Miyo Miyashita

A 2.2-V operation, 2.4-GHz single-chip GaAs MMIC transceiver for wireless applications

A 2.2-V operation, single-chip GaAs MMIC transceiver has been successfully developed for 2.4-GHz-band wireless applications such as wireless local area network terminals. The chip is fabricated using a planar self-aligned gate field-effect transistor. To generate sufficient negative voltage for gate-biasing and to enhance switch power handling capability under a 2.2-V supply, a newly designed negative voltage generator with a voltage doubler (NVG-VD) and a switch control logic circuit are integrated on the chip, together with a power amplifier, a transmit/receive switch, and a low-noise amplifier. The NVG-VD is designed to produce both a 3.3-V positive step-up voltage and a -2.1-V negative voltage under 2.2 V in operation voltage. Biased with these outputs, the logic circuit accommodates high power outputs of over 25 dBm with a low operating voltage of 2.2 V in transmit mode, With a 2.45-GHz modulated signal based on IS-95 standards, a 21-dBm output power and a 33% efficiency are obtained at a /spl plusmn/1.25-MHz-offset adjacent channel power rejection of -45 dBc. In receive mode, a low-noise amplifier achieves a 1.8-dB noise figure and an 11-dB gain with a 3.0-mA current. This transceiver enables significant size and weight reductions in 2.4-GHz-band wireless application terminals.

Long-Wavelength Receiver Optoelectronic Integrated Circuit on 3-Inch-Diameter GaAs Substrate Grown by InP-on-GaAs Heteroepitaxy.

A monolithic long-wavelength receiver optoelectronic integrated circuit (OEIC), which integrates an InGaAs PIN-photodiode (PD) and a GaAs field-effect transistor (FET), has been successfully fabricated on a 3-inch-diameter GaAs substrate using InP-on-GaAs heteroepitaxy, by metalorganic chemical vapor deposition (MOCVD) and conventional GaAs-IC process technology. The epitaxial quality of the PD layer has been improved by use of a low-temperature-grown buffer layer, thermal cyclic annealing and an InGaAs/InP strained-layer superlattice. The integrated PD has low dark current of 10 nA at -5 V bias voltage, and exhibited stable operation at 175°C. The fabricated receiver OEIC has 1.4 GHz bandwidth and sensitivity of -28.1 dBm at the transmission rate of 622 Mb/s with bit error rate of 10-9, which is applicable to practical subscriber optical communication systems.

An ultra-broadband GaAs MESFET preamplifier IC for a 10 Gb/s optical communication system

An ultrabroadband GaAs MESFET preamplifier IC was developed for a 10-Gb/s optical communication system. A high transimpedance of 44 dB- Omega has been obtained from DC to 12 GHz. A receiver has also been fabricated by using this preamplifier IC and a photodiode. The receiver operated with an extremely low equivalent input noise current of 12.6 pA/ square root Hz from DC to 7.8 GHz. The circuit design and the high-frequency characteristics of the preamplifier IC and the receiver are described. >

An AlGaAs/InGaAs pseudomorphic HEMT modulator driver IC with low power dissipation for 10-Gb/s optical transmission systems

An optical modulator driver integrated circuit (IC) has been developed for 10-Gb/s optical communication systems. To achieve both high-frequency (HF) operation and low power dissipation, 0.2-/spl mu/m T-shaped gate AlGaAs/InGaAs pseudomorphic high electron-mobility transistors (HEMTs) have been employed for their large transconductance g/sub m/ of 610 mS/mm and high cutoff frequency f/sub T/ of 67.5 GHz. In addition, optimizing input logic swing, switching transistor size in the output driver, and using cascode-current mirror circuits with small output conductance enable power dissipation as low as 1 W to be achieved at a 10-Gb/s nonreturn-to-zero (NRZ) signal output with 3 V/sub p/./sub p/. This is the lowest value ever reported for power dissipation. As an additional function, the output-voltage swing can be controlled in the range from 2 to 3.3 V/sub p/./sub p/. by the current mirror circuit for the purpose of adjusting the optical-output-signal duty factor through an optical modulator.

High-Directivity Enhancement With Passive and Active Bypass Circuit Techniques for GaAs MMIC Microstrip Directional Couplers

This paper describes monolithic microwave integrated circuit microstrip directional couplers based on a new directivity enhancement technique. This technique utilizes a bypass circuit-a phase shifter and an attenuator-placed between the coupling and isolation ports to cancel out backward wave leakage to the coupling port, thereby enhancing directivity of the couplers. The bypass circuit can be implemented with a simple passive LCR circuit or an active heterojunction bipolar transistor (HBT) phase-inversion attenuation circuit. Edge-coupled-type microstrip spiral couplers using the passive and active bypass circuits were fabricated in a GaAs HBT process. Measurements are as follows. The coupler with the passive LCR bypass circuit delivers a -21-dB coupling factor and a 0.14-dB insertion loss (IL) at 2.6 GHz while keeping enhanced directivity of more than 30 dB with a 23.1% relative bandwidth. This corresponds to more than 21-dB improvement of directivity at the same frequency, compared to the coupler without the bypass circuit. For the coupler with the active attenuator, a peak directivity of 46 dB and more than 30-dB directivity with a 120% relative bandwidth are achieved while a -21-dB coupling factor and a 0.13-dB IL are delivered at 2 GHz. Additional measurements of HBT power detectors integrated with the couplers show that the couplers with passive and active bypass circuits can suppress detection errors of less than ±0.20 and ±0.10 dB, respectively, under 4:1 voltage standing-wave ratio load mismatching conditions, thus proving the effectiveness of the bypass techniques.

