Broadband Frequency Response Research Articles

A 17–35 GHz Broadband, High Efficiency PHEMT Power Amplifier Using Synthesized Transformer Matching Technique

This paper presents a 17 GHz to 35 GHz broadband power amplifier (PA) using 0.15-μm GaAs pHEMT technology. The synthesized transformer using microstrip line matching technique is proposed in this PA design to enhance the broadband frequency response and minimize the chip size. The design procedures are also presented. A high efficiency broadband PA in commercial 0.15 μm GaAs pHEMT process with the best P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1dB</sub> of 22 dBm, P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sat</sub> of 23.5 dBm, and PAE of 40% are demonstrated to verify the design concepts. This PA has the highest PAE, smallest chip size, and wide fractional bandwidth among the broadband GaAs HEMT PAs from K to Ka band.

Development of dolphin-speaker

Dolphin speaks broadband sound of ten octave ranges. The vocalization of dolphin sound is categorized into three types, whistle, burst pulse, and echolocation clicks. The frequency range of whistle is below 20 kHz, while that of echolocation clicks and burst pulse is from about several kHz to 150 kHz. Whistle and burst pulse are used social communication. Whistle is used identifying each other and burst pulse may contain emotive factor. Few burst pulse researches are conducted compared to whistle. Until now, burst pulse researches are mainly collecting the dolphin sound using hydrophone but not speaking their sound from human side. The main reason why is no speaking from human side is no speaker of broadband frequency range for burst pulse. The newly developed Dolphin-Speaker has the broadband frequency response from 15 to 150 kHz. The Dolphin-Speaker is developed by advanced technology using multilayer piezoelectric device. We introduce the frequency characteristics of Dolphin-Speaker and the spoken soun...

Modelling and experimental characterization of an energy harvester with bi-stable compliance characteristics

This paper presents a novel design for a vibrational energy harvester. The design uses high permeability magnetic materials which brings about two key advantages. First, it gives strong coupling between the mechanical and electrical domains, thus enabling effective energy conversion. Second, it gives the device a bi-stable compliance characteristic, which gives the harvester a broad-band frequency response. An explicit analytical model is developed using a combination of experimental data and finite element modelling in order to accurately incorporate the magnetic forces. The model is then validated using dynamic tests of the experimental rig. The main features of the dynamic response of the bi-stable oscillator are highlighted and benefits discussed in the context of energy harvesting. Finally, comments are made on the relationship between the complicated behaviour resulting from the bi-stable compliance characteristic and the benefits of increased electrical coupling.

A High-Efficiency, Broadband CMOS Power Amplifier for Cognitive Radio Applications

This paper presents a wideband power amplifier (PA) for the application of intelligent cognitive radios. Resistive feedback and transformer matching network are proposed in this PA design to enhance the broadband frequency response. The broadband load impedance match is realized using series stack topology. The limitation of stack PA in both GaAs and CMOS processes are discussed. A high-efficiency broadband PA in commercial 0.18 μm CMOS process with the best <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">P</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1dB</sub> of 20 dBm and PAE of 30% are demonstrated to verify the design concepts. This PA also shows the widest fractional bandwidth performance among CMOS PAs below 10 GHz.

A lasing wavelength stabilized simultaneous multipoint acoustic sensing system using pressure-coupled fiber Bragg gratings

Abstract A fiber Bragg grating (FBG) sensor head, using a pressure coupling mechanism, was designed for broadband frequency response and structural strain-free characteristic. The pressure-coupled sensor heads were connected to a simultaneous multipoint acoustic sensing system based on a tunable laser. An intelligent lasing wavelength stabilization algorithm capable of identifying the direction of spectrum movement, the wavelength shifting speed, and a fiber bending event was developed so that the simultaneous multipoint acoustic sensing system could be used in environments with rapid temperature variations. The lasing wavelength feedback control algorithm updated the lasing wavelength into the steep slope of the FBG spectrum even under conditions of rapid temperature change. The averaging lasing wavelength updating time was only 21 s because the system can decide a minimal size in scan window by finding the FBG spectrum shifting speed and direction in real time. The system was able to update the lasing wavelength which missed the steep slope of the FBG spectrum under maximum temperature variation rates 0.3014 and −0.3246 °C/s. The proposed system detected simultaneous impact waves at multiple points under conditions of rapid temperature change and change in dynamic strain.

