Huey Ru Chuang

An X-Band Microwave Life-Detection System

An X-band microwave life-detection system has been developed for detecting the heartbeat and breathing of human subjects lying on the ground at a distance of about 30 m or located behind a cinder block wall. The basic principle of the system is to illuminate the subject with a low-intensity microwave beam, and then from the back-scattered microwave signal, extract the heart and breathing signals that modulate it. The circuit description of the system and some experimental results are presented. Potential applications of the system are noted.

A planar triangular monopole antenna for UWB communication

The paper presents a printed planar triangular monopole antenna (PTMA) for UWB communication. The HFSS 3D EM simulator is employed for design simulation. The printed PTMA is realized on an FR-4 PCB substrate. The measured VSWR is less than 3 from 4 GHz to 10 GHz. The measured phase distribution of the input impedance is quite linear and the H-plane patterns are almost omnidirectional in the UWB frequency band. To compute efficiently the far-field antenna parameters from the near-field over a wide frequency range, the Kirchhoffs surface integral representation (KSIR) is used in the developed FDTD code to compute the time-domain far-field distribution. This is to investigate the radiated power density spectrum (PDS) shaping to comply with the FCC emission limit mask. The effect of various source pulses (first-order Rayleigh pulses with /spl sigma/ of 25, 50 and 100 ps) on the radiated PDS shaping is studied. It is found that the radiated PDS of the first-order Rayleigh pulse with /spl sigma/=50 ps can comply with the FCCs indoor mask from 2 GHz. As for the outdoor mask, the same pulse can comply with the FCC emission limit.

3-D FDTD design analysis of a 2.4-GHz polarization-diversity printed dipole antenna with integrated balun and polarization-switching circuit for WLAN and wireless communication applications

Detailed numerical simulation, fabrication, and experimental measurements of a 2.4-GHz polarization-diversity printed dipole antenna are presented for wireless communication applications. Two orthogonal printed dipole antennas, each with a microstrip via-hole balun feeding structure, are combined and fabricated on an FR-4 printed-circuit-board substrate. A p-i-n diode circuit is used to switch and select the desired antenna polarization. In the antenna design simulation, a full-wave method of a three-dimensional finite-difference time-domain (FDTD) method is employed to analyze the entire structure of the printed antenna including the lumped elements of the polarization-selected p-i-n diode switching circuit. The Berenger perfectly matched layer absorbing-boundary condition is used for the FDTD computation. Numerical and measured results of antenna radiation characteristics, including input standing-wave ratio, radiation patterns, and polarization diversity are presented.

A 3-12 GHz UWB Planar Triangular Monopole Antenna with Ridged Ground-Plane

A novel technique to increase the bandwidth of the conventional planar triangular monopole antenna (PTMA) is presented. With two symmetrical corrugations extended from the flat ground plane, a significant improvement on the impedance bandwidth up to about 4:1 can be achieved. The proposed antenna design is a modification from the conventional volcano smoke antenna (VSA) and can be more compact and easily fabricated. The HFSS 3-D EM solver is employed for design simulation. The effects of the ridged ground plane on the impedance bandwidth are studied. A printed PTMA is fabricated on the FR-4 PCB substrate. Measured VSWR of the printed PTMA with the ridged ground plane is less than 2 from 3 to 12 GHz which covers the UWB frequency band. The measured antenna patterns also show the monopole-type omni-directional radiation patterns from 3 to about 10 GHz.

Human operator coupling effects on radiation characteristics of a portable communication dipole antenna

EM coupling effects of a human operator on antenna radiation characteristics, such as the antenna input impedance, radiation patterns, the radiation power (into free space), the power absorbed by the body, the radiation efficiency, etc., of a portable communication dipole antenna were investigated in detail. A realistically shaped 3D man model and an approximate linear dipole antenna were used to model this problem. Coupled integral equations (CIE) and the method of moments (MoM) were employed to numerically solve this antenna-body coupling problem. Numerical examples are presented for the antenna located in front of the head (distance ranging from 5 to 1 cm) or adjacent to the abdomen (0.6 cm distance) at 830 MHz. It is found that, when coupled with the operator body, the antenna input impedance will have significant deviation from those in free space and different positions. Due to the operator body absorption effect, the maximum attenuation of the H-plane antenna gain may reach about 15 dB for the antenna at the head position and 25 dB for the abdomen position, toward the direction of the body side. Also, the antenna radiation efficiency is reduced to the range from 0.72 to 0.29 for the head position and 0.15 for the abdomen position, respectively. Moreover, the cross-polarization field is significant, especially in the E plane of /spl phi/=90/spl deg/. This is important for the antenna RF design and communication link budget consideration of portable radio systems. >

