$S$ - and $C$ -Band Ultra-Compact Phase Shifters Based on All-Pass Networks

Ultra-compact phase shifters are presented. The proposed phase-shifting circuits utilize the lumped element all-pass networks. The transition frequency of the all-pass network, which determines the size of the circuit, is set to be much higher than the operating frequency. This results in a significantly small chip size of the phase shifter. To verify this methodology, 5-bit phase shifters have been fabricated in the $S$ - and $C$ -band. The $S$ -band phase shifter, with a chip size of 1.87 mm $,times,$0.87 mm (1.63 mm $^{2}$), has achieved an insertion loss of ${hbox{6.1 dB}} pm {hbox{0.6 dB}}$ and rms phase-shift error of less than 2.8$^{circ}$ in 10% bandwidth. The $C$ -band phase shifter, with a chip size of 1.72 mm $,times,$0.81 mm (1.37 mm $^{2}$), has demonstrated an insertion loss of 5.7 dB $pm$ 0.8 dB and rms phase-shift error of less than 2.3 $^{circ}$ in 10% bandwidth.      

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.      

Compact $S$ -/$Ka$-Band CMOS Quadrature Hybrids With High Phase Balance Based on Multilayer Transformer Over-Coupling Technique

This paper presents compact CMOS quadrature hybrids by using the transformer over-coupling technique to eliminate significant phase error in the presence of low-$Q$ CMOS components. The technique includes the inductive and capacitive couplings, where the former is realized by employing a tightly inductive-coupled transformer and the latter by an additional capacitor across the transformer winding. Their phase balance effects are investigated and the design methodology is presented. The measurement results show that the designed 24-GHz CMOS quadrature hybrid has excellent phase balance within ${pm}{hbox{0.6}}^{circ}$ and amplitude balance less than ${pm} {hbox{0.3}}$ dB over a 16% fractional bandwidth with extremely compact size of 0.05 mm$^{2}$. For the 2.4-GHz hybrid monolithic microwave integrated circuit, it has measured phase balance of ${pm}{hbox{0.8}}^{circ}$ and amplitude balance of ${pm} {hbox{0.3}}$ dB over a 10% fractional bandwidth with a chip area of 0.1 mm$^{2}$ .      

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.      

10-GHz and 20-GHz Channel Spacing High-Resolution AWGs on InP

This letter reports on 10-GHz and 20-GHz channel-spacing arrayed waveguide gratings (AWGs) based on InP technology. The dimensions of the AWGs are 6.8$,times,$8.2 mm$^{2}$ and 5.0$,times,$6.0 mm$^{2}$, respectively, and the devices show crosstalk levels of $-$12 dB for the 10-GHz and $-$17 dB for the 20-GHz AWG without any compensation for the phase errors in the arrayed waveguides. The root-mean-square phase errors for the center arrayed waveguides were characterized by using an optical vector network analyzer, and are 18 $^{circ}$ for the 10-GHz AWG and 28$^{circ}$ for the 10-GHz AWG.      

A 300 nW, 15 ppm/$^{circ}$C, 20 ppm/V CMOS Voltage Reference Circuit Consisting of Subthreshold MOSFETs

A low-power CMOS voltage reference was developed using a 0.35 $mu$m standard CMOS process technology. The device consists of MOSFET circuits operated in the subthreshold region and uses no resistors. It generates two voltages having opposite temperature coefficients and adds them to produce an output voltage with a near-zero temperature coefficient. The resulting voltage is equal to the extrapolated threshold voltage of a MOSFET at absolute zero temperature, which was about 745$~$mV for the MOSFETs we used. The temperature coefficient of the voltage was 7 ppm/ $^{circ}$C at best and 15 ppm/$^{circ}$C on average, in a range from ${-}$ 20 to 80$^{circ}$ C. The line sensitivity was 20 ppm/V in a supply voltage range of 1.4–3 V, and the power supply rejection ratio (PSRR) was ${-}$45 dB at 100 Hz. The power dissipation was 0.3 $mu$W at 80$^{circ}$C. The chip area was 0.05 mm$^2$ . Our device would be suitable for use in subthreshold-operated, power-aware LSIs.      