Formation of colorimetric fingerprints on nano-patterned deterministic aperiodic surfaces

Periodic gratings and photonic bandgap structures have been studied for decades in optical technologies. The translational invariance of periodic gratings gives rise to well-known angular and frequency filtering of the incident radiation resulting in well-defined scattered colors in response to broadband illumination. Here, we demonstrate the formation of highly complex structural color patterns, or colorimetric fingerprints, in two-dimensional (2D) deterministic aperiodic gratings using dark field scattering microscopy. The origin of colorimetric fingerprints is explained by rigorous full-wave numerical simulations based on the generalized Mie theory. We show that unlike periodic gratings, aperiodic nanopatterned surfaces feature a broadband frequency response with wide angular intensity distributions governed by the distinctive Fourier properties of the aperiodic structures. Finally, we will discuss a range of potential applications of colorimetric fingerprints for optical sensing and spectroscopy.

Embedded Cement-Based Piezoelectric Sensors for Acoustic Emission Detection in Concrete

In this research, the feasibility of using embedded cement-based piezoelectric sensors to detect the acoustic emission (AE) activities in concrete has been studied. A sensor is presented that is made with the 0–3 cement-based piezoelectric composite as sensing element. The composite is formed by pressing mixed cement-piezoelectric powder into a penny-shaped thin plate. In the terminology of 0–3, 0 represents the dimension of the piezoelectric particle and 3 stands for the dimensions of the matrix. By adjusting the dosage of the piezoelectric ceramic powder, the properties of the composite can be tailored to suit designated applications. Sensors made of the composite (0–3 sensor) are able to be embedded into concrete and have broadband frequency response. It is shown by a four-point bending test on a concrete beam that the sensors have excellent ability in AE activity detection. High sensitivity is also observed for the embedded sensors.

The Influence of Complex Permeability on the Broadband Frequency Response of a Power Transformer

This paper considers the effect of the complex permeability of a power transformer core on the frequency response analysis (FRA) test spectrum. Current work in FRA generally neglects the core beyond a few hundred kHz. This research demonstrates that the effective complex permeability is significant at 1 MHz and greater than unity at frequencies exceeding 15 MHz. The paper also shows that for broadband small signal testing, such as FRA, the low field conditions induced by the injected signal result in a relative permeability that approaches the initial permeability of the core. This ensures that the relative permeability remains approximately constant over a large range of frequencies and will have a degree of independence with respect to the amplitude of the injection voltage.

Planck-LFI radiometers' spectral response

The Low Frequency Instrument (LFI) is an array ofpseudo-correlation radiometers on board the Planck satellite, theESA mission dedicated to precision measurements of the CosmicMicrowave Background. The LFI covers three bands centred at 30, 44 and70 GHz, with a goal bandwidth of 20% of the central frequency. Thecharacterization of the broadband frequency response of eachradiometer is necessary to understand and correct for systematiceffects, particularly those related to foreground residuals andpolarization measurements. In this paper we present the measured band shape of all the LFIchannels and discuss the methods adopted for their estimation. Thespectral characterization of each radiometer was obtained by combiningthe measured spectral response of individual units through a dedicatedRF model of the LFI receiver scheme. As a consistency check, we alsoattempted end-to-end spectral measurements of the integratedradiometer chain in a cryogenic chamber. However, due to systematiceffects in the measurement setup, only qualitative results wereobtained from these tests. The measured LFI bandpasses exhibit amoderate level of ripple, compatible with the instrument scientificrequirements.

The application of 1–3 cement-based piezoelectric transducers in active and passive healthmonitoring for concrete structures

1–3 cement-based piezoelectric composite has been developed for health monitoring ofconcrete structures. Transducers made of this type of composite have broadbandfrequency response. Plain concrete and engineered cement composite (ECC) beamswith embedded 1–3 cement-based piezoelectric transducers were prepared andtested. During experiments, the transducers were used to perform active andpassive detection of the damage evolution of the beams. In active detection, adamage index based on the average energy of the received waves was proposed andused. In passive detection, acoustic emission (AE) events were recorded and theaccumulated AE event number was analyzed with the loading history. Cracklocalization was also accomplished in the passive monitoring. The results of the twomethods demonstrated similar trends in interpreting the damage evolution of theconcrete beam. The results were also consistent with each material’s characteristics.

