Hisao Shigematsu

Millimeter-wave CMOS circuit design

We have developed a 27- and 40-GHz tuned amplifier and a 52.5-GHz voltage-controlled oscillator using 0.18-mum CMOS. The line-reflect-line calibrations with a microstrip-line structure, consisting of metal1 and metal6, was quite effective to extract the accurate S-parameters for the intrinsic transistor on an Si substrate and realized the precise design. Using this technique, we obtained a 17-dB gain and 14-dBm output power at 27 GHz for the tuned amplifier. We also obtained a 7-dB gain and a 10.4-dBm output power with a good input and output return loss at 40 GHz. Additionally, we obtained an oscillation frequency of 52.5 GHz with phase noise of -86 dBc/Hz at a 1-MHz offset. These results indicate that our proposed technique is suitable for CMOS millimeter-wave design

40Gb/s CMOS distributed amplifier for fiber-optic communication systems

This paper describes a 0.18 /spl mu/m CMOS distributed amplifier with optimized source degeneration which achieves a 4 dB gain and 39 GHz bandwidth within 1 dB gain variation.

A 49-GHz preamplifier with a transimpedance gain of 52 dB/spl Omega/ using InP HEMTs

This paper describes a new preamplifier IC with 0,15-/spl mu/m gate InP-based high electron mobility transistors (HEMTs) for a high-speed fiber optic communication system. The preamplifier consists of a lumped-element transimpedance amplifier (TIA) for the input stage and a highly stabilized distributed amplifier with cascode-configured unit cells for the gain stage. A gain-peaking technique for a distributed amplifier was employed to enhance the bandwidth and gain flatness of the preamplifier. This gain peaking profile compensates for a lack of bandwidth of a TIA. As a result, we achieved a flat transimpedance gain of 52 dB/spl Omega/ and a bandwidth of 49 GHz.

A 54-GHz distributed amplifier with 6-V/sub PP/ output for a 40-Gb/s LiNbO/sub 3/ modulator driver

We have developed a distributed amplifier for a LiNbO/sub 3/ modulator driver using double-doped AlGaAs-InGaAs-AlGaAs pseudomorphic high electron mobility transistors (p-HEMTs). By using a stabilization and negative resistance control technique with source inductance and grounded coplanar waveguided lines, we obtained a gain of 15 dB, a bandwidth of 54 GHz, and 6-V/sub PP/ output. These results indicate that our circuit is a leading candidate for use as a LiNbO/sub 3/ modulator driver in 40-Gb/s fiber-optic communication systems.

1.5 V Low-Voltage Microwave Power Performance of InAlAs/InGaAs Double Heterojunction Bipolar Transistors

In this paper, we report the first demonstration of microwave power performance of InAlAs/InGaAs double heterojunction bipolar transistors (DHBTs) obtained at an extremely low operating voltage of 1.5 V. In order to obtain a high output power (P out) at a low operating voltage, we used DHBTs rather than single heterojunction bipolar transistors (SHBTs) and thus reduced the offset voltage (V CE,offset). We obtained a much lower V CE,offset of 50 mV for the DHBT than that of 300 mV for a SHBT. At a low operation voltage of 1.5 V, the DHBT exhibited a P out of 20.6 dBm with a power added efficiency (η add) of 36.6% and a power gain (G a) of 8.5 dB biased for class-B operation at 1.9 GHz. The high-speed performance of the DHBT are a unity cutoff frequency (f T) of 76 GHz and a maximum oscillation frequency (f max) of 157 GHz. We also studied the reliability of DHBTs by conducting a 1000-hour accelerated life test. The InGaAs HBTs had a lifetime of 2×106 h at a junction temperature of 125°C with an activation energy of 0.95 eV.

C-band 340-W and X-band 100-W GaN power amplifiers with over 50-% PAE

In this paper, we report a C-band power amplifier with over 340-W output power using 0.8-µm GaN-HEMTs and an X-band power amplifier with over 100-W output power using 0.25-µm GaN-HEMTs. We used two-chip configurations and the three-stage impedance transformers to extend the bandwidth for both circuits. The input and output lines adjacent to each chip are divided by four to suppress the non-uniform heat distribution in a chip at high frequencies. As a result, we obtained 343-W output power and 53-% power added efficiency (PAE) at 4.8 GHz. This is the highest output power ever reported C-band power amplifiers. We also obtained 101-W output power and 53-% PAE at 9.8 GHz. This is also the highest PAE ever reported X-band power amplifiers with over 50-W output power.

Reliability of GaN HEMTs: current status and future technology

In this paper, we describe highly reliable GaN high electron mobility transistors (HEMTs) for high-power and high-efficiency amplifiers. First, we present the reliability mechanisms and progress on the previously reported GaN HEMTs. Next, we introduce our specific device structure for GaN HEMTs for improving reliability. An n-GaN cap and optimized buffer layer are used to realize high efficiency and high reliability by suppressing current collapse and quiescent current (Idsq)-drift. Finally, we propose a new device process around the gate electrode for further improvement of reliability. Preventing gate edge silicidation leads to reduced gate leakage current and suppression of initial degradation in a DC-stress test under high-temperature and high-voltage conditions. Gate edge engineering plays a key role in reducing the gate leakage current and improving reliability.

45 GHz distributed amplifier with a linear 6-Vp-p output for a 40 Gb/s LiNbO/sub 3/ modulator driver circuit

We developed a coplanar waveguided-type distributed amplifier for a LiNbO/sub 3/ modulator driver (LN driver) using double-doped AlGaAs/InGaAs/AlGaAs-pseudomorphic High Electron Mobility Transistors (p-HEMTs). By using a stabilization and impedance control technique, we obtained a 45 GHz bandwidth for coplanar waveguided (CPW) lines with a 600 /spl mu/m thick substrate and 54 GHz bandwidth for grounded coplanar waveguided (GCPW) lines with a 75 /spl mu/m thick substrate, and a linear 6-Vp-p output at 40 Gb/s. These results indicate that our circuit design technique is suitable for use in fiber-optic communication systems.

Degradation-Mode Analysis for Highly Reliable GaN-HEMT

We analyzed the degradation mode of GaN-HEMTs. We observed the sudden degradation to make serious influence on the reliability. In this paper, we proposed a new approach to eliminate sudden-degradation devices. By measuring the gate leakage current before stress test, we can predict the sudden degradation. We also discussed the gate leakage current factor, for example, the surface hexagonal pits. Using this eliminating method, we could select the reliable devices with a life of over 1 times 106 hours at high-temperature of 200degC.

Over 10W C-Ku band GaN MMIC non-uniform distributed power amplifier with broadband couplers

A 6–18 GHz monolithic microwave integrated circuit (MMIC) power amplifier (PA) was successfully developed using a quarter wavelength short stub and a monolithic broadband coupler for a non-uniform distributed power amplifier (NDPA) topology. This topology improved the output power at 18 GHz and attained a flat output power profile over 6–18 GHz. It also achieved filtering characteristics for both lower and higher cut-off frequencies. A fabricated MMIC PA with 0.25µm GaN HEMTs delivered an output power of more than 10 W with average power added efficiency (PAE) of 18% over 6 to 18 GHz. To the best of our knowledge, this is the best combination of output power and bandwidth for any solid-state MMIC amplifier operating up to the full Ku-band.