Min-Hua Ho

Design of Circularly Polarized Annular-Ring Slot Antennas Fed by a Double-Bent Microstripline

A novel design of a circularly polarized annular-ring slot antenna is discussed. The circular polarization is attained through a newly proposed double-bent microstripline that feeds the antenna at two different positions. Several structural parameters were experimentally studied with care to establish a design procedure, which was subsequently drawn into a design flow chart. Validation was carried out using the antennas designed at 3.5 and 1.59 GHz. The measured 3-dB axial-ratio bandwidth (ARBW) for the former is 10.5% and for the latter, 10.0%, which is larger than the 8.5% 3-dB ARBW required by an Inmarsat application.

Waveguide excited microstrip patch antenna-theory and experiment

An arbitrarily shaped microstrip patch antenna excited through an arbitrarily shaped aperture in the mouth of a rectangular waveguide is investigated theoretically and experimentally. The metallic patch resides on a dielectric substrate grounded by the waveguide flange and may be covered by a dielectric superstrate. The substrate (and superstrate, if present) consists of one or more planar, homogeneous layers, which may exhibit uniaxial anisotropy. The analysis is based on the space domain integral equation approach. More specifically, the Greens functions for the layered medium and the waveguide are used to formulate a coupled set of integral equations for the patch current and the aperture electric field. The layered medium Greens function is expressed in terms of Sommerfeld-type integrals and the waveguide Greens function in terms of Floquet series, which are both accelerated to reduce the computational effort. The coupled integral equations are solved by the method of moments using vector basis functions defined over triangular subdomains. The dominant mode reflection coefficient in the waveguide and the far-field radiation patterns are then found from the computed aperture field and patch current distributions. The radar cross section (RCS) of a plane-wave excited structure is obtained in a like manner. Sample numerical results are presented and are found to be in good agreement with measurements and with published data. >

Suspended Substrate Stripline Bandpass Filters with Source-Load Coupling Structure Using Lumped and Full-Wave Mixed Approach

This paper presents the design of two suspended substrate stripline (SSS) bandpass fllters (BPFs), both with a source-load coupling structure embedded to create a transmission zero (TZ) near each side of the passband edges. For the flrst BPF, the physical circuit layout is proposed flrst and followed by the establishment of an equivalent LC circuit. The optimization of element values of the LC circuit using a circuit-level simulator leads to quick adjustment of the structural parameters of the physical circuit layout with the aid of a full-wave simulator. For the second BPF, the ingenious equivalent LC circuit modifled from that of the flrst one is proposed for bandwidth enhancement, which is achieved by exciting two extra loaded resonances in the passband. With the element values of the LC circuit optimized, proper reshaping the physical circuit layout from that of the flrst BPF is easily accomplished. The presented lumped and full-wave mixed approach is very e-cient in that the circuit- level simulator is used to the largest extent and the time-consuming full-wave simulator is employed only at the later stage of the design. Experiments are conducted to verify the design of the two SSS BPFs and agreements are observed between the measured and simulated data.

A Parallel Doubly Coupled Dual-Band Bandpass Filter

A parallel doubly coupled stepped impedance resonators (SIRs) structure is proposed in this paper to build a 2.4/5.2 GHz dual-band bandpass filter for a WLAN application. The prototype filter is a three-stage design composed by four SIRs in conjunction with the tapped-line used in the I/O ports to create zeros by the passband skirts. The proposed filter has the advantages of a much wider fractional bandwidth in both the passbands without sacrificing the passbands insertion losses. The conventional parallel-coupled microstrip line model is applicable in the proposed filter design. The filter has obtained almost twice wider bandwidth compared to that possessed by the counterpart filter of a conventional parallel-coupled line configuration. It is convinced that this filter design can be apply to the 2.4/5-GHz dual-band operation that needs a wider second passband. The experiment is conducted for filter performance validation. A very good agreement is observed between the simulation and the measurements

The Quasi-elliptic Bandpass Filter Using Quarter-wavelength Stepped Impedance Resonators

A bandpass fllter is designed using two end-connected quarter-wavelength stepped impedance resonators. The quarter-wavelength stepped impedance resonators are implemented by a half-wavelength stepped impedance resonator with its middle shorting to ground. Hence, the modes that the ‚=4 stepped impedance resonator supports are the (1+2n)=4 which also occur on the branches of a combline. An enhanced U-shape coupling feed is adopted in the fllter design to reduce the insertion losses as well as suppressing the harmonics. The proposed fllter has a quasi-elliptic frequency response. An equivalent circuit model is developed and the experiments are conducted for circuit design veriflcation.

