Fabrication and performance of novel RF spiral inductors on silicon

This paper presents and discusses the fabrication and the performance of RF circular spiral inductors on silicon. The substrate materials underneath the inductor coil are removed by wet etching process. In the fabrication process, fine polishing of the photoresist is used to simplify the processes and ensure the seed layer and the pillars contact perfectly, and dry etching technique is used to remove the seed layer. The results show that Q-factor of the novel inductor is greatly improved by removing the silicon underneath the inductor coil. The spiral inductor for line width of 50 μm has a peak Q-factor of 17 at frequency of 1 GHz. The inductance is about 3.2 nH in the frequency range of 0.05-3 GHz and the resonance frequency of the inductors is about 6 GHz. If the strip is widened to 80 μm, the peak Q-factor of the inductor reduces to about 10 and the inductance is 1.5 nH in the same frequency range.     

Fabrication and performance of a micromachined 3-D solenoid inductor

A high-Q and f_res (self-resonant frequency)solenoid inductor was fabricated by using the microelectromechanical systems(MEMS) technology with air-core structure. This inductor has an air core and an electroplated copper coil to reduce the series resistance, and the solenoid structure with laterally laid out structure saves the chip area significantly. The measurement results show that this inductor has high Q-factor and stable inductance over wide range of operating frequency. The maximum Q-factor of this inductor is 38 and the inductance is 1.78 nH at 5 GHz with an air core of 45 μm. Moreover, the Q-factor and the inductance grow with the increasing of the air core.     

Optimized Quality Factor of Graphene Oxide-Reinforced PVC Nanocomposite

Graphene oxide (GO)-reinforced polyvinyl chloride (PVC) composite films were prepared by solution blending. The homogeneity of GO dispersion with PVC was confirmed by an optical microscope. Quality factor (Q-factor) as a function of temperature (40–150 °C) was measured within a broadband frequency range of 50–35 MHz. The controlled GO loading demonstrates a crucial impact on the optimization of the Q-factor, resonance frequency (f ₀) and wide bandwidth. This nanocomposite may be well suited for electronic applications. The further development of GO-reinforced polymer nanocomposites based on an optimized Q-factor may result in a material for electromagnetic frequency radiation shields for radar and communication towers/devices.     

A microfluidic system with embedded acoustic wave sensor for in situ detection of dynamic fluidic properties

A microfluidic system with acoustic wave sensor employing quartz crystal microbalance embedded in the microfluidic channel was developed by soft-lithography technique and characterized by measuring resonance frequency of the sensor under different service conditions. Detections of dynamic fluids in various concentrations and flow rates showed that shift of resonant frequency was observed when there was variation in mass or viscosity of the fluid passing through the microchannels. Through a calibration experiment by monitoring continuous flowing fluids with suspended microparticles, the sensitivity of the system was found to be ∼15 Hz cm²/ng. All these results suggest that the microfluidic system can be employed in in situ monitoring of chemical and biochemical processes involving mass and/or viscosity changes within the microfluidic system.     

RF CMOS active inductor band pass filter with post fabrication calibration

This paper presents an active inductor bandpass filter (BPF) architecture with selectable 50 Ω driving capability and post fabrication calibration for gain, center frequency, and quality factor. The design details, and performance assessment that facilitate selecting an offline calibration mode to measure and tune post fabrication BPF performance are discussed. A specific design example for a L1/L2 channel GPS receiver is included with a BPF that is required to pass the L2 signal centered at 1.227 GHz with a gain of approximately16 dB at the center frequency, have a 3 dB bandwidth of 30 MHz (Q = 41) and rejection of the L1 signal at 1.575 GHz by at least 60 dB relative to the center frequency. A multistage active inductor BPF 90 nm CMOS design is presented that meets these specifications with typical process parameters. It is demonstrated that the post fabrication design based on typical corner analysis can be re-tuned to the desired performance for process variations across the slow and fast corners using the offline measuring and tuning control inputs.     

Selective Filters and Sinusoidal Oscillators Using CFA Transimpedance Pole

Using a single current feedback amplifier (CFA) device, two new variable frequency sinusoidal RC oscillators are presented. The transadmittance pole of the device (AD-844) has been utilized in the design for generating sine wave signals covering a range of 1 MHz≤f ₀≤31 MHz. Under open-loop conditions, both circuits exhibit resonance characteristics at moderate Q-values (1≤Q≤9). These responses have been experimentally verified with hardware circuit implementation and PSPICE macromodel simulation.     

