Ching-Wen Tang

A Microstrip Ultra-Wideband Bandpass Filter With Cascaded Broadband Bandpass and Bandstop Filters

This paper develops a novel ultra-wideband bandpass filter by cascading a broadband bandpass filter with another broadband bandstop filter. Properly selected impedances of transmission lines achieve broadband bandpass and bandstop filters and make independent designs possible. Detailed design and synthesis procedures are provided; moreover, agreement between measured and theoretically predicted results demonstrates feasibility of the proposed filter. Due to its simple structure, the ultra-wideband bandpass filter newly introduced in this paper is suitable for integration in the single-chipped circuit or implementation on printed circuit boards.

Synthesizing Microstrip Branch-Line Couplers With Predetermined Compact Size and Bandwidth

A new method for designing the microstrip branch- line couplers with predetermined compact size and bandwidth is proposed in this paper. With the proposed approach, the size of the quarter-wavelength transmission line in the branch-line coupler can be reduced greatly. In addition, the proposed couplers can be easily fabricated on the printed circuit board without any lumped element. A chart concludes the relationship between bandwidth and size reduction rate. It shows that open stubs with low impedance perform better than those with high impedance; moreover, the more open stubs with low impedance utilized, the broader the bandwidth will be. Furthermore, the measured frequency responses show good agreement with the theoretical results.

Design methodologies of LTCC bandpass filters, diplexer, and triplexer with transmission zeros

A new method for designing the multilayered filter, diplexer, and triplexer is proposed in this paper. The main structure of the multilayered filter is a parallel-coupled line connected with a capacitor. By properly controlling the coupling coefficient between the parallel-coupled line and the capacitor, the transmission zero will appear at the lower or higher passbands skirt. Moreover, such characteristics can be employed to design the diplexer as well for dual- or quad-band portable telephones. In order to miniaturize the size of the circuit and to improve its performance, multilayered structure and the low-temperature co-fired ceramic technology are employed to design and fabricate the filter. Theoretical analysis and design procedures are also provided. Measurement results of fabricated examples are shown to match well with the electromagnetic simulation, which validate the proposed structure.

Realization of transmission zeros in combline filters using an auxiliary inductively coupled ground plane

The out-band transmission zeros of the multilayer low-temperature co-fired ceramic bandpass filter are studied. The design target of this filter, with passband between 2.3-2.65 GHz (the true application is 2.4-2.483 GHz), is to reject the local oscillator and image signals and, in the mean time, to suppress the harmonic frequency. This filter is a modified three-pole combline filter, which can easily achieve a high rejection rate and low insertion loss. The source-load coupling capacitor incorporation with cross-coupling grounding inductors can generate three transmission zeros. By properly adjusting the inductance values of the inductors between three resonators and ground the transmission zero can easily be manipulated at a high-side skirt to suppress the harmonic frequency. The measured results match well with the electromagnetic simulation that provides evidence for the feasibility of the proposed design.

Harmonic-suppression LTCC filter with the step-impedance quarter-wavelength open stub

An effective method to design a low-temperature co-fired ceramic RF bandpass filter with suppression of the harmonic frequency is demonstrated in this paper. The second harmonic, which appears in the frequency band of 4.8-5.0 GHz, is very significant and should be reduced in the 2.4-GHz wireless local area network and Bluetooth application. This feature of harmonic frequency suppression is very important in a communication system to improve linearity, output power, intermodulation performance, etc. The harmonic-suppression filter can be easily obtained by adopting the characteristic of equivalent quarter-wavelength resonators. The detailed three-dimensional layout of each layer is disclosed. By analyzing the influences of the dielectric constant and layer thickness of a ceramic sheet by electromagnetic simulation, the optimal condition for the filter design can be obtained. The measured results agree well with the simulation.

Miniaturization of Microstrip Branch-Line Coupler With Dual Transmission Lines

The dual transmission lines are proposed to replace conventional quarter-wavelength transmission lines for a compact microstrip branch-line coupler in this study. The developed coupler can be easily fabricated on the printed circuit board without lumped element; moreover, its size is greatly reduced compared to the conventional branch-line coupler. Furthermore, simulated and measured frequency responses match well to validate the proposed coupler with dual transmission lines.

Parallel-coupled stacked SIRs bandpass filters with open-loop resonators for suppression of spurious responses

A novel method to develop microstrip bandpass filters has been proposed in this letter. The unit cell elements are adopted to design bandpass filters. This unit cell element is composed of the parallel-coupled stacked stepped-impedance-resonators (SIRs) and the open-loop resonators. Compared to the uniform parallel-coupled line, the unit cell element is shorter. Moreover, the mutual couplings of the open-loop resonators can generate the transmission zero for suppression of spurious responses. The fabricated examples are presented for validating the filter configuration.

A Microstrip Bandpass Filter With Ultra-Wide Stopband

This paper develops a novel microstrip bandpass filter with ultra-wide stopband. With the assistance of open stubs and interdigital capacitors, a very wide stopband with a sufficient rejection level can be achieved easily. Detailed design and synthesis procedures are provided. Moreover, the electromagnetic simulator IE3D is used, and the prototype of the bandpass filter is fabricated and measured. Good agreement between measured and theoretically predicted results demonstrates feasibility of the proposed filter.

Wide Stopband Parallel-Coupled Stacked SIRs Bandpass Filters With Open-Stub Lines

In this letter, spurious passband suppression in parallel-coupled stacked stepped-impedance-resonators (SIRs) bandpass filters (BPFs) by means of open-stub lines is proposed and implemented. These filters are composed of parallel-coupled stacked SIRs and open stubs. Moreover, the structure with tapped feeding is employed to create transmission zeros near both sides of the passband skirt. The proposed structure can improve the harmonic suppression so that a wide upper stopband with a satisfactory attenuation level would appear in this BPF. Measured results of the fabricated circuits show that the idea works very well

Design of a dual-band bandpass filter with low-temperature co-fired ceramic technology

A novel dual-band bandpass filter with low-temperature co-fired ceramic technology is proposed in this paper. By adopting the structure of an asymmetrical short-circuit coupled line, two open-stub lines, and two reactances, the transmission zeros, which increase the degree of isolation between the passbands, will easily appear at the higher side of two passbands skirts. The analysis of theorem and the procedure of design are described. The measurements of fabricated units match well with the electromagnetic simulation results, which is an evidence of the feasibility of the proposed filter configuration