Frequency Circuit Research Articles

Optimization and Testing of a 1H/3He Double-Nuclear Quadrature Transmit Coil, Applying the Analytical Method at 0.06T

Application of polarized noble gas technology in lung functional magnetic resonance imaging (fMRI) has garnered attention for its unique advantages, such as high resolution and a lack of radiation exposure. This paper presents a 4-channel radio frequency (RF) coil design method for applications of an 1H/3He MRI system at the ultra-low field of 0.06T. For the complex model of the double-nuclear 1H/3He coil, the analytical optimization method (based on the theories of Biot-Savart law and PSO algorithm) and the electromagnetic (EM) field and radio frequency (RF) circuit co-simulation method was implemented to optimize the analysis, resulting in an effective evaluation. The simulation results demonstrated that the proposed model has the potential for imaging of the lung with the 1H/3He MRI system at an ultra-low field.

Synthesis and binder-free assembly of SrFe12O19 nano-platelets for wafer-scale patterning of magnetic components

Monolithic integration of high-frequency magnetic components such as hexaferrite circulators at the wafer scale can lead to a significant improvement in radio frequency (RF) circuit performance and functionality. However, current methods to monolithically integrate hexaferrite films, such as liquid phase epitaxy, require high temperature (> 900 °C) annealing to create crystalline alignment, which is not compatible with integrated circuit process temperatures (< 350 °C) or thick patterned films (> 50 μm). In this work, we report the synthesis of pure phase, faceted, and high crystallinity hexaferrite [SrFe12O19] nano-platelets using a direct hydrothermal approach, followed by self-assembly of binder free SrFe12O19 films with high film density and high magnetic isotropy. The nano-platelets exhibit high staturation magnetization (~ 60 emu/g) and coercivity (Hc) of 815 Oe. The magnetic films exhibit dense nano-particle concentration and a magnetic squareness (Mr/Ms) of 0.7. They can be patterned using a selective assembly process through a thick photoresist mask. Thicknesses of up to 70 μm have been deposited on 4-in.-diamater wafers.

The Impact of Connection Failure of Bonding Wire on Signal Transmission in Radio Frequency Circuits

Bonding wires are widely used in microwave circuits and chip packaging. The exposure to harsh environments may lead to connection failure in these wires. In this article, the impact of such failures on signal transmission was studied using model analysis and experimental testing. The effects of gold bonding wire failure on both the dc and high frequency characteristics were analyzed. Signal reflection and loss caused by failed gold bonding wire at different positions and a number of failed gold bonding wire were also investigated. Based on computational electromagnetics and transmission line theory, a 3-D electromagnetic field numerical calculation model and a distributed parameter circuit model were developed. The electromagnetic field model results are in good agreements with those obtained from the distributed parameter circuit model. The results obtained by the model simulation are validated using experimental tests. The results of this investigation provide a better understanding of the influence of the position and the number of failed bonding wires on the signal integrity of the circuit and theoretical support for identifying failure features in fault diagnosis.

Advanced 650 V SiC Power MOSFETs With 10 V Gate Drive Compatible With Si Superjunction Devices

Advanced SiC planar-gate power MOSFET s have been successfully manufactured in a 6-inch commercial foundry with device structures optimized for operation with gate drive voltage of 10 V, compatible with gated drive voltage for Si superjunction products. The electrical characteristics of three advanced SiC MOSFET options are described in this article and compared with those of a state-of-the art Si superjunction MOSFET . The new advanced SiC power MOSFET s are demonstrated to exhibit superior on -state and switching losses with significantly better body-diode reverse recovery performance. Their short-circuit withstand time is also found to be significantly longer than typical commercially available planar-gate SiC power MOSFET s. These improved characteristics make the advanced SiC power MOSFET s suitable replacements for Si superjunction transistors to enhance high frequency circuit performance.

Bond characteristics and microwave dielectric properties of (Li0.5Ga0.5)2+ doped Mg2Al4Si5O18 ceramics

Cordierite ceramic is one kind of important electronic materials for radio frequency circuit. In this work, Mg2-x (Li0.5Ga0.5)xAl4Si5O18 (0 ≤ x ≤ 0.1) ceramics with pure cordierite phase, were successfully synthesized via the traditional solid state reaction method. The dependence of microwave dielectric properties on the crystal structure was analyzed in detail by the complex chemical bond theory (P–V-L theory) and classical dielectric polarizability theory. The dielectric constant (εr) was mainly related to the density, bond ionicity and ionic polarizability of Mg2-x (Li0.5Ga0.5)xAl4Si5O18 ceramics. The quality factor (Q × f) was in relationship to the lattice energy, atomic packing fraction and centrosymmetry of [Si4Al2O18] hexagonal ring in cordierite crystal structure. The temperature coefficient of resonant frequency (τf) value was dominated by the bond energy and distortions of [MgO6] octahedron. The maximum values of Q × f = 50,560 GHz and εr = 4.72 were obtained for undoped Mg2Al4Si5O18 and Mg1.98Li0.01Ga0.01Al4Si5O18, respectively.

