Spiral Inductors Research Articles

Designing Surface Chemistry of Silver Nanocrystals for Radio Frequency Circuit Applications.

We introduce solution-based, room temperature- and atmospheric pressure-processed silver nanocrystal (Ag NC)-based electrical circuits and interconnects for radio frequency (RF)/microwave frequency applications. We chemically designed the surface and interface states of Ag NC thin films to achieve high stability, dc and ac conductivity, and minimized RF loss through stepwise ligand exchange, shell coating, and surface cleaning. The chemical and structural properties of the circuits and interconnects affect the high-frequency electrical performance of Ag NC thin films, as confirmed by high-frequency electromagnetic field simulations. An all solution-based process is developed to build coplanar structures, in which Ag NC thin films are positioned at both sides of the substrates. In addition, we fabricated flexible transmission lines and broadband electrical circuits for resistors, interdigitated capacitors, spiral and omega-shaped inductors, and patch antennas with maximum inductance and capacitance values of 3 nH and 2.5 pF at frequencies up to 20 GHz. We believe that our approach will lead to a cost-effective realization of RF circuits and devices in which sensing and wireless communication capabilities are combined for internet-of-things applications.

Area and Power Efficient Ultra-Wideband Transmitter Based on Active Inductor

This brief presents the design of an impulse radio ultra-wideband (IR-UWB) transmitter for low-power, short-range, and high-data rate applications such as high density neural recording interfaces. The IR-UWB transmitter pulses are generated by modulating the output of a local oscillator. The large area requirement of the spiral inductor in a conventional on-chip LC tank is overcome by replacing it with an active inductor topology. The circuit has been fabricated in a UMC CMOS 180-nm technology, with a die area of 0.021 mm2. The temporal width of the output waveform is determined by a pulse generator based on logic gates. The measured pulse is compliant with federal communications commission power spectral density limits and within the frequency band of 3–6 GHz. For the minimum pulse duration of 1 ns, the energy consumption of the design is 20 pJ per bit, while transmitting at 200-Mbps data rate with an amplitude of 130 mV.

Comparative Study of the Accuracy of Analytical Inductance Formulae for Square Planar Spiral Inductors

In the design of radio frequency (RF) microelectronic integrated circuits (IC’s) and of antennas for short-wave radio frequency identification (RFID) and telemetry systems, planar spiral coils are important components. Many approximate analytical formulae for calculating the inductance of such coils can be found in the literature. They can simplify the problem of designing inductors to a predefined inductance considerably. But the error statistics given by different authors cannot be compared because they are based on different or unknown domains of definition. Hence, it is not possible to decide which formula is best in a given case by merely studying the literature. This paper compares the maximum relative errors of six of some of the most cited formulae in the literature. To all formulae, the same domains of definition are applied. Each of them spans all four dimensions of the parameter space. Precise inductances are obtained numerically with the help of the free scientific and industrial standard software FastHenry2 and used as reference values to calculate the errors of the formulae. It has been found that the alleged maximum errors reported by some authors are far too optimistic. Only two formulae feature small enough errors to be useful in circuit design. The method and the domains of definition applied in the present study may also prove useful for the assessment of future formulae.

Increasing sensing distance of passive wireless IOP sensor

Continuous intraocular pressure monitoring is very necessary for glaucoma patients. In this paper, a passive wireless intraocular pressure (IOP) sensor using an inductively coupled wireless sensing technique is presented. IOP sensor is consist of a multipath circular spiral coil inductor, variable capacitor and a SU-8 pressure sensitive diaphragm. Capacitor and inductor of sensor are made of high-conductivity and biocompatible metal gold that are encapsulated inside biocompatible SU-8 to prevent damage to eye tissue. By measuring impedance phase dip frequency shift from the external reader coil, the intraocular pressure signal is obtained from the IOP sensor. Small size of the sensor coil due to the biological constrains reduces the sensing distance. The purpose of this paper is increasing the quality factor of sensor coil using the multipath technique in order to enhancement of sensing distance. Simulation has been taken using COMSOL Multiphysics and ADS software. The proposed structure, due to its small size could increase the sensing distance. The dimension of proposed wireless sensor and sensing distance is $$ 2.5\;{\text{mm }} \times 2.5\;{\text{mm}} $$ and 2 cm, respectively, that has a larger sensing distance and smaller size compared with previous works and its sensitivity is 4281 ppm/mmHg.

A High-Frequency-Compatible Miniaturized Bandpass Filter with Air-Bridge Structures Using GaAs-Based Integrated Passive Device Technology.

