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In this paper, fully inkjet printed multilayer capacitors and inductors are fabricated and characterized using poly 4-vinylphenol (PVP) ink as the dielectric layer and silver nanoparticle ink as the conductor. Inkjet printed through vias, created with a novel dissolving method are used to make RF structures in a multilayer inkjet printing process. The vias have been realized in a 350-nm PVP film and exhibit resistance better than 0.1 $\Omega $ . Spiral inductors from 10 to 75 nH have been realized with maximum quality factors around five. The 10-nH inductor exhibits a self-resonant frequency slightly below 1 GHz. Metal–insulator–metal capacitors are realized with densities of 50 pF/mm ^{2} . These capacitors demonstrate values ranging from 16 to 50 pF. The 16-pF capacitor shows a self-resonant frequency over 1.5 GHz. The successful implementation of inductors and capacitors in an all inkjet printed multilayer process with vias is an important step toward fully inkjet-printed large area and flexible RF systems. [ABSTRACT FROM AUTHOR]

In this paper, an analytical model for calculating the ac resistance due to the proximity effect in thick coil integrated spiral inductors is proposed. Based on 2-D Maxwell’s equations, the redistribution of magnetic field and current in the coils caused by the proximity effect is modeled, and the ac resistance of the inductor is extracted. The analytical model is compared with both numerical simulations and experimental results. The ac resistance calculated by the model is good (within 14.8% discrepancy) up to the frequency of the peak quality factor for thick coil integrated spiral inductors. [ABSTRACT FROM AUTHOR]

A growing number of on-chip inductors have been applied in the millimeter-wave IC design. The coupling effects between them have a negative impact on the performance of the circuit and each on-chip inductor. In this paper, a new equivalent-circuit model and a parameter extraction method for multiple on-chip inductors in the millimeter-wave region are proposed. The impacts of coupling effects on every on-chip inductor are comprehensive considered in the proposed parameter extraction method. The characteristics of the multiple on-chip-coupled inductors are analyzed, modeled, and measured. The test structures were fabricated by 0.18- \mu \textm and 90-nm CMOS processes. The inductances, quality factors, and S-parameters of the model agree well with the measured performance of on-chip-nested and side-by-side-coupled inductors over a wide frequency range from 10 MHz up to millimeter-wave frequency band. [ABSTRACT FROM PUBLISHER]

High-resistivity(HR) silicon-on-insulator (SOI) substrates provide low substrate loss, so planar spiral inductors integrated on them presenting higher quality factor ( $Q$ ) than those on traditional Si substrates. However, the parasitic surface conduction (PSC) effect in the SOI substrate constitutes a conductive layer underneath the buried oxide layer, which deteriorates the inductors performance. This effect can be effectively eliminated by introducing a trap-rich layer. In this paper, physical models that can accurately characterize the behavior of inductors integrated on the HR and radio frequency enhanced signal integrity (RFeSI) SOI substrates are presented, and the analysis and evaluation of PSC effect on the performance of inductors, i.e., the inductance, the quality factor, the self-resonant frequency, and the frequency, where $Q$ peaks, are shown. Planar spiral inductors integrated on HR and RFeSI SOI substrates are fabricated and measured, validating the feasibility of the models we use. The experiment results show that the value of $Q$ and the frequency where it peaks can be improved significantly by eliminating the PSC effect. The temperature effects are also explored, showing that the PSC effect gets worse with raising temperature and accelerates the degradation rate of $Q$ . [ABSTRACT FROM PUBLISHER]

High-quality inductors are difficult to realize in stretchable electronics, since the thick parallel traces needed to minimize resistance also result in a highly rigid structure. Adding periodic waves or kinks to the traces of an inductor coil has been found to result in a more compliant structure that will not permanently deform or break after stretching by tens of percent. In this paper, the effects on electrical performance of creating inductor coils from stretchable wavy traces are investigated. Eight different tortuous trace designs were modeled and experimentally tested in one- and three-turn inductors, as well as an electrical transformer design. Incorporating waves into an inductor was found to result in a negative mutual coupling along the traces, degrading the inductor performance. The incremental self-inductance per resistance of the added length due to the waviness, $\sim 1.2$ nH/ $\Omega $ , was similar for all interconnect types tested. This value is less than a third that of using a longer straight conductor of similar cross section (4.4 nH/ $\Omega )$ , resulting in a drop in ratio of inductance to resistance and resulting peak quality factor in the measured inductors by as much as a factor of two. [ABSTRACT FROM PUBLISHER]

In order to further enhance the power capacity, and speed up the microwave start-up and saturation, an improved Ku-band magnetically insulated transmission line oscillator (MILO) with tapered choke cavity and enlarged first interaction cavity is proposed and investigated in this paper. The simplified plate model of MILO is analyzed to investigate the movement of individual electron. According to the theoretical analysis, the Ku-band MILO is optimized designed. In order to make the electrons emitted from the launch point of the cathode closer to the slow wave structure (SWS), especially the surface of the first interaction cavity, help to speed up the microwave start-up and saturation, the launch point of the cathode is optimized and designed 1.5 cm in front of the second choke vane. A tapered choke cavity is used to replace traditional uniform choke cavity, which helps further speed up the microwave start-up and saturation. An enlarged first interaction cavity with increased cavity gap is introduced to enhance the power capacity. Typical particle simulation results show that the improved Ku-band MILO can generate a microwave with a power of 1.65 GW and a frequency of 12.3 GHz under the diode voltage of 474 kV and the beam current of 42 kA. Compared with the traditional Ku-band MILO, the microwave start-up and saturation of the improved one are 2.5 and 5.5 ns faster, respectively. The power capacity of the improved Ku-band MILO is enhanced greatly due to that the RF electric field is decreased much from 1.3 to 1 MV/cm. At last, the experimental investigation of the improved Ku-band MILO is conducted. The device achieves a microwave output with a power of 1.2 GW, a frequency of 12.36 GHz, and a pulsewidth of 35 ns in the experiment. Both the power and the pulsewidth are enhanced significantly. [ABSTRACT FROM PUBLISHER]

