Showing papers on "Q factor published in 2010"
01 Jan 2010
TL;DR: In this paper, an experimental setup has been constructed for simultaneous measurements of the frequency, the absolute Q factor, and the amplitude of oscillation of a quartz crystal microbalance (QCM).
Abstract: An experimental setup has been constructed for simultaneous measurements of the frequency, the absolute Q factor, and the amplitude of oscillation of a quartz crystal microbalance (QCM). The technical solution allows operation in vacuum, air, or liquid. The crystal is driven at its resonant frequency by an oscillator that can be intermittently disconnected causing the crystal oscillation amplitude to decay exponentially. From the recorded decay curve the absolute Q factor (calculated from the decay time constant), the frequency of the freely oscillating crystal, and the amplitude of oscillation are obtained. AI1 measurements are fully automated. One electrode of the QCM in our setup was connected to true ground which makes possible simultaneous electrochemistry. The performance is illustrated by experiments in fluids of varying viscosity (gas and liquid) and by protein adsorption in situ. We found, in addition to the above results, that the amplitude of oscillation is not always directly proportional to the Q factor, as the commonly used theory states. This puts limitations on the customary use of the amplitude of oscillation as a measure of the Q factor. 8 1995 American Institute of Physics.
1,021 citations
TL;DR: A new method is reported on how to measure the local pressure amplitude and the Q factor of ultrasound resonances in microfluidic chips designed for acoustophoresis of particle suspensions.
Abstract: A new method is reported on how to measure the local pressure amplitude and the Q factor of ultrasound resonances in microfluidic chips designed for acoustophoresis of particle suspensions. The method relies on tracking individual polystyrene tracer microbeads in straight water-filled silicon/glass microchannels. The system is actuated by a PZT piezo transducer attached beneath the chip and driven by an applied ac voltage near its eigenfrequency of 2 MHz. For a given frequency a number of particle tracks are recorded by a CCD camera and fitted to a theoretical expression for the acoustophoretic motion of the microbeads. From the curve fits we obtain the acoustic energy density, and hence the pressure amplitude as well as the acoustophoretic force. By plotting the obtained energy densities as a function of applied frequency, we obtain Lorentzian line shapes, from which the resonance frequency and the Q factor for each resonance peak are derived. Typical measurements yield acoustic energy densities of the order of 10 J/m3, pressure amplitudes of 0.2 MPa, and Q factors around 500. The observed half wavelength of the transverse acoustic pressure wave is equal within 2% to the measured width w = 377 μm of the channel.
240 citations
TL;DR: This work develops a method for fabricating very small silica microbubbles having a micrometer-order wall thickness and demonstrates the first optical microbubble resonator, based on blowing a microbuble using stable radiative CO(2) laser heating rather than unstable convective heating in a flame or furnace.
Abstract: We develop a method for fabricating very small silica microbubbles having a micrometer-order wall thickness and demonstrate the first optical microbubble resonator. Our method is based on blowing a microbubble using stable radiative CO(2) laser heating rather than unstable convective heating in a flame or furnace. Microbubbles are created along a microcapillary and are naturally opened to the input and output microfluidic or gas channels. The demonstrated microbubble resonator has 370 microm diameter, 2 microm wall thickness, and a Q factor exceeding 10(6).
214 citations
TL;DR: In this paper, the authors present the modeling, design, fabrication, and measurement of microelectromechanical systems-enabled continuously tunable evanescent-mode electromagnetic cavity resonators and filters with very high unloaded quality factors (Qu).
Abstract: This paper presents the modeling, design, fabrication, and measurement of microelectromechanical systems-enabled continuously tunable evanescent-mode electromagnetic cavity resonators and filters with very high unloaded quality factors (Qu). Integrated electrostatically actuated thin diaphragms are used, for the first time, for tuning the frequency of the resonators/filters. An example tunable resonator with 2.6:1 (5.0-1.9 GHz) tuning ratio and Qu of 300-650 is presented. A continuously tunable two-pole filter from 3.04 to 4.71 GHz with 0.7% bandwidth and insertion loss of 3.55-2.38 dB is also shown as a technology demonstrator. Mechanical stability measurements show that the tunable resonators/filters exhibit very low frequency drift (less than 0.5% for 3 h) under constant bias voltage. This paper significantly expands upon previously reported tunable resonators.