DESIGN OF HIGH ORDER SUSPENDED STRIPLINE BANDPASS FILTER WITH MINIATURIZATION

A quasi-lumped design of a suspended stripline (SSL) bandpass filter (BPF) exhibiting high signal selectivity is proposed. In the circuit, transmission zeros were implanted to enhance the stopband signal rejection. A sample BPF having an operation band of 6.77– 7.33GHz was fabricated and measured for performance verification of the proposed design. Corresponding author: M.-H. Ho (ho@cc.ncue.edu.tw).

The Dual-Band Bandpass Filters Using Doubly Parallel-Coupled SIRs with Multiple Zeros for WLAN Applications

Two dual-band bandpass filters (BPFs) based on the doubly parallel-coupled stepped impedance resonators (SIRs) structures have been proposed in this paper. The coupled-SIRs with/without open-stub-loads are introduced in the filter design. The dual-band filters exhibiting multiple zeros design operate at 2.45/5.2-GHz for the WLAN applications. Two three-staged filters composed of four SIRs have been proposed with the tapped-line adapted in the I/O sections. A five-staged filter is constructed based on the same design principle to achieve a better band-rejection. The proposed filters have the advantages of a much wider bandwidth in both the passbands without sacrificing the passbands insertion loss and passband flatness. The design procedure for a conventional parallel-coupled microstrip lines model is still suitable to design the proposed filters. The proposed filters have achieved almost twice the band-width of a conventional parallel-coupled lines configuration under the same design parameters. The experiments have been conducted to verify filter performance. Measured results are in good agreement with the full-wave simulation results.

Balanced BPF design using the substrate integrated waveguide

In this paper, we present a novel design of a balanced bandpass filter using the substrate integrated waveguide cavity. Two square-shaped substrate integrated waveguide cavities are side-by-side with removing the vias on the common sidewall to form the BPF. Pared microstrip lines are used to construct the balanced ports of the proposed circuit. Slots are utilized to perturb the degenerated modes of TE102 and TE201 modes. Common-mode signals are managed to be suppressed for a better performance.

Design of the UWB band-pass filter with a notch response using the suspended stripline

The quasi-lumped approach is proposed to design a low-pass, a high-pass, and a band-rejection filter composing of suspended stripline (SSL) structure. The filters operation band may possess a notch response. The notch rejection circuit is implemented from embedding a resonant slotline in the SSLs signal strip. A sample UWB filter is built from cascading the notch response circuit, the low-pass, and the high-pass filter. The two sides of suspended substrate which bearing the filters metal patterns diversities the circuit design and might effectively reduce the circuit size. Experiment is conducted to verify the circuit design and the good agreement is observed between the measurement and simulation.

Radiation and scattering from planar microstrip structures of arbitrary shape

Summary form only given. A space-domain approach based on the mixed-potential integral equation formulation is applied to the computation of electromagnetic fields radiated and scattered by planar microstrip structures having arbitrary or irregular shapes. The effects of the substrate are rigorously incorporated in the analysis by means of the vector and scalar potential Greens functions. The current distribution induced on the conducting patch is approximated in terms of vector basis functions defined over triangular elements. Once the current expansion coefficients are computed by the method of moments, the far zone fields are easily found by the stationary phase method, and are given in terms of the Fourier-transformed basis functions and the transmission line voltages evaluated at the stationary point values of the spectral variables. Current distributions, radiation patterns, and RCS (radar cross section) results have been computed for several microstrip patch antennas of various shapes.<<ETX>>