5.7 GHz low-power variable-gain LNA in 0.18 /spl mu/m CMOS

A variable-gain low-noise amplifier (LNA) suitable for low-voltage and low-power operation is designed and implemented in a standard 0.18 /spl mu/m CMOS technology. With a current-reused topology, the common-source gain stages are stacked for minimum power dissipation while achieving high small-signal gain. The fully integrated 5.7 GHz LNA exhibits 16.4 dB gain, 3.5 dB noise figure and 8 dB gain tuning range with good input and output return losses. The LNA consumes 3.2 mW DC power from a supply voltage of 1 V. A gain/power quotient of 5.12 dB/mW is achieved in this work.     

A low-voltage folded-switching mixer in 0.18-/spl mu/m CMOS

Scaling of CMOS technologies has a great impact on analog design. The most severe consequence is the reduction of the voltage supply. In this paper, a low voltage, low power, AC-coupled folded-switching mixer with current-reuse is presented. The main advantages of the introduced mixer topology are: high voltage gain, moderate noise figure, moderate linearity, and operation at low supply voltages. Insight into the mixer operation is given by analyzing voltage gain, noise figure (NF), linearity (IIP3), and DC stability. The mixer is designed and implemented in 0.18-/spl mu/m CMOS technology with metal-insulator-metal (MIM) capacitors as an option. The active chip area is 160 /spl mu/m/spl times/200 /spl mu/m. At 2.4 GHz a single side band (SSB) noise figure of 13.9 dB, a voltage gain of 11.9 dB and an IIP3 of -3 dBm are measured at a supply voltage of 1 V and with a power consumption of only 3.2 mW. At a supply voltage of 1.8 V, an SSB noise figure of 12.9 dB, a voltage gain of 16 dB and an IIP3 of 1 dBm are measured at a power consumption of 8.1 mW.     

RF noise in 0.18-/spl mu/m and 0.13-/spl mu/m MOSFETs

Studied the gate finger number and gate length dependence on minimum noise figure (NF/sub min/) in deep submicrometer MOSFETs. A lowest NF/sub min/ of 0.93 dB is measured in 0.18-/spl mu/m MOSFET at 5.8 GHz as increasing finger number to 50 fingers, but increases abnormally when above 50. The scaling gate length to 0.13 /spl mu/m shows larger NFmin than the 0.18-/spl mu/m case at the same finger number. From the analysis of a well-calibrated device model, the abnormal finger number dependence is due to the combined effect of reducing gate resistance and increasing substrate loss as increasing finger number. The scaling to 0.13-/spl mu/m MOSFET gives higher NF/sub min/ due to the higher gate resistance and a modified T-gate structure proposed to optimize the NF/sub min/ for further scaling down of the MOSFET.     

1.49-/spl mu/m-band gain-shifted thulium-doped fiber amplifier for WDM transmission systems

This paper describes in detail the amplification characteristics of gain-shifted thulium-doped fiber amplifiers (GS-TDFAs) operating in the 1480to 1510-nm wavelength region (1.49-/spl mu/m S-band) for use in wavelength-division-multiplexing (WDM) systems. Gain shifting of a TDFA, which normally has a gain band at 1.47 /spl mu/m (S/sup +/-band), is achieved by two types of dual-wavelength pumping: (1) 1.05 and 1.56 /spl mu/m or (2) 1.4 and 1.56 /spl mu/m. The main pump source at 1.05 or 1.4 /spl mu/m creates population inversion between /sup 3/F/sub 4/ (upper laser level) and /sup 3/H/sub 4/ (lower laser level), while the auxiliary pump source at 1.56 /spl mu/m reduces the average fractional inversion down to approximately 0.4, which is a desired level for gain shifting. We show experimentally that the former provides a low internal noise figure (<4 dB) due to high fractional inversion at the input end of a thulium fiber, while the latter provides a very high optical efficiency but a higher internal noise figure (/spl sim/5 dB) due to the lower fractional inversion at the input end. These characteristics were verified by numerical simulation based on a comprehensive rate equation modeling. We demonstrated a 1.4- and 1.56-/spl mu/m laser-diode-pumped GS-TDFA with an optical efficiency of 29.3% and high output power of +21.5 dBm. Gain flatness and tilt control were also investigated. These results strongly confirm the feasibility of using GS-TDFAs in practical ultralarge-capacity WDM networks.     

