Joon Ho Oum

Two frequency radar sensor for non-contact vital signal monitor

We propose a two frequency radar sensor structure for non-contact vital signs monitor. The vital signs measured by traditional Doppler sensor are diminished if the body has a large motion. The radar structure is proposed which is strong to human motions. This utilized frequency dependent dielectric characteristics of human body tissues.

Tx Leakage Cancellers for 24 GHz and 77 GHz Vehicular Radar Applications

Tx leakage cancellers for 24 and 77 GHz vehicular radar systems are presented. These have high Tx-to-Rx isolation and wideband characteristics. Tx leakage cancellers are composed of four Lange couplers, a 90deg delay line, and a Wilkinson combiner. Tx leakage cancellers are implemented on GaAs substrate. A 24 GHz Tx leakage canceller shows the transmitting loss of 5.7 dB and Tx leakage cancellation of 28.1 dB. Also a 77 GHz Tx leakage canceller shows the transmitting loss of 3.6 dB and Tx leakage cancellation of 28.2 dB. Isolations due to Lange coupler are 15.1 dB in 24 GHz Tx leakage cancellers and 13.1 dB in 77 GHz Tx leakage cancellers, respectively. The isolations due to the topology of the Tx leakage canceller are expected to be 13 dB and 15.1 dB, respectively. These compact Tx leakage cancellers show wideband characteristics of bandwidth beyond 4 GHz

A study on doping density in InAs/GaAs quantum dot infrared photodetector

We study the influence of doping density and the resulting optimum operation voltage on the performance of quantum dot infrared photodetectors (QDIPs). The optimum operation voltage, where detectivity becomes maximum, becomes smaller as the doping density increases. This is because the optimum dark current levels are similar regardless of the doping density. We confirmed experimentally that the optimum dark current level is ~5 mA (current density: ~A/cm2) for our samples. It is found that the higher doping density improves the performance in the range used in this experiment (5×1016–5×1017/cm3). The response to a normal incident light is confirmed and the possibility of high-temperature operation of QDIP is shown.

Non-contact heartbeat sensor using LC oscillator circuit

This paper proposes non-contact heartbeat sensor using LC oscillator for personal healthcare. The signals from chest and wrist are measured using LC oscillator and electrodes. The proposed sensor can detect human heartbeat signal without direct contact to skin and is readily a portable heartbeat monitoring sensor. The capacitive and inductive electrodes are addressed, which are key elements of the sensor circuit.

Quantum-well infrared phototransistor with pHEMT structure

A quantum-well infrared phototransistor with a pseudomorphic high-electron mobility transistor (pHEMT) structure is presented. The proposed phototransistor uses four periods of a GaAs/Al/sub 0.3/Ga/sub 0.7/As (50 /spl Aring//120 /spl Aring/) quantum-well absorption region, as well as an In/sub 0.15/Ga/sub 0.85/As quantum well conducting channel under the absorption layer. The phototransistor shows a large responsivity of 140 A/W around 6 /spl mu/m at 23 K (for a cutoff wavelength of 7.5 /spl mu/m). The relation between the photoconductive gain and the transconductance of the pHEMT structure is also investigated.

Study On Low Bias Avalanche Multiplication In Modulation Doped Quantum‐Dot Infrared Photodetectors

An avalanche gain mechanism of InAs/GaAs quantum dot infrared photodetector is presented. We observed a low voltage avalanche process from the modulation doped n‐i‐n quantum‐dot infrared photodetector. This is due to the remained electrons at modulation doped region.

Quantum Well Infrared Photodetector with pHEMT structure

This work was supported, in part, by KISTEP (under Nano-Structure Technology Projects and IMT2000 R&D donation support program) and the MOE BK21 program