Frequency Selective Components Research Articles

Nonlinear model and characteristic analysis of fractional-order high frequency oscillator

Recently, fractional calculus theory has been widely used in various fields, including the design of oscillators. However, there are still some issues that need to be studied in depth. Firstly, it is necessary to classify the fractional-order oscillators according to the properties of the frequency selective network components, and analyze the influence of the fractional order of components on the characteristics of different types of fractional-order oscillators. Secondly, for fractional-order oscillators with nonlinear devices such as transistors, the traditional linear models cannot describe them accurately. Thirdly, due to the complexity of fractional differential equation, it is difficult to obtain the general analytical solution of the fractional-order oscillator. For these reasons, this paper takes the fractional-order capacitive feedback LC oscillator as an example, and establishes a nonlinear model of this oscillator based on the transistor characteristic mechanism. With the help of the equivalent small parameter method, the influence of the fractional-order characteristics of the components on the output waveform is analyzed. It is revealed that for the fractional-order capacitive feedback LC oscillator, the order of capacitance C1 has the most significant effect on frequency and amplitude, followed by the order of inductance L2, and the order of the feedback capacitor C2 has very little effect on the oscillator. In addition, although the introduction of fractional order increases the oscillation frequency, it will also lead to an increase in THD in some cases. Simulation and experimental results verify the correctness of the proposed nonlinear model and characteristic analysis of fractional-order high frequency oscillator.

전자전에 사용되는 S-대역 스위치 필터 뱅크의 초소형화 광대역 MEMS 대역 통과 필터 구현

Wideband MEMS bandpass filters are important frequency-selective components in communications, radar and other microwave systems, and their performances affect overall system performances directly. Thus, it is critical to develop a compact and lightweight switch filter banks that can be applied to an unmanned aerial vehicle for electronic warfare, which is recently considered important in the defense industry. This paper introduces a high-performance wideband band pass filter fabricated by micro electromechanical systems (MEMS) process based on a high-resistance silicon substrate for low insertion loss. The center frequency of the filter is 4GHz, and it is designed in an inter-digital structure to have a fractional bandwidth of 100%. The fabricated filter has a volume of 6.95 mm × 4.7 mm × 0.42 mm and achieves an insertion loss of 4.0 dB, an attenuation of > 25 dB at 1.0 GHz and 7.5 GHz, and a return loss of < 10 dB.

Electrically tunable terahertz switch based on superconducting subwavelength hole arrays.

We experimentally demonstrate an electrically tunable superconducting device capable of switching the extraordinary terahertz (THz) transmission. The planar device consists of subwavelength hole arrays with real-time control capability. The maximum transmission coefficient at 0.33 THz is 0.98 and decreases to 0.17 when the applied voltage only increases to 1.3 V. A relative intensity modulation of 82.7% is observed, making this device an efficient THz switch. Additionally, this device exhibits good narrow-bandpass characteristics within 2 THz, which can be used as a frequency-selective component. This study offers an ideal tuning method and delivers a promising approach for designing active and miniaturized devices in THz cryogenic systems.

Frequency-tunable logic gates in graphene nano-waveguides

In this study, simple basic plasmonic logic gates of XOR, OR, and NOT based on graphene nano-ribbon resonators coupled to properly designed arrangements of nano-waveguides, as input and output logic ports, are demonstrated. The operation of the structures as frequency selective components is based on the propagation of edge modes in nano-waveguides and coupling to nano-ribbon resonators located in appropriate locations. The gates performance is investigated through analytic approaches and verified numerically using the finite difference time domain method. Typical extinction ratio of about 8 dB between ON and OFF logic states has been attained. According to the fantastic feature of voltage-dependent chemical potential of graphene conductivity, the characteristics of the structures can be actively manipulated. These sub-wavelength plasmonic components can be employed extensively in terahertz demanded applications.

