Octagonal Inductors Research Articles

Numerical Simulation for Cooling of Integrated Toroidal Octagonal Inductor Using Nanofluid in a Microchannel Heat Sink

This paper presents a comprehensive numerical simulation study focused on the cooling of integrated toroidal octagonal inductor using nanofluids within a microchannel heat sink. The investigation utilizes COMSOL Multiphysics 6.0 integrated with the Fluid Flow and Conjugate Heat Transfer Module. The primary objective is to explore and understand fluid flow and heat transfer characteristics within the integrated inductor. The study involves testing three distinct fluids, water, CuO-water nanofluid, and Al2O3-water nanofluid, under laminar flow conditions within microchannels. The choice of fluid plays a significant role in heat transfer, interacting with the microchannel geometry to optimize performance. Three-dimensional computational fluid dynamics (CFD) models are meticulously developed; focusing on toroidal inductors equipped with micro pin fins heat sinks. The study commences by detailing the geometry of the micro coil and the integrated heat sink. The simulation encompasses a mathematical model that captures the intricate interplay between the governing Navier-Stokes equations for fluid dynamics and the heat transfer equations within the integrated inductor. As φ increases, temperature, viscosity, and pressure decrease. CuO-water and Al2O3-water nanofluids play a significant role in influencing laminar flow and key thermal parameters in the toroidal inductor. These nanofluids, which consist of base fluids (water) with dispersed nanoparticles (CuO or Al2O3), are employed as cooling agents to enhance heat transfer. The presence of nanoparticles in the fluid alters its thermal properties, leading to changes in the flow dynamics and overall heat dissipation within the toroidal inductor.The laminar flow characteristics are affected by the nanofluid's viscosity, density, and thermal conductivity. Additionally, the Nusselt number, Reynolds number, and thermal resistance are key thermal parameters that reflect the performance of the cooling system. The nanofluid's influence on these parameters is crucial for understanding and optimizing the thermal management of the integrated toroidal inductor. The enhancement of heat dissipation in the toroidal inductor is achieved through improved thermal properties of the nanofluid. Higher nanoparticle concentrations result in better heat transfer rates, leading to lower temperatures in the toroidal inductor. This, in turn, improves the overall efficiency and performance of the cooling system. The viscosity of the nanofluid is influenced by the presence of nanoparticles. The pressure within the microchannels is also affected by the nanoparticle concentration. An increase in φ can lead to changes in pressure drop along the microchannels. Understanding these variations is crucial for designing an effective cooling system.

Integrated Inductor Layout Optimization for Synthesis of Microwave LC-Filters in Si/SiGe/GaAs Systems on a Chip

The paper proposes models of planar symmetric octagonal inductors that differ in the method of inductance calculating and consideration of the structure and characteristics of the technological process. The equations in a closed form for calculating models of integral planar inductors of various configurations are derived. The models were verified by comparing the frequency response of the developed 14-18 GHz bandpass filter model with the frequency response of experimental samples produced in the SiGe 130 nm process. The AFC of the produced filter samples is in the range of the developed filter model AFCs at the extreme points of the manufacturing tolerance. The developed algorithm of optimization for integral planar inductors layouts according to the criterion of maximum quality factor at the required frequency is presented. The use of the developed algorithm for integral planar inductors layouts optimization makes it possible to synthesize integrated LC-filters in Si, SiGe and GaAs technological processes with minimal passband losses and maximum gain slopes. The optimization algorithm is implemented as the program in the MathCad software. The optimal inductor layout calculation according to the criterion of maximum quality factor in the program takes tens of seconds a few minutes depending on the technological process structure complexity.

Enhancing on-chip performance of single-turn octagonal inductor at millimeter wave and Sub-THz frequencies through grounded guard ring optimization

The performance dependence of a single-turn octagonal inductor on its guard ring spacing at millimeter-wave (mm-wave) and sub-THz frequencies is investigated in this paper. The typical range of inductance that is employed in RFIC circuit designs at these frequencies is in the order of a few tens to a few hundreds of picohenries (pH). This paper shows that for such inductors at mm-wave/sub-THz frequencies, the quality factor (Q) is affected by the spacing of the guard ring (Sg) around it. At certain frequencies the Q sharply drops. This behavior is not typically seen at lower GHz-range frequencies and hence the guard ring design has not been critically studied. The coupling between the inductor and the guard ring surrounding it is observed to have magnetic resonant behavior and hence results in sharp reduction in Q at certain frequencies. The observed phenomenon is correlated to the theoretical framework developed for understanding this phenomenon including model and necessary equations. The dependence of quality factor on the guard ring current is modeled. An empirical model is also proposed to identify the frequency at which the sharp reduction in Q occurs. The impact of Sg on the inductors is relatively less pronounced for large-sized inductors. The Inductance (L) and Self Resonant Frequency (fSR) are shown to remain unaffected with changes in guard ring spacing. Guidelines, along with an example, are provided for determining optimal guard ring spacing for inductors operating at millimeter-wave/sub-THz frequencies.