Fully Integrated GaAs HBT MMIC Power Amplifier Modules for 2.5/3.5-GHz-Band WiMAX Applications

This paper describes two GaAs HBT MMIC power amplifier modules (PAs) for 2.5-GHz- and 3.5-GHz-band WiMAX applications. Each amplifier module integrates a fully 50-Omega input/output matched three-stage amplifier, a 0/20-dB step attenuator, an attenuator controller, and an RF detector together with all bias circuits, featuring on-module full integration. The step attenuator operating with high power handling capability, low-distortion, and low-bias current is placed between the first and second stages, thereby suppressing the change of the input return loss between thru and attenuation modes. With the 4.5 mm x 4.5 mm small-size module, optimized circuit design approaches lead to the following good measurement results under the 6-V supply voltage and WiMAX modulation (64QAM) test condition. The 2.5-GHz-band PA is capable of delivering a high gain (Gp) of over 31.9 dB, EVM of less than 2.1%, and PAE of more than 13.4% at a 28-dBm high output power (Pout). For the 3.5-GHz-band PA, a high Gp of over 28.1 dB, EVM of less than 2.4%, and PAE of over 11% are achieved at a Pout, of 28 dBm.

A multiband power amplifier using combination of CMOS and GaAs technologies for WCDMA handsets

A multiband power amplifier using combination of CMOS and GaAs technologies (Combo MB PA) which supports quad WCDMA bands (Band V, VIII, II, I) is described. With four chips - two GaAs-HBT chips, a GaAs-HEMT chip, and a CMOS chip - mounted on a 5.5×5mm2 laminate, the Combo MB PA comprises two amplifier chains and two SPDT HEMT band-select switches, covering 824-915MHz and 1850-1980MHz. Each amplifier chain has switchable signal paths corresponding to dual (high and low) power modes (HPM and LPM) for saving battery current in practical handset use. In the PA, driver stages, RF switches, and their bias- and switch-control circuits are integrated on the CMOS chip for cost reduction. Only the final power stages are fabricated in a GaAs HBT process. Measurements were carried out under the condition of a 3.4V supply voltage and a WCDMA (3GPP R99) modulated signal. Due to optimized broadband matching design, the Combo MB PA achieves a power-added efficiency (PAE) as high as 40% at a Pout of 28dBm over 824-915MHz in the HPM while keeping adjacent channel leakage power ratio (ACLR) less than -39dBc. In the LPM, PAE of 15 % at a Pout of 17dBm is obtained with ACLR of less than -40dBc. For 1850-1980MHz, the PA shows 35% PAE with ACLR of less than -37dBc at 28dBm of Pout in the HPM and 14% PAE at 17dBm of Pout in the LPM.

A Current-Mirror-Based GaAs-HBT RF Power Detector for Wireless Applications

This paper describes circuit design and measurement results of a newly developed GaAs-HBT RF power detector for use in wireless applications. The detector features logarithm-like, frequency-independent characteristics. The detector can be also driven with small input power levels, enabling base-terminal monitor which can utilize directivity of a power stage. Since a unique current-mirror-based topology is successfully employed for realizing these features, the detector is easy to implement on a GaAs HBT power amplifier. Measurement results of a prototype detector fabricated with a single-stage amplifier on the same die are as follows. The detector can deliver a detection voltage of 0.4-2.5 V and its slope of less than 0.17 V/dB over a 2-22-dBm output power range at 3.5 GHz while drawing a current of less than 1.8 mA from a 2.85-V supply. The detector is also capable of suppressing voltage dispersion within 50 mV over a 3.1-3.9-GHz wide frequency range operation, and this dispersion is less than one-seventh of that of a conventional collector-terminal-monitor type diode detector.

3.5-GHz-Band Low-Bias-Current Operation 0/20-dB Step Linearized Attenuators Using GaAs-HBT Compatible, AC-Coupled, Stack Type Base-Collector Diode Switch Topology

This paper describes two different types of GaAs-HBT compatible, base-collector diode 0/20-dB step attenuators-diode-linearizer type and harmonics-trap type-for 3.5-GHz-band wireless applications. The two attenuators use an AC-coupled, stacked type diode switch topology featuring high power handling capability with low bias current operation. Compared to a conventional diode switch topology, this topology can improve the capability of more than 6 dB with the same bias current. In addition, successful incorporation of a shunt diode linearizer and second- and third-harmonic traps into the attenuators gives the IM3 distortion improvement of more than 7 dB in the high power ranging from 16 dBm to 18 dBm even in the 20-dB attenuation mode when IM3 distortion levels are basically easy to degrade. Measurement results show that both the attenuators are capable of delivering power handling capability (P 0.2dB ) of more than 18 dBm with IM3 levels of less than -35 dBc at an 18-dBm input power while drawing low bias currents of 3.8 mA and 6.8 mA in the thru and attenuation modes from 0/5-V complementary supplies. Measured insertion losses of the linearizer-type and harmonics-trap type attenuators in the thru mode are as low as 1.4 dB and 2.5 dB, respectively.

Compact multi-chip modules with integrated functions for 10-Gbps lightwave transceivers

Summary form only given. Recently, as various 10-Gbps devices have been developed, reduction of size as well as cost of 10-Gbps lightwave transceivers is required. To meet this demand, compact modules having integrated transceiver functions will become one of the promising candidates, and we have already developed compact multi-chip-modules (MCMs) for high-speed lightwave transmitters and receivers. In this paper, we have developed two more MCMs for 10-Gbps receivers and confirmed the applicability of all developed MCMs for 10-Gbps lightwave transceivers.