A 16–44 GHz Compact Doubly Balanced Monolithic Ring Mixer

A novel and compact 16–44 GHz ultra-broadband doubly balanced monolithic ring mixer for Ku- to Ka-band applications implemented with a 0.15-$mu$m pHEMT process is presented. The proposed mixer is composed of a C-band miniature spiral balun and a 180$^{circ}$ hybrid formed with an interdigital coupler, a low-pass $pi$-network, and a high-pass T-network. The 180$^{circ}$ hybrid eliminates the use of a cross-over structure for application in the balanced mixer, as well as provides an output port for the RF extraction of up-converter application. This proposed configuration leads to a die size of less than 0.8$,times,$ 0.8 mm$^{2}$ . From the measured results, the mixer exhibits an 11–14 dB conversion loss, a 27–50 dB high LO-to-IF isolation over 16–44 GHz RF/LO bandwidth, and a 1-dB compression power of 14 dBm for both down- and up-converter applications.      

180$^{circ}$ and 90$^{circ}$ Phase Shifting Networks With an Octave Bandwidth and Small Phase Errors

A new phase shifting network for both 180 $^{circ}$ and 90 $^{circ}$ phase shift with small phase errors over an octave bandwidth is presented. The theoretical bandwidth is 67% for the 180$^{circ}$ phase bit and 86% for the 90$^{circ}$ phase bit when phase errors are $pm 2^{circ}$. The proposed topology consists of a bandpass filter (BPF) branch, consisting of a LC resonator and two shunt quarter-wavelength transmission lines (TLs), and a reference TL. A theoretical analysis is provided and scalable parameters are listed for both phase bits. To test the theory, phase shifting networks from 1 GHz to 3 GHz were designed. The measured phase errors of the 180$^{circ}$ and the 90$^{circ}$ phase bit are $pm 3.5^{circ}$ and $pm 2.5^{circ}$ over a bandwidth of 73% and 102% while the return losses are better than 18 dB and 12 dB, respectively.      

$hbox{TiN/ZrO}_{2}$/Ti/Al Metal–Insulator–Metal Capacitors With Subnanometer CET Using ALD-Deposited $hbox{ZrO}_{2}$ for DRAM Applications

We provide the first report of the structural and electrical properties of $hbox{TiN/ZrO}_{2}$/Ti/Al metal–insulator–metal capacitor structures, where the $hbox{ZrO}_{2}$ thin film (7–8 nm) is deposited by ALD using the new zirconium precursor ZrD-04, also known as Bis(methylcyclopentadienyl) methoxymethyl. Measured capacitance–voltage ($C$– $V$) and current–voltage ( $I$–$V$) characteristics are reported for premetallization rapid thermal annealing (RTP) in $hbox{N}_{2}$ for 60 s at 400 $^{circ}hbox{C}$, 500 $^{circ}hbox{C}$, or 600 $^{ circ}hbox{C}$. For the RTP at 400 $^{circ}hbox{C}$ , we find very low leakage current densities on the order of nanoamperes per square centimeter at a gate voltage of 1 V and low capacitance equivalent thickness values of $sim$ 0.9 nm at a gate voltage of 0 V. The dielectric constant of $ hbox{ZrO}_{2}$ is 31 $pm$ 2 after RTP treatment at 400 $^{circ}hbox{C}$.      

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.      

A Low-Complexity, Low-Phase-Noise, Low-Voltage Phase-Aligned Ring Oscillator in 90 nm Digital CMOS

An 8-phase phase-aligned ring oscillator in 90 nm digital CMOS is presented that operates up to 2 GHz. The low-complexity circuit consumes 13 mW at 2 GHz and 1.2 mW at 400 MHz, while a flat in-band phase noise below $-$120 dBc$/$Hz is achieved, in close agreement with the presented theory. The circuit occupies an area of 0.008 mm$^{2}$ .      