This paper reports on the use of gallium arsenide-based integrated passive device technology for the implementation of a miniaturized bandpass filter that incorporates an intertwined circle-shaped spiral inductor and an integrated center-located capacitor. Air-bridge structures were introduced to the outer inductor and inner capacitor for the purpose of space-saving, thereby yielding a filter with an overall chip area of 1178 μm × 970 μm. Thus, not only is the chip area minimized, but the magnitude of return loss is also improved as a result of selective variation of bridge capacitance. The proposed device possesses a single passband with a central frequency of 1.71 GHz (return loss: 32.1 dB), and a wide fractional bandwidth (FBW) of 66.63% (insertion loss: 0.50 dB). One transmission zero with an amplitude of 43.42 dB was obtained on the right side of the passband at 4.48 GHz. Owing to its miniaturized chip size, wide FBW, good out-band suppression, and ability to yield high-quality signals, the fabricated bandpass filter can be implemented in various L-band applications such as mobile services, satellite navigation, telecommunications, and aircraft surveillance.

Design and Realization of a Compact High-Frequency Band-Pass Filter with Low Insertion Loss Based on a Combination of a Circular-Shaped Spiral Inductor, Spiral Capacitor and Interdigital Capacitor

In this study, the proposed bandpass filter (BPF) connects an interdigital and a spiral capacitor in series between the two symmetrical halves of a circular intertwined spiral inductor. For the mass production of devices and to achieve a higher accuracy and a better performance compared with other passive technologies, we used integrated passive device (IPD) technology. IPD has been widely used to realize compact BPFs and achieve the abovementioned. The center frequency of the proposed BPF is 1.96 GHz, and the return loss, insertion loss and transmission zero are 26.77 dB, 0.27 dB and 38.12 dB, respectively. The overall dimensions of BPFs manufactured using IPD technology are 984 × 800 μ m 2 , which is advantageous for miniaturization and integration.

A Fundamental Approach for Design and Optimization of a Spiral Inductor

A Fundamental Approach for Design and Optimization of a Spiral Inductor

Design Equations for Spiral and Scalable Cross Inductors on 0.35 μm CMOS Technology

This paper presents a set of design equations for spiral and new scalable cross inductors in CMOS 0.35 μm technology, relating electrical parameters of the inductor’s equivalent circuit as functions of its geometric dimensions. The procedure used to derive the design equations is described and involves electromagnetic simulation of inductors with different geometric dimensions, extraction of values for equivalent circuit model elements for each inductor and the use of multivariate regression analysis applied to generalized linear models (GLM) based on design of experiments (DoE). A p-type nine elements equivalent electrical circuit was used for the inductors, where all elements values are constants, allowing simulation on SPICE-like softwares. Results from the models obtained for both spiral and scalable cross inductors presented close match to the simulated results.

Integrated passive wireless pressure and temperature dual-parameter sensor based on LTCC technology

This paper presents a kind of passive wireless pressure and temperature integrated inductor-capacitor (LC) resonant sensor based on low temperature co-fired ceramic (LTCC) technology. The pressure sensing part is dependent on a traditional cavity capacitor. The temperature sensing part is composed of an interdigital capacitor and a planar spiral inductor. The capacitance and the resistance of inductor coil would change as a response to temperature. The LTCC material with a low Young's modulus of ~65 GPa prepared by our laboratory was used to obtain high pressure sensitivity. The experimental results showed that the prepared sensor has a pressure sensitivity of 1.16 kHz/kPa, and a temperature sensitivity of 0.062% dB/°C within the range of 140–850 kPa, 50–500 °C, respectively.

Area Efficient Dual-Fed CMOS Distributed Power Amplifier

In this paper, an area-efficient 4-stage dual-fed distributed power amplifier (DPA) implemented in a 0.35 μm Complementary Metal Oxide Semiconductor (CMOS) process is presented. To effectively reduce the area of the circuit, techniques such as using multilevel inductors and closely-placing conventional spiral inductors are employed. Additionally, a novel technique based on stacking inductors one on top of others is implemented. Based on these techniques, a 32% area reduction is achieved compared to a conventional design without a noticeable performance degradation. This reduction could be further exploited as the number of stages of the dual-fed DPA increases.

