an alternative to porous metal foams, for turbulent boundary layer trailing-edge (TBL-TE) noise attenuation. The present permeable topology has unconventional characteristics with respect to the metal foams: a combination of low flow resistivity r and high form drag coefficient C. The unconventional characteristics are realized by a Kevlar-covered 3D-printed perforated structure. An experimental study featuring a NACA 0018 airfoil model with a Kevlar-covered 3D-printed TE insert at chord-based Reynolds numbers up to [Formula: see text] is carried out. The airfoil with this TE insert gives a broadband TBL-TE noise reduction up to approximately 5 dB, compared to a solid TE. This reduction varies only slightly with airfoil loading (lower than 1 dB variation), in contrast to the porous metal foams (up to 3 dB variation). When comparing the variation of noise attenuation given by all the permeable materials considered, the variation is found to decrease with the increasing C. This is because C specifies the permeable material's ability to withstand the increasing pressure difference, which causes cross flow that might interfere with the noise attenuation mechanism. Additionally, the drag coefficients as well as the roughness noise of the airfoil equipped with the present TE insert are also significantly lower than those of the metal-foam TE, and are mostly negligible compared to the fully solid airfoil. Based on the findings, design guidelines for permeable TE are proposed: the permeable material shall have a combination of a low flow resistivity and a high form drag coefficient as well as a negligible surface roughness.

Manipulating multipole resonances in spoof localized surface plasmons for wideband filtering

The spoof localized surface plasmon (LSP) has been widely investigated but mostly with fixed multipole resonances. This Letter proposes a method to generate multipole resonances by adding a slit on the metallic ring of a complementary LSP. This slit theoretically introduces two new boundary conditions and new modes. To validate this approach, complementary LSPs with and without slits at three different angular positions are theoretically analyzed and numerically simulated. To validate and demonstrate the potential application of the proposed LSP structure, a bandpass filter (BPF) in a single-layer substrate is designed and measured by exciting the LSP with a slit on the metallic ring. The measured results show that by simply adding a slit, the BPF achieves a fractional bandwidth of 42.7% (2.5 GHz), for both |S11|<-10dB and |S21| within 1 dB variation. In the passband, a flat group delay between 0.57 ns and 0.75 ns is obtained. Moreover, the proposed structure features a low profile and a compact radius of 0.136 wavelength. By dynamically controlling slit/slits with varactors or diodes, the proposed structure is theoretically promising to be reconfigurable at microwave and even terahertz frequencies.

Outage Probability Due to Crosstalk from Multiple Interfering Cores in PAM4 Inter-Datacenter Connections

In this work, we propose to use four-level pulse amplitude modulation (PAM4) and multi-core fibers (MCFs) to support very high capacity datacenter interconnect (DCI) links. The limitations imposed by inter-core crosstalk (ICXT) on the performance of 112 Gb/s up to 80 km-long optically amplified PAM4 inter-DCI links with intensity-modulation and direct-detection and full chromatic dispersion compensation in the optical domain are analyzed through numerical simulation for high and low skew-symbol rate product (SSRP). With only one interfering core, we show that those PAM4 inter-DCI links achieve an outage probability (OP) of 10−4 with a maximum ICXT level of −13.9 dB for high SSRP and require an ICXT level reduction of about 8.1 dB to achieve the same OP for low SSRP. Due to using full dispersion compensation, for an OP of 10−4, the maximum acceptable ICXT level shows only a 1.4 dB variation with the MCF length increase from 10 km to 80 km. When considering the ICXT induced by several interfering cores, the maximum ICXT level per interfering core for an OP of 10−4 decreases around 3 dB when doubling the number of interfering cores. This conclusion holds for high and low SSRP regimes. For two interfering cores, we show that a single interfering core with low SSRP is enough to induce a severe reduction of the maximum acceptable ICXT level.

