Arbitrary Frequency Research Articles

Compact Dual Band Ring Coupler Using Miniaturized Metamaterial Left-Handed Impedance Inverters

A compact 3-dB dual band ring coupler is designed, fabricated and tested. The coupler consists of three identical miniaturized Left-Handed (LH) impedance inverter transmission lines (TLs) and a dual one. The general principle of using LH TLs' duality to reduce the size of a dual band ring coupler is explained in detail, showing the equivalent lumped element circuits and the designing relations. A numerical example is considered for the duality analysis and the results are used to obtain a size reduction for both the coupler's dimensions and the number of utilized components. Other arbitrary coupling levels (1 dB and 5 dB) and frequency ratios are investigated and the results of simulations show very good results, proving the validity of the general principle of using LH transmission line's duality. The 3-dB coupler is implemented in microstrip technology and using high-quality lumped components. It works at two arbitrary frequencies, 1.1 GHz and 2.5 GHz, respectively with similar performances. The overall dimension of the proposed coupler is 0.07λ×0.07λ for a wavelength, λ computed at 1.1 GHz. The measured results are in good agreement with the predicted ones for both frequencies, having the return loss and isolation loss better than 33 dB, whereas keeping the insertion and coupling losses at around 3.5 dB in both frequency bands. The phase imbalance at the output ports is less than 1.5°, when the difference and sum ports are excited.

A Nanoplasmonic Branchline Coupler for Subwavelength Wireless Networks

This article presents the new nanoplasmonic branchline coupler (BLC) by using an edge coupled coplanar waveguide (CPW) with a finite length suspended backed conductor. The proposed coupler is designed by using the theoretical transmission line (TL) method, which is established based on the basic characteristics of the related CPW structures. For this purpose, the normalized propagation constant, propagation length, and characteristic impedance of the conductor backed coplanar waveguide (CBCPW) structure are studied and analyzed by applying a fullwave analysis using CAD simulation software tool CST microwave studio suite. Mainly, the coupling coefficient of the BLC can be controlled by changing the length of the backed conductor. In this article, the BLC is designed and analyzed by using a finite length backed conductor based on the theoretical TL method at a 3-dB coupling coefficient. This newly designed coupler can operate at two arbitrary optical frequency bands (O-band and L-band). Hence, it allows us to exchange many other couplers with their narrow bandwidths using this branchline coupler for subwavelength nanoscale wireless network applications and photonic integrated circuits (PICs).

Physical principles of operation and basic capabilities of the four channel receiver 1288хк1т (mf-01)

In radar detection and radio navigation ensuring the reception of signals transmitted over the meteor channel of radio communication is often controversial[1-3]. Solving these problems requires the ability to synthesize precision signals directly[4, 5] for heterodyning systems in addition to modern analog-to-digital conversion devices, correlation analysis, and statistical processing of signal-noise complex. The step of adapting four channel receivers to dynamically changing conditions of transmitting information may include determining the composition of the signal-noise mixture, determining the phase characteristics of the communication channel, estimating the channel transmission rate, and obtaining QoS information. In addition, adaptation often implies the use of a logical channel control loop, which entails the need for complex feedback procedures. Software-defined radio systems are radio and telecommunication systems that can be tuned to an arbitrary frequency band and receive various types of modulated signal, consisting of programmable equipment with program control. SDR performs a significant part of digital signal processing on a conventional personal computer, signal processor or FPGA. In such systems and complexes, the parameters are changed by software configuration. The article considers the implementation of DDS for heterodyning an intermediate frequency signal on the FPGA basis for four channel receiver 1288хк1т (mf-01), which allows you to work with both narrow-band and wide-band communication channels (with simultaneous operation of 4 channels, the band can be expanded) and can be used in modern telecommunication communication systems.