192 citations
TL;DR: The design of elliptical resonators with a wavelength-size notch at the boundary are reported, which support in-plane highly unidirectional laser emission from WGMs and are scalable to the visible and the near infrared, thus opening the door to very low-threshold, highly unIDirectional microcavity diode lasers.
Abstract: Optical microcavities can be designed to take advantage of total internal reflection, which results in resonators supporting whispering-gallery modes (WGMs) with a high-quality factor (Q factor). One of the crucial problems of these devices for practical applications such as designing microcavity lasers, however, is that their emission is nondirectional due to their radial symmetry, in addition to their inefficient power output coupling. Here we report the design of elliptical resonators with a wavelength-size notch at the boundary, which support in-plane highly unidirectional laser emission from WGMs. The notch acts as a small scatterer such that the Q factor of the WGMs is still very high. Using midinfrared (λ ∼ 10 μm) injection quantum cascade lasers as a model system, an in-plane beam divergence as small as 6 deg with a peak optical power of ∼5 mW at room temperature has been demonstrated. The beam divergence is insensitive to the pumping current and to the notch geometry, demonstrating the robustness of this resonator design. The latter is scalable to the visible and the near infrared, thus opening the door to very low-threshold, highly unidirectional microcavity diode lasers.
192 citations
TL;DR: In this paper, a broadband gigahertz region metamaterial absorber with a maximum absorption of 99.9% at 2.4 GHz and a full width at half maximum bandwidth of 700 MHz, all while maintaining low reflection inside and outside of resonance.
Abstract: Artificially engineered metamaterials have enabled the creation of electromagnetic materials with properties not found in nature. Recent work has demonstrated the feasibility of developing high performance, narrowband electromagnetic absorbers using such metamaterials. These metamaterials derive their absorption properties primarily through dielectric loss and impedance matching at resonance. This paper builds on that work by increasing the bandwidth through embedding resistors into the metamaterial structure in order to lower the Q factor and by using multiple elements with different resonances. This is done while maintaining an impedance-matched material at normal incidence. We thus present the design, simulation, and experimental verification of a broadband gigahertz region metamaterial absorber, with a maximum absorption of 99.9% at 2.4 GHz, and a full width at half maximum bandwidth of 700 MHz, all while maintaining low reflection inside and outside of resonance.
182 citations
TL;DR: Using suspended nanochannel resonators (SNRs), measurements of mass in solution with a resolution of 27 ag in a 1 kHz bandwidth are demonstrated, which represents a 100-fold improvement over existing suspended microchannel resonators and is the most precise mass measurement in liquid today.
Abstract: Using suspended nanochannel resonators (SNRs), we demonstrate measurements of mass in solution with a resolution of 27 ag in a 1 kHz bandwidth, which represents a 100-fold improvement over existing suspended microchannel resonators and, to our knowledge, is the most precise mass measurement in liquid today. The SNR consists of a cantilever that is 50 μm long, 10 μm wide, and 1.3 μm thick, with an embedded nanochannel that is 2 μm wide and 700 nm tall. The SNR has a resonance frequency near 630 kHz and exhibits a quality factor of approximately 8000 when dry and when filled with water. In addition, we introduce a new method that uses centrifugal force caused by vibration of the cantilever to trap particles at the free end. This approach eliminates the intrinsic position dependent error of the SNR and also improves the mass resolution by increasing the averaging time for each particle.
170 citations
01 Nov 2010
TL;DR: In this article, the authors show that series resonance in both the sender and the receiver increases the power transfer in weakly coupled series resonators, where the magnetic coupling is weak enough that the effect of the receiver coil on the sender coil can be neglected.
Abstract: Wireless power transfer can create the illusion of portable devices with infinite power supplies and enable applications that are currently unimaginable because of power constraints. Magnetic induction has been extensively used for wireless power transfer, but its efficiency depends on magnetic coupling that decays as the inverse cube of distance. At long enough distances, the magnetic coupling is weak enough that the effect of the receiver coil on the sender coil can be neglected. In this weakly coupled limit, series resonance in both the sender and the receiver increases the power transfer. Compared to magnetic induction, the power transfer increases by the sum of the quality factors of the sender and the receiver times the quality factor of the sender. Similarly, the efficiency increases by half of the product of the quality factors of the sender and the receiver. However, the overall efficiency of the power transfer is less than 50% for all weakly coupled series resonators. Resonators with a Q of 1,000 should be able to send power over a distance 9 times the radius of the devices with an efficiency of 10%.