The Reentrant Four-Layer Quasi-Elliptic Bandstop Filter

The novel microwave quasi-elliptic bandstop filter, which uses the initially uncoupled strip transmission lines, is considered in this work. The proposed filter is based on the reentrant structure, where the metallic body with a floating potential is asymmetric. Generally speaking, the internal and external dielectric fillings must have their unequal relative permittivities. As a result, additional symmetrical reflection zeros are reached at the lower and upper pass bands of the stop band leading to the quasi-elliptic function response that improves the filter selectivity. The general transverse electromagnetic (TEM) circuit model for the proposed filter in terms of a series connection of the multi-ports is presented and then used to predict the initial electrical and geometrical parameters. An experimental printed circuit prototype has been manufactured and evaluated to validate the design concept. The measured filter parameters correlate well with the simulation-derived ones and that increases the degree of freedom in the fabrication of microwave frequency selective components.

Design and Experimental Evaluation of Equalization Algorithms for Line-of-Sight Spatial Multiplexing at 60 GHz

With large bandwidths, millimeter wave (mmWave) line-of-sight (LoS) multi-input multi-output (MIMO) technology employing parallel stream transmission is well suited for future wireless backhaul systems. However, hardware imperfections of mmWave transceivers cause additional signal processing challenges. Considering the channel and hardware properties, this paper proposes a novel frame structure with high temporal efficiency. The required MIMO processing can be decomposed into two steps. The first one removes the interantenna interference including the carrier frequency offsets. In the second step, the intersymbol interference brought by the frequency-selective components is canceled with a parallel structure. As a comparison, a more general decision-directed least-mean-square approach (DD-LMS) for joint processing of all effects is introduced. With a 60 GHz 2 × 2 LoS MIMO demonstrator, only the widely linear version of DD-LMS achieves performance of about 0.2-0.6 dB better than the proposed method but requires approximately four times more complexity. The proposed method with parallel processing chains is well suited especially for larger LoS MIMO systems, e.g., for a system with 16 streams, its required complexity is less than 7% of the widely linear DD-LMS.

Self-Oscillating Optical Frequency Comb Based on a Raman-Pumped Brillouin Optoelectronic Oscillator

We demonstrate the generation of a self-oscillating optical frequency comb using a Raman-pumped Brillouin optoelectronic oscillator. In this scheme, stimulated Brillouin scattering is utilized as a frequency selective component. Due to the narrow gain bandwidth of stimulated Brillouin scattering, which is ~30 MHz in a single mode fiber with about 11 GHz frequency shift, microwave signal with very low phase noise can be generated. Thus, the optical comb driven by this optoelectronic oscillator is highly coherent. In our experiment, a 7-line optical comb with 2.7 dB variation of 10.89 GHz spacing is obtained with a phase noise of -93 dBc/Hz at 10 kHz offset.

A Conceptual Study of Microelectromechanical Disk Resonators

Microelectromechanical systems (MEMS) resonators serve as frequency-selective components in applications ranging from biology to communications. In this paper, the dynamic behavior of an RF MEMS disk resonator is formulated using an analytical method. The resonator is simultaneously subjected to a DC-bias voltage superimposed with an ac harmonic voltage applied across the electrode-to-resonator gap. The governing equation of motion is derived by minimization of the Hamiltonian and generalized to include the viscous damping effect. Periodic solutions are determined by means of a shooting method and their stability is investigated by determining the well-known Floquet exponents of the perturbed motions. The influence of intermolecular forces such as van der Waals and Casimir on the dynamics of each mode of the disk resonator are investigated and the influence of design parameters are discussed. The results indicate that a high quality factor at ultrahigh frequency (UHF), a weak nonlinearity, and a low actuation voltage make polydiamond disk resonators excellent contenders for the next generation of micromechanical RF filters and channelizers. Furthermore, the resonant frequencies observed in the second (1.3 GHz) and third (2.1 GHz) modes allow for power-efficient operation of the disk resonator in the UHF range.

Application of RPN analysis to parameter optimization of passive components

In the trend toward the development of electronic products that are compact and lightweight, as portable consumer electronic products, such as the cell phone, Bluetooth, GPS, W-LAN, digital camera, wireless phone, and notebook computer, increase in demand, the frequency control components needed for communications related industries receive increased attention. The crystal oscillator is widely used as a frequency selective passive component in communications related industries because of excellent characteristics, such as temperature stability and a low loss. A crystal oscillator consists mainly of a quartz crystal and an IC that controls the oscillation circuits, and is applied to high precision communications products, requiring high frequency accuracy. A crystal oscillator with an output frequency that deviates or is unstable will seriously degrade the quality and functionality of an expensive communications product. This present research investigates the crystal oscillator manufacturing processes, developing risk priority number analysis specifically for critical-to-quality processes and identifying the optimum priority for improvements in the process quality. Using Taguchi experimental design techniques the optimal parameter design is determined for quality characteristics and a mathematic programming method establishes an objective mode for monitoring quality. Lastly, the present research uses a real case to verify the modes proposed in this project, to enhance customer satisfaction, and produce crystal oscillators with a competitive advantage.