Designing Efficient Phase-Gradient Metasurfaces for Near-Field Meta-Steering Systems

We investigate the aptness of various 4 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sup> order (90°) rotationally symmetric phase-transforming cells for the upper phase-gradient metasurface, which always receives an oblique incidence wave from the lower metasurface in a Near-Field Meta-Steering system. A comprehensive study on the behavior of various phase-transforming cells and corresponding supercells when a rotating oblique plane wave impinges on them is presented. First, we select the supercell with high transmission in the desired output Floquet modes, for both TE and TM input modes, when an oblique incidence wave is rotated. The selected supercell is then optimized using Floquet analysis in conjunction with particle swarm optimization (PSO). All the undesired modes are successfully suppressed below -32 dB in the optimized supercell, and the predicted broadside radiation pattern is free of spurious grating lobes. A Near-Field Meta-Steering system with an aperture diameter of 7.3λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> (110mm @ 20 GHz) is presented. It has a pair of optimized phase-gradient metasurfaces and a dipole antenna array. A maximum peak directivity of 24.2 dB is achieved when the beam is in the broadside direction. The proposed steering system is capable of scanning a conical range with an apex angle of 126° when a 6 dB reduction in peak directivity is allowed. For a 3 dB variation in the peak directivity, the corresponding apex angle is 103°.

High Gain, Low Noise, Spectral-Gain-Controlled, Broadband Lumped Fiber Raman Amplifier

We demonstrate an 80 nm bandwidth (extending from 1529 to 1609 nm), dual-stage, diode-pumped, lumped Raman amplifier using a relatively short total length (2 km) of highly nonlinear fiber. The impact of Rayleigh back scattering is mitigated and the build-up of thermally generated wavelength dependent noise is controlled by suitably adjusting the spectral gain profile in the two amplifier stages. In this way a high overall gain of 27 dB with 2.6 dB gain flatness and an average noise figure of 5.8 dB with <1 dB variation is achieved across the full amplifier bandwidth.

Gain-control technique in double-pass parallel hybrid fiber amplifier

In this paper, the effect of gain control technique in double pass parallel hybrid fiber amplifier in terms of gain level as well as pump powers optimization are simulated using Optisystem and experimentally validated. An average gain level of 22.8 dB and overall gain variation of 3 dB within C and L band regions are achieved. The gain flatness bandwidth of 60 nm from 1530 to 1590 nm are obtained. A comparison with a single pass parallel hybrid fiber amplifier is presented. This comparison showed an average gain level of 38.5% higher than single pass-structure utilizing only 650 mW of Raman pump which is 18.7% lower.

A Compact Slotted Patch Hybrid-Mode Antenna for Sub-6 GHz Communication

A compact hybrid-mode antenna is proposed for sub-6 GHz communication. The proposed antenna is composed of a slotted rectangular patch, a feeding dipole, and a balun. Three modes are sequentially excited in a shared patch to achieve a compact size. A prototype antenna with a major size of 0.48 λ0 × 0.31 λ0 × 0.16 λ0 (λ0 is the wavelength in the free space at the center of the operating frequency band) is fabricated and measured. The measured results demonstrate an impedance bandwidth of 56.87% from 2.97 GHz to 5.33 GHz and an average gain of approximately 8.00 dBi with 1 dB variation in the operating frequency band of 3.0–5.0 GHz. The proposed antenna can be an element for microbase stations in sub-6 GHz communication.

