Keiichi Sakuno

A 184 mW Fully Integrated DVB-H Tuner With a Linearized Variable Gain LNA and Quadrature Mixers Using Cross-Coupled Transconductor

A fully integrated direct conversion DVB-H tuner is realized in a 0.5-mum SiGe BiCMOS technology. To meet the stringent linearity requirement while keeping low power consumption, novel linearization techniques for a variable-gain low-noise amplifier (VG-LNA) and a mixer are proposed. The proposed linearized VG-LNA has a variable gain range of over 50 dB, noise figure of less than 2.6 dB over the frequency range from 200 to 1000 MHz, and IIP3 of more than -10 dBm at a current consumption of 2.1 mA. The quadrature mixer with the proposed linearization technique achieves OIP3 of more than 25 dBm at a current consumption of 5 mA. In addition, a new offset-cancel feedback is introduced for the baseband block of a direct conversion receiver, which keeps the high-pass cutoff frequency independent of the baseband VGA gain. The fabricated tuner IC satisfies all the DVB-H requirements at a power consumption of 184 mW

A 3.5 W HBT MMIC power amplifier module for mobile communications

A 900 MHz-band GaAs/GaAlAs HBT MMIC power amplifier module has been developed for mobile communications by using a novel assembly technique called BHS and an AlN package as the MMIC chip carrier. The power module gave a peak output power of 3.7 W and a power-added efficiency of 54.5% with a +6 V single supply voltage.<<ETX>>

Bump heat sink technology - A novel assembly technology suitable for power HBTs

A novel assembly technique, bump heat sink (BHS), suitable for compound semiconductor power HBTs is proposed and demonstrated. In this technique, the heat generated in the transistor junction is effectively conducted away through a gold bump which is located on the top of each transistor unit. Using this technique, power transistors are demonstrated with power added efficiencies /spl eta//sub add/ of 74%, 66% and 61% for 5.0 W, 8.0 W and 10.0 W output CW, respectively, at 0.9 GHz with V/sub cc/=6 V. A three-stage HBT MMIC power amplifier for GSM class 4 is also demonstrated with /spl eta//sub add/ >55% at V/sub cc/=4 V CW operation.<<ETX>>

A High-Power Low-Distortion GaAs HBT Power Amplifier for Mobile Terminals Used in Broadband Wireless Applications

This paper describes technologies of miniaturized high-power low-distortion GaAs HBT power amplifiers with a low-voltage operation for mobile terminals used in 5-6 GHz broadband wireless applications. In conjunction with diode-based linearizing techniques, wideband matching network techniques including trap circuits for second harmonics allow us to obtain a compact broadband power amplifier module with harmonic filtering, achieving the high linear output power at a low supply voltage together with the low distortion and the low second-harmonic spurious outputs in a wide frequency range. The fabricated power amplifier exhibited linear output power levels of 21 and 22 dBm at EVM values of 2.0 and 3.0%, respectively, measured with 54 Mb/s 64-QAM-OFDM signals at a supply voltage of 3.3 V in a frequency range of 5-6 GHz. Second harmonic spurious outputs below -35 dBc were also attained.

A 5 GHz high efficiency and low distortion InGaP/GaAs HBT power amplifier MMIC

An InGaP/GaAs two-stage HBT power amplifier for 5 GHz Wireless-LAN applications was developed. By using a self-aligned base contact formation process and an external base region side etching process, a high gain HBT was realized. A small-sized via hole fabrication process was developed. The gain of multi-finger HBT was improved by locating via holes between each finger. Linearity was also improved by developing a new variable negative feedback circuit. A power amplifier MMIC utilizing this technology was fabricated, and 19.7 dBm output power, 22 dB gain, 22.5% power-added-efficiency (PAE), 5.0% error vector magnitude (EVM) were obtained at 54 Mbps transmission under a supply voltage of 3.3 V. These state of the art data represent the highest PAE reported for a the power amplifier MMIC in the 5 GHz Wireless-LAN application.

Analytical model for electrical and thermal transients of self-heating semiconductor devices

Transients of self-heating semiconductor devices are theoretically investigated based on a feedback circuit model, which is composed of three sub-circuits describing the isothermal electrical characteristics, thermal impedance, and temperature dependence of the electrical characteristics of the devices, respectively. Analytical expressions of the frequency and transient responses have been derived for both the electrical and thermal characteristics of self-heating devices, yielding accurate methods to extract the thermal time constant in both the time and frequency domains. The model is verified by the transient electrical-response measurement of a GaInP/GaAs heterojunction bipolar transistor.

A 184mW Fully Integrated DVB-H Tuner Chip with Distortion Compensated Variable Gain LNA

A single chip direct conversion DVB-H tuner with a distortion compensated variable gain LNA is implemented in 0.5mum SiGe BiCMOS. The LNA exhibits 0dBm IIP3 and 2.8dB NF at 860MHz. A new offset cancel feedback is introduced that keeps the cutoff frequency independent of the baseband gain. The IC consumes 184mW at 2.8V while achieving a sensitivity of -96dBm for QPSK, CR=1/2 signal

Enhanced linearity and efficiency of HBT power amplifiers for 5-GHz wireless-LANs

This paper describes two advanced techniques to enhance linearity and efficiency in HBT power amplifiers (PA) for 5-GHz wireless-LANs (W-LANs). The diode-based linearizing circuit successfully compensates the gain expansion of PAs operating at a low quiescent current. The output matching circuit consisting of on-chip MIM capacitors and bond wires effectively reduces the loss of the circuit as well as allowing the miniaturization of the PA module. The PA MMIC fabricated incorporating these techniques achieved an improvement in linear output power and PAE of 2.4 dBm and 4.8%, respectively, compared to our previous PA with the same device dimensions, and exhibited an output power of 22.1 dBm and a PAE of 27.3% at an EVM of 5%, measured with 54Mbps 64-QAM-OFDM signals at 5.25 GHz.

A High Efficiency InGaP/GaAs HBT Power Amplifier MMIC for the 5GHz Wireless-LAN Application

An InGaP/GaAs two-stage HBT linear power amplifier MMIC for the 5GHz Wireless-LAN Application was developed. By using a novel linearizer and a small-size via-hole technology, the power amplifier showed high output power (19dBm) with high power-added-efficiency (PAE : 18.5%), sufficient gain (21.0dB) and high linearity (4.78% error vector magnitude : EVM) at supply voltage 3.3V. It is the highest PAE in the power amplifier MMIC for the 5GHz Wireless-LAN application ever reported.

Low-Resistivity V/Al/Mo/Au Ohmic Contacts on AlGaN/GaN Annealed at Low Temperatures

We investigated the electrical characteristics of V/Al/Mo/Au ohmic contacts on AlGaN/GaN heterostructure field effect transistors (HFETs). A minimum ohmic contact resistivity of 1.6×10-6 Ω cm2 was achieved after annealing at 550 °C by optimizing V thickness to 15 nm. Cross-sectional transmission electron microscope (TEM) images exhibited a large difference in the extent of metal reaction between V/Al/Mo/Au and Ti/Al/Mo/Au. In addition to their lower contact resistivities, the low-temperature annealed V/Al/Mo/Au ohmic contacts exhibited better characteristics, such as enhanced breakdown voltages by about 100 V and smooth surface morphology, than the Ti/Al/Mo/Au ohmic contact annealed at the optimum annealing temperature.