Radio-Frequency Capacitive Gate-Based Sensing

Developing fast, accurate and scalable techniques for quantum state readout is an active area in semiconductor-based quantum computing. Here, we present results on dispersive sensing of silicon corner state quantum dots coupled to lumped-element electrical resonators via the gate. The gate capacitance of the quantum device is configured in parallel with a superconducting spiral inductor resulting in resonators with loaded Q-factors in the 400-800 range. For a resonator operating at 330 MHz, we achieve a charge sensitivity of 7.7 $\mu$e$/\sqrt{\text{Hz}}$ and, when operating at 616 MHz, we get 1.3 $\mu$e$/\sqrt{\text{Hz}}$. We perform a parametric study of the resonator to reveal its optimal operation points and perform a circuit analysis to determine the best resonator design. The results place gate-based sensing at par with the best reported radio-frequency single-electron transistor sensitivities while providing a fast and compact method for quantum state readout.

Flexible Tri-Axis Tactile Sensor Using Spiral Inductor and Magnetorheological Elastomer

This paper describes a flexible and soft tactile sensor that measures the tri-axis force based on inductance measurement. The proposed sensor has four spiral inductors printed on a flexible circuit board and a mounted cylindrical elastomer (silicon rubber). A disk-shaped magnetorheological elastomer (ferromagnetic marker) is embedded in the cylindrical elastomer and its 3-D displacement is estimated by monitoring the inductance changes of the four inductors. In this paper, we investigated the relationship between the applied tri-axis force and inductance changes. Our results can be summarized as follows: 1) the inductance changes of the four inductors were monotonic and linear against the applied normal and shear force; 2) the applied tri-axis force could be estimated well with linear functions of the sum and difference of the measured inductances; and 3) the estimation error of the tri-axis force increased when a larger force was applied and/or faster contact speeds were used.

Design and analysis of a three-dimensional millimeter-wave frequency-shift based CMOS biosensor using vertically stacked spiral inductors in LC oscillators

This paper proposes a novel millimeter-wave frequency-shift based CMOS biosensor capable of providing three-dimensional (3D) resolution. The vertical resolution from the sensor chip surface can be obtained by using vertically stacked on-chip inductors of LC oscillators in dual metal layers, which enables 3D detection of biomolecular target. The LC oscillators with spiral inductors stacked in upper and lower metal layers produce different shifts in the frequencies from the desired resonant frequency of 60 GHz due to frequency dependent complex relative permittivity of targeted bio-molecular structure. The vertical resolution of the sensor can also be improved by changing the supply voltage. The effectiveness of the proposed approach is verified by fabricating a test chip in 65 nm CMOS process. The measurement results show variation in the resonant frequency shifts due to upper and lower spiral inductors of LC oscillators which demonstrates the capability of the proposed biosensor to provide 3D resolution.

Design and Characterization of Inductors for Self-Powered IoT Edge Devices

This paper discusses the design, fabrication, and characterization of packaged planar inductors with magnetic material [nickel zinc (NiZn) ferrite]. Inductors are designed specifically for Internet of Things (IoT) applications based on power loss in an IoT architecture. Different spiral inductor geometries are demonstrated on a printed wiring board with varying thicknesses using a stencil printing process. The magnetic material can be applied to one or both sides of the inductor and, therefore, provides size reduction. This paper examines the role of varying dimensions on inductor performance along with model-to-hardware correlation. The fabrication process demonstrates inductance increase through a very simple procedure for applying a magnetic material on both sides of the inductor, while having flexibility to customize the geometry for minimal power loss in an IoT architecture. With NiZn ferrite material added to both sides of the inductor, the inductance increases between approximately 60% and 80% for the two substrate thicknesses studied, as compared to air-core inductors.

A novel monofilar‐Archimedean metamaterial inspired leaky‐wave antenna for scanning application for passive radar systems

AbstractA novel backfire‐to‐endfire leaky‐wave antenna is presented with ability to scan from −25° to +45°. The antenna is based on metamaterial transmission‐lines and is implemented using monofilar Archimedean spiral and rectangular slots, spiral inductors, and metallic via‐holes. The slots act as series left‐handed capacitances, and the spirals with via‐holes provide the shunt left‐handed inductances to realize the metamaterial antenna. A prototype antenna was fabricated prototype on FR4 dielectric substrate, which has an electrical size of 0.0302λ0 × 0.0357λ0 × 0.0008λ0, where λ0 is free space wavelength at 165 MHz. Measured bandwidth of the antenna is 710 MHz (165–875 MHz) corresponding to a fractional bandwidth of 136.5%. The main advantage of the antenna is its ability to scan over a wide angle from −25° to +45° with acceptable gain and radiation efficiency of 1.2 dBi and 50.1%, respectively, measured at 400 MHz. The wide scanning attributes of the antenna make it suitable for passive radar applications to scan across the VHF–UHF bands for FM‐Radio, television, mobile phones, and GPS applications.