Effect of Growth Temperature on InP QD Lasers

We describe the effect of growth temperature on the optical absorption, gain, and threshold current density of 730-nm emitting, metal–organic vapor phase epitaxy (MOVPE) grown, InP–AlGaInP quantum-dot lasers. Decreasing the growth temperature from 750 $^{circ}hbox{C}$ to 690 $^{circ}hbox{C}$ leads to an increase in ground state absorption, while sufficient optical gain and low 300 K threshold current density is obtained in the growth temperature window between 710 $^{circ}hbox{C}$ and 730 $^{circ}hbox{C}$ . Wider (16 nm compared to 8 nm) interlayer barriers lead to lower threshold current density with 300 K values as low as 165 $hbox{Acm}^{-2}$ for 2-mm-long lasers with uncoated facets.      

A 2.4–2.5 GHz WLAN Direct-Conversion Receiver Front-End With Low-Distortion Baseband Filters

Low-distortion I/Q baseband filters interface with a 2.5 GHz RF receiver front-end configured as a Gm-cell in a direct-conversion architecture targeted towards WLAN 802.11b application. The active I/Q current-mode filters use AC current to carry the large swing of both desired and blocker signals, relaxing the voltage headroom requirement to a 1.2 V supply. An on chip master–slave automatic tuner is used to lock the filter bandwidth to a precision 20 MHz reference crystal oscillator, resulting in a $≪ ,$3% tuning accuracy and $≪, $ 0.5% I/Q bandwidth matching. The receiver achieves a 3.2 dB DSB NF, ${-}$14 dBm out-of-band IIP3, and ${+}$ 27 dBm worst case IIP2, all referred to the LNA input, while drawing 30mA from a 2.7 V supply. The chip is fabricated in a 0.5 $mu$m 46 GHz $f_{T}$ SiGe BiCMOS process. The active area is 2.54 mm$^{2}$ .      

A 30 GHz Variable Gain Amplifier With High Output Voltage Swing for Ultra-Wideband Radar

This paper reports on the analysis, design and characterization of a 30 GHz fully differential variable gain amplifier for ultra-wideband radar systems. The circuit consists of a variable gain differential stage, which is fed by two cascaded emitter followers. Capacitive degeneration and inductive peaking are used to enhance bandwidth. The maximum differential gain is 11.5 dB with ${pm}1.5$ dB gain flatness in the desired frequency range. The amplifier gain can be regulated from 0 dB up to 11.5 dB. The circuit exhibits an output 1 dB compression point of 12 dBm. The measured differential output voltage swing is 1.23 V$_{pp}$ . The 0.75 mm$^2$ broadband amplifier consumes 560 mW at a supply voltage of ${pm}3.3$ V. It is manufactured in a low-cost 0.25 $mu$ m SiGe BiCMOS technology with a cut-off frequency of 75 GHz. The experimental results agree very well with the simulated response. A figure of merit has been proposed for comparing the amplifier performance to previously reported works.      

Electrical Properties of $hbox{Bi}_{5}hbox{Nb}_{3} hbox{O}_{15}$ Thin Film Grown on $hbox{TiN}/hbox{SiO}_{2}/ hbox{Si}$ at Room Temperature for Metal–Insulator–Metal Capacitors

Buckling was observed in $hbox{Bi}_{5}hbox{Nb}_{3}hbox{O}_{15}$ (BiNbO) films grown on $hbox{TiN}/hbox{SiO}_{2}/hbox{Si}$ at 300 $^{circ}hbox{C}$ but not in films grown at room temperature and annealed at 350 $^{circ}hbox{C}$. The 45-nm-thick films showed a high capacitance density and a low dissipation factor of 8.81 $hbox{fF}/muhbox{m}^{2}$ and 0.97% at 100 kHz, respectively, with a low leakage current density of 3.46 $hbox{nA}/hbox{cm}^{2}$ at 2 V. The quadratic and linear voltage coefficients of capacitance of this film were 846 $hbox{ppm}/hbox{V}^{2}$ and 137 ppm/V, respectively, with a low temperature coefficient of capacitance of 226 $hbox{ppm}/^{circ}hbox{C}$ at 100 kHz. This suggests that a BiNbO film grown on a $hbox{TiN}/ hbox{SiO}_{2}/hbox{Si}$ substrate is a good candidate material for high-performance metal–insulator–metal capacitors.      