163 citations
TL;DR: The first system penalty measurements for all-optical wavelength conversion via four wave mixing in an integrated, CMOS compatible, ring resonator are presented, obtaining < 0.3 dB system penalty at 2.5Gb/s for ∼22dBm average pump power.
Abstract: We present the first system penalty measurements for all-optical wavelength conversion in an integrated ring resonator. We achieve wavelength conversion over a range of 27.7nm in the C-band at 2.5 Gb/s by exploiting four wave mixing in a CMOS compatible, high index glass ring resonator at ~22 dBm average pump power, obtaining < 0.3 dB system penalty.
161 citations
TL;DR: In this article, the authors demonstrate spectral tunability for microphotonic add-drop filters manufactured as ring resonators in a commercial 130 nm SOI CMOS technology, where the filters are provisioned with integrated heaters built in CMOS for thermal tuning.
Abstract: We demonstrate spectral tunability for microphotonic add-drop filters manufactured as ring resonators in a commercial 130 nm SOI CMOS technology. The filters are provisioned with integrated heaters built in CMOS for thermal tuning. Their thermal impedance has been dramatically increased by the selective removal of the SOI handler substrate under the device footprint using a bulk silicon micromachining process. An overall ~20x increase in the tuning efficiency has been demonstrated with a 100 µm radius ring as compared to a pre-micromachined device. A total of 3.9 mW of applied tuning power shifts the filter resonant peak across one free spectral node of the device. The Q-factor of the resonator remains unchanged after the co-integration process and hence this device geometry proves to be fully CMOS compatible. Additionally, after the cointegration process our result of 2π shift with 3.9mW power is among the best tuning performances for this class of devices. Finally, we examine scaling the tuning efficiency versus device footprint to develop a different performance criterion for an easier comparison to evaluate thermal tuning. Our criterion is defined as the unit of power to shift the device resonance by a full 2π phase shift.
144 citations
TL;DR: This work reports the realization and performance of a distributed feedback channel waveguide laser in erbium-doped aluminum oxide on a standard thermally oxidized silicon substrate and the diode-pumped continuous-wave laser, which demonstrated a threshold of 2.2 mW absorbed pump power and a maximum output power of more than 3 mW.
Abstract: We report the realization and performance of a distributed feedback channel waveguide laser in erbium-doped aluminum oxide on a standard thermally oxidized silicon substrate. The diode-pumped continuous-wave laser demonstrated a threshold of 2.2 mW absorbed pump power and a maximum output power of more than 3 mW with a slope efficiency of 41.3% versus absorbed pump power. Single-longitudinal-mode and single-polarization operation was achieved with an emission linewidth of 1.70+-0.58 kHz (corresponding to a Q factor of 1.14 × 10e11), which was centered at a wavelength of 1545.2 nm.
TL;DR: In this article, an ultrahigh-Q slotted two-dimensional photonic crystal cavity capable of obtaining strong interaction between the internal light field and the mechanical motion of the slotted structure was demonstrated.
Abstract: We demonstrate an ultrahigh-Q slotted two-dimensional photonic crystal cavity capable of obtaining strong interaction between the internal light field and the mechanical motion of the slotted structure. The measured optical quality factor is Q = 1.2×10^6 for a cavity with an effective modal volume of V_(eff) = 0.04(λ)^3. Optical transduction of the thermal motion of the fundamental in-plane mechanical resonance of the structure (ν_m = 151 MHz) is performed, from which a zero-point motion optomechanical coupling rate of g∗/2π = 320 kHz is inferred. Dynamical back-action of the optical field on the mechanical motion, resulting in cooling and amplication of the mechanical motion, is also demonstrated.
TL;DR: The resonant body transistor (RBT), a silicon-based dielectrically transduced nanoelectromechanical (NEM) resonator embedding a sense transistor directly into the resonator body, marks the highest frequency acoustic resonance measured to date on a silicon wafer.
Abstract: This paper introduces the resonant body transistor (RBT), a silicon-based dielectrically transduced nanoelectromechanical (NEM) resonator embedding a sense transistor directly into the resonator body. Combining the benefits of FET sensing with the frequency scaling capabilities and high quality factors (Q) of internal dielectrically transduced bar resonators, the resonant body transistor achieves >10 GHz frequencies and can be integrated into a standard CMOS process for on-chip clock generation, high-Q microwave circuits, fundamental quantum-state preparation and observation, and high-sensitivity measurements. An 11.7 GHz bulk-mode RBT is demonstrated with a quality factor Q of 1830, marking the highest frequency acoustic resonance measured to date on a silicon wafer.