An wide-range tunable on-chip radio-frequency LC-tank formed with a post-CMOS-compatible MEMS fabrication technique

An on-chip-micromachined tunable LC-tank, which consists of a metal inter-digitated variable capacitor and a metal solenoid inductor, is developed for wide-range radio-frequency (RF) tuning in multi-GHz band. A low-temperature metal MEMS process is developed to on-chip fabricate the passives. The process can be used for post-CMOS-compatible integration with RF ICs. Both the varactor and the inductor are suspended with a gap from the low-resistivity silicon wafer (i.e. standard CMOS wafer) for effectively depressing RF loss. The fabricated variable capacitor part, the inductor part and the whole tunable LC resonator are sequentially tested, finally resulting in a wide resonance-frequency tuning range of 72% (between about 3.5 and 6.0 GHz) under a low tuning voltage range of 0-4 V, while the Q-factor ranged within 23 and 8.     

Inductively coupled small self resonant coil (SSRC) reader antennas for HF RFID applications

A new model of inductively coupled high frequency radio frequency identification (HF RFID) reader antennas is presented in this paper based on the idea of using the self resonance frequency (SRF) of a small multi turn coil. The introduced multi turn small self resonant coil (MT SSRC) antenna is mathematically analyzed in terms of SRF, number of turns, dimensions and dielectric characteristics of the insulation, where present. Based on the analysis, a compact planar version of MT SSRC antennas having two turns, the two turn planar SSRC (TTP SSRC), is investigated and the dependency of the SRF to the antenna dimension is observed. A TTP SSRC antenna operating at 13.56 MHz is fabricated and is compared with an old model of HF RFID antennas; an optimized Q factor and a more uniform near field pattern is obtained for the new antenna. The benefits of the obtained optimized Q factor and uniform near pattern is explained for smart shelf application. Also, a number of TTP SSRC antennas operating at a distinct frequency, 13.56 MHz here, are fabricated on different substrates and it is shown that the Q factor and dimension of the TTP SSRC antenna could be controlled and adjusted based on the dielectric characteristics of the substrate. The new antenna prototype has a beneficial application to smart shelf applications in HF RFID.     

Design of Sub-1 mW CMOS LC VCO based on current reused topology with Q-enhancement and body-biased technique

A CMOS LC voltage controlled oscillator (VCO) based on current reused topology with low phase noise and low power consumption is presented for IEEE 802.11a (Seller et al. A 10 GHz distributed voltage controlled oscillator for WLAN application in a VLSI 65 nm CMOS process, in: IEEE Radio Frequency Integrated Circuits (RFIC) Symposium, 3–5 June, 2007, pp. 115–118.) application. The chip1 is designed with the tail current-shaping technique to obtain the phase noise −116.1 dBc/Hz and power consumption 3.71 mW at the operating frequency 5.2 GHz under supply voltage 1.4 V. The second chip of proposed VCO can achieve power consumption Sub 1 mW and is still able to maintain good phase noise. The current reused and body-biased architecture can reduce power consumption, and better phase noise performance is obtained through raising the Q value. The measurement result of the VCO oscillation frequency range is from 5.082 GHz to 5.958 GHz with tuning range of 15.8%. The measured phase noise is −115.88 dBc/Hz at 1 MHz offset at the operation frequency of 5.815 GHz. and the dc core current consumption is 0.71 mA at a supply voltage of 1.4 V. Its figure of merit (FOM) is −191 dBc/Hz. Two circuits were taped out by TSMC 0.18 μm 1P6M process.     

Ultra low voltage, high performance operational transconductance amplifier and its application in a tunable Gm-C filter

This paper presents an ultra low voltage, high performance Operational Transconductance Amplifier (OTA) and its application to implement a tunable Gm-C filter. The proposed OTA uses a 0.5 V single supply and consumes 60 μw. Employing special CMFF and CMFB circuits has improved CMRR to 138 dB in DC. Using bulk driven input stage results in higher linearity such that by applying a 500 mv_p-p sine wave input signal at 2 MHz frequency in unity gain closed loop configuration, third harmonic distortion for output voltage is −46 dB and becomes −42.4 dB in open loop state for 820 mv_p-p output voltage at 2 MHz. DC gain of the OTA is 47 dB and its unity gain bandwidth is 17.8 MHz with 20 pF capacitance load due to both deliberately optimized design and special frequency compensation technique. The OTA has been used to realize a wide tunable Gm-C low-pass filter whose cutoff frequency is tunable from 1.4 to 6 MHz. Proposed OTA and filter have been simulated in 0.18 μm TSMC CMOS technology with Hspice. Monte Carlo and temperature dependent simulation results are included to forecast the mismatch and temperature effects after fabrication process.     

