Browsing by Author "Tseng, WJ"

Now showing 1 - 6 of 6

A dual CP slot antenna using a modified Wilkinson power divider configuration
(1998-05-01)
Tseng, WJ
;
Chung, SJ
;
電信工程研究所
;
Institute of Communications Engineering
A dual circularly polarized (CP) slot antenna based on a proposed equal-split Wilkinson power divider is presented, An offset-fed slot antenna, which was analyzed using the method of moments together with a mixed potential integral equation, was used to replace the lumped resistor in the divider. A dual CP slot antenna operating at S-band was designed and demonstrated experimentally. The antenna possessed a return loss bandwidth of 39.3%, an isolation bandwidth of 10% for VSWR <2, and 3-dB axial ratio bandwidth of 28%.
A planar Van Atta array reflector with retrodirectivity in both E-plane and H-plane
(2000-02-01)
Tseng, WJ
;
Chung, SJ
;
Chang, K
;
電信工程研究所
;
Institute of Communications Engineering
A planar antenna array reflector with retrodirectivity in both the E-plane and the H-plane is analyzed and demonstrated at X band. The reflector consists of six pairs of slot-coupled patch antennas arranged using the Van Atta approach. The total reflected field from the reflector is separated into three primary components; that is, the reradiation field from the patch antennas (RFPA), the scattering field from the patch antennas (SFPA), and the scattering field from the ground plane (SFGP). The first two components are calculated by using the method of moments together with a mixed potential integral equation and the last one is by the physical optics (PO) method combined with the method of equivalent currents (MEC). By tuning the microstrip-line lengths, the total reflected held contributed by the three components is designed to possess a broad-beamed pattern in both the E-plane and the H-plane. The measured patterns show good agreement with the designed ones.
Analysis and application of a two-port aperture-coupled microstrip antenna
(1998-05-01)
Tseng, WJ
;
Chung, SJ
;
電信工程研究所
;
Institute of Communications Engineering
A two-port aperture-coupled microstrip antenna was analyzed using the method of moments together with a mixed potential integral equation (MPIE), The antenna contains two microstrip-line ports (i.e., a feeding port and a coupling port), The field coming from one microstrip line on the circuit layer is fed into the patch through an aperture on the ground plane, Part of the field is then coupled back to a second microstrip line through another aperture on the same ground. The influences of the stub lengths, along with the positions and sizes of the apertures, on the coupling power and the resonant frequency were investigated. As an application, a feedback antenna oscillator was designed using the present structure where the antenna served not only as a radiator, but also as a feedback resonator. The oscillation was stable and with a clean spectrum at the frequency of 9.79 GHz, which was only 0.2% different from the design one. An effective isotropic radiated power (EIRP) of 39 mW was achieved. The measured cross-polarized fields were at least 15 dB lower than the copolarized ones.
Analysis of a two-port aperture-coupled microstrip antenna
(1997)
Tseng, WJ
;
Chung, SJ
;
交大名義發表
;
電信工程研究所
;
National Chiao Tung University
A two-port microstrip antenna is investigated the method of moment. The antenna is a two-layer structure. The field coming from one microstrip line on the circuit layer is fed into the patch through an aperture on the ground plane. Part of the field is then coupled back to a second microstrip line through another aperture on the same ground. This configuration serves not only as a radiator but also as a feedback resonator, which is useful in designing an active antenna with a broad injection-locking bandwidth. Numerical results together with some measurements are illustrated and discussed.
On accelerated cross-reference maximum likelihood estimates for positron emission tomography
(1998)
Lu, HHS
;
Tseng, WJ
;
統計學研究所
;
Institute of Statistics
The state of art of positron emission tomography (PET) takes into account the accidental coincidence events and attenuation. The maximum likelihood estimator can handle this kind of random variation in the reconstruction of a PET image. However, the reconstruction is ill-posed and needs regularization. The boundary information, either from an expert or from the other medical modality of the same object, like the X-ray CT scan, MRI, and so forth, can be used to regularize the reconstruction. We have investigated new, efficient and robust approaches to extract the related but incomplete boundary information. Fast algorithms adapted from the expectation/conditional maximization (ECM) and space alternating generalized expectation maximization (SAGE) algorithms are proposed to accelerate the computation. The method of generalized approximate cross validation (GACV) is adjusted to select the penalty parameter from observed data quickly. The Monte Carlo studies demonstrate the improvement.
Planar retrodirective array reflector using dual-slot antennas
(1998-07-09)
Tseng, WJ
;
Hu, CS
;
Chung, SJ
;
電信工程研究所
;
Institute of Communications Engineering
An X-band planar reflector with a broad responding beam was developed using the Van Atta retrodirective antenna array. The reflector contained four antenna sub-arrays, each with six dual-slot antennas appropriately fed and paired by microstrip lines on the backside of the substrate. Good agreement has been achieved between theoretical and measured results.