TL;DR: Experimental results on nonlinear, ultra-low power photonics applications based on a silica whispering-gallery-mode microresonator that combines an ultrahigh quality factor of Q > 10(8) with a small mode volume V is presented and the same set-up can be operated as an optical memory.
Abstract: We present experimental results on nonlinear, ultra-low power photonics applications based on a silica whispering-gallery-mode microresonator. Our bottle microresonator combines an ultrahigh quality factor of Q > 108 with a small mode volume V. The resulting Q2/V-ratio is among the highest realized for optical microresonators and allows us to observe bistable behavior at very low powers. We report single-wavelength all-optical switching via the Kerr effect at a record-low threshold of 50 µW. Moreover, an advantageous mode geometry enables the coupling of two tapered fiber waveguides to a bottle mode in an add-drop configuration. This allows us to route a CW optical signal between both fiber outputs with high efficiency by varying its power level. Finally, we demonstrate that the same set-up can also be operated as an optical memory.
TL;DR: In this Letter, it is demonstrated that what is believed to be the first mechanically fully tunable spheroidal microresonator created of a silica microbubble having a 100microm order radius and 1microm orders wall thickness is demonstrated.
Abstract: An optical resonator is often called fully tunable if its tunable range exceeds the spectral interval that contains the resonances at all the characteristic modes of this resonator. For high-Q-factor spheroidal and toroidal microresonators, this interval coincides with the azimuthal free spectral range (FSR). In this Letter, we demonstrate what we believe to be the first mechanically fully tunable spheroidal microresonator created of a silica microbubble having a 100μm order radius and 1μm order wall thickness. The tunable bandwidth of this resonator is more than two times greater than its azimuthal FSR.
TL;DR: In this article, the authors reported quality factors of up to 500x10³ in superconducting resonators at the single photon levels needed for circuit quantum electrodynamics.
Abstract: We report quality factors of up to 500x10³ in superconducting resonators at the single photon levels needed for circuit quantum electrodynamics. This result is achieved by using NbTiN and removing the dielectric from regions with high electric fields. As demonstrated by a comparison with Ta, the crucial sources of intensity-dependent loss are dielectrics on the surface of the metal and substrate.
TL;DR: A compact optoelectronic oscillator based on phase modulation and ultra-high Q disk resonators is demonstrated, with a phase noise of -90 dBrad2/Hz at 10 kHz from the carrier and -110 dBrad1/ Hz at 100 kHz.
Abstract: We demonstrate a compact optoelectronic oscillator based on phase modulation and ultra-high Q disk resonators. A 10.7 GHz microwave is generated, with a phase noise of −90 dBrad2/Hz at 10 kHz from the carrier, and −110 dBrad2/Hz at 100 kHz.
TL;DR: In this article, a high-Q micro-resonator made of low-loss, thermoplastic polymer poly(methyl methacrylate) (PMMA) directly processed on a silicon substrate is presented.
Abstract: We report on the fabrication of high-Q microresonators made of low-loss, thermoplastic polymer poly(methyl methacrylate) (PMMA) directly processed on a silicon substrate. Using this polymer-on-silicon material in combination with a thermal reflow step enables cavities of conical geometry with an ultrasmooth surface. The cavity Q factor of these PMMA resonators is above 2×106 in the 1300 nm wavelength range. Finite element simulations show the existence of a variety of “whispering gallery” modes in these resonators explaining the complexity of the measured transmission spectra.
TL;DR: In this paper, the possibility of using an active internal matching element in several types of metamaterial-inspired, electrically small antennas to overcome their inherent narrow bandwidths is demonstrated.
Abstract: The possibility of using an active internal matching element in several types of metamaterial-inspired, electrically small antennas (ESAs) to overcome their inherent narrow bandwidths is demonstrated. Beginning with the Z antenna, which is frequency tunable through its internal lumped element inductor, a circuit model is developed to determine an internal matching network, i.e., a frequency dependent inductor, which leads to the desired enhanced bandwidth performance. An analytical relation between the resonant frequency and the inductor value is determined via curve fitting of the associated HFSS simulation results. With this inductance-frequency relation defining the inductor values, a broad bandwidth, electrically small Z antenna is established. This internal matching network paradigm is then confirmed by applying it to the electrically small stub and canopy antennas. An electrically small canopy antenna with k? = 0.0467 that has over a 10% bandwidth is finally demonstrated. The potential implementation of the required frequency dependent inductor is also explored with a well-defined active negative impedance converter circuit that reproduces the requisite inductance-frequency relations.