Vanadium dioxide (VO2) is a unique phase change material (PCM) that possesses a metal-to-insulator transition property. Pristine VO2 has a negative temperature coefficient of resistance, and it undergoes an insulator-to-metal phase change at a transition temperature of 68 °C. Such a property makes the VO2 thin-film-based variable resistor (varistor) a good candidate in reconfigurable electronics to be integrated with different RF devices such as inductors, varactors, and antennas. Series single-pole single-throw (SPST) switches with integrated VO2 thin films were designed, fabricated, and tested. The overall size of the device is 380~\mu \textm\times 600~\mu \textm . The SPST switches were fabricated on a sapphire substrate with integrated heating coil to control VO2 phase change. During the test, when VO2 thin film changed from insulator at room temperature to metallic state (low-resistive phase) at 80 °C, the insertion loss of the SPST switch was <3 dB at 10 GHz. In addition, the isolation of the SPST improved to better than 30 dB when the temperature dropped to 20 °C. These tunable characteristics of the RF switch provide evidence for VO2 as a useful PCM for the broad range of applications in reconfigurable electronics. [ABSTRACT FROM AUTHOR]

A helium-3 ion bombardment technique is proposed to realize high- Q inductors by creating locally semi-insulating substrate areas. A dose of 1.0\times 10^{13} cm ^{-2} helium-3 increases a Si substrate resistivity from 4 \Omega \cdot cm to above 1 \text{k}\Omega \cdot cm, which improves the quality factor of a 2-nH inductor with a 140- \mu \text{m}$ diameter by 38% ( Q=16.3$ ). An aluminum mask is used for covering active areas, and at least 15- \mu \text{m} distance from the mask edge is required to avoid the p-n junction leakage. The proposed technique is applied to an 8-GHz oscillator, and an 8.5 dB improvement of the measured phase noise has been achieved. [ABSTRACT FROM AUTHOR]

In this brief, closed-form analytical expressions are obtained to accurately calculate the oxide and substrate (both lateral/vertical) capacitances of the $\pi $ -equivalent circuit model for on-chip tapered spiral inductors. A lateral RC substrate network using the above-mentioned expressions is shown to significantly improve the model accuracy, especially with lower substrate resistivities. Furthermore, improvement in Qmax with reverse excitation in tapered spirals is also accurately predicted by the proposed model. The accuracy of the proposed model is validated till 15 GHz using several inductor geometries across process parameters suitable for the design of RF circuits. Excellent agreement is observed between the model, electromagnetic simulations, and measurements. [ABSTRACT FROM AUTHOR]

Ultra-thick metals are known to be counter productive for quality factor ( Q ) improvement at high frequencies in multiturn inductors. From the experimental results, assisted by electromagnetic simulations, it is first shown that Q improvement with ultra-thick metals can be pushed to higher frequencies using variable width and spaced (tapered) spirals. Furthermore, it is also shown that the extent of tapering is proportional to the metal thickness for the highest performance. Second, dense-tapered layouts are shown to be good candidates for higher Q rather than hollow ones for a given inductance density. [ABSTRACT FROM AUTHOR]

In this brief, a novel combination of multilayer up–down series stacking and multipath architecture for equal path length is explored for the first time to improve the performance of on-chip inductors. The up–down series winding reduces the interlayer capacitance, thereby increasing both the peak quality-factor ( Q ) frequency ( fQmax ) and self resonant frequency (SRF). The crossover interconnection architecture ensures equal path length at every pair of spiral turns in the series stack. This architecture lowers skin and proximity effect losses in the spiral, increasing the slope of Q characteristics. Thus, using the proposed architecture, both the ac resistance and capacitance are simultaneously reduced while realizing higher inductance values. Implemented in a $0.18~\mu $ m high resistivity silicon-on-insulator technology using a dual thick metal stack, the proposed inductor achieves more than 10% improvement in peak- Q value, 50% improvement in fQmax , and 100% improvement in SRF values when compared with a conventional series stacked multipath inductor. [ABSTRACT FROM AUTHOR]

In this brief, we present a novel multipath parallel-stacked inductor structure that significantly reduces the current crowding effects. Both the metal layers of the parallel stack are divided into multiple segments and crossovers are provided midway of each turn to steer the current in such a way that all its segments have equal path lengths. Following the multipath architecture, prototype inductor structures are fabricated in a 0.18- \(\mu \) m high-resistivity silicon-on-insulator technology using a dual thick metal stack process. Measurements show >30% improvement in quality factor (Q) with the proposed architecture when compared with a standard parallel-stacked inductor. The Q improvement achieved by the proposed inductor structure is shown to increase with the spiral thickness making them suitable for both radio frequency circuits and DC–DC buck converters without having to use magnetic materials. Via resistance is shown to limit the Q improvement possible with proposed inductor configuration. [ABSTRACT FROM AUTHOR]