Development and Thorough Investigation of Dual-Band Wilkinson Power Divider for Arbitrary Impedance Environment

In the design and development of front-end communication systems, the arbitrary impedance environments are encountered frequently. In this article, a three-port dual-band equal power divider is proposed which also transforms all types of impedance environments at its ports inherently. The power divider is suitable for a wide range of arbitrary frequency ratios and impedance terminations at each of the input and output ports. A systematic design procedure with a design flow graph is provided. The closed-form design equations make the design process simple and quick for prototyping purposes. The proposed design approach enhances the design flexibility significantly with the presence of multiple independent variables. Design examples with distinct design specifications are provided to demonstrate the effectiveness and flexibility of the architecture. A prototype working at 1/2.6 GHz and with frequency-dependent complex load (FDCL) terminations at the input and output ports is fabricated and measured to validate the proposed architecture and design methodology. The proposed dual-band impedance transforming power divider exhibits controllable bandwidths, planar structure without any reactive element, compact size, and the ability to provide port matching for any real, complex, and frequency-dependent complex impedance terminations.

Detection of Arbitrary Frequency Ultrasonic Guided Wave Signals Based on the Time-Shift Duffing Oscillator

Low detection accuracy and narrow detection range are observed when detecting weak guided wave signals with the Duffing oscillator as a result of a limited frequency band. In order to solve these problems, we proposed a detection method for detecting weak ultrasonic guided waves of arbitrary frequency based on a defect detection method using the Duffing oscillator scanned by a moving window and combined with variable scale and resampling. In this paper, the proposed method by examining the defect echo signals collected on steel pipe samples and detecting ultrasonic guided wave signals excited by arbitrary frequency was effectively validated. Experiment results show that the proposed approach can be used to detect guided wave signals of arbitrary frequency and arbitrary sampling step size with the fixed system. It is very important for expanding the range of defect detection in pipes with guided ultrasonic waves and improving the sensitivity for detecting small defects in engineering applications.

Wavefront shaping with a tunable metasurface: Creating cold spots and coherent perfect absorption at arbitrary frequencies

Modern electronic systems operate in complex electromagnetic environments and must handle noise and unwanted coupling. The capability to isolate or reject unwanted signals for mitigating vulnerabilities is critical in any practical application. In this work, we describe the use of a binary programmable metasurface to (i) control the spatial degrees of freedom for waves propagating inside an electromagnetic cavity and demonstrate the ability to create nulls in the transmission coefficient between selected ports; and (ii) create the conditions for coherent perfect absorption. Both objectives are performed at arbitrary frequencies. In the first case a novel and effective optimization algorithm is presented that selectively generates coldspots over a single frequency band or simultaneously over multiple frequency bands. We show that this algorithm is successful with multiple input port configurations and varying optimization bandwidths. In the second case we establish how this technique can be used to establish a multi-port coherent perfect absorption state for the cavity.

Design and miniaturization of dual-band Wilkinson power dividers

Abstract In this paper, four differently shaped Wilkinson power dividers are presented by selecting the same physical length of two-section transmission lines, dual arbitrary frequency band Wilkinson power dividers can be achieved. The 2.4 GHz (WLAN) and 5.9 GHz (DSRC IEEE 802.11p) frequency bands are selected to complement the future development of multi-band, multi-standard transceivers. To improve physical separation and electrical isolation between the two output ports a parallel RLC circuit is employed. For verification, the simulated and measured performance results of dual-band Wilkinson power dividers implemented on the Rogers 4003C laminate are presented. The measurement results for the fabricated Wilkinson power dividers were in good agreement with theoretical simulation results and show dual-band characteristics.

High performance hardware design of compressor adder in DA based FIR filters for hearing aids

Hearing aid is an acoustic device which is worn by hearing loss people. To compensate the different types of hearing loss, it is necessary to selectively amplify sounds at required frequencies. The main aim of the hearing aid is to selectively remove the noise signal such that the processed sound matches ones audiogram. To achieve this, the decimation filter in hearing aids can be design using multiplier less architecture which should be able to adjust sound levels at arbitrary frequencies within a given spectrum. In hearing aids, decimation filter plays a key role. This paper presents a low complexity design of a digital finite impulse response (FIR) filter for digital hearing aid application. This paper proposed approximate 4:2 compressor adders in memory less DA based FIR filter architecture. In DA architecture the area of the ROM increases gradually when filter order is increased. Memory less DA is designed using compressor adders is a solution to decrease the power consumption and area of the FIR filters and makes the area and power reduction for hearing aid application. The proposed DA based FIR filter architecture is synthesized on 90 nm technology using Synapsis Application Specific Integrated circuit design compiler. The proposed architecture has 45% reduction in area delay product when distinguish with systolic architecture and 10% less ADP when compare with OBC DA architecture. The proposed design is also implemented Field Programmable Gate Array and the results shows that the proposed architecture has less slices than best existing designs. The proposed architecture is used in decimation filter of hearing aids applications using matlab simulink, which removes the unwanted signal.