Ultra-Broadband Bandpass Filter Using Linearly Tapered Coupled-Microstrip Line and Open Loop Defected Ground Structure

This brief presents a novel highly compact ultrabroadband bandpass filter (BPF) using linearly tapered coupled-microstrip line (LTC-ML) and open loop defected ground structure (OL-DGS). The filter structure consists of a LTC-ML with open-circuited stubs (OCSs) and an OL-DGS etched on the ground. The linearly tapered and tightly coupled microstrip OCS can function as two resonators, and with an associated enhanced coupling structure to OL-DGS, it leads to a very compact three-pole filter. The proposed filter also exhibits a quasi-elliptic function response, where two transmission zeros (TZ) closer to each side of the passband to improve selectivity and one TZ at higher side of the upper stopband, can be observed. An approximate in-line synthesis of the proposed third-order filter with three TZs has also been performed, which shows similar characteristics like the desired response. The simulated and measured results of the filter are in good agreement with each other, showing a wide 10 dB return loss (RL) bandwidth from 4.5 to 12 GHz, insertion loss better than 1.5 dB and group delay variation of lesser than 0.2 ns in the whole passband. Furthermore, it has a very compact size of 0.31λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g</sub> × 0.55λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g</sub> at the central frequency of 8.25 GHz.

Simple Dual-Polarized Filtering Antenna With Enhanced Bandwidth for Base Station Applications

In this article, a simple dual-polarized antenna with filtering responses and enhanced bandwidth is proposed for base station applications. The antenna concludes three parts: dipole elements, baluns, and a ground plane, which is the same as that of a widely used traditional base-station cross-dipole antenna. By employing only two parasitic elements without using very complicated circuits, the proposed dual-polarized antenna achieves not only filtering response but also widened bandwidth. Each parasitic element produces one transmission zero at higher frequency for the polarization it is associated with, while the other parasitic element produces another transmission zero at lower frequency band for the perpendicular polarization. The two introduced radiation nulls near the passband edge are also controllable. The working mechanism for achieving filtering responses is given. To demonstrate the idea, a simple dual-polarized filtering base-station antenna element is fabricated. The proposed antenna obtains 63% (1.68–3.23 GHz) impendence bandwidth with voltage standing wave ratio (VSWR) less than 1.5. The antenna also features good isolation of more than 32 dB and stable beamwidth variation of less than ±5°. The measured gain within working band is around 8.5 dBi, while the radiation suppression level in stopband is 13 dB.

A 4.2-to-5.4 GHz stacked GaAs HBT power amplifier for C-band applications

PurposePower amplifiers (PAs) play an important role in wireless communications because they dominate system performance. High-linearity broadband PAs are of great value for potential use in multi-band system implementation. The purpose of this paper is to present a cascode power amplifier architecture to achieve high power and high efficiency requirements for 4.2∼5.4 GHz applications.Design/methodology/approachA common emitter (CE) configuration with a stacked common base configuration of heterojunction bipolar transistor (HBT) is used to achieve high power. T-type matching network is used as input matching network. To increase the bandwidth, the output matching networks are implemented using the two L-networks.FindingsBy using the proposed method, the stacked PA demonstrates a maximum saturated output power of 26.2 dBm, a compact chip size of 1.17 × 0.59 mm2 and a maximum power-added efficiency of 46.3 per cent. The PA shows a wideband small signal gain with less than 3 dB variation over working frequency. The saturated output power of the proposed PA is higher than 25 dBm between 4.2 and 5.4 GHz.Originality/valueThe technology adopted for the design of the 4.2-to-5.4 GHz stacked PA is the 2-µm gallium arsenide HBT process. Based on the proposed method, a better power performance of 3 dB improvement can be achieved as compared with the conventional CE or common-source amplifier because of high output stacking impedance.

Ultra‐wideband complementary metal‐oxide semiconductor low noise amplifier using CS‐CG noise‐cancellation and dual resonance network techniques

In this paper, a low power ultra-wideband (UWB) low noise amplifier (LNA) with high and flat voltage gain is proposed using CS-CG noise-cancellation and dual resonance network techniques based on TSMC 180 nm technology. The CS-CG noise cancellation technique reduced the noise figure in 3-10.6 GHz frequency band, and the dual resonance network technique is applied to reach an acceptable input matching. In order to reduce the number of inductors, the active inductor is used in the noise cancellation stage. Also, to control voltage gain and input return loss, a resistor is connected in parallel to channel length modulation resistance of the transistor in the first stage. The developed LNA circuit provides a high and flat voltage gain of 12.75 dB with 0.65 dB variation, which is the result of using two stages common-source topology. An average noise figure of 2 dB, with its maximum value of 2.3 dB, an IIP3 of -8 dBm are obtained from 3 to 10.6 GHz, respectively. The obtained input and output matching value are better than -10 dB. The layout of proposed LNA occupies an area of 0.55 mm2 including ring pad and this structure consumes 11.56 mW from 1-V dc supply.