An 8-bit low power DAC with re-used distributed binary cells architecture for reconfigurable transmitters

In this work an 8-bit DAC is presented which uses a new segmented architecture, where distributed binary cells are re-used in thermometric manner to realize the MSB unit cells. The DAC has been fabricated in 0.18 μm five-metal CMOS n-well process to be embedded in multi-standard reconfigurable wireless transmitters for low-speed applications. The proposed architecture has an inherent ability to reduce midcode glitch like the unary architecture, and the simulated midcode glitch is only 0.01 pV s. Simulation results show that the proposed DAC performs with an integral nonlinearity (INL) of 0.33 LSB and a differential nonlinearity (DNL) of 0.14 LSB. The DAC can achieve a maximum measured SFDR of 65.19 dB for 97.50 kHz signal at a sampling rate of 100 MSPS, without using any calibration or dynamic element matching (DEM) technique. For 1.07 MHz signal the measured SFDR is 56.84 dB at 100 MSPS sampling rate. At 50 MSPS sampling frequency and 146 kHz signal the SFDR of the DAC is 65.90 dB. The measured SFDR at 538 kHz signal is 63.62 dB for a sampling rate of 50 MSPS. Measured third order intermodulation distortion of the DAC is 58.55 dB, for a dual tone test with 1.03 MHz and 1.51 MHz signals at 50 MSPS sampling rate. Low power is also an important aspect in portable wireless devices. For 10.06 MHz signal and 100 MSPS sampling frequency, the power dissipation of the DAC is 20.74 mW with 1.8 V supply.     

Surface acoustic wave characteristics of AlN thin films grown on a polycrystalline 3C-SiC buffer layer

In this study, AlN thin films were deposited on a polycrystalline (poly) 3C-SiC buffer layer for surface acoustic wave (SAW) applications using a pulsed reactive magnetron sputtering system. AFM, XRD and FT-IR were used to analyze structural properties and the morphology of the AlN/3C-SiC thin film. Suitability of the film in SAW applications was investigated by comparing the SAW characteristics of an interdigital transducer (IDT)/AlN/3C-SiC structure with the IDT/AlN/Si structure at 160 MHz in the temperature range 30-150 °C. These experimental results showed that AlN films on the poly (1 1 1) preferred 3C-SiC have dominant c-axis orientation. Furthermore, the film showed improved temperature stability for the SAW device, TCF = −18 ppm/°C. The change in resonance frequency according to temperature was nearly linear. The insertion loss decrease was about 0.033 dB/°C. However, some defects existed in the film, which caused a slight reduction in SAW velocity.     

Fabrication of 3D MEMS toroidal microinductor for high temperature application

Based on Microelectromechanical systems (MEMS) technique and thick photoresist lithography technology, a new toroidal-type inductor for high temperature application has been successfully developed. In the fabrication process, heat-resistant materials are used, alumina as insulator and supporting materials instead of polyimide, heat resistant glass for underlay instead of normal glass, and copper for coil. The maximum inductance is 87 nH at 0.826 GHz and maximum of quality factor (Q-factor) is 4.63 at 0.786 GHz, at room temperature. With simulation of thermal deformation, it shows that the developed toroidal inductor can be suitable for high temperature application, from 300 to 700 °C.     

Frequency and temperature dependent dielectric properties of Al/Si3N4/p-Si(1 0 0) MIS structure

The dielectric properties of Al/Si₃N₄/p-Si(1 0 0) MIS structure were studied from the C-V and G-V measurements in the frequency range of 1 kHz to 1 MHz and temperature range of 80-300 K. Experimental results shows that the ε′ and ε″ are found to decrease with increasing frequency while the value of ε′ and ε″ increase with increasing temperature, especially, above 160 K. As typical values, the dielectric constant ε′ and dielectric loss ε″ have the values of 7.49, 1.03 at 1 kHz, and only 0.9, 0.02 at 1 MHz, respectively. The ac electrical conductivity (σ_ac) increases with both increasing frequency and temperature. The activation energy of 24 meV was calculated from Arrhenius plot at 1 MHz. The results indicate that the interfacial polarization can be more easily occurred at low frequencies and high temperatures.     

