Symmetrical Spiral Inductors Research Articles

An Electromagnetic Bandgap Structure Integrated With RF LNA Using Integrated Fan-Out Wafer-Level Package for Gigahertz Noise Suppression

This paper presents a periodic electromagnetic bandgap (EBG) structure in the integrated fan-out wafer-level package (InFO-WLP) technology for gigahertz-band noise suppression. The proposed EBG structure consists of an $LC$ resonator with two symmetrical spiral inductors in series and a shunt metal–insulator–metal capacitor between power and ground planes. The third-order equivalent model of the EBG structure is also proposed and extracted by field solver ANSYS Q3D to model the performance. In addition, the EBG arrays with different sizes of unit cell and the corresponding stopband bandwidth and isolation were characterized. The measurement results show that the proposed $1 \times 4$ EBG array of 600- $\mu \text{m}$ square unit cell can achieve a 29.5-GHz stopband bandwidth together with an over 30-dB isolation level. Furthermore, by using the InFO-WLP technology, the proposed EBG structure is integrated with an RF low-noise amplifier (LNA) fabricated in a 16-nm FinFET technology as a case study to validate the power noise immunity. The experimental results show that the measured output spectrum of LNA integrated with the proposed EBG structure at the power plane can suppress the noise tone from −37.37 to −68.65 dBm.

Design of MCI single and symmetrical on-chip spiral inductors**Project supported in part by the National Natural Science Foundation of China (No. 61401101), the Anhui Provincial Natural Science Foundation (Nos. 1408085QF122, 1608085QF159), the Open Research Program of State Key Laboratory of Millimeter Waves, Southeast University (No. K201401), and the Anhui Provincial Outstanding Top-notch Talent Cultivation Project (No. gxfxZD2016164).

In this paper, the MCI (multipath crossover interconnection) technique for octagon single and symmetrical spiral inductors has been presented to improve the quality factor. The metal wires of the single and symmetrical inductors formed by the top metal are divided into multiple segments according to the depth of the skin effects. The outermost path of the metal is crossover-interconnected to the innermost path by the underlayer metal and via The crossover technique makes the lengths of the total current paths between two ports approximately equal to each other. Therefore, the induced magnetic flux and resistance of each path can be balanced and the Q-factor of spiral inductors can be enhanced. The proposed MCI technique has been validated by the electromagnetic simulation with the 130-nm 1P6M SiGe BiCMOS process. For the devices with occupying areas of 240 × 240 μm, results of electromagnetic simulation show that about 24% improvement in the Q-peak (3.3 GHz) of the MCI single inductor as compared to conventional single inductors (3.1 GHz), and about 88.1% improvement in the Q-peak (3.2 GHz) of the MCI symmetrical inductor as compared to conventional symmetrical inductors (1.8 GHz).

Symmetrical Spiral Inductor-Coupled Bandpass Filter with a Stepped-Down Metal Width

A compact microstrip symmetrical rectangular spiral inductor-coupled bandpass filter using a variable stepped-down metal width is presented. The proposed filter is based on an electromagnetic coupling between two symmetrical spiral turns with variable metal widths and spacing. The asymmetrical port terminals are coupled to the main inductor–resonators as a new coupling scheme using two narrow tuning stubs. The coupling scheme of the ports with the stubs maintains the 50 Ω impedance matching with input and output devices. The two symmetrical spiral inductors in the design structure are precisely mounted and adjusted together with equal spacing and gaps, so that the combined configuration behaves as a single resonator as inductor–interdigital coupling. The structure of combining two such resonators enables strong inductive coupling and effective capacitive coupling between the two ports and generates a resonant frequency of 5.597 GHz. The measured insertion loss (S21) was −0.93 dB, and the measured return loss (S11) was −24.4 dB.

Microstrip Symmetrical Twin-Spiral Inductor Resonator Filter for UWB Applications

This paper presents a novel microstrip type double symmetrical twin-square-shaped spiral inductor resonator bandpass filter for ultra wideband (UWB) applications. The power transformation from port to port is achieved by utilizing electromagnetic coupling phenomena between two symmetrically opposite mounted twin-spiral inductors. The inductor resonator filter is based on self-resonance frequency of the symmetrical spiral inductors and electromagnetic coupling between them. The two twin-symmetrical spiral inductors are connected with stepped-impedance-resonator (SIR) ports for 50 Ω impedance matching. This microstrip symmetrical twin-spiral inductor resonator type filter is resonated at 5.1 GHz frequency. In the experiment, the insertion loss (S21) and the return loss (S11) were measured −0.34 and −26.8 dB, respectively. The proposed compact inductor resonator filter exhibits a significant size reduction compared to existing distributed filter topologies and it can be used for terrestrial microwave UWB applications.

