Spiral Capacitor Research Articles

RFID-Based Microwave Biosensor for Non-Contact Detection of Glucose Solution.

Due to the increasing number of diabetic patients, early monitoring of glucose levels is particularly important; therefore, glucose biosensors have attracted enormous attention from researchers. In this paper, we propose a glucose microwave biosensor based on RFID and achieve a non-contact measurement of the concentration of glucose solutions. The Reader is a complementary split-ring resonator (CSRR), and the Tag is comprised of a squared spiral capacitor (SSC). A polydimethylsiloxane microfluidic quantitative cavity with a volume of 1.56 μL is integrated on the Tag to ensure that the glucose solution can be accurately set to the sensitive area and fully contacted with the electromagnetic flux. Because the SSC exhibits different capacitances when it contacts glucose solutions of different concentrations, changing the resonant frequency of the CSRR, we can use the relationship to characterize the biosensing response. Measurement results show that bare CSRR and RFID-based biosensors have achieved sensitivities of 0.31 MHz/mg·dL−1 and 10.27 kHz/mg·dL−1, and detection limits of 13.79 mg/dL and 1.19 mg/dL, respectively, and both realize a response time of less than 1 s. Linear regression analysis of the abovementioned biosensors showed an excellent linear relationship. The proposed design provides a feasible solution for microwave biosensors aiming for the non-contact measurement of glucose concentration.

Aerosol deposited BaTiO3 film based interdigital capacitor and squared spiral capacitor for humidity sensing application

In this article, ultra-high sensitive aerosol deposited BaTiO3 film based inter-digital capacitors (IDCs), and a squared spiral capacitor (SSC) have been investigated for humidity sensing application. BaTiO3 based sensing film is prepared at room temperature, then post-annealed at 200 °C and 400 °C to enhance material's sensing properties. Thermal exposure of BaTiO3 sensing film increases electron density, improves material defects, enhances grain to grain connectivity, and escalates hydrophilicity. The sensitivity of all fabricated devices is evaluated by comparing capacitive variation at different relative humidity (RH) levels. The electric field distribution and open area ratio (OAR) are scrutinized to understand the effect of these parameters on the BaTiO3 integrated capacitive type humidity sensor. The obtained results indicate that the IDC-1 with large OAR reveals high sensitivity due to the availability of the wider interaction area between fringing electric field intensity and water vapors adsorbed on sensing material surface. Similarly, the SSC structure reveals high sensitivity over IDC-2 and IDC-3 due to the existence of concentrated electric field intensity and large OAR. The intensified electric field polarizes the water vapor molecules and sensing material ions that upsurge the device capacitance at various RH levels, which enhances sensitivity. This study reveals that the design structure, electric field intensity, and sensing material property are equally responsible for high sensitivity in capacitive humidity sensors.

Screen Printed Passives and Interconnects on Bio-Degradable Medical Hydrocolloid Dressing for Wearable Sensors

The healthcare system is undergoing a noticeable transformation from a reactive, post-disease treatment to a preventive, predictive continuous healthcare. The key enabler for such a system is a pervasive wearable platform. Several technologies have been suggested and implemented as a wearable platform, but these technologies either lack reliability, manufacturing practicability or pervasiveness. We propose a screen-printed circuit board on bio-degradable hydrocolloid dressings, which are medically used and approved, as a platform for wearable biomedical sensors to overcome the aforementioned problems. We experimentally characterize and prepare the surface of the hydrocolloid and demonstrate high-quality screen-printed passive elements and interconnects on its surface using conductive silver paste. We also propose appropriate models of the thick-film screen-printed passives, validated through measurements and FEM simulations. We further elucidate on the usage of the hydrocolloid dressing by prototyping a Wireless Power Transfer (WPT) sensor and a humidity sensor using printed spiral inductors and interdigital capacitors, respectively.

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.

Electromechanics of suspended spiral capacitors and inductors

Most electromechanical devices are in two-dimensional metallic drums under high tensile stress, which causes increased mechanical frequency and quality factor. However, high mechanical frequencies lead to small zero-point displacements xzp, which limits the single-photon interaction rate g0. For applications which demand large g0, any design with increased xzp is desirable. It is shown that a patterned drum by a spiral shape can resolve this difficulty, which is obtained by a reduction of mechanical frequency while the motion mass is kept almost constant. An order of magnitude increase in g0 and agreement between simulations and interferometric measurements is observed.