A single-input dual-output 13.56 MHz CMOS AC–DC converter with comparator-driven rectifiers for implantable devices

A highly efficient single-input, dual-output AC–DC converter for wireless power transfer in implantable devices is implemented using the 0.18-µm CMOS process. The proposed AC–DC converter, consisting of three rectifiers with cross-coupled NMOS transistors and comparator-driven PMOS transistors, achieves up to 79.5% power conversion efficiency at 13.56 MHz operation frequency in order to provide dual outputs of 1.2 V and 2.2 V DC voltages along with 6.2 mA and 22.6 mA of current, respectively, to the implant device from a single RF input. The designed IC consumes a core die area of 0.18 mm².     

A low-power, high-frequency, all-NMOS all-current-mirror sinusoidal quadrature oscillator

A low-power, high-frequency, sinusoidal quadrature oscillator is presented through the use of only current mirrors where the small-signal paths are realized through all NMOS transistors. The technique is relatively simple based on (i) inherent time constant of current mirrors, i.e. the internal capacitances and the transconductance of a diode-connected NMOS, (ii) a negative resistance formed by a transconductance of a diode-connected NMOS load of a current mirror. No external passive components are required. As a particular example, a 2.83 GHz, 0.374 f_T, 0.38 mW sinusoidal quadrature oscillator is demonstrated. Total harmonic distortions are less than 0.8%. The oscillation frequency is current-tunable over a range of 640 MHz or 22.62%. The amplitude matching and the quadrature phase matching are better than 0.04 dB and 0.17°, respectively. A figure of merit called a normalized carrier-to-noise ratio is 158.23 dBc/Hz at the 2 MHz offset from 2.83 GHz. Comparisons to other approaches are also presented.     

CMOS RF class-D power amplifier with bandpass sigma-delta modulation

A CMOS radio frequency class-D amplifier is analysed and simulated with a bandpass ΣΔ modulated drive signal. The design includes a five stage driver and operates from 3.3 V. The simulated power efficiency at 181 MHz is 40.1% for a two tone source, and 16.6% for a 8.7 dB peak-to-average wideband code-division multiple access source signal. Equations are derived which demonstrate the relationship between amplifier load power, power efficiency, and modulator parameters called coding efficiency and average transition frequency.     

DXCCII-based grounded inductance simulators and filter applications

In this paper two new grounded inductance simulators based on DXCCII suitable for operation in 30 kHz-30 MHz frequency range, are presented. The proposed circuits both employ only a single dual X second-generation current conveyor (DXCCII) active device accompanied with three and four passive elements, respectively. The accuracy of the simulated inductors is verified by implementing them in some filter applications. Also, a novel multi-input single-output universal filter derived from one of the new grounded inductance simulators is simulated to demonstrate the functionality of the proposed circuit. Simulation results using AMS 0.35 μm CMOS process technology parameters are included.     

The protective effect of thin amorphous hydrogenated carbon a-C:H films during metallisation of metal-carbon-oxide-silicon (MCOS) diodes

Capacitance-voltage (C-V) characteristics of the as-grown metal(Al)-carbon-oxide(SiO₂)-semiconductor(Si) structures are examined at the frequency of 1 MHz and compared with the C-V characteristics of the conventional metal(Al)-SiO₂-Si (MOS) structures. The density of the oxide charge Q_o/q is extracted from the experimental results. Q_o/q was found to be 1×10¹² cm⁻² for the MOS structures and 7×10¹¹ cm⁻² for the metal-carbon-oxide-silicon structures. This difference can be attributed to the presence of the carbon layer which acts as a protective coating during metallisation of the wafers.     

Super-regenerative receiver at 433 MHz

This paper presents a receiver for operation in the 433 MHz ISM band. The selected architecture explores the super-regeneration phenomena to achieve a high sensitivity for applying in wireless implantable microsystems. This radio-frequency (RF) chip can be supplied with a voltage of only 3 V for demodulating signals with powers in the range (−100, −40) dB. The codulation (modulation and coding) scheme of the binary data is a variation of the Manchester code combined with on/off keying (OOK) modulation. The AMIS 0.7 μm CMOS process was selected for targeting the requirement to fabricate a low-cost receiver, whose prototype was integrated in a die with an area of 5×5 mm². Also, this receiver is fully compatible with commercial transmitters for the same frequency.