Micromachined optical microphone structures with low thermal-mechanical noise levels

Micromachined microphones with diffraction-based optical displacement detection have been introduced previously [Hall et al., J. Acoust. Soc. Am. 118, 3000-3009 (2005)]. The approach has the advantage of providing high displacement detection resolution of the microphone diaphragm independent of device size and capacitance-creating an unconstrained design space for the mechanical structure itself. Micromachined microphone structures with 1.5-mm-diam polysilicon diaphragms and monolithically integrated diffraction grating electrodes are presented in this work with backplate architectures that deviate substantially from traditional perforated plate designs. These structures have been designed for broadband frequency response and low thermal mechanical noise levels. Rigorous experimental characterization indicates a diaphragm displacement detection resolution of 20 fm radicalHz and a thermal mechanical induced diaphragm displacement noise density of 60 fm radicalHz, corresponding to an A-weighted sound pressure level detection limit of 24 dB(A) for these structures. Measured thermal mechanical displacement noise spectra are in excellent agreement with simulations based on system parameters derived from dynamic frequency response characterization measurements, which show a diaphragm resonance limited bandwidth of approximately 20 kHz. These designs are substantial improvements over initial prototypes presented previously. The high performance-to-size ratio achievable with this technology is expected to have an impact on a variety of instrumentation and hearing applications.

Space-dependent damping for reducing vibration of continuous systems

Structural vibration in continuous systems is a common source of problems for many mechanical systems. Much research has considered ways to reduce the vibration in continuous systems. Some research uses passive techniques that are simple to implement, whereas other methods implement active control that can be quite complex. The research presented here investigates the effect space-dependent damping has on the vibration of continuous systems. Specifically, the work at hand will focus on the flexural vibration of beams. In a distributed damping beam system, the damping is variable as a function of position along the length of the beam. Such a system could be physically realized through the use of magneto-rheological or electro-rheological fluids. Along its length, a beam could be divided into several isolated sections containing such a fluid. By controlling the magnetic or electric field across each section of the beam, the damping would vary along the length of the beam. The work presented here optimizes the damping as a function of beam position to reduce the broadband frequency response of the beam. A number of support conditions for the vibrating beam are considered.

A Three-Dimensional Time-Domain Finite-Element Formulation for Periodic Structures

A formulation is presented for a three-dimensional time-domain finite-element method that can be used to analyze the scattering of a plane wave obliquely incident on a (doubly) infinite periodic structure using one unit cell. A broadband frequency response can be obtained in a single execution. The specifics of the method are shown for scattering problems, but it should be straightforward to extend it to radiation problems. The method solves for a transformed field variable (instead of solving directly for the electric field) in order to easily enable periodic boundary conditions in the time domain. The accuracy and stability of the method is demonstrated by a series of examples where the new formulation is compared with reference solutions. Accurate results are obtained when the excitation (frequency range) and the geometry are such that no higher order propagating Floquet modes are present. The accuracy is degraded in the presence of higher order propagating modes due to the rather simple absorbing boundary condition that is used with the present formulation. The method is found to be stable even for angles of incidence close to grazing.

A digitally controlled constant envelope phase-shift modulator for low-power broad-band wireless applications

A low-power constant envelope phase-shift modulator is presented. The circuit switches the phase of a constant amplitude carrier at output according to the input digital data. Design issues and their impact on the performance of the modulator are discussed. A test chip was fabricated in a 0.18-mum CMOS process. Experiment results verified the design principle of the modulator. The modulator consumes 2 mA and is suitable for low-power wireless applications like sensor network and personal area network. Since the circuit is implemented mostly by digital circuit, has broad-band frequency response, and supports high data rate, the modulator can be used at various wireless bands. The measured operating range of carrier frequency is 1.75 to 3.5 GHz, and the modulation data rate can go up to 500 Mb/s. In addition, the modulator can be modified to generate different modulations by digitally controlling both the phase and amplitude of the output signal from a phasor-combining circuit. Therefore, the modulator can potentially be used for software configurable radios

Single channel analog data links for use with high bandwidth recording systems for the National Ignition Facility

The National Ignition Facility at the Lawrence Livermore National Laboratory requires high bandwidth and high dynamic range data transmission from the target chamber area to diagnostic recording equipment approximately 46 m away. The systems need to pass short pulse signals with high fidelity, requiring a broadband frequency response from below 10 MHz to greater than 6 GHz, that has flat amplitude and a linear phase response. We present here the characterization of a few selected fiber optic systems and work done to optimize the performance of a fiber link and single-shot transient digitizer system. Each link is evaluated by its bandwidth, the fidelity of its step response, the signal loss, and its usable dynamic range.