Liquid‐metal capacitors with a 42:1 tuning ratio

Four types of liquid-metal-based tunable capacitors with a high tuning range are demonstrated. The capacitors are easily fabricated by placing a pair of liquid-metal-filled tubes in contact with one another. Tunability is achieved by varying the length of the liquid metal in one of the tubes using a mechanical pump. Four different structures are demonstrated: parallel-tube, folded-tube, coil, and spiral capacitors. The highest measured tuning ratio is 42:1, and the highest change in capacitance per unit length of the pumped liquid metal is 0.07 pF/mm.

Fractal spiral capacitor for wireless applications

Single-layer spiral capacitor utilising fractal geometry is investigated. This capacitor makes use of both lateral and vertical fluxes to improve the capacitance density. Both PCB and on-chip capacitors are designed and simulated using high-frequency structural simulator. The structures are fabricated on PCB using PCB fabrication techniques. The measurement of PCB prototype is carried out by vector network analyser. The result shows the inclusion of fractal concept to spiral capacitor increases capacitance by 10.3%, quality factor by 52.4% and 20% improvement in self-resonant frequency over conventional spiral capacitor.

Ultra-compact UHF Band-pass Filter Designed by Archimedes Spiral Capacitor and Shorted-loaded Stubs

Abstract UHF microstrip band-pass filters (BPFs) that much smaller than the referred BPFs are proposed in this communication. For the designing purpose of compactness, archimedes spiral capacitor and ground-loaded stubs are utilized to enhance capacitances and inductance of a filter. Two compact BPFs denoted as BPF 1 and BPF 2 are designed by applying these techniques. The size of BPF 1 and BPF 2 are 0.062 λg × 0.056 λg and 0.047 λg × 0.043 λg, respectively, where λg are guided wavelengths of the centre frequencies of the corresponding filters. The proposed filters were constructed and measured, and the measured results are in good agreement with the simulated ones.

Design and fabrication of a carbon-nanotube-based capacitor patterned on an Archimedean spiral

To achieve the maximum area utilization ratio for a parallel electrode capacitor, an Archimedean spiral was used to design the capacitor pattern. Multi-walled vertically aligned carbon nanotubes (VACNTs) were used for the capacitor electrodes because of their metallic properties and their endurance toward various chemical reagents. In contrast to the parallel plate capacitor, the total capacitance was formed by parallel connections of all unit cells of the individual VACNT capacitors, so that a relatively higher capacitance was obtained. This design can provide a new approach to fill diverse dielectrics into a spiral capacitor to obtain different capacitances for various applications.

COMPACT LATTICE-TYPE LC BALUN EMBEDDED INTO FR-4 PCB WITH BaTiO3 COMPOSITE FILM

ABSTRACT In this paper, fully embedded lattice type LC balun into a PCB substrate was investigated for advanced RF SOP products with low cost and small size. The proposed balun was miniaturized by embedding high Q circular spiral inductors and MIM capacitors into the FR-4 PCB substrate. Especially, the area of embedded capacitor was extremely reduced by applying high dielectric composite RCC film which was comprised of BaTiO3 power and epoxy resin. These embedded capacitors exhibited excellent performance characteristics at high frequency regime by achieving the capacitance density ranged from 15 pF/mm2 to 25 pF/mm2. The embedded LC baluns had much smaller area than previously reported PCB based ones and excellent performance characteristics. The measured results were well agreed with 3D-EM simulated ones. They are promising for advanced RF SOP products with multi functionalities, small size, and low cost.

Ultra-Wide Suppression Band of Surface Waves Using Periodic Microstrip-Based Structures

We propose the use of microstrip-based elements: spiral inductors and interdigital capacitors connected through transmission lines to provide a higher order wide surface wave suppression band. Design, modeling, and realization of optimum values for spiral inductors and interdigital capacitors are studied in detail. A grid of 77 2-D unit cells consisting of these designed interdigital capacitors and spiral inductors is manufactured and tested experimentally. The excitation of surface waves using different schemes are addressed and compared. Also, for comparative purposes, two reference cases of copper surface and dielectric backed copper are studied. The obtained results demonstrate the potential of this structure to be used as a very wideband suppressor.