Quantum-corrected scattering and absorption of a Schwarzschild black hole with GUP

In this paper we have implemented quantum corrections for the Schwarzschild black hole metric using the generalized uncertainty principle (GUP) in order to investigate the scattering process. We mainly compute, at the low energy limit, the differential scattering and absorption cross section by using the partial wave method. We determine the phase shift analytically and verify that these quantities are modified by the GUP. We found that due to the quantum corrections from the GUP the absorption is not zero as the mass parameter goes to zero. A numerical analysis has also been performed for arbitrary frequencies.

The generalized finite amplitude insert substitution method for estimation of the ultrasound parameter of nonlinearity

The estimation of the ultrasound parameter of nonlinearity (B/A) has shown promise for improved tissue characterization. The finite amplitude insert substitution method (FAIS) is a simple technique that measures B/A. It derives B/A based on the ratio between the 2nd harmonic generated in a reference medium (known B/A) and in the sample of interest, measured in transmission mode between a source and a receiver transducer. The classical FAIS was presented for media with a linear frequency dependence of attenuation, and assumes the sample to be positioned close to the receiver. In this work, the FAIS was generalized to allow arbitrary sample positions and arbitrary frequency dependence of attenuation. The introduced generalization of the method and the utilized setup for B/A measurement were validated by measuring B/A in corn oil and 2 animal tissues: porcine liver and porcine fat, whose B/A are known. The experimental conditions which optimize the accuracy of the estimated B/A were also investigated. The mean B/A for the chosen measurements was 10.8 ± 0.8 for oil (ref. B/A = 10.3), 5.1 ± 0.8 for porcine liver (ref. B/A = 6.9) and 11.9 ± 1.6 for porcine fat (ref. B/A = 10.9), showing the feasibility of B/A measurement by the proposed generalized method.

Absorption and scattering by a self-dual black hole

In this paper we investigate the process of massless scalar wave scattering due to a self-dual black hole through the partial wave method. We calculate the phase shift analytically at the low energy limit and we show that the dominant term of the differential scattering cross section at the small angle limit is modified by the presence of parameters related to the polymeric function and minimum area of a self-dual black hole. We also find that the result for the absorption cross section is given by the event horizon area of the self-dual black hole at the low frequency limit. We also show that, contrarily to the case of a Schwarzschild black hole, the differential scattering/absorption cross section of a self-dual black hole is nonzero at the zero mass limit. In addition, we verify these results by numerically solving the radial equation for arbitrary frequencies.

Spectral analysis techniques using Prism signal processing

The Prism is a new signal processing module which implements fully recursive, linear phase FIR filtering, so its computational cost is fixed irrespective of filter length. The Prism also has negligible design cost. Recent work has demonstrated how, using simple design rules, a chain of six Prisms can create a narrowband filter with arbitrary central frequency and bandwidth. In this paper, the technique is applied to spectral analysis of data, whereby a sequence of filters is applied to a data set to provide narrow frequency analysis, yielding accurate estimates of the frequencies and amplitudes of spectral peaks in the data. Although this time domain technique remains computationally expensive compared to the FFT, it can identify and reject spectral leakage, offering an alternative analysis for low amplitude and/or adjacent spectral peaks, including hidden tones, where FFT discrimination may be limited.

On the frequency dependence of viscoelastic material characterization with intermittent-contact dynamic atomic force microscopy: avoiding mischaracterization across large frequency ranges.