RF performances at cryogenic temperature of inductors integrated in a FDSOI technology

This paper investigates the RF performances of octagonal inductors integrated in a Fully Depleted Silicon On Insulator (FD-SOI) technology at cryogenic temperature. The RF performances characterization of passive and active components is a first necessary step towards the design of RF circuits optimized for cryogenic CMOS applications. Among passive components, inductors are key to design low noise amplifier needed for instance in qubits read-out circuit. First, the experimental set-up and the experimental protocol is presented in detail. Then inductance with 0.5nH to 4nH values are characterized in frequency from room temperature down to 4.2 K and modelled by a lumped elements circuit. We used a simple RLC circuit to describe the self-resonance behaviour. A calculation is proposed for the inductance and the capacitance, whereas the resistance is extracted by DC measurements. This circuit description is improved by including coil proximity and skin effects. We observed that the quality factor is improved by a factor of two at low temperature, thanks to the metal resistivity decreases, in qualitative agreement with DC measurements. We also discussed the limits of the proposed model.

Divide‐by‐2 injection‐locked frequency divider exploiting an 8‐shaped inductor

AbstractThis letter presents a wide‐band 2:1 injection‐locked frequency divider (ILFD) in the 0.18 μm BiCMOS process with circuit model of class‐AB. The ILFD uses an 8‐shaped inductor in shunt with parasitic capacitors as the resonator, and it also employs two capacitive cross‐coupled pairs to generate negative resistance for oscillation. The gate biases of capacitive cross‐coupled pairs are fully utilized to tune the free‐running ILFD oscillation frequency. At the power consumption of 2.064 mW and the input power of 0 dBm, the locking range frequency is 71.3% (from 3.7 to 7.8 GHz) and the figure of merit (FOM) is 34.54. As compared to other ILFDs using octagonal inductors, this ILFD has low EM radiation level and less sensitivity to received EM noise.

4.02-5.48 GHz wideband VCO with coupling reduction and small Kvco variation

ABSTRACT A wideband voltage-controlled oscillator (VCO) with coupling reduction and small VCO gain () variation has been fabricated for multi-standard RF transceivers. A high-quality factor 8-shaped inductor is adopted to reduce the magnetic coupling between inductors and optimise the phase noise of the VCO. Electromagnetic simulations of magnetic coupling are carried out between an octagonal inductor and an 8-shaped inductor, and as high as 36 dB reduction in magnetic coupling is achieved by using 8-shaped inductors. A novel varactor group is proposed to realise a constant in the fine-tuning process, in which the scheme adopts an inversion-mode MOS varactor to revise the capacitance variation of an accumulation-mode MOS varactor. Meanwhile, an extra 3-bit varactor array is employed to reduce variation in the coarse tuning process. Based on a conventional TSMC 0.18-μm CMOS process, a nearly constant of 58 MHz/V is obtained for a wide frequency range of 4.02 to 5.48 GHz. The proposed VCO achieves a phase noise of less than −119.8 dBc/Hz at 1 MHz offset. The current consumption is 4.3–8.8 mA under a source voltage of 1.8 V.

Simulation and implementation of CMOS 8:1 LC‐tank injection‐locked frequency divider

AbstractThis letter simulates and measures a wide locking range LC‐resonator injection‐locked frequency divider (ILFD) designed in the TSMC 0.18 μm process. The balanced‐injection 8:1 ILFD uses a current‐mode design method with one 2:1 p‐core LC sub‐ILFD and one 4:1 n‐core LC sub‐ILFD with wide locking range. The 4:1 sub‐ILFD uses a 5‐turn symmetric octagonal inductor and two 4‐turn inter‐wound transformers and parasitic capacitors to build the LC‐resonator. The primary and the secondary inductors in the 1:1 transformer are identical for simple design. At the core power consumption 9.537 mW and at the incident power of 0 dBm, the measured 8:1 locking range is 1.11 GHz, from the incident frequency 16.83 to 17.94 GHz. The whole CMOS die occupies an area of 0.931 × 1.2 mm2. The simulated 8:1 sub‐ILFD also has wide locking range.

An Analytical Scalable Lumped-Element Model for GaN on Si Inductors

In this paper, a wide-band distributed model that can approximate the behaviour of square and octagonal inductors, both with and without tapering, is presented. This paper also presents a novel way of accurately modelling the lateral coupling in the substrate. The presented model can be applied to any foundry process, and its validity has been demonstrated using a novel technology, the D01GH GaN process developed by OMMIC, which has a high resistivity substrate. To do so, seventeen inductors have been designed and manufactured. The proposed model has been verified against EM simulations and measurements of the designed inductors. Comparisons show that the model can correctly estimate the behaviour of the inductor, improving the results of the EM simulations for most cases. The root mean square (RMS) error calculated across the samples when estimating the inductance is 0.0565. The RMS error for the quality factor results (2.2727) is also adequate, although there is more deviation when comparing the results with the measurements.