A Horizontally Polarized Omnidirectional Printed Antenna for WLAN Applications

The design simulation, fabrication, and measurement of a 2.4-GHz horizontally polarized omnidirectional planar printed antenna for WLAN applications is presented. The antenna adopts the printed Alford-loop-type structure. The three-dimensional (3-D) EM simulator HFSS is used for design simulation. The designed antenna is fabricated on an FR-4 printed-circuit-board substrate. The measured input standing-wave-ratio (SWR) is less than three from 2.40 to 2.483 GHz. As desired, the horizontal-polarization H-plane pattern is quite omnidirectional and the E-plane pattern is also very close to that of an ideal dipole antenna. Also a comparison with the popular printed inverted-F antenna (PIFA) has been conducted, the measured H-plane pattern of the Alford-loop-structure antenna is better than that of the PIFA when the omnidirectional pattern is desired. Further more, the study of the antenna printed on a simulated PCMCIA card and that inserted inside a laptop PC are also conducted. The HFSS model of a laptop PC housing, consisting of the display, the screen, and the metallic box with the keyboard, is constructed. The effect of the laptop PC housing with different angle between the display and keyboard on the antenna is also investigated. It is found that there is about 15 dB attenuation of the gain pattern (horizontal-polarization field) in the opposite direction of the PCMCIA slot on the laptop PC. Hence, the effect of the large ground plane of the PCMCIA card and the attenuation effect of the laptop PC housing should be taken into consideration for the antenna design for WLAN applications. For the proposed antenna, in addition to be used alone for a horizontally polarized antenna, it can be also a part of a diversity antenna

Design of Miniature Planar Dual-Band Filter Using Dual-Feeding Structures and Embedded Resonators

A new dual-band planar filter has been proposed. It is shown that the two transmission bands can be excited and designed using proposed resonators which combine different sizes of open-loop resonators. The main resonators control the low-band resonant frequency and the sub resonators control the high-band resonant frequency. With dual-feeding structures added, the performances of the filter such as frequency selectivity and insertion loss are much improved. The embedded resonators structure can further miniaturize the dimensions of the overall structure. The proposed dual-band filter will find applications in wireless communication circuits

Automatic clutter-canceler for microwave life-detection systems

A microprocessor-controlled automatic clutter-cancellation subsystem, consisting of a programmable microwave attenuator and a programmable microwave phase-shifter controlled by a microprocessor-based control unit, has been developed for a microwave life-detection system (L-band 2 GHz or X-band 10 GHz). This system can remotely sense breathing and heartbeat movements of living subjects. This automatic clutter-cancellation subsystem improves manual clutter-cancellation in microwave systems. A series of experiments have been conducted to demonstrate the applicability of this microwave life-detection system for rescue purposes. The 2-GHz system performs well for remotely detecting human breathing and heartbeat signals through a pile of rubble of up to about three feet thick. >

A 0.25-μm 20-dBm 2.4-GHz CMOS power amplifier with an integrated diode linearizer

A 2.4-GHz CMOS power amplifier (PA) with an output power 20 dBm using 0.25-/spl mu/m 1P5M standard CMOS process is presented. The PA uses an integrated diode connected NMOS transistor as a diode linearizer. It is believed that this is the first reported use of the diode linearization technique in CMOS PA design. It shows effective improvement in linearity from gain compression and ACPR measured results. Measurements are performed by using an FR-4 PCB test fixture. The fabricated power amplifier exhibits an output power of 20 dBm and a power-added efficiency as high as 28%. The obtained PA performances demonstrate the standard CMOS process potential for medium power RF amplification at 2.4 GHz wireless communication band.

A 5.7-GHz 0.18-μm CMOS gain-controlled differential LNA with current reuse for WLAN receiver

This letter presents a 5.7 GHz 0.18 /spl mu/m CMOS gain-controlled differential LNA for an IEEE 802.11a WLAN application. The differential LNA, fabricated with the 0.18 /spl mu/m 1P6M standard CMOS process, uses a current-reuse technology to increase linear gain and save power consumption. The circuit measurement is performed using an FR-4 PCB test fixture. The LNA exhibits a noise figure of 3.7 dB, linear gain of 12.5 dB, P/sub 1dB/ of -11 dBm, and gain tuning range of 6.9 dB. The power consumption is 14.4 mW at V/sub DD/=1.8 V.