Atomic force microscopy (AFM) is a widely use technique to acquire topographical, mechanical, or electromagnetic properties of surfaces, as well as to induce surface modifications at the micrometer and nanometer scale. Viscoelastic materials, examples of which include many polymers and biological materials, are an important class of systems, the mechanical response of which depends on the rate of application of the stresses imparted by the AFM tip. The mechanical response of these materials thus depends strongly on the frequency at which the characterization is performed, so much so that important aspects of behavior may be missed if one chooses an arbitrary characterization frequency regardless of the materials properties. In this paper we present a linear viscoelastic analysis of intermittent-contact, nearly resonant dynamic AFM characterization of such materials, considering the possibility of multiple characteristic times. We describe some of the intricacies observed in their mechanical response and alert the reader about situations where mischaracterization may occur as a result of probing the material at frequency ranges or with probes that preclude observation of its viscoelastic behavior. While we do not offer a solution to the formidable problem of inverting the frequency-dependent viscoelastic behavior of a material from dynamic AFM observables, we suggest that a partial solution is offered by recently developed quasi-static force–distance characterization techniques, which incorporate viscoelastic models with multiple characteristic times and can help inform dynamic AFM characterization.

Multifrequency Heterodyne Detection of Molecules Using a Hot Electron Bolometer Mixer pumped by Two Phase-Locked THz-Quantum Cascade Lasers

We have successfully demonstrated the simultaneous phase-locking of two terahertz quantum cascade lasers (THz-QCLs). These phase-locked THz-QCLs are used as local oscillators of a hot electron bolometer mixer (HEBM). The HEBM was simultaneously pumped by two phase-locked THz-QCLs for the multifrequency heterodyne detection of emission line spectra of methanol [CH3OH] at 2 THz using a gas cell. The phase-locking of THz-QCLs with arbitrary frequencies using an optical comb and a photomixer to generate THz references was also demonstrated. An advantage of this technique is that it expands the RF bandwidth of an HEBM.

Can a Population Targeted by a CRISPR-Based Homing Gene Drive Be Rescued?

CRISPR-based homing gene drive is a genetic control technique aiming to modify or eradicate natural populations. This technique is based on the release of individuals carrying an engineered piece of DNA that can be preferentially inherited by the progeny. The development of countermeasures is important to control the spread of gene drives, should they result in unanticipated damages. One proposed countermeasure is the introduction of individuals carrying a brake construct that targets and inactivates the drive allele but leaves the wild-type allele unaffected. Here we develop models to investigate the efficiency of such brakes. We consider a variable population size and use a combination of analytical and numerical methods to determine the conditions where a brake can prevent the extinction of a population targeted by an eradication drive. We find that a brake is not guaranteed to prevent eradication and that characteristics of both the brake and the drive affect the likelihood of recovering the wild-type population. In particular, brakes that restore fitness are more efficient than brakes that do not. Our model also indicates that threshold-dependent drives (drives that can spread only when introduced above a threshold) are more amenable to control with a brake than drives that can spread from an arbitrary low introduction frequency (threshold-independent drives). Based on our results, we provide practical recommendations and discuss safety issues.

Non-Markovianity of quantum Brownian motion

We study quantum non-Markovian dynamics of the Caldeira-Leggett model, a prototypical model for quantum Brownian motion describing a harmonic oscillator linearly coupled to a reservoir of harmonic oscillators. Employing the exact analytical solution of this model one can determine the size of memory effects for arbitrary couplings, temperatures, and frequency cutoffs. Here, quantum non-Markovianity is defined in terms of the flow of information between the open system and its environment, which is quantified through the Bures metric as distance measure for quantum states. This approach allows us to discuss quantum memory effects in the whole range from weak to strong dissipation for arbitrary Gaussian initial states. A comparison of our results with the corresponding results for the spin-boson problem show a remarkable similarity in the structure of non-Markovian behavior of the two paradigmatic models.