A miniature CMOS VCO with symmetric trace differential stacked spiral inductor

In this study, a miniature silicon-based symmetric trace differential stacked spiral inductor (SDSSI) was used in the design of a voltage controlled oscillator (VCO) using standard 0.18 μm CMOS technology. The SDSSI has a high self-resonance frequency (fsr) and quality factor (Q) in spite of using the stacking technique, because the parasitic capacitance between the layers is reduced by alternatively locating traces at different positions in each layer. The output power spectrum and phase noise of the designed VCO is −0.79 dBm and 114 dBc/Hz at 1-MHz offset frequency, respectively. The oscillation frequencies cover from 1.84 GHz to 2.38 GHz with a tuning range of 26%, while the occupied on-chip area of the VCO is only 350 × 450 μm2. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26073

A low-power and low-phase-noise LC digitally controlled oscillator featuring a novel capacitor bank

A monolithic low-power and low-phase-noise digitally controlled oscillator (DCO) based on a symmetric spiral inductor with center-tap and novel capacitor bank was implemented in a 0.18 μm CMOS process with six metal layers. A third new way to change capacitance is proposed and implemented in this work. Results show that the phase noise at 1 MHz offset frequency is below −122.5 dBc/Hz while drawing a current of only 4.8 mA from a 1.8 V supply. Also, the DCO can work at low supply voltage conditions with a 1.6 V power supply and 4.1 mA supply current for the DCO's core circuit, achieving a phase-noise of −21.5 dBc/Hz at offset of 1 MHz. It demonstrates that the supply pushing of DCO is less than 10 MHz/V.

CMOS symmetric trace differential stacked spiral inductor

A miniature silicon-based symmetric trace differential stacked spiral inductor (SDSSI) has been implemented using standard 0.18 µm CMOS technology. Based on the measured two-port S-parameter using a standard de-embedding procedure, the self-resonance frequency (fsr) and quality factor (Q) of the SDSSI were compared to a conventional differential stacked spiral inductor (DSSI). The fsr of the SDSSI was nearly 2.5 times higher than that of the DSSI, and the Q value of the SDSSI was also enhanced.

Modeling of double-π equivalent circuit for on-chip symmetric spiral inductors

We present a novel methodology to extract model parameters from measured S-parameters for silicon on-chip center-tapped symmetric spiral inductors. The double-π equivalent circuit topology is employed in which conductor skin effect is considered. The automated extraction procedure based on modified differential evolution is demonstrated to be efficient and effective. To verify the accuracy of the new methodology, 17 center-taped symmetric inductors were fabricated and the equivalent circuit parameters were extracted from two-port S-parameters measurements over the frequency range of 0.3–8.5GHz. The excellent accuracy of the results demonstrates the flexibility of the modeling methodology. The new methodology should be useful in the design of RF ICs and mixed signal ICs.

Group-Cross Symmetrical Inductor (GCSI): A New Inductor Structure With Higher Self-Resonance Frequency and<tex>$Q$</tex>Factor

We propose a novel structure for a group-cross symmetrical spiral inductor (GCSI). The inductor has higher self-resonance frequency and quality factor, but the same dc inductance and layout area as a conventional symmetrical inductor. We compare measured data of the GCSI and conventional inductors to show the advantages of the new inductor structure.

Improved and physics-based model for symmetrical spiral inductors

Recent growth in RF applications has increased the use of spiral inductors and thus demanded a more accurate model for such devices. In this paper, the authors focus on the model development of spiral inductors with symmetrical terminals, but the same approach can be applied readily to asymmetrical inductors. Relevant and important physics such as the current crowding in metal line, frequency-dependent permittivity in oxide, and overlap parasitics are accounted for. Experimental data and results calculated from the existing inductor models are included in support of the model development.

Detailed analysis of high-quality symmetrical octagonal spiral inductors on Si substrate

Research studies of symmetrical spiral inductors for silicon technology have become very important and challenging. In this article, we attempt to give a detailed explanation of how symmetrical spiral inductors help to improve the quality factor (Q) as compared to conventional nonsymmetrical inductors. The experimental results are presented to verify our theory. © 2005 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2005.

Characterization of symmetrical spiral inductor in 0.35 μm CMOS technology for RF application

Characteristics of symmetrical spiral inductor in differential mode is studied and optimized in this work. The characteristics of interest include inductor value, quality factor, peak frequency and self-resonance frequency. Both single-layer and double-layer inductor using top metals are characterized. Inductor excited in differential mode and single-ended mode are characterized for comparison. The optimized symmetrical spiral inductors are fabricated in standard digital 0.35 μm CMOS process. Experimental results show 60–100% improvement of quality factor and peak frequency, meanwhile 10–20% improvement of self-resonance frequency by exciting the symmetrical spiral inductors in differential mode compared with single-ended mode. To further validate the characterized inductor, the differential spiral inductors are adopted in optimizing low power and low phase noise fully integrated 2.4 GHz voltage-controlled oscillator (VCO). The designed VCO achieved phase noise of more than −105 dBc/Hz at 100 kHz offset with approximately 4.5 mA at 3.0 V supply.