Ko-Wen Hsu

Filter-Based Wilkinson Power Divider

A bandpass Wilkinson power divider with a wide stopband is proposed in this letter. A three-terminal and two-pole bandpass filter and two lowpass filters are employed to substitute two quarter-wavelength transformer in the conventional Wilkinson power divider. The proposed divider achieves not only bandpass response but also a very wide stopband. The rejection is greater than 20 dB up to 22.2 f0. Experiments are carried out to validate design concept of the proposed power divider.

High-Isolation Microstrip Triplexer Using Multiple-Mode Resonators

A microstrip triplexer with high isolation is proposed in this letter. The triplexer utilizes multi-mode resonators, stepped-impedance resonators, and distributed coupling technique. To begin with, we design a diplexer with near passbands according to the excitation condition of the multi-mode resonators. The first passband is excited in odd mode, and the second one is of even mode. In this way, one can improve the isolation. Furthermore, without increasing any circuit size, the diplexer can be promoted to triplexer due to the third channel using distributed coupling technique.

Compact Sext-Band Bandpass Filter With Sharp Rejection Response

Compact sext-band bandpass filter based on stepped-impedance resonators is presented. Two types of rejection responses beside passbands can be designed by I/O gap capacitance. Considering design freedom and circuit complexity, each pair of resonators determine respective channel characteristics. The proposed sext-band filters occupy an extremely small area of 0.26λg × 0.15λg as well as keep good selectivity among channels.

Design of a novel four-band microstrip bandpass filter using double-layered substrate

A novel four-band microstrip bandpass filter using double-layered structure is proposed. The basic components used to build the proposed filter are four pairs of stepped impedance resonators on the top metal layer and middle metal layer. The four pairs of resonators have different fundamental frequencies. The first and second fundamental frequencies are designed to operate at 3 and 5 GHz on the middle layer; the third and fourth fundamental frequencies are designed to operate at 7 and 9 GHz on the top layer. Due to cross-coupling effect, attenuation poles at both sides of the passbands can be created to improve the filter selectivity. The full-wave simulator IE3D is used to design the four-band bandpass filter and to calculate the coupling coefficients of the resonators.

Design of Sext-Band Bandpass Filter and Sextaplexer Using Semilumped Resonators for System in a Package

In this paper, using semilumped resonators, one sext-band bandpass filter and one sextaplexer are proposed. The two circuits are fabricated using microstrip technology, and the semilumped resonator consists of two identical microstrip lines and a chip inductor at the center. In comparison with conventional half-wavelength uniform resonator, the semilumped resonator is compact and has better control over harmonic frequencies. In addition, the two circuits utilize a distributed coupling technique to integrate bandpass channel filters. This technique has a low loading effect resulting in a high design freedom that is essential for multiband circuits.

Compact quint-band microstrip bandpass filter using double-layered substrate

A quint-band bandpass filter using double-layered substrate is proposed. The basic components used to build the proposed filter are three pairs of microstrip stepped-impedance resonators on the top and middle metal layer, and two pairs of slot uniform-impedance resonators on the bottom metal layer. Since each pairs of resonators control a respective passband, the proposed design is flexible and features a high design freedom. The proposed filter has the advantages of compact size and sharp passband selectivity. Due to crossed coupling, the transmission zeros at the both sides of the passbands enhance passband selectivity.

Switchable and High-Isolation Diplexer With Wide Stopband

This letter presents a switchable diplexer composed of a stepped-impedance distributed coupling feeding line, four different quarter-wavelength stepped-impedance resonators (SIRs), two shunt open stubs, two p-i-n diodes, and bias circuitry. Compared with previous works, the proposed circuit features compactness, wide stopband, high selectivity, and independently switchable channels. To suppress harmonics, various quarter-wavelength SIRs with the same fundamental frequency but harmonic frequencies in stagger are used. Open stubs are also adopted to achieve an optimal stopband response. To meet the demands of reconfigurable application in wireless communication systems, switching circuit is integrated into the proposed diplexer to develop a switchable diplexer. In this way, mismatch losses during integration and circuit size are both further reduced. Simulations and measurements have