Error estimation and enhanced stiffness sensitivity in contact resonance force microscopy with a multiple arbitrary frequency lock-in amplifier (MAFLIA)

In contact resonance force microscopy and related dynamic atomic force microscopy methods, an accurate description of the real-time cantilever dynamics is essential to the mapping of local material properties, such as viscoelasticity, piezo response, and chemical composition. Stiffness and damping variations of the tip-sample contact result in variations in the cantilever’s resonance frequency and quality factor as it scans a sample of interest. When measuring characteristics of the resonance, generally, there is a tradeoff between full spectral coverage, best obtained by sweeping the amplitude versus frequency response in the time or frequency domain, and high-speed information, obtained by observing the cantilever response at one or two discrete frequencies, that may be required to track a resonance frequency that changes spatially. Here, we introduce a new option for performing contact resonance force microscopy with a low-cost multifrequency lock-in amplifier system with up to eight simultaneous independent excitation and detection frequencies. We demonstrate how the multifrequency approach can measure contact resonance frequency, quality factor, amplitude, and phase during imaging, with high precision and error estimation, without the need for frequency-tracking feedback. We show, using a wood composite sample, that this multifrequency approach can determine resonance frequency and quality factor, and associated uncertainty. This ability to estimate uncertainty of resonance parameters is not possible with 1 and 2 frequency methods. We further utilize the multifrequency lock-in to develop a novel means of increasing the stiffness range for highly sensitive nanomechanical sensing by dividing the eight lock-in frequencies to monitor two or four simultaneous eigenmodes, each of which is optimized for sensitivity in a particular stiffness regime. Overall, we show how multifrequency lock-in amplifiers with observation frequency chosen to coincide with an expected eigenmode’s contact resonance can benefit the characterization of strongly heterogeneous samples, while maintaining fast measurement speed.

Demonstration of Channel Multiplexing Quantum Communication Exploiting Entangled Sideband Modes.

Channel multiplexing quantum communication based on exploiting continuous-variable entanglement of optical modes offers great potential to enhance channel capacity and save quantum resource. Here, we present a frequency-comb-type control scheme for simultaneously extracting a lot of entangled sideband modes with arbitrary frequency detuning from a squeezed state of light. We experimentally demonstrate fourfold channel multiplexing quantum dense coding communication by exploiting the extracted four pairs of entangled sideband modes. Due to high entanglement and wide frequency separation between each entangled pairs, these quantum channels have large channel capacity and the cross talking effect can be avoided. The achieved channel capacities have surpassed that of all classical and quantum communication under the same bandwidth published so far. The presented scheme can be extended to more channels if more entangled sideband modes are extracted.

A Direct Solving Approach for High-Order Power Amplifier Matching Network Design

In this article, a direct solving method for power amplifier (PA) matching network design is explored from a theoretical perspective. Commonly, the input impedance function of a multivariable matching network is a transcendental equation and it is unsolvable. In the proposed new method, this problem can be solved to some extent by transforming the transcendental equations into solvable linear equations, where the unknown coefficients can be calculated easily. A family of impedance functions is obtained if the order of matching network is higher than the number of functions, and the best one can be selected according to the practical demand in PA design. As a design example, a triband PA with arbitrary frequency points (0.9/2.3/3.5 GHz) is implemented to validate the proposed approach. The calculation results show that the proposed method can solve the matching problem of high-order circuits. And the simulation and experiment results agree with the calculation results very well, which verified the validity of the proposed method.

Coupling theory of quasinormal modes for lossy and dispersive plasmonic nanoresonators

A quasinormal mode (QNM) coupling theory is proposed for a system of coupled resonators. The theory is generally applicable to systems with energy loss and arbitrary frequency dispersion of permittivity such as plasmonic nanoresonators. The QNM coupling coefficients in the theory are obtained with first-principle calculations without fitting the full-wave numerical results or experimental data. The theory is built up based on the Green's-function formalism, which shows that the coupling between resonators originates from the mutual excitation of scattered field of each resonator. With the theory, the source-excited scattered field or the source-free QNMs of the coupled system can be obtained as an expansion in terms of QNMs of each individual resonator in the system. The theory provides an intuitive physical picture and also shows superior computational efficiency compared with the full-wave numerical method if the scattered field of each resonator in the system can be expanded with a small set of QNMs. The theory is tested against full-wave numerical method and is used to design metallic nanoantennas with a broadband enhancement of the spontaneous emission rate.