TL;DR: In this article, the photonic crystals (PCs) nano-ring resonators were constructed by removing holes of a hexagon from a two-dimensional (2-D) silicon PC slab in hexagonal lattice.
Abstract: We investigated the characteristics of photonic crystals (PCs) nano-ring resonators as biochemical sensors theoretically. The new nano-ring resonators were formed by removing holes of a hexagon from a two-dimensional (2-D) silicon PC slab in hexagonal lattice. Resonant peak with quality factor of about 3000 is reported. Biomolecules, e.g., DNAs, trapped in a hole functionalized with molecule probes made the wavelength shift of resonant peak derived in the output terminal. The sensitivity of various sensing holes along the nano-ring was characterized. This new PC nano-ring resonator demonstrated promising features as a biochemical sensor.
TL;DR: In this article, a novel mixed electric and magnetic coupling scheme is proposed to control the coupling coefficient variation, which is able to achieve desired coupling coefficients between the proposed resonators at various frequencies so as to obtain constant absolute bandwidth.
Abstract: This paper presents a novel approach to design frequency-agile bandpass filters with constant absolute bandwidth and passband shape, as well as a suppressed second harmonic. A novel mixed electric and magnetic coupling scheme is proposed to control the coupling coefficient variation. Theoretical analysis indicates that it is able to achieve desired coupling coefficients between the proposed resonators at various frequencies so as to obtain constant absolute bandwidth. Moreover, this half-wavelength resonator has a Q higher than the quarter- and half-wavelength counterparts, thus resulting in low insertion loss. A filter of this type is designed to validate the proposed idea. To remove the spurious responses of the filter, a method is then introduced to suppress the second harmonic without degrading the passband performance. For demonstration, two frequency-agile filters with 60- and 80-MHz constant absolute bandwidth are implemented with the frequency tuning range from 680 to 1000 MHz. Comparisons of experimental and simulated results are presented to verify the theoretical predications.
01 Dec 2010
TL;DR: In this article, high-Q silicon ring resonators fabricated by selective oxidation without any silicon etching are presented. And they achieve an intrinsic quality factor of 510,000 in 50 μm-radius ring resonator with ring losses of 0.8 dB/cm.
Abstract: We demonstrate high-Q silicon ring resonators fabricated by selective oxidation without any silicon etching. We achieve an intrinsic quality factor of 510,000 in 50 μm-radius ring resonators with ring losses of 0.8 dB/cm.
TL;DR: Both analytical and simulation results reveal that the demultiplexing wavelength of each channel has linear and nonlinear relationships with length and width of the nano-capillary structure.
Abstract: A structure based on plasmonic nano-capillary resonators for optical wavelengths demultiplexing is proposed and numerically investigated. The structure consists of main/bus waveguide connected with series of nano-capillary resonators, each of which tuned at different wavelength transmission band. A model based on resonator theory is given to design the working wavelength of the structure. Both analytical and simulation results reveal that the demultiplexing wavelength of each channel has linear and nonlinear relationships with length and width of the nano-capillary structure.
TL;DR: In this paper, a cross-coupled bandpass filter using new substrate integrated waveguide (SIW) resonators is presented, which is built up by a SIW cavity loaded with a complementary split-ring resonator on its top metal plane.
Abstract: A novel cross-coupled bandpass filter using new substrate integrated waveguide (SIW) resonators is presented. The resonator is built up by a SIW cavity loaded with a complementary split-ring resonator (CSRR) on its top metal plane. The resonant modes of the proposed resonator are analyzed, with the Q-factor of the dominant mode also extracted. It is shown that our proposed compact filter operates below the cutoff frequency of conventional SIWs. No spurious responses, corresponding to the higher-order resonant modes of the resonator, appear within an octave band of the central frequency. Its attractive performance is validated numerically and experimentally.
TL;DR: Since using a single tank makes quadrature generation at the local oscillator level costly and power-hungry, two alternative quadratures generation techniques in the RF path are proposed, together with the corresponding input matching strategies.
Abstract: Two very compact and low power quadrature receivers for ZigBee applications are presented. Area and power savings are obtained through both current reuse and oscillator tank sharing between the I and Q paths. Since this choice can cause I and Q amplitude/phase mismatches, the conversion gain is analyzed and a technique to minimize these errors is implemented. Moreover, since using a single tank makes quadrature generation at the local oscillator level costly and power-hungry, two alternative quadrature generation techniques in the RF path are proposed, together with the corresponding input matching strategies.