A Simple Low-Profile Coaxially-Fed Magneto-Electric Dipole Antenna Without Slot-Cavity

A simple coaxially-fed magneto-electric dipole (ME dipole) antenna is designed and experimentally evaluated. The proposed antenna does not require the conventional quarter-wavelength slot cavity for generating the magnetic dipole mode, and only consists of two simple rectangular horizontal patches, a vertical semi-rigid coaxial cable and a square ground plane. It makes the fabrication easier and can reduce the production cost. Also, as the quarter-wavelength slot cavity is removed in the proposed design, the thickness of the antenna can be reduced to 21 mm, i.e., 16.4% of the free space wavelength at the center frequency. The low-profile antenna shows comparable wide impedance bandwidth of 41.03% (S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> ≤ -10 dB), and a more stable and higher realized gain from 7.90 - 9.74 dBi (± 0.92 dB variation) over the operating frequency band from 1.86 GHz to 2.82 GHz (centered at 2.34 GHz). The maximum gain has increased around 9.4% when compare with that of the highest reported. While the gain variation in the passband of the proposed antenna is about 58% lower than that of those ME dipole antennas reported in the literature. The radiation mechanism and the effects of the critical parameters of the antenna are also explained with the assistance of the parametric study presented.

Multiple Parameters Optical Sensing Using Fiber Ring Laser Based on Fiber Bragg Gratings and 1064 nm Semiconductor Optical Amplifier

In this paper, a semiconductor optical amplifier (SOA) based 1064 nm fiber ring laser with 63.56 dB optical signal-to-noise ratio (OSNR) is demonstrated. The stable performance is measured for six hours with lasing peak variation of ≤±0.115 dB and wavelength variation of ≤±0.006 nm. Combining the fiber ring laser with fiber Bragg gratings (FBGs), the SOA based fiber ring laser is applied to sense stretch, squeeze, and temperature variation. The results show high linearity, which is suitable for interpolation method prediction and evaluation. A large dynamic range of up to 10 km is also demonstrated for remote sensing applications.

A Label-Free, Non-Intrusive, and Rapid Monitoring of Bacterial Growth on Solid Medium Using Microwave Biosensor.

Microwave resonator sensors are attractive for their contactless and label-free capability of monitoring bacterial growth in liquid media. This paper outlines a new label-free microwave biosensor based on a pair of planar split ring resonators for non-invasive monitoring of bacterial growth on a solid agar media. The sensor is comprised of two split ring resonators with slightly different resonant frequencies for differential operation. The transmission coefficient (S21) of the sensor is considered as the sensor's response with a designed and measured quality factor above 200 to ensure a high-resolution operation of the biosensor. Two resonant frequencies of 1.95 and 2.11 GHz represent the sensing signal and the reference signal, respectively. The developed sensor demonstrates high performance in monitoring the growth dynamics of Escherichia coli (E. coli) on Luria-Bertani (LB) agar with 4 mm thickness. The sensor's resonant amplitude response demonstrated 0.5 dB variation corresponding to the bacterial growth over 48 hours when bacteria were spread on LB agar starting with initial OD600 = 1.5. Moreover, 0.6 dB change in the sensor's response was observed over 96 hours of bacterial growth starting with an initial OD600 = 1.17 spotted on LB agar. The measured results fit well to the curves created using Richards' bacterial growth model, showing the strength of the sensor as a potential candidate for use in predictive food microbiology systems.