Switch-Matrix-Based High-Density Microelectrode Array in CMOS Technology

We report on a CMOS-based microelectrode array (MEA) featuring 11,011 metal electrodes and 126 channels, each of which comprises recording and stimulation electronics, for extracellular bidirectional communication with electrogenic cells, such as neurons or cardiomyocytes. The important features include: (i)$~$high spatial resolution at (sub)cellular level with 3150 electrodes per mm$^{2}$ (electrode diameter 7 $mu$ m, electrode pitch 18$ mu$m); (ii) a reconfigurable routing of the recording sites to the 126 channels; and (iii) low noise levels.      

Evaluation of High-Temperature Absorption Coefficients of Ionized Gas Plasmas in Optical Fibers

The large absorption coefficient $alpha$ of a fiber core at high temperatures is closely related to the generation of a fiber fuse. When silica glass is heated to a temperature above 4500 K, it forms Si $^{+}$ and O $^{+}$ ions and electrons in the ionized gas plasma state. We estimate the $alpha$ value for the plasma in the fiber core at high temperatures. $alpha$ begins to increase at 3500 K, then increases rapidly with increasing temperature above 4000 K, reaching a value of $1times 10^{7}$ m$^{-1}$ at 6000 K. This value is about 300 times that necessary for initiating a fiber fuse.      

A Wideband Superconducting Filter Using Strong Coupling Resonators for Radio Astronomy Observatory

A 12-pole wideband superconducting microstrip bandpass filter, which has a fractional bandwidth of 38% and a center frequency of 1455 MHz, is presented for the Miyun 50-m radio astronomy telescope, Beijing, China. A novel resonator, which can not only generate very large coupling, but also push its first spurious resonant peak away from the passband, is introduced. A new style interleaved coupling structure is proposed and successfully used in this study to realize the remarkably required strong coupling. To achieve high edge slope on the high side of the passband, as required, a single transmission zero was introduced. The filter was fabricated on a 36 mm$,times,$ 30 mm$,times,$ 0.5 mm double-sided YBa$_{2}$ Cu$_{3}$ O$_{7}$ film deposited on an MgO substrate. The measured results showed that the filter had 0.05-dB minimum insertion loss, 0.08-dB passband ripple, and 23-dB return loss at a temperature of 40 K. The first spurious peak did not appear until 2632 MHz. The overall measured performance showed good agreement with the simulation.      

A 100 MS/s 4 MHz Bandwidth 70 dB SNR $Delta Sigma$ ADC in 90 nm CMOS

This paper describes the results of an implementation of a high speed $Delta Sigma$ ADC in 90 nm CMOS process, which is developed for a direct-conversion digital TV receiver. The $Delta Sigma$ ADC is based on a switched-capacitor fourth-order single-loop $Delta Sigma$ modulator with a 4-bit quantizer. The ADC uses a triple sampling technique and a two-step summation scheme for low power and high speed operation. Also, a digital signal processing block, including a decimation filter, a channel selection filter and a digital programmable gain amplifier (PGA), is implemented in the same process. The decimation filter is based on a polyphase IIR filter with a decimation ratio of 5, while the channel selection filter is based on two path lattice wave digital IIR filter. The ADC achieves 69.95 dB SNR and 66.85 dB SNDR over a 4 MHz bandwidth with a sampling frequency of 100 MHz. The fabricated $Delta Sigma$ ADC and the digital signal processing block occupy 0.53$~$mm$^2$ and 0.09 mm$^{2}$, and consume 11.76 mW per channel.      

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.