Powen Hsu

Uniplanar Log-Periodic Slot Antenna Fed by a CPW for UWB Applications

A coplanar waveguide-fed uniplanar log-periodic slot antenna suitable for use in the ultra-wideband radio systems is presented. The in-band impedances and radiation performances are quite stable and satisfactory. A rejected narrow frequency band is further obtained within the wide bandwidth by inserting a pair of metallic stubs into two vertical slots of the proposed antenna. Experimental results reveal that the stub pair provides significant attenuation in the desired notched band but has little effect on the antenna operation outside of the notch. By means of a normalized antenna transfer function, the time-domain characteristics of the proposed antennas are also investigated. The transient responses show that the designs with and without the notched band are both acceptable for the pulsed systems

A Differential-Mode Wideband Bandpass Filter With Enhanced Common-Mode Suppression Using Slotline Resonator

A novel design of a differential-mode (DM) wideband bandpass filter (BPF) with enhanced common-mode (CM) suppression using a slotline resonator is presented. The BPF consists of two pairs of parallel microstrip transmission lines, a pair of transverse microstrip sections connected to the transmission lines, and a longitudinal slotline resonator placed in the ground plane. With proper placement of the slotline resonator, the mode coupling between the slotline mode and the (DM) signals can be maximized, while that between the slotline mode and the CM signals can be minimized. It is found that throughout the (DM) passband, the insertion loss of the CM signals is higher than 47.5 dB, the fractional bandwidth defined by the 10 dB return loss for the (DM) signals is about 105%, and the insertion loss for the (DM) signals ranges from 1.22 to 5.82 dB over the fractional bandwidth. Good agreement between simulated and measured results is obtained.

Full-wave characterization of the mode conversion in a coplanar waveguide right-angled bend

A full-wave algorithm is proposed to analyze thoroughly a 90/spl deg/ bend of coplanar waveguide (CPW). Based on the mixed potential integral equation (MPIE) formulation, the equivalent magnetic current distribution on the apertures is solved by the moment method using overlapping rooftop basis functions and the Galerkln weighting procedure. The matrix pencil approach is then utilized to do the de-embedding procedure and extract both the coplanar and slotline modes scattering off the asymmetric discontinuity. Experiments are performed to measure the scattering parameters and the results verify the accuracy of the present algorithm. The full 4/spl times/4 scattering matrix between these two modes is presented from which the occurrence of the mode conversion is investigated. The mode conversion is noticed to become almost complete at certain frequencies, which may be useful in the design of CPW to coupled slotline transition. >

Analysis of coplanar waveguide-fed microstrip antennas

A moment method analysis of a microstrip antenna fed by an open-end coplanar waveguide is presented. The surface electric current on the microstrip antenna is represented by the entire domain basis functions, while the surface magnetic currents in the open-end slot and in the slots of the coplanar waveguide near the open end are expanded by the subsectional roof-top basis functions. Some practical numerical aspects are carefully discussed, and a numerical device is introduced to reduce the computation time for the integrals involving roof-top basis functions and the spectral-domain Greens function. The solution accuracy is thus improved. Computed results for the reflection coefficients and input impedances are given and compared with measured values. Good agreement between theory and experiment is obtained. >

Isosceles Triangular Slot Antenna for Broadband Dual Polarization Applications

An isosceles triangular slot antenna is proposed for broadband dual polarization applications. The proposed design has a very simple antenna structure and a wide impedance bandwidth ( ~ 19.7% for |S11| and |S22| les -10 dB) which can cover the 5 ~ 6 GHz frequency band for Wireless Local Area Network applications. Good isolation between the two input ports |S21| and low cross-polarization radiation level (<-15 dB) are achieved, and the antenna gains radiated from the two diversity ports are almost equal and stable over the entire operating band. These features make the proposed antenna very attractive in broadband dual polarization applications.

Admittance and resonant length of inclined slots in the narrow wall of a rectangular waveguide

The admittance properties and the resonant length of an inclined slot in the narrow wall of a rectangular waveguide have been investigated. The depth of cut of the slot in the broad walls of the waveguide has been taken into account. The internal power storage in evanescent modes in the waveguide, neglected in previous studies, is included. Theoretical results for the variations of conductance and resonant length with the angle of inclination of slots are presented. Through comparisons of the calculated results with previously available experimental data, the importance of the inclusion of the waveguide internal power storage is emphasized. >

CPW-Fed Aperture-Coupled Slot Dipole Antenna for Tri-Band Operation

A uniplanar aperture-coupled slot dipole antenna capable of tri-band operation is presented. Design considerations for the three operating frequencies are extensively discussed. The lower and middle operating frequencies can be obtained by varying the lengths of the lower and middle pairs of the protruded slots, respectively, while the upper frequency can be determined by adjusting the lengths of the upper protruded slot pair and the coupling aperture pair. Within each band, slot-dipole-like radiation patterns, low cross-polarized radiations, and moderate antenna gains can be observed.

Integrated Dual Planar Inverted-F Antenna With Enhanced Isolation

An integrated dual planar inverted-F antenna (PIFA) with enhanced isolation is proposed. The antenna is composed of two PIFAs merged together through a common metallic strip and a via connected to the ground plane. An additional folded resonator with electrical length of about half a guided wavelength is placed above the antenna to enhance the isolation between the two PIFAs. The whole antenna structure remains very simple and compact. Good impedance matching and high isolation are obtained in the frequency band of 2.4 -2.484 GHz for IEEE 802.11b/g wireless local area network (WLAN) applications. The details of the antenna design are presented, and simulation and measurement results are also presented and discussed.

Broad-band radial slot antenna fed by coplanar waveguide for dual-frequency operation

A novel design of a broad-band radial slot antenna fed by a coplanar waveguide for dual-frequency operation is presented. Various frequency ratios, within the range of about 1.3 to 2.1, of the two operating frequencies can be obtained by varying the included angle between the radial slots and/or by varying the length of the central slot pair. The bandwidth of the lower operating band lies in the range of 2.4% to 9.7%, while that of the upper band is much wider and ranges from 17.4% to 23.2%. Radiation patterns at the two operating frequencies are broadside and bidirectional. Details of the antenna design and the experimental results are presented and discussed.

Moment method analysis of sidewall inclined slots in rectangular waveguides

The main feature is the use of a 90 degrees wedge Greens function to model the external coupling between the parts of the slot in the narrow and broad walls of the waveguide. The aperture field distributions of the inclined slots are solved directly. It is found that for resonant slots, the aperture field is approximately of constant phase, while its amplitude is nearly sinusoidal but with a slight tilt. From the field distribution, various characteristics of the slot can be extracted, such as the conductance, susceptance, and resonant length. The numerical computations are in good agreement with experimental results available in the literature. >