Design and Realization of a Fully On-Chip High-$Q$ Resonator at 15 GHz on Silicon

We develop and demonstrate an on-chip resonator working at 15 GHz with a high quality factor ( $Q$-factor) of 93.81 while only requiring a small chip size of $hbox{195} muhbox{m} times hbox{195} muhbox{m}$ on Si by using our new design methodology. In our design, unlike previous approaches, we avoid the need for any external capacitance for tuning; instead, we utilize the film capacitance as the capacitor of the LC tank circuit and realize a fully on-chip resonator that shows a strong transmission dip of $≫hbox{30} hbox{dB}$ on resonance as required for telemetric-sensing applications. We present the design, theory, methodology, microfabrication, experimental characterization, and theoretical analysis of these resonators. We also demonstrate that the experimental results are in excellent agreement with the theoretical (both analytical and numerical) results. Based on our proof-of-concept demonstration, such high- $Q$ on-chip resonators hold great promise for use in transmissive telemetric sensors.      

Comparative Study of High-Power Continuous-Wave Laser Performance of Yb-Doped Vanadate Crystals

A comprehensive experimental investigation has been conducted into the high-power continuous-wave (CW) laser performance of isostructural Yb-doped vanadates, including three ordered crystals of Yb:YVO $_{4}$, Yb:GdVO $_{4}$, and Yb:LuVO $_{4}$, and two mixed ones with compositional disorder: Yb$_{0.007}$ :Y$_{0.407}$ Gd$_{0.586}$ VO$_{4}$ and Yb$_{0.015}$ :Lu$_{0.52}$ Gd$_{0.465}$ VO$_{4}$ . The CW laser operation of the different vanadates is compared under nearly identical experimental conditions by using a high-power diode laser as the pump source. In addition to the output characteristics of the individual vanadate lasers, the polarization properties and optical bistability exhibited in the laser oscillation are also discussed. The spectroscopic properties closely related to the laser performance are compared and summarized for these Yb-doped vanadates.      

Virus Spread in Networks

The influence of the network characteristics on the virus spread is analyzed in a new—the $N$ -intertwined Markov chain—model, whose only approximation lies in the application of mean field theory. The mean field approximation is quantified in detail. The $N$ -intertwined model has been compared with the exact $2^{N}$-state Markov model and with previously proposed “homogeneous” or “local” models. The sharp epidemic threshold $tau_{c}$ , which is a consequence of mean field theory, is rigorously shown to be equal to $tau_{c}=1/(lambda_{max}(A))$ , where $lambda_{max}(A)$ is the largest eigenvalue—the spectral radius—of the adjacency matrix $A$ . A continued fraction expansion of the steady-state infection probability at node $j$ is presented as well as several upper bounds.      

Optical bistability in reflective fiber gratings

Optical bistability in a nonlinearly reflective fiber grating through the mode coupling between the LP₀₁ and counter propagation LP₀₂ modes (i,e., the reflective LP₀₁&rlhar2;LP₀₂ mode converter) is investigated by using the coupled-mode theory. Both the transmissive and the reflective properties of this nonlinear device are analyzed, which show that the output-versus-input relation exhibits the optical bistability. The switching power and the bistable hysteresis performances are also discussed. In addition, the comparison between the nonlinearly reflective mode converter (LP₀₁&rlhar2;LP₀₂) and the nonlinear fiber Bragg grating reflector (i,e., the LP₀₁ and counter-propagation LP₀₁ modes) is also presented. It is shown that the former has much lower switching power than the latter     

Design and Analysis of Isolated Noise-Tolerant (INT) Technique in Dynamic CMOS Circuits

Along with the progress of advanced VLSI technology, noise issues in dynamic circuits have become an imperative design challenge. The twin-transistor design is the current state-of-the-art design to enhance the noise immunity in dynamic CMOS circuits. To achieve the high noise-tolerant capability, in this paper, we propose a new isolated noise-tolerant (INT) technique which is a mechanism to isolate noise tolerant circuits from noise interference. Simulation results show that the proposed 8-bit INT Manchester adder can achieve 1.66$times$ average noise threshold energy (ANTE) improvement. In addition, it can save 34% power delay product (PDP) in low signal-to-noise ratio (SNR) environments as compared with the 8-bit twin-transistor Manchester adder under TSMC 0.18-$mu$ m process.      