Impact of Device Geometrical Parameter Variation on RF Stability of SELBOX Inverted-T Junctionless FINFET

In recent times, the role of FINFET devices is increasing in the field of RF-IC design for realizing the high frequency circuits. As a result, high frequency characteristics including RF stability needs to be investigated carefully. Hence this work presents the impact of device geometrical and process parameter variations on the RF stability of 20 nm SELBOX Inverted-T Junctionless FINFET (SELBOX ITJLFET). The stability factor (K), critical frequency (fk) and its dependency on small signal parameters (SSP) are investigated by varying the device and process parameters like Gate Workfunction (GWF), fin height (Hfin), fin width (Wfin), Source underlap spacer length (LUS) and SELBOX length (LG). In addition, the relation between the bias and the stability factor of the device is also studied to identify the bias operating point in a stability perspective. From the simulation results, it is found that larger the SELBOX and LUS, lower the critical frequency and thereby making the device unconditionally stable at lower frequencies. Finally, an optimized design guideline is proposed, which makes the device suitable for high bandwidth applications.

Modulation of PSSW resonance field affected by exchange stiffness A in Fe/NiFe/Fe multi-layer films with different Fe film thicknesses

Microwave devices, designed by the electromagnetic characteristics of spin waves, are widely used in radio frequency circuits and microwave systems, such as magnetic tunable filters, frequency multiplier, and signal-to-noise ratio enhancers. In order to manufacture these devices, it is not only the saturation magnetization (4πMs) and ferromagnetic resonance linewidth (ΔH) that need to be regulated, but also the exchange stiffness (A). In this study, the Fe (t nm)/Ni81Fe19 (50 nm)/Fe (t nm) multilayer films were proposed to regulate the 4πMs, ΔH, and A, which were fabricated using electron beam evaporation, and the dynamic magnetic properties of the film were studied by ferromagnetic resonance (FMR) spectroscopy. Firstly, we obtain the 4πMs, γ and Ha by fitting the uniform FMR mode. Then we obtain the exchange stiffness by fitting the first (p = 1) perpendicular standing spin wave (PSSW) mode. With the increasing Fe film thickness, the calculated saturation magnetization increased from 9250 to 14060Gs, FMR linewidth increased from 111.5 to 140.3Oe and the exchange stiffness decreased from 22.1 × 10−12 to 7.8 × 10−12J/m.

Distortion-free frequency response measurements

We propose and experimentally demonstrate a distortion-free network analyzer (DFNA) using a noise source and an average power sensor for measuring the frequency property of an electronic device. DFNA makes use of the global algorithm and therefore typically save 60% measurements than conventional network analyzer which measures frequency response locally, under the same conditions. Furthermore, conventional network analyzer could be significantly affected by distortion due to its direct point-by-point scanning manner in frequency domain. In contrast, by utilizing the coincidence measurement principle, DFNA shows strong robustness against distortion. The results demonstrate that the proposed technique provides an efficient and robust way for anti-distortion frequency response analysis and has potential applications in communications, radio frequency circuits, radar and even electronic warfare.

Optimal design of a lightweight and thin radar absorbing nanocomposite

Recently, attention to polymeric nanocomposites has gained a great extent as they present new opportunities to provide superior properties in microwave absorbing materials. In this study polystyrene (PS) nanocomposites containing various nano-fillers were successfully synthesized and employed as microwave absorbing materials. The mentioned materials are usually designed to solve protection against electromagnetic interference in wireless communication systems and high frequency circuit mechanisms. In this study the performance of three various polystyrene (PS) nanocomposites containing: semi-conductor zinc oxide, non-metallic conductive graphene oxide and magnetic Fe3O4 were compared. The fillers type was selected as variable parameter and its influence on the electromagnetic wave absorption and reflection loss (RL) amount was investigated. The scanning electron microscopy (SEM) was used in morphological and particle size study of the nanocomposites. The electromagnetic wave absorption properties of nanocomposites were studied and compared using a vector network analyzer (frequency range of 5-8 GHz). The results indicate that at the same preparation conditions the polystyrene/graphene oxide nanocomposites have higher absorption compared with others.