Plug-in type 1.3-/spl mu/m fiber amplifier module for rack-mounted shelves

We have successfully developed a plug-in type PDFA module for rack mounted shelves which is assembled on a printed-board. In this module, we use a newly developed Pr/sup 3+/-doped high-NA PbF/sub 2//InF/sub 3/-based fluoride fiber and wavelength stabilized 1.017-/spl mu/m laser diodes (LDs). We have obtained a small-signal gain of 24 dB and a noise figure of 6.6 dB at 1.30 /spl mu/m with an LD drive current of 240 mA/spl times/2. We achieved an output power of 10 dBm with a signal input power of 0 dBm. The total power consumption of this module, including that of a Peltier cooler, was 3.5 W when the LD drive current was 240 mA/spl times/2.     

Low-noise metamorphic HEMTs with reflowed 0.1-/spl mu/m T-gate

A 0.1-/spl mu/m T-gate fabricated using e-beam lithography and thermally reflow process was developed and applied to the manufacture of the low-noise metamorphic high electron-mobility transistors (MHEMTs). The T-gate developed using the thermally reflowed e-beam resist technique had a gate length of 0.1 /spl mu/m and compatible with the MHEMT fabrication process. The MHEMT manufactured demonstrates a cutoff frequency f/sub T/ of 154 GHz and a maximum frequency f/sub max/ of 300 GHz. The noise figure for the 160 /spl mu/m gate-width device is less than 1 dB and the associated gain is up to 14 dB at 18 GHz. This is the first report of a 0.1 /spl mu/m MHEMT device manufactured using the reflowed e-beam resist process for T-gate formation.     

Polarization independent bulk active region semiconductor optical amplifiers for 1.3 /spl mu/m wavelengths

Semiconductor optical amplifiers for 1.3 /spl mu/m are realized combining single-step grown bulk InGaAsP active region with ridge-waveguides. Achieved fiber-to-fiber gains are in excess of 27 dB with spectral ripples below 0.2 dB. Gain is polarization insensitive to within 1 dB over the entire range of driving current, 1.28 /spl mu/m to 1.34 /spl mu/m wavelength and 10/spl deg/C to 50/spl deg/C heat sink temperature. Intrinsic noise figure is 6.3 dB. Gain saturates at +10 dBm.     

1.58-/spl mu/m broad-band erbium-doped tellurite fiber amplifier

This paper describes the development of a 1.58-/spl mu/m broad-band and gain-flattened erbium-doped tellurite fiber amplifier (EDTFA). First, we compare the spectroscopic properties of various glasses including the stimulated emission cross sections of the Er/sup 3+4/ I/sub 13/2/ /sup 4/I/sub 15/2/ transition and the signal excited-state absorption (ESA) cross sections of the Er/sup 3+4/ I/sub 13/2/ - /sup 4/I/sub 9/2/ transition. We detail the amplification characteristics of a 1.58-/spl mu/m-band EDTFA designed for wavelength-division-multiplexing applications by comparing it with a 1.58-/spl mu/m-band erbium-doped silica fiber amplifier. Furthermore, we describe the 1.58-/spl mu/m-band gain-flattened EDTFA we developed using a fiber-Bragg-grating-type gain equalizer. We achieved a gain of 25.3 dB and a noise figure of less than 6 dB with a slight gain excursion of 0.6 dB over a wide wavelength range of 1561-1611 nm. The total output power of the EDTFA module was 20.4 dBm and its power conversion efficiency reached 32.8%.     

35-dB gain Tm-doped ZBLYAN fiber amplifier operating at 1.65 /spl mu/m

We demonstrate the first high gain rare-earth-doped fiber amplifier operating at 1.65 /spl mu/m. It consists of ZBLYAN fiber with a Tm/sup 3+/-doped core and Tb/sup 3+/-doped cladding, pumped by 1.22 /spl mu/m laser diodes. It is possible to achieve efficient amplification with Tm/sup 3+/ ions if their amplified spontaneous emission (ASE) in the 1.75 to 2.0 /spl mu/m wavelength region is suppressed by doping Tb/sup 3+/ ions in the cladding. A two-stage-type fiber amplifier is constructed and a signal gain of 35 dB is achieved for a pump power of 140 mW. A gain over 25 dB is realized in the 1.65 /spl mu/m to 1.67 /spl mu/m wavelength region.     