Polarization and angular dependent transmissions on transferred nanomembrane Fano filters

We report angular and polarization dependent transmission properties of Fano resonance optical filters with transferred silicon nanomembrane on glass substrate. The transmission spectra of the filters can have either weak or strong polarization and angular dependence, depending on properties of individual Fano resonance modal dispersion. Measurement results agree very well with simulations based on a rigorous coupled-wave analysis for the transmission spectra, on planewave expansion wave-vector technique for the dispersion property analysis, and on a three-dimensional finite-difference time-domain technique for the propagating modal study. These results will provide importance guidance for the design of a new class of ultra-compact surface-normal frequency selective components with preferred polarization and angular properties. These components are highly desirable for silicon photonic integration.

Piezoelectric-on-Silicon Lateral Bulk Acoustic Wave Micromechanical Resonators

This paper reports on the design, fabrication, and characterization of piezoelectrically-transduced micromechanical single-crystal-silicon resonators operating in their lateral bulk acoustic modes to address the need for high-Q microelectronic-integrable frequency-selective components. A simple electromechanical model for optimizing performance is presented. For verification, resonators were fabricated on 5-mum-thick silicon-on- insulator substrates and use a 0.3-mum zinc oxide film for transduction. A bulk acoustic mode was observed from a 240 mum times 40 mum resonator with a 600-Omega impedance (Q=3400 at P=1 atm) at 90 MHz. A linear resonator absorbed power of -0.5 dBm and an output current of 1.3 mA rms were measured. The same device also exhibited a Q of 12 000 in its fundamental extensional mode at a pressure of 5 torr.

Frequency selective IR-filter produced by using EB-lithography

This paper reports on the fabrication of Jerusalem cross diplexer by direct write electron beam (EB) lithography followed by reactive ion etching (RIE) on a phosphorus doped polished silicon wafer substrate. Such structures can be used as frequency selective components in visible, microwave and near infra-red wavelength region. Replication of the patterns is accomplished by micron or sub-micron order mould fabricated from the silicon (Si) master. Fourier transform infra-red reflectance (FT-IR) measurements were performed to characterize the structured patterns. The spectral reflectance from these patterns clearly show a reflection dip due to surface plasmon excitation in the near infra-red wavelength at about 1.42 and 2.5 μm, respectively. Potential applications such as antireflection surface (ARS) can be realized.

IQ-imbalance and its compensation for non-ideal analog receivers comprising frequency-selective components

Abstract. Within current implementations of mobile terminals, more and more analog components are replaced by appropriate digital processing. On the one hand, the analog front-ends become less complex. On the other hand, more digital signal processing is required to compensate for the spurious effects of the front-end. In this article, the frequency-selective imbalance of the in-phase and quadrature-phase signals is addressed. A closed representation of arbitrary signals being processed by an arbitrary imbalanced analog front-end is provided. The analysis is valid for both, direct conversion and intermediate frequency (IF) reception. With the consideration of practical variations of amplitude and phase impairments, the influence of only the frequency-dependent portions of the impairments is investigated. It is shown, that the compensation of the quasi-linear impairments is sufficient and complex deconvolutive IQ-regeneration procedures are not stringently required to obtain sufficient signal qualities.

Two-dimensional photonic crystal slabs in parallel-plate metal waveguides studied with terahertz time-domain spectroscopy

In this paper, we report our experimental study on two-dimensional photonic crystal slabs embedded inside parallel-plate metal waveguides, using terahertz time-domain spectroscopy. We observe that the temporal response of the photonic crystal slabs is significantly dispersed, indicative of strong dispersion near the edges of the photonic band gap. In the frequency domain, we observe several gaps whose sizes compare well with those from transfer matrix calculations. The group velocity and group velocity dispersion are characterized using a short-time Fourier transform analysis, and the results are consistent with the predictions from the photonic band structure. We have also measured reflection spectra using the photonic crystal as a 90° turning mirror, and in this way demonstrated frequency-selective components for quasi-optic guided wave propagation of terahertz pulses.