Analysis of DGS filters using π‐circuit model

AbstractThe design and analysis of two defected ground structures (DGS)‐based filters have been proposed in this article. The first is a multifrequency bandstop filter (BSF) which utilizes a semi‐H defect in the ground plane. This structure is then prototyped on a Rogers 4350B substrate of overall size 45 mm × 15 mm with an external SMD capacitors employed to control the resonance of the circuit for the stopband frequencies of 433, 700, and 915 MHz. An equivalent π‐circuit is modified to validate this multiband filter. The second filter is a combination of a BSF and bandpass filter in one structure. The filter operating with a controllable passband and stopband frequency is fabricated on Rogers 4350B lossy substrate. Two SMD capacitors are loaded in the filter structure to control the passband and stopband frequencies of the filter with a structure size of 20 mm x 20 mm. Finally, the equivalent circuit from the BSF is modified further to encompass the bandpass and bandstop frequency response of the proposed work.

Satellite Communications Millimeter Wave and RF Technical Analysis

This paper introduces the development status and trend of millimeter band of satellite communication. Based on the analysis of the frequency division, spectrum advantages and transmission characteristics of EHF satellite communication, the new technologies adopted in EHF satellite communication are studied, and the special technology and application of the EHF radio frequency circuit are analyzed.

Design of On chip Spiral Inductors for Millimeter Wave Frequency Synthesizers

The energy storing element, inductor plays a vital role in CMOS based high frequency integrated circuits, especially in signal generation and impedance matching blocks.An on chip inductor is considered as a critical component because its performance directly impacts the associated circuitry when it is used as a load device or as a matching element. Out of the various requirements of an inductor which resides inside a chip, the inductance value,quality factor and self resonance frequency with smaller area is often preferred. This paper focuses on the lumped model of inductors for high frequency circuits working in the Millimeter wave region from 30 GHz to 300 GHz. For millimeter wave oscillators,inductance value in the range of pico Henry are essential and hence a complete model of an inductor is presented. Using electromagnetic simulator SONNET, all the parameters are extracted. The extracted model is used in the design of an LC Oscillator for millimeter wave band. A Q factor of 26 is achieved for an inductor value close to 153 pH at 60 GHz.The circuits employing this inductor shows promising results when simulated using 45 nm CMOS pdks

RF Matching Networks Using S-Parameters

The paper presents a design and study of impedance matching for radio frequency (RF) circuit application of common-source amplifier topology. Matching networks for input and output sides of the amplifier were determined from the S-parameters given for the transistor at frequency of 2.6 GHz and ensuring unconditional stability requirement. Impedance matching is necessary in RF circuit design to provide maximum possible power transfer between the source and the load. Two designs were modeled, simulated and analyzed employing L-network input and output matching networks. The design with inductor-capacitor combination in the L-matching networks exhibited a stable and smoother behavior for higher frequencies compared to an all-inductor design. Complex tradeoffs among technology specifications and design parameters are inevitable, therefore should be carefully handled in designing the impedance matching networks, to optimize the performance of the common-source amplifier. Ultimately, the common-source amplifier achieved a gain of 6.569 dB at 2.6 GHz. For future research, physical implementations of the impedance matching networks could be studied in order to improve and optimize the simulated models.

Design and study of slow wave structure of the THz folded waveguide TWT over 60W

In this paper, the equivalent circuit method is used to analyze the dispersion characteristics of the folded waveguide and calculate the coupling impedance. The influence of the surface roughness and conductivity of the waveguide on the loss of the high frequency circuit is considered. In order to improve the efficiency of the beam wave interaction, the two kinds of slow wave structures of the folded waveguide TWT are designed by using the variable period technology. The three-dimensional electromagnetic software Microwave Tube Simulation Software (MTSS) is used to simulate the beam wave interaction of TWT. After optimization, the output power of both structures is over 60W, the electronic efficiency is more than 5.5%and the gain is greater than 32dB in the 211GHz-221GHz frequency range.

Permittivity experimental determination as a frequency function

Objective: To determine the behavior of dielectric permittivity of class II ceramic capacitor in function of frequency up to 10MHz.&#x0D; Context: in telecommunications and high frequency circuits is necessary to take into account the diminishing of permittivity on dielectrics of ceramic capacitors with the frequency growth, two quantitative methods are proposed to determine this behavior.&#x0D; Method: First, the impedance meter bridge FLUKE PM5306 was used in the frequency range from 10^2 Hz to 10^5 Hz; and second, a novel low-cost electronic circuit for the frequency range between 10^4 Hz to 10^7.&#x0D; Results: The results from the circuit were validated using the impedance meter bridge RLC FLUKE PM 6306. The measure of the complex capacitance from three capacitors and their loss tangent were obtained.&#x0D; Conclusions: The capacitance decreasing with the increment of the frequency was observed in the impedance meter bridge and the implemented circuit, finding a convergence between both methods in the common frequency region.