1.2-V 5-/spl mu/W class-AB CMOS log-domain integrator with multidecade tuning

An integrator employing the log-domain principle and fabricated in a 0.8-/spl mu/m CMOS process is presented. It uses floating-gate MOS transistors biased in weak inversion to achieve low-voltage operation and low power consumption. The circuit does not suffer from initial charge trapped in the floating gates, thus not requiring postfabrication charge removal. It can be frequency tuned over more than three decades, from 25 Hz to 35 kHz, and uses a 1.2-V single supply to achieve a dynamic range at 1% THD of 75 dB thanks to its balanced class-AB operation. For cutoff frequencies in the range of 100 Hz, the supply voltage can be reduced down to 1 V. The circuit occupies an active area of 0.1 mm/sup 2/ and dissipates 4.7 /spl mu/W. The technique employed can be readily extended to high-order filters.     

A 25-MS/s 14-b 200-mW /spl Sigma//spl Delta/ Modulator in 0.18-/spl mu/m CMOS

The design of a fifth-order 4-b quantizer single-loop /spl Sigma//spl Delta/ modulator is presented that achieves 25-MS/s conversion rate with 84 dB of dynamic range and 82 dB of signal-to-noise ratio. Implemented in a 0.18-/spl mu/m CMOS technology, the 0.95-mm/sup 2/ chip has a power consumption of 200 mW from a 1.8-V supply.     

GaInAsSb-AlGaAsSb distributed feedback lasers emitting near 2.4 /spl mu/m

We have investigated fabrication and characteristics of continuous wave (cw) GaInAsSb-AlGaAsSb distributed feedback (DFB) lasers in the 2.4-/spl mu/m range. Single-mode DFB emission is obtained without overgrowth by first order Cr-Bragg gratings on both sides of a laser ridge. The cw threshold currents for a cavity with a length of 800 /spl mu/m and a width of 4 /spl mu/m are around 30 mA. At 20/spl deg/C and at an injection current of 190 mA output powers of 8.5 mW were realized. Monomode emission with a side-mode suppression ratio (SMSR) of 33 dB has been obtained.     

InP-based 1.3-1.6-/spl mu/m VCSELs with selectively etched tunnel-junction apertures on a wavelength flexible platform

In this letter, the authors demonstrate a wavelength flexible platform for the production of long-wavelength vertical-cavity surface-emitting lasers which provide full wavelength coverage from 1.3-1.6 /spl mu/m. All-epitaxial InP-based devices with AsSb-based distributed Bragg reflectors were achieved through a common design, process, and growth technology at both the important telecommunications wavelengths of 1.3 and 1.5 /spl mu/m. Thin selectively etched tunnel junctions were implemented as low-loss apertures and offer scalability to small device dimensions. Devices showed low threshold currents (<2 mA), near single-mode (SMSR>20 dB) operation, and high differential efficiency (>40% at 1.3 /spl mu/m and >25% at 1.5 /spl mu/m).     

1.65 /spl mu/m-band optical amplification with Er/sup 3+/-doped fluorozirconate fibre using 0.8 /spl mu/m upconversion pumping

In order to expand the available bandwidth for wavelength division multiplexing transmission systems, a 1.65 /spl mu/m-band optical fibre amplifier with Er/sup 3+/-doped fluorozirconate fibre using 0.8 /spl mu/m upconversion pumping has been demonstrated. The positive gain, 3.8 dB, is the first ever achieved by means of (/sup 2/H/sub 11/2/, /sup 4/S/sub 3/2/) /spl rarr/ /sup 4/I/sub 9/2/ stimulated emission transition.     

A novel ultracompact two-mode-interference wavelength division multiplexer for 1.5-/spl mu/m operation

A novel ultracompact 2/spl times/2 wavelength division multiplexer (WDM) for 1.55-/spl mu/m operation based on highly dispersive two-mode interference (TMI) was designed, theoretically modeled, and verified using a finite-difference-time-domain (FDTD) method. A two-moded waveguide assisted with a dispersive tooth-shaped grating provided a mode-dependent reflection band of central wavelength at 1.55 /spl mu/m. The wavelengths of 1538 and 1572 nm that were at the band edges and had the lowest reflection losses and relatively high dispersion were selected for wavelength multiplexing. The result showed that the wavelengths were separated by grating dispersion in a coupler length of 75 /spl mu/m which was much shorter than the required length of 1.1 mm in a regular TMI multiplexer of no grating. Insertion loss of about 1.7 dB and channel contrast of about 12 dB were achieved.     