TL;DR: Numerical calculations based on a Discontinuous Galerkin Time-Domain approach are in good agreement with the experiments and support the physical interpretation of the findings.
Abstract: Extinction cross-section spectra of split-ring-resonator dimers have been measured at near-infrared frequencies with a sensitive spatial modulation technique. The resonance frequency of the dimer's coupled mode as well as its extinction cross-section and its quality factor depend on the relative orientation and separation of the two split-ring resonators. The findings can be interpreted in terms of electric and magnetic dipole-dipole interaction. Numerical calculations based on a Discontinuous Galerkin Time-Domain approach are in good agreement with the experiments and support our physical interpretation.
08 Apr 2010
TL;DR: In this paper, passive temperature compensation techniques for high quality factor (Q) silicon microresonators based on engineering the geometry of the resonator and its material properties are reported.
Abstract: This paper reports on passive temperature compensation techniques for high quality factor (Q) silicon microresonators based on engineering the geometry of the resonator and its material properties. A 105 MHz concave silicon bulk acoustic resonator (CBAR) fabricated on a boron-doped substrate with a resistivity of 10−3 Ω-cm manifests a linear temperature coefficient of frequency (TCF) of −6.3 ppm/°C while exhibiting a Q of 101,550 (fQ = 1.06×1013). The TCF is further reduced by engineering the material property via a wafer-level aluminum thermomigration process to −3.6 ppm/°C while maintaining an fQ of over 4×1012. Such high fQ products with low TCF values are being reported for the first time in silicon and are critical for successful insertion of these devices into low-power low-phase noise frequency references and high performance resonant sensors.
08 Apr 2010
TL;DR: In this article, the authors report on lateral mode thin-film piezoelectric-on-substrate (TPoS) resonators with techniques to enhance the quality factor and reduce the temperature coefficient of frequency (TCF).
Abstract: In this paper we report on lateral mode thin-film piezoelectric-on-substrate (TPoS) resonators with techniques to enhance the quality factor (Q) and reduce the temperature coefficient of frequency (TCF). Such techniques utilize a highly or degenerately doped Si substrate layer as the ground electrode, and reduce the thickness and volume ratio between the AlN piezoelectric layer and the Si substrate. By patterning the AlN and eliminating the bottom metal electrode, a record quality factor of over 30,000 is observed in air at 27MHz (≫66,000 in vacuum). The highly-doped Si brings the resonator average TCF to around −12ppm/°C.
TL;DR: In this paper, the authors describe the strong optomechanical dynamical interactions in ultrahigh-Q/V slot-type photonic crystal cavities with light localization in an air mode with 0.02(λ/n)3 modal volumes.
Abstract: We describe the strong optomechanical dynamical interactions in ultrahigh-Q/V slot-type photonic crystal cavities. The dispersive coupling is based on mode-gap photonic crystal cavities with light localization in an air mode with 0.02(λ/n)3 modal volumes while preserving optical cavity Q up to 5 × 106. The mechanical mode is modeled to have fundamental resonance Ωm/2π of 460 MHz and a quality factor Qm estimated at 12,000. For this slot-type optomechanical cavity, the dispersive coupling gom is numerically computed at up to 940 GHz/nm (Lom of 202 nm) for the fundamental optomechanical mode. Dynamical parametric oscillations for both cooling and amplification, in the resolved and unresolved sideband limit, are examined numerically, along with the displacement spectral density and cooling rates for various operating parameters.
TL;DR: In this article, the performance properties of several fundamental small-antenna designs are compared as a function of overall length and size (ka), where the antennas operate at or very near the same frequency.
Abstract: In this paper, the performance properties of several fundamental small-antenna designs are compared as a function of overall length and size (ka), where the antennas operate at or very near the same frequency. The objective of this work is to determine which basic design approach or configuration, if any, offers the best performance in terms of: achieving an impedance match; the radiation-pattern shape; the radiation efficiency; the half-power bandwidth; and the 2:1 VSWR bandwidth. The fundamental antenna designs studied here include the spherical folded helix, the cylindrical folded helix, the matched disk-loaded dipole, the matched spherical-cap dipole, and the multi-arm spherical resonator. In addition to discussing the different antenna designs, the fundamental approaches used in impedance matching and optimizing the bandwidth of these small antennas are described. Both numerical simulations and measured results are presented.