Tadashige Fujita

A series of InGaP/InGaAs HBT oscillators up to D-band

In this paper, the development of a series of fixed-frequency heterojunction bipolar transistor (HBT) oscillators from the W- to D-bands is reported. The oscillators are designed based on feedback theory with a small-signal equivalent circuit. This design method enables the achievement of high-output-power oscillators for the management of the power that is generated at the current source inside the HBT. We use a 1 /spl mu/m/spl times/10 /spl mu/m single-emitter InGaP/InGaAs HBT as an active device for each oscillator, and 50-/spl Omega/ coplanar waveguides as transmission lines and resonators. Emitter output topology is adopted to reduce the chip size. The series of oscillators achieve the oscillation frequency of 74.8-146.7 GHz. To our knowledge, the 146.7-GHz fundamental oscillation frequency is the highest oscillation frequency achieved thus far using InGaP/InGaAs HBT technology. The output power of the 146.7-GHz oscillator is -18.4 dBm. The chip size of the oscillator is 731 /spl mu/m/spl times/411 /spl mu/m.

Monolithic rat-race mixers for millimeter waves

This paper reports on fully monolithic millimeter-wave Schottky barrier diode down-converters with an IF amplifier using heterojunction bipolar transistors (HBTs). The measured conversion gain and the isolation are 8.0 dB and 25 dB in the W-band design, and 7.1 dB and 29 dB in the V-band design, respectively.

System architecture and key components of a multi-Giga-Hertz A/D converter with HBT

This paper reports the design and performance of a very fast 6-bit ADC system with GaAs HBT technology. The ADC system consists of a track/hold circuit and an ADC. The track/hold circuit employs an open-loop architecture and uses Schottky barrier diodes for a diode switch, and achieves 3 GS/s operation with better than 6-bit linearity. The 6-bit ADC employs folding/interpolation architecture to reduce hardware and power maintaining the high-speed operation, and it achieves DC linearity better than 7-bit.

High-speed ADC systems with HBTs for measuring instrument applications

Abstract This paper presents very high-speed Analog-to-Digital Converter (ADC) systems for measuring instrument applications, and also related theoretical results. First we describe the design, testing and performance of ≈1 GS/s 6-bit and 7-bit ADCs using SiGe heterojunction bipolar transistor (SiGe HBT), and a 3 GS/s 6-bit ADC and Track/Hold (T/H) circuit using GaAs heterojunction bipolar transistor (GaAs HBT). We show that SiGe HBTs and GaAs HBTs have technological potential, and that the folding/interpolation architecture is suitable for high-speed ADC systems. Next, we derive three theoretical results aimed at very high-speed, wideband ADC systems. ⋅A folding/interpolation architecture is suitable for very high-speed ADCs implemented with HBTs, and digital error correction is required to improve their AC performance. We show an error correction algorithm, as well as its effectiveness and limitation for high-frequency inputs. ⋅Aperture jitter is crucial in wideband ADC systems, and we have derived very general results about aperture jitter effects of such systems. ⋅A time-interleave ADC system can realize very high-speed ADC system, but timing skews in the system degrade its overall accuracy. We have derived the error power corresponding to timing skews. Finally, we discuss several issues relating to standardizing the specifications of very high-speed ADCs targeted at measuring instrument applications.

Full-WDM-band photodiode modules for optical communications at 40 Gb/s and beyond

This paper presents the first demonstration of the high-speed full-WDM-band photodiode modules for the WDM systems throughout the S (1460-1530 nm) to U (1625-1675 nm) bands with bit-rates up to 40 Gb/s or above.