A 1.5-V 75-dB dynamic range third-order G/sub m/-C filter integrated in a 0.18-/spl mu/m standard digital CMOS process

A design methodology of a CMOS linear transconductor for low-voltage and low-power filters is proposed in this paper. It is applied to the analog baseband filter used in a transceiver designed for wireless sensor networks. The transconductor linearization scheme is based on regulating the drain voltage of triode-biased input transistors through an active-cascode loop. A third-order Butterworth low-pass filter implemented with this transconductor is integrated in a 0.18-/spl mu/m standard digital CMOS process. The filter can operate down to 1.2-V supply voltage with a cutoff frequency ranging from 15 to 85 kHz. The 1% total harmonic distortion dynamic range measured at 1.5 V for 20-kHz input signal and 50-kHz cutoff frequency is 75 dB, while dissipating 240 /spl mu/W.     

A true-1-V 300-/spl mu/W CMOS-subthreshold log-domain hearing-aid-on-chip

This paper presents a true very low-voltage low-power complete analog hearing-aid system-on-chip as a demonstrator of novel analog CMOS circuit techniques based on log companding processing and using MOS transistors operating in subthreshold. Low-voltage circuit implementations are given for all of the required functions including amplification and automatic gain control filtering, generation, and pulse-duration modulation. Based on these blocks, a single 1-V 300-/spl mu/A application specific integrated circuit integrating a complete hearing aid in a standard 1.2-/spl mu/m CMOS technology is presented along with exhaustive experimental data. To the authors' knowledge, the presented system is the only CMOS hearing aid with true internal operation at the battery supply voltage and with one of the lowest current consumptions reported in literature. The resulting low-voltage CMOS circuit techniques may also be applied to the design of A/D converters for digital hearing aids.     

High-power 1.3-/spl mu/m InGaAsP-InP amplifiers with tapered gain regions

Tapered structures fabricated in InGaAsP-InP 1.3-/spl mu/m quantum-well material have been evaluated as high-gain high-saturation-power amplifiers. The devices, which had a 1-mm-long ridge-waveguide input gain section followed by a 2-mm-long tapered section, demonstrated an unsaturated gain of 26 dB at 2.0 A and about 30 dB at 2.8 A. Saturated output power at 2.8 A was >750 mW. At 2.0-A drive current and /spl ap/10-mW input power, the relative intensity noise of the amplified signal was /spl les/-160 dB/Hz at frequencies /spl ges/2 GHz.     

A 1.8-/spl mu/W sigma-delta modulator for 8-bit digitization of cardiac signals in implantable pacemakers operating down to 1.8 V

Implantable biomedical devices can highly benefit from submicrometer CMOS technologies both in terms of duration-time increase and size shrinking. This work shows how design techniques for submicrometer CMOS technologies lead to improvements in the sensing stage of a cardiac implantable pacemaker. A sigma-delta modulator is presented for 8-bit quantization of the natural electrical activity of the heart, fabricated in a 0.8-/spl mu/m CMOS technology. The low-voltage, low-power design procedure employs switched-opamp and weak inversion CMOS circuits. Measurement results confirm a power dissipation of 1.8 /spl mu/W, a minimum supply voltage of 1.8 V, and more than 50 dB of dynamic range.     

High-efficiency 1.3 /spl mu/m InAsP-GaInP MQW electroabsorption waveguide modulators for microwave fiber-optic links

High-efficiency electroabsorption waveguide modulators have been designed and fabricated using strain-compensated InAsP-GaInP multiple quantum wells at 1.32-/spl mu/m wavelength. A typical 200-/spl mu/m-long modulator exhibits a fiber-to-fiber optical insertion loss of 9 dB and an optical saturation intensity larger than 10 mW. The 3-dB electrical bandwidth is in excess of 20 GHz with a 50-/spl Omega/ load termination. When used in an analog microwave fiber-optic link without amplification, a RF link efficiency as high as -38 dB is achieved at 10 mW input optical carrier power. These analog link characteristics are the first reported using MQW electroabsorption waveguide modulators at 1.32 /spl mu/m.