Improving Radar Absorbing Capability of Polystyrene Nanocomposites: Preparation and Investigation of Microwave Absorbing Properties

Microwave absorbing materials are usually designed to solve protection against electromagnetic interference in wireless communication systems and high frequency circuit mechanisms. In this research polystyrene (PS) nanocomposites containing various nano-fillers were successfully synthesized. The novelty of this work is comparing of three various nanostructures: non-metallic conductive graphene oxide, magnetic Fe3O4 and semi-conductor zinc oxide were used as additive. The effect of different fillers loading and homogenizer speed on the reflection loss (RL) amount and electromagnetic wave absorption was investigated. In order to investigate particle size and morphology of the nanostructures the scanning electron microscopy (SEM) was used. The frequency range of 5-8 GHz was employed in the investigation of electromagnetic wave absorption properties of nanocomposites using a vector network analyzer and eventually their absorption properties were analyzed and compared. The results indicate that graphene oxide has substantial effect on absorption in compare with the other nanocomposite samples. Increase of homogenizer speed led to a dispersion improvement of nanostructures and absorption. Therefore, the broadening of the microwave absorption band-width is attributed to the suitable dispersion of nanostructures in polymeric matrix.

High quality factor fractal inductor with complementary split-ring array inclusion

PurposeThis paper aims to present an efficient method to improve quality factor of printed fractal inductors based on electromagnetic band-gap (EBG) surface.Design/methodology/approachHilbert fractal inductor is designed and simulated using high-frequency structural simulator. To improve the quality factor, an EBG surface underneath the inductor is incorporated without any degradation in inductance value.FindingsThe proposed inductor and Q factor are measured based on well-known three-dimensional simulator, and the results are compared experimentally.Practical implicationsThe proposed method was able to significantly decrease the noise with increase in the speed of radio frequency and sensor-integrated circuit design.Originality/valueFractal inductor is designed and simulated with and without EBG surfaces. The measurement of printed circuit board prototypes demonstrates that the inclusion of split-ring array as EBG surface increases the quality factor by 90 per cent over standard fractal inductor of the same dimensions with a small degradation in inductance value and is capable of operating up to 2.4 GHz frequency range.

Fabrication process of integrated inductors on flexible substrate for radio frequency and microwave applications

This paper presents a fabrication process for integrated inductors on a flexible substrate using a simple and cost effective method. Kapton was the choice for the substrate due to its attractive characteristics such as thermal stability and electrical insulation. Metal layers were formed by the deposition of a thin Ni film onto the substrate as a seed for Au electroplating deposition and to improve the adhesion between the metal and the substrate. Au lines were patterned by lift-off and served as a mask for Ni wet etching. SiO2 was selected as the dielectric, also patterned by lift-off and preceded by a Cr e-beam deposition step to enhance adhesion. Inductor structures were formed by a conventional photolithography process. There was no need for substrate modification to improve metal adhesion with the use of an Ni intermediate layer. Using this process, it was possible to fabricate integrated inductors appropriate for radio frequency and microwave circuits on a flexible substrate with values compatible with those from the simulation and the literature.

Long distance measurement by dynamic optical frequency comb.

In this paper, we propose a method aiming to measure the absolute distance via the slope of the inter-mode beat phase by sweeping the repetition frequency of the frequency comb. The presented approach breaks the inertial thinking of the extremely stable comb spacing, and the bulky phase-locking circuit of the repetition frequency is not required. In particular, the non-ambiguity range can be expanded to be infinite. To verify the performance of presented method, a series of distance experiments have been devised in different scenarios. Compared with the reference values, the experimental results show the differences within 25 µm at 65 m range in the laboratory, and within 100 µm at 219 m range out of the lab.

Design of C-band Low-noise Amplifier (LNA) Using E-pHEMT Device for Satellite Communication System

A low-noise amplifier (LNA) plays an indispensable role in a communication system for amplification purposes at the transceiver. LNA design in radio frequency (RF) circuits involve various key attributes, namely noise figure (NF), gain, and power consumption. This paper focuses on the design of a C-band LNA for satellite communication system with a centre frequency of 6 GHz using ATF-55143 enhancement-mode pseudomorphic high-electron-mobility transistor (E-pHEMT) technology. The LNA performance is augmented by adding inductors to the drain and gate of the ATF-55143 transistor. Smith chart impedance matching technique is implemented to foster a more precise matching for input and output of the LNA. In this work, the C-band LNA is biased at VDS of 2.7 V and IDS of 10 mA. Electromagnetic (EM) software is used to design and simulate the performance of the LNA circuit layout. Simulation results indicate NF of 2.66 dB and power gain (S21) of 12.29 dB. The LNA consumes 27 mW from a 3 V DC supply.