Kwang-Eui Pyun

A low noise amplifier for a multi-band and multi-mode handset

Using a low noise active balun and a push-pull active matching circuit, a wideband low noise amplifier MMIC is designed and fabricated. For the frequency up to 3 GHz, output VSWR is less than 1.3 and the output power handling capability of 9.4 dB is enhanced compared with conventional active matching circuit.

A new extraction method to determine bias-dependent source series resistance in GaAs FET's

A new method is proposed to determine bias-dependent source resistances for GaAs field-effect transistors (FETs). This method, which is a cold-FET measurement technique, utilizes the relations between the real part of the two-port impedances transformed from the measured S-parameters and their algebraic derivatives. It is based on the fact that the algebraic derivatives of the two-port resistances result in the simple form at the normal cold-FET condition. A bias-independent gate resistance is extracted at the pinched-off cold-FET condition to fulfill necessary and sufficient conditions in extraction. The proposed method is a direct measurement because only algebraic calculation is required, and it is general enough to need only one assumption of the laterally symmetric channel-doping profile. The deleterious results of dispersion (frequency dependence) and negative value in source resistances at the pinched-off cold-FET condition are explained by the effects of the leakage current and the on-wafer pad parasitics, respectively. The problem of deviation of /spl alpha//sub 21/ and /spl alpha//sub 12/ from 0.5 at the normal cold-FET condition is also resolved by deembedding the on-wafer pad parasitics. This method allows one to extract bias-dependent source resistances for GaAs FETs.

Molecular beam epitaxy growth of indium-rich InxGa1 − xAsInyAl1 − yAs/InP structures towards high channel conductivity for a high electron mobility transistor using a linearly graded buffer layer

InxGa1 − xAsInyAl1 − yAs heterostructure with both high electron mobility and high carrier concentration has been fabricated on InP substrate by molecular beam epitaxy. The measured electron mobilities were 11 491 cm2/V · s at 300 K and 53 316 cm2/V · s at 77 K for two-dimensional electron gas concentrations of 4.7 × 1012 and 3.5 × 1012 cm−2, respectively. The high electron mobility and concentration resulted from the dislocation-free, relatively thick (200 A), and high indium content (80%) channel layer. The high-quality InxGa1 − xAs channel layer was successfully grown at a growth temperature of 520°C after introducing a linearly graded InyAl1 − yAs buffer structure grown at a reduced growth temperature of 420°C. The cross-sectional transmission electron microscopy observation revealed that the dislocations generated due to a large lattice mismatch between InyAl1 − yAs and InP substrate were locked up in the middle of the graded buffer layer. We believe that we have achieved to date for this materials system the highest room-temperature conductivity (mobility times carrier concentration) of 5.4 × 1016/V · s.

Fabrication of optical Tx/Rx subscriber modules incorporating passive alignment technique

Compact optical transmitter/receiver modules for STM-1 transmission systems have been developed incorporating custom ASICs (application specific integrated circuit) and novel packaging technologies. Coupling of optical chips and fibers for both modules is accomplished utilizing passive alignment method to lessen package cost and size. A fully integrated module is as compact as 3 cc in volume.

A 3.3 V front-end receiver GaAs MMIC for the digital/analog dual-mode hand-held phones

A front-end receiver MMIC for 3.3 V-operating CDMA/AMPS dual-mode hand held phone has been developed using a GaAs MESFET process. The developed MMIC, chip size of which is 1.9/spl times/3.9 mm/sup 2/ shows noise figure of 2.8 dB, power gain of 35/25 dB at the nominal current consumption of 22.5/16.1 mA in CDMA/AMPS modes, respectively.

Optical Binary-Phase-Shift-Keying Modulation of 10 GHz Using an Integrated Hybrid Device

An integrated optical/RF hybrid device was designed and fabricated for binary-phase-shift-keying (BPSK) subcarrier modulation. The device is composed of two identical high-speed multiple quantum well electroabsorption modulators branched with two multimode interference couplers. Using the device, we demonstrated that a RF subcarrier of 10 GHz is directly modulated in a BPSK scheme with an independently applied RF carrier and digital signal.

High performance directional coupler filter using novel phase-shift pair grating

A novel phase-shift pair grating (PSPG) structure was proposed and demonstrated to suppress sidelobe in a grating-assisted codirectional coupler filter. A PSPG is composed of two unit gratings. The position of one unit grating inside PSPG is fixed and that of the other is shifted in order to control the coupling strength. We demonstrate sidelobe level of -19 dB with a linearly shifted PSPG, which is the lowest to our knowledge.

Sidelobe-Suppression of Grating-Assisted Codirectional Coupler Filter by Selective Area Growth

We propose and demonstrate a technique for the sidelobe suppression in an InP/InGaAsP semiconductor grating-assisted codirectional coupler (GACC) optical filter. By employing selective area growth (SAG) in an InP separation layer, the epitaxial film thickness was spatially controlled so that the coupling coefficient distribution between two waveguides has the Hamming functional form. Most sidelobes are suppressed below -12 dB, which is low compared to the conventional GACC filters.

An empirical lifetime projection method for laser diode degradation

An empirical method for lifetime projection of 1.55 /spl mu/m InGaAs-InP MQW-DFB laser diodes (LD) is presented. On the basis of experimental results of an accelerated aging test for 1500 hours, relationship between LD degradation, operating voltage, and ambient temperature has been determined. The presented method makes it possible to predict the lifetime of LDs by determining the thermal voltage ratio.

An empirical reliability prediction method for 1.55 /spl mu/m InGaAs/InP MQW-DFB laser diodes

An empirical method for lifetime projection of 1.55 /spl mu/m InGaAs/InP MQW-DFB laser diodes (LD) is presented. On the basis of experimental results of accelerated aging test for 1500 hours, relationship between LD degradation, operating voltage, and ambient temperature has been determined. The presented method makes it possible to predict the lifetime of LDs by determining the thermal voltage ratio.