Synthetic aperture focusing techniques in time and frequency domains for photoacoustic imaging

Synthetic aperture focusing techniques (SAFT) have been applied to B-scan images of artificial defects produced by a scanning photoacoustic probe operating under water. The probe consisted of a fibre-optic laser beam delivery system combined with a polymer (PVDF) transducer mounted at the tip of the probe for ultrasonic reception. This system had a broadband frequency response in the 1-10 MHz range. Such an integral probe was designed to optically transmit and receive near on-axis ultrasonic transients. A frequency domain synthetic aperture method was successfully applied using phantom samples to produce refined 2D images from initial B-scans. In this paper, the phantom consisted of a black nylon rectangular sample with a 1.0 mm circular defect at a depth of 5.9 mm from the surface. A comparison was made of conventional B-scan images with SAFT images. Results showed that synthetic focusing apertures, in time or frequency domains, offer better signal-to-noise ratios with improved capabilities in lateral resolution.

Electrooptic Crystal Multiplier Based on Two Cascaded Pockels Crystals

A novel electrooptic crystal multiplier is proposed which can perform voltage multiplication by using two cascaded Pockels crystals with different polarization azimuths. Different from a conventional analog multiplier, the novel crystal-based multiplier allows us to modulate light wave by voltage product signal, and to obtain the voltage product signal from the measurement of light intensity. Thus, this multiplier possesses electrical insulation property and broad-band frequency response characteristics. The primary experimental result has demonstrated the feasibility of this crystal-based multiplier and its four-quadrant multiplication performance.

Low‐cost geophysical investigations of a paleochannel aquifer in the Eastern Goldfields, Western Australia

Compressional (P) wave and shear (S) wave seismic reflection techniques were used to delineate the sand and gravel aquifer within a highly saline clay‐filled paleochannel in the Eastern Goldfields of Western Australia. The seismic refraction and gravity methods were also used to investigate the paleochannel. The unsaturated loose fine‐grained sand up to 10 m in depth at the surface is a major factor in degrading subsurface imaging. The seismic processing needed to be precise, with accurate static corrections and normal moveout corrections. Deconvolution enhanced the aquifer and other paleochannel reflectors. P‐wave reflection and refraction layer depths had good correlation and showed a total of six boundaries: (1) water table, (2) change in velocity (compaction) in the paleochannel sediments, (3) sand and gravel aquifer, (4) red‐brown saprolite and green saprolite boundary, (5) weathered bedrock, and (6) unweathered bedrock. P‐wave explosive and hammer sources were found to have similar signal characteristics, and the aquifer and bedrock were both imaged using the hammer source. The deep shots below the water table have the most broadband frequency response for reflections, but stacking clear reflections was difficult. The S‐wave reflection results showed high lateral and vertical resolution of the basal saprolite clay, the sand and gravel aquifer, and very shallow clays above the aquifer. The S‐wave reflection stacking velocities were 10–20% of the P‐waves, increasing the resolution of the S‐wave section. The gravity data were modelled to fit the known drilling and P‐wave seismic reflection depths. The refraction results did not identify the top of bedrock, so refraction depths were not used for the gravity modeling in this highly weathered environment. The final gravity model mapped the bedrock topography beyond the lateral extent of the seismic and drilling data.

Portable communication device with collapsible speaker enclosure

A portable communication device includes a speaker enclosure having a speaker and a plurality of telescoping nested shells moveable between a collapsed configuration and an expanded configuration. The shells have a top and bottom surface and interlocking sidewalls such that when the enclosure is deployed into an expanded configuration the shells form a rigid enclosure with a substantially sealed acoustic space therein. The space tunes an acoustic compliance for the speaker so as to improve broadband frequency response whether the communication device is using a privacy or speakerphone mode of operation.

A Relativistic‐Plasma Compton Maser

A relativistic pair-plasma that contains a high excitation of electrostatic turbulence could produce intense radiation by stimulated scattering at a brightness temperature in excess of 1020 K. Important relativistic effects would include the broadband frequency response of the plasma and Compton-boosting of the scattered radiation. In radio-frequency relativistic plasma, the optical depth can be as small as tens of meters. When the plasma wave excitation is one-dimensional and particle distributions have T⊥ T||, the frequency-dependent angular distribution of the emission exhibits characteristics of pulsar emission.