FABRICATION AND CHARACTERIZATION OF EMBEDDED PASSIVE COMPONENTS FOR LOW COST ORGANIC RF SOP APPLICATIONS

ABSTRACT In this paper, embedded passive components are investigated into the PCB substrate for low cost RF SOP applications. PCB embedded spiral inductors, MIM capacitors, and low pass filters are designed, fabricated and characterized by using 3D EM simulator, 8 layered PCB standard process, and HP 8510B network analyzer for verifying their applicability. The fabricated embedded spiral inductor has inductance of 9.4 nH at 800 MHz and maximum quality factor of 64.8 at 1.09 GHz and the embedded MIM capacitor has capacitance of 4.8 pF and maximum quality factor of 36.5 at 1 GHz. The fabricated embedded LPF has cutoff frequency of 2GHz at the insertion loss of −0.472 dB and return loss of −32.8 dB. The measured performance characteristics are well matched with the simulated ones.

A 2.7-v 1.8-GHz fourth-order tunable LC bandpass filter based on emulation of magnetically coupled resonators

A low-voltage fourth-order RF bandpass filter structure based on emulation of two magnetically coupled resonators is presented. A unique feature of the proposed architecture is using electric coupling to emulate the effect of the coupled inductors, thus providing bandwidth tuning with small passband ripple. Each resonator is built using on-chip spiral inductors and accumulation-mode pMOS capacitors to provide center frequency tuning. The filter has been implemented in HP 0.5-/spl mu/m CMOS process and occupies an area of 0.15 mm/sup 2/. It consumes 16 mA from a single 2.7-V supply at a center frequency of 1.84 GHz and a bandwidth of 80 MHz while providing a passband gain of 9 dB and more than 30 dB of image attenuation for an IF frequency of 100 MHz. The measured output 1-dB compression point and output noise power spectral densities are -16 dBm and -137 dBm/Hz, respectively. This results in a 1-dB compression dynamic range of 42 dB. The filter minimum power supply voltage for proper operation is 2 V. The chip experimental results are in good agreement with theoretical results.

A 23.8-GHz SOI CMOS tuned amplifier

A 23.8-GHz tuned amplifier is demonstrated in a partially scaled 0.1-/spl mu/m silicon-on-insulator CMOS technology. The fully integrated three-stage amplifier employs a common-gate, source-follower, and cascode with on-chip spiral inductors and MOS capacitors. The gain is 7.3 dB, while input and output reflection coefficients are -45 and -9.4 dB, respectively. Positive gain is exhibited beyond 26 GHz. The amplifier draws 53 mA from a 1.5-V supply. The measured on-wafer noise figure is 10 dB, while the input-referred third-order intercept point is -7.8 dBm. The results demonstrate that 0.1-/spl mu/m CMOS technology may be used for 20-GHz RF applications and suggest even higher operating frequencies and better performance for further scaled technologies.

2.4 GHz single-balanced diode mixer fabricated on Al2O3 substrate by thin-film technology

A passive balun using spiral inductors and interdigital capacitors has been developed for a 2.4 GHz balanced diode mixer on Al2O3 substrates. Using this passive balun on the input port (RF port and LO port) of a mixer circuit and incorporating the Schottky diode model, a wideband single-balanced diode mixer was designed, fabricated, and characterized © 2000 John Wiley & Sons, Inc. Microwave Opt Technol Lett 25: 83–86, 2000.

A 2.4-GHz silicon-on-sapphire CMOS low-noise amplifier

A low-noise amplifier operating at 2.4 GHz has been fabricated with MOSFETs in silicon-on-sapphire technology. The amplifier has a 2.8-dB noise figure, 10-dB gain, and 14-dBm output referred IP3 with 14-mW power dissipation. The amplifier was matched for minimum noise with on-chip spiral inductors and capacitors.