Design and modeling of integrated octagonal shape inductor with substrate silicon in a buck converter

The paper discusses the design and modeling of an integrate octagonal shaped inductor with silicon substrate. A validated equivalent electrical model of the integrated octagonal shaped spiral inductor is developed. The model is used to analyze and evaluate the quality factor and the inductance of the inductor structure proposed under different physical parameters setting. These include the number of turns, spacing between turns and the inner diameter. The simulation results show that an appropriate selection of physic a parameters can achieve an enhanced quality factor and improved inductance. PSIM simulator is used for the implementation of the integrated inductor in a micro buck converter. The simulation results demonstrate that our proposals are very promising approaches for the monolithic integration of DC-DC converters.

RFIC 설계에 응용 가능한 90nm 공정 기반 인덕터의 Quality factor 및 Effective inductance 분석

본 논문에서는 RFIC 설계에 응용 가능한 인덕터의 Quality factor 및 Effective inductance를 비교 분석하기 위해 Octagonal 인덕터를 90nm CMOS 공정을 이용하여 제작하였다. 내부반경을 설계변수로 갖는 인덕터의 경우 내부반경이 증가함에 따라 Quality factor가 감소하고 Effective inductance의 값이 증가하였다. 회전수를 설계변수로 갖는 인덕터의 경우 금속의 회전수가 증가함에 따라 Quality factor의 값이 감소하고 Effective inductance의 값이 증가하는 것을 확인하였다. 따라서 RFIC 회로 설계에 있어서 인덕터의 구조는 Q-factor 및 inductance 각각의 상대적 중요도에 따라 선택 되어져야 된다고 할 수 있다.

A comparative evaluation of de‐embedding methods for on‐wafer RF CMOS inductor S‐parameter measurements

AbstractThe impact of existing de‐embedding methods applied on on‐wafer RF s‐parameter measurements to evaluate the characteristics of CMOS integrated inductors is examined. Probe pad and metal interconnect line associated parasitic elements need to be removed (de‐embedded) from on‐wafer measurements of inductors fabricated on silicon substrates for proper evaluation of inductor characteristics, such as inductance, quality factor and resonance frequency. For this purpose a chip was fabricated in 0.5 μm CMOS TM1P twin‐tub AMIS technology (Figure 1), with octagonal and spiral inductors and various types of dummy structures, such as different types of open, and short structures as well as a thru structure. The dummy structures are necessary in order to extract the parasitic element components. The Device‐under‐Test (DUT) was a 3.5 turn octagonal inductor of line width 12 μm, spacing 2 μm and external diameter of 160 μm. Existing de‐embedding methods include the open‐short de‐embedding method, a three‐step de‐embedding method, a pads‐short‐open (psod), and a modified four‐step de‐embedding method. These methods have been tested mostly for small devices such as MOS transistors. The impact of each de‐embedding method on inductor characteristics extraction is evaluated and results show differences in the order of 36% for the value of peak quality factor and a maximum difference of 9% for the resonance frequency. The comparative evaluation of the existing de‐embedding methods is based on results extracted from measured S‐parameter data for measurements up to 20 GHz, as well as on results obtained by using the HFSS EM simulator. Based on the results, the modified four‐step method is the most accurate method, and a discussion of improvements to further increase the accuracy of the de‐embedding is done, for a precise characterization of the DUT. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Physics-based wideband predictive compact model for inductors with high amounts of dummy metal fill

A computationally efficient physics-based wideband predictive inductor compact model is presented that is capable of evaluating the impact on inductance and quality factor of dummy metal fill-cells. In a modern integrated-circuit process, high amounts of these fill-cells are required to meet metal density rules and guarantee adjacent circuit integrity. The predictions made with this model are shown to be in agreement with data measured on symmetrical octagonal inductors realized in a 90-nm CMOS process with varying amounts of dummy metal fill-cells. We further provide all inductance equations, list additional sources of eddy current losses, and discuss layout modifications, which would further improve the performance of the integrated inductors

Local scalable description of global characteristics of various on-chip asymmetrically octagonal inductors

We present a parametric investigation of various groups of on-chip asymmetrically octagonal inductors on silicon substrates. The inductors have different numbers of turns, strip widths, spacings, outer dimensions, and inner radii. Using two-port S parameters measured by a deembedding technique, we derive some local scalable formulas for extrapolating Q factor, resonance frequency, inductance, overlapping, and oxide capacitances of these octagonal inductors with different geometries. The effects of all geometric parameters on Q factor and so forth are explored, analyzed, and compared with each other in detail.