Design of small size and high sensitive less‐invasive wireless blood pressure sensor using MEMS technology

This study presents an implantable passive wireless blood pressure sensor using an inductive coupling wireless sensing technique that is designed for long-term monitoring of blood pressure in hypertension patients. This sensor includes a gold tapered square spiral inductor and a circular capacitor with a polyimide diaphragm. The purpose of this study is to minimise the dimension of the sensor due to the limitation of space around the vessel; therefore, a microelectromechanical systems (MEMS) inductor and a capacitor with small dimension and high sensitivity are used. In this structure, the diaphragm is deflected by applied pressure which capacitance and then resonance frequency are changed. These changes are sensed remotely with inductive coupling, which eliminates the need of wires connection for monitoring. In this method, a blood pressure signal can be obtained by measuring the impedance phase dip from the external coil. The distance between two coils is 8 mm. The sensor is designed to provide a resonance frequency range of 282-381 MHz for a pressure range of 0-250 mmHg. Simulation has been done using COMSOL Multiphysics and ADS software. The dimension of the sensor is 2.2 mm × 2.2 mm and the sensitivity of the sensor is 1550. This sensor has a small size and high sensitivity rather than previous works.

Micro-Fabricated Resonator Based on Inscribing a Meandered-Line Coupling Capacitor in an Air-Bridged Circular Spiral Inductor.

This letter presents a high-performance micro-fabricated resonator based on inscribing a meandered-line square coupling capacitor in an air-bridged circular spiral inductor on the GaAs-integrated passive device (IPD) technology. The main advantages of the proposed method, which inserts a highly effective coupling capacitor between the two halves of a circular spiral inductor, are the miniaturized size, enhanced coupling coefficient, and improved selectivity. Moreover, using an air-bridge structure utilizes the enhanced mutual inductance in which it maximizes the self-inductance by a stacking inductor layout to obtain a high coupling effect. The simulated and measured S-parameters of a prototype resonator with an effective overall circuit size of 1000 µm × 800 µm are in good agreement. The measured insertion and return losses of 0.41 and 24.21 dB, respectively, at a measured central frequency of 1.627 GHz, as well as an upper band transmission zero with a suppression level of 38.7 dB, indicate the excellent selectivity of the developed resonator.

Analysis and Design of High-Frequency Converter With Resistive Matching Network and Spiral Inductor

In this paper, two resistive matching networks are proposed, which can maintain the resistive transferring property under different load conditions. The high-frequency converter based on the resistive network can adequately achieve the soft-switching characteristics within a large load variation range, which helps to reduce switching losses and improve system efficiency. At the same time, a detailed design method for planar spiral inductor is described. In addition, the quality factor characteristics of different winding structures are analyzed. A 20-MHz high-frequency dc/dc converter based on the T-type matching network and circular spiral inductor is designed in this paper. The experimental results verify the advantages of the proposed resistive matching network and spiral inductor.

Integrated Very-High-Frequency Switch Mode Power Supplies: Design Considerations

This paper presents a power supply using an increased switching frequency to minimize the size of energy storing components, thereby addressing the demands for increased power densities in power supplies, and 100-MHz and higher switching frequencies have been used in resonant power converters, which along with the possible integration of passive components on silicon wafer present a beneficial solution in applications such as mobile phones. This paper presents a design for a 9-W class E resonant power converter in a 0.18- $\mu \text{m}$ CMOS process. The converter is driven by a self-oscillating gate drive, which is presented in an in-depth mathematical analysis. The gate resistance of the designed transistors is of critical importance in order to achieve the correct phase shift required for zero voltage switching. The Z-parameter method is used to characterize the transistors, which is verified through simulations. The required spiral inductors were modeled, and simulations show $Q$ values of as high as 14 at a switching frequency of 250 MHz. Simulations of the converter show an efficiency of 55% with a self-oscillating gate drive. However, the modeled inductor was not adequate for operating with the self-oscillating gate drive, presenting a future challenge for power supplies on chip.

Circularly polarize antenna array for electromagnetic energy harvesting

Electromagnetic energy harvesting from ambient sources have been presented more than 50 years. In this paper, electromagnetic energy harvesting by using circular polarize antenna array is presented. The proposed antenna is having 2 similar size of spiral inductor that feed by microstrip feed line. The gain, momentum visualization were investigated. The circular polarize antenna are fabricated on Roger 4003 substrates. Based on the observations, it is expected that the gain obtained by the antenna array is higher than the single element antenna. The simulation results show that 3.22 dBi gain can be achieved for single spiral antenna whereas the antenna array can achieved as high as 5.14dBi at frequency 527MHz. The work concluded that investigations of electromagnetic energy harvesting antenna array is successful.