Silicon-on-insulator based nanoresonators for mechanical mixing at radio frequencies

Nanomechanical resonators now allow operating frequencies approaching the range of several 100 MHz. Thus, nanomechanical devices become interesting for applications in signal processing. The main advantage of these devices is their high robustness against thermal and electrical shocks. Therefore, they can be used as very sensitive detectors or frequency selective components in communication electronics. Driving the resonators into nonlinear response increases the sensitivities further. Most importantly, such resonators can be used for a novel kind of mechanical mixing. Here, the mechanical oscillations of tiny bridges and oscillators can be used to realize such novel devices for high-frequency signal processing. We present measurements on mechanical mixing in a nanomechanical resonator operated at 100 MHz.

Characterization and application of dichroic filters in the 0.1-3-THz region

Low-loss dichroic filters, a subgroup of frequency-selective components, have been characterized by terahertz time-domain spectroscopy in the region from 0.1 to 3 THz and with Fourier transform spectroscopy. The two data sets are fully consistent. The time-domain spectrometer is used to investigate the phase velocity behavior of dichroic filters. The dichroic filters have various applications in frequency mixing, multiplying, and diplexing experiments. In a novel application, cascaded filters were used to limit the terahertz pulse bandwidth and to monitor molecular transitions of atmospheric water vapor in a selected frequency band.

Long-period fiber gratings with variable coupling for real-time sensing applications

We demonstrate a long-period grating whose resonance varies in strength but remains fixed in wavelength with either temperature or strain. Using this fiber-grating sensor, we resolved a change of 1 muepsilon of strain or 0.04 degrees C in temperature. Such sensors require no spectrometer or other frequency-selective components and can operate in real time.

Transmission features of frequency-selective components in the far infrared determined by terahertz time-domain spectroscopy

Transmission and phase-shift characteristics of dichroic high-pass filters with cutoff frequencies as high as 1.11 THz and of a cross-shaped grid bandpass filter with a resonance frequency of 280 GHz were measured with an electro-optic sampling terahertz time-domain spectrometer operating between 0.1 and 2 THz. Good agreement with transmission theories is found. We also compare the transmission performance of cascaded dichroic filters with that of cross-shaped grid bandpass filters. Both types of bandpass filter permit frequency-selective ultrafast experiments in the far-infrared spectral region. In the millimeter and the submillimeter wavelength regions, which are difficult to access by conventional means, knowledge of the frequency response of frequency-selective components is important for applications in frequency mixing, multiplying, and multiplexing in quasi-optical systems.

Application of a continuously tunable, cw optical parametric oscillator for high-resolution spectroscopy

We report the use of a smoothly tunable, single-frequency continuous-wave optical parametric oscillator (OPO) for high-resolution spectroscopy. The OPO is based on potassium titanyl phosphate and is resonant for both signal and idler fields, resulting in a device with a very low pump power threshold of 30 mW. The frequency-selective nature of the doubly resonant oscillator ensures that the signal and idler modes can be tuned across the entire phase-match bandwidth without the need for additional intracavity frequency-selective components. Smooth frequency tuning of the output of the OPO is obtained by tuning of the pump laser. To demonstrate the practicality of our OPO we recorded the absorption spectrum of cesium vapor in the 1-microm spectral region.

Photonic highway switches based on ring resonators used as frequency-selective components

A new concept for a highway switch, which can be used to connect different optical wavelength division multiplexing data highways for data exchange, is proposed and the system relevant properties are outlined. For the required add-drop filter elements we used ring resonators. Typical characteristics of channel bandwidth, channel spacing, free spectral range, amplification, and cross-talk behavior of a highway switch with double-cavity ring resonators are basically examined and to some extent compared with solutions that were obtained with standard single-ring resonators. A signal flow chart transformation for evaluating filter transfer functions is presented.