Separated Unicast/Multicast Splitter-and-Delivery Switch and Its Use in Multicasting-Capable Optical Cross-Connect

We propose a novel separated unicast/multicast splitter-and-delivery (SUM-SaD) switch for mixed unicast and multicast traffic. Only multicast connections undergo extra splitting loss but are compensated by incorporated optical amplifiers. A typical multicasting-capable optical cross-connect is constructed by using the proposed SUM-SaDs. Theoretically, we prove that it is strictly nonblocking for both unicast and multicast connections if $d=N/2$, where $N$ and $d$ are the dimension of SUM-SaD and the number of SaD input ports, respectively. Therefore, $d$ means the maximum accommodated trees in the SUM-SaD. To save cost, $d$ can be less than $N/2$ , and the throughput performance is investigated by simulation. The results show that the throughput is improved when $d$ increases. In the experiment, we construct a 4 $times$ 4 SUM-SaD prototype and measure the bit-error rate (BER) of unicast connection, multicast connection with or without optical amplifier. There is no clear BER difference between them for the small dimensional SUM-SaD switch.      

Polarization-Independent Liquid-Crystal Fresnel Lenses Based on Surface-Mode Switching of 90$^{circ}$ Twisted-Nematic Liquid Crystals

A simple polarization-independent liquid-crystal Fresnel lens is developed using the surface-mode switching of 90$^{circ}$ twisted-nematic liquid crystals (TN-LCs). In the surface-mode switching of LCs, the major reorientation of LCs occurs near the substrates. Optical calculations indicate that 90$^{circ}$ TN-LCs are polarization-independent under surface-mode switching, when the applied voltage exceeds four times the threshold voltage for director reorientation. The maximum tunable phase shift in this polarization-independent state of 90$^{circ}$ TN-LCs is $sim$ 11% of LC cell retardation. An LC Fresnel lens that is polarization-independent and has a fast response with a response time of $≪$10 ms is demonstrated using the surface-mode switching of 90$^{circ}$ TN-LC.      

The Electrical and Interfacial Properties of Metal-High-$kappa$ Oxide-Semiconductor Field-Effect Transistors With $hbox{LaAlO}_{3}$ Gate Dielectric

$hbox{LaAlO}_{3}$ is a promising candidate for gate dielectric of future VLSI devices. In this letter, n-channel metal–oxide–semiconductor field-effect transistors with $hbox{LaAlO}_{3}$ gate dielectric were fabricated, and the electron mobility degradation mechanisms were studied. The leakage current density is $hbox{7.6} times hbox{10}^{-5} hbox{A/cm}^{2}$ at $-!$ 1 V. The dielectric constant is 17.5. The surface-recombination velocity, the minority-carrier lifetime, and the effective capture cross section of surface states were extracted from gated-diode measurement. The rate of threshold voltage change with temperature $(Delta V_{T} / Delta T)$ from 11 K to 400 K is $-!$ 1.51 mV/K, and the electron mobility limited by surface roughness is proportional to $E_{rm eff}^{-0.66}$.      

A 2.4 GHz Low-Power Sixth-Order RF Bandpass $DeltaSigma$ Converter in CMOS

A sixth-order RF bandpass $DeltaSigma$ ADC operating on the 2.4 GHz ISM band, which is suitable for RF digitization is presented. The bandpass loop filter is based on digitally programmable $Gm$ –$LC$ resonators that can be calibrated online to adjust the RF center frequency. By sampling below the input Nyquist frequency, the clock in the system was reduced to 3$~$ GHz, allowing a large reduction of the power consumption. Implemented in a standard 90 nm CMOS process, the IC achieves 40 $~$dB and 62 dB of SNDR and SFDR, respectively, on a 60 MHz bandwidth with 40 mW of power consumption leading to a FoM of 245 GHz/W (4.1 pJ/conversion step). This implementation paves a possible way towards direct RF digitization receiver architectures.      

A Programmable 25-MHz to 6-GHz $K/L$ Frequency Multiplier With Digital $K_{rm vco}$ Compensation

A programmable rational-$K/L$ frequency multiplier that can synthesize any frequency between 25 MHz and 6 GHz from an input clock ranging from 1 to 5.5 GHz is presented. The architecture employs a fractional-$N$ input clock divider followed by a fractional- $N$ PLL. In contrast to conventional architectures, this allows large $K$ and $L$ , whose maximum values are limited only by the word-length of digital $SigmaDelta$ modulators. Additionally, to alleviate large $K_{rm vco}$ variation and fractional spurs, which are inevitable in wide tuning range VCOs and fractional-$N$ synthesizers, new compensation techniques are implemented without involving additional circuitry. This is an ideal solution to support a programmable serializer/deserializer on a field-programmable gate array.      

A 0.13 $mu$ m CMOS Quad-Band GSM/GPRS/EDGE RF Transceiver Using a Low-Noise Fractional-N Frequency Synthesizer and Direct-Conversion Architecture

This paper presents a single-chip CMOS quad-band (850/900/1800/1900 MHz) RF transceiver for GSM/GPRS/EDGE applications which adopts a direct-conversion receiver, a direct-conversion transmitter and a fractional-N frequency synthesizer with a built-in DCXO. In the GSM mode, the transmitter delivers 4 dBm of output power with 1$^{circ}$ RMS phase error and the measured phase noise is ${-}$164.5 dBc/Hz at 20 MHz offset from a 914.8$~$MHz carrier. In the EDGE mode, the TX RMS EVM is 2.4% with a 0.5 $~$dB gain step for the overall 36 dB dynamic range. The RX NF and IIP3 are 2.7 dB/ ${-}$12 dBm for the low bands (850/900 MHz) and 3 dB/${-}$ 11 dBm for the high bands (1800/1900 MHz). This transceiver is implemented in 0.13 $mu$m CMOS technology and occupies 10.5 mm$^{2}$ . The device consumes 118 mA and 84 mA in TX and RX modes from 2.8 V, respectively and is housed in a 5$,times,$ 5 mm$^{2}$ 40-pin QFN package.      

Experimental-Numerical Comparison for a High-Density Data Center: Hot Spot Heat Fluxes in Excess of 500 W/ft $^{2}$

This paper uses previously published experimental data to present a comparison between test results and numerical simulations. The example considered is a large 7400 ft$^{2}$ data canter that houses over 130 heat-producing racks (1.2 MW) and 12 air conditioning units. Localized hot spot heat fluxes were measured to be as high as 512 W/ft$^{2}$ (5.5 kW/m$^{2}$ ) for a 400 ft$^{2}$ (37 m$^{2}$ ) region. A numerical model based on Computational Fluid Dynamics (CFD) was constructed using inputs from the measurements. The rack inlet air temperature was considered to be the basis for experimental versus numerical comparison. The overall mean rack inlet temperature predicted numerically at a height of 1.75 m is within 4 $^{circ}$ C of the test data with a rack-by-rack standard deviation of 3.3 $^{circ}$C.      

An FIR-Embedded Noise Filtering Method for $Delta Sigma$ Fractional-N PLL Clock Generators

This paper describes a noise filtering method for $Delta Sigma$ fractional- $N$ PLL clock generators to reduce out-of-band phase noise and improve short-term jitter performance. Use of a low-cost ring VCO mandates a wideband PLL design and complicates filtering out high-frequency quantization noise from the $Delta Sigma$ modulator. A hybrid finite impulse response (FIR) filtering technique based on a semidigital approach enables low-OSR $Delta Sigma$ modulation with robust quantization noise reduction despite circuit mismatch and nonlinearity. A prototype 1-GHz $Delta Sigma$ fractional-$N$ PLL is implemented in 0.18 $muhbox{m}$ CMOS. Experimental results show that the proposed semidigital method effectively suppresses the out-of-band quantization noise, resulting in nearly 30% reduction in short-term jitter.      

Demonstration of Pinhole Laser Beam Profiling Using a Digital Micromirror Device

Demonstrated for the first time, to the best of the authors' knowledge, is two-dimensional (2-D) pinhole laser beam profiling using a Texas Instruments visible band digital micromirror device (DMD). Software controlled micromirror digital tilt positions across the DMD plane create a moving pinhole for sampling an arbitrary distribution laser beam power profile. A 532-nm 0.5-W laser coupled to an optically addressed nematic liquid crystal spatial light modulator is used to generate a laser beam black-and-white high-resolution test line pattern having a 62.5-$mu$ m linewidth. The test pattern is successfully profiled using a DMD formed 27.36 $mu$ m$,times,$ 27.36 $mu$ m pinhole. Demonstrated for the first time is 2-D knife-edge DMD-based profiling of an ultraviolet 337-nm 4-ns pulsewidth 10-Hz pulsed laser beam.      

A Two-Port Single-Mode Fiber–Silicon Wire Waveguide Coupler Module Using Spot-Size Converters

In this paper, the performance of a two-port single-mode fiber–silicon wire waveguide coupler module which utilizes an identical spot-size converter (SSC) at the input and output ports is reported. Each of the silicon (Si)-based SSCs comprised cascaded horizontal linear and vertical nonlinear up-tapers measured 300 and 200 $mu$ m in length, respectively, in a common silicon-on-insulator (SOI) substrate. The structural parameters of the tapers were designed for compactness and relaxed tolerance to fabrication errors. The total length of the two-port coupler module was 1000 $mu$ m plus the variable length of the wire waveguide connecting the two SSCs. The mode-field diameter (MFD) of the Si-wire waveguide, 0.32$,times,$0.46 $mu$m $^{2}$, was transformed to the diameter of 2.8$,times,$ 8.0 $mu$ m$^{2}$ at the wavelength of 1.55 $mu$ m (corresponding to an area expansion of about 150 times) and vice versa by the SSCs with a net transmission loss of 4.1 dB/port. The field-mismatch loss between the SSC and the single-mode fiber with the MFD of 5.2 $mu$m was 2.1 dB/port.      

Distance Bounds for an Ensemble of LDPC Convolutional Codes

An ensemble of $(J,K)$ -regular low-density parity- check (LDPC) convolutional codes is introduced and existence-type lower bounds on the minimum distance $d _ {rm L}$ of code segments of finite length $L$ and on the free distance $d _{rm free}$ are derived. For sufficiently large constraint lengths $nu$ , the distances are shown to grow linearly with $nu$ and the ratio $d_ {rm L}/nu$ approaches the ratio $d _{ {rm free}}/nu$ for large $L$ . Moreover, the ratio of free distance to constraint length is several times larger than the ratio of minimum distance to block length for Gallager's ensemble of $(J,K)$-regular LDPC block codes.      

Widely Tunable Micro-Mechanical External-Cavity Diode Laser Emitting Around 2.1 $mu$ m

A widely tunable $(Delta lambda/lambda =7hbox{%})$ micro-mechanical external cavity GaSb-based diode laser ($mu$ ECL) emitting around 2.1 $mu$ m is presented. A micro-machined grating with a rectangular grating profile, which can be tilted electrostatically, is employed as wavelength selective element within the external cavity using a Littrow configuration. An optimized grating profile leads to a high diffraction efficiency in the ${-}1$st diffraction order and therefore to a broad tuning range of 152 nm. The maximum output power of the fiber coupled $mu$ ECL system varied only moderately between 22 and 10 mW across the tuning range.      

A Hybrid Spur Compensation Technique for Finite-Modulo Fractional-N Phase-Locked Loops

A finite-modulo fractional-$N$ PLL utilizing a low-bit high-order $DeltaSigma$ modulator is presented. A 4-bit fourth-order $DeltaSigma$ modulator not only performs non-dithered 16-modulo fractional-$N$ operation but also offers less spur generation with negligible quantization noise. Further spur reduction is achieved by charge compensation in the voltage domain and phase interpolation in the time domain, which significantly relaxes the dynamic range requirement of the charge pump compensation current. A 1.8–2.6 GHz fractional-$N$ PLL is implemented in 0.18 $mu{hbox {m}}$ CMOS. By employing high-order deterministic $DeltaSigma$ modulation and hybrid spur compensation, the spur level of less than $-$55 dBc is achieved when the ratio of the bandwidth to minimum frequency resolution is set to 1/4. The prototype PLL consumes 35.3 mW in which only 2.7 mW is consumed by the digital modulator and compensation circuits.      

A 5-GHz Wireless LAN Transmitter with Integrated Tunable High-Q RF Filter

A tunable, high-$Q$ RF filter suitable for wireless transmitters has been implemented in a standard digital 0.18-$muhbox{m}$ CMOS technology. Active circuits are used to enhance the $Q$ of two independent LC resonators, which are cascaded to form a wide bandwidth filter that can be tuned in both center frequency and bandwidth. A 5.145-GHz stagger-tuned filter with a 200-MHz bandwidth and 0.8 dB of ripple is demonstrated in an 802.11a sliding-IF transmitter. The transmitter provides spectral mask and EVM-compliant output power of $-$8.26 dBm for a 64-QAM OFDM signal. At lower output power, an EVM of $-$ 32.3 dB is achieved.      

A Low Phase-Noise QVCO With Integrated Back-Gate Coupling and Source Resistive Degeneration Technique

A 0.18 $mu$ m CMOS quadrature voltage-controlled oscillator with an extremely-low phase noise is presented. The excellent phase noise performance is accomplished by integration of the back-gate quadrature phase coupling and source resistive degeneration techniques into a complementary oscillator topology. The measured phase noise is as low as ${-}133$ dBc/Hz at 1 MHz offset from 3.01 GHz. The output phase imbalance is less than 1$^{circ}$ . The output power is $-1.25{pm} 0.5$ dBm and harmonic suppression is greater than 30.8 dBc. The oscillator core consumes 5.38 mA from a 1.5 V power supply. This QVCO achieves the highest figure-of-merit of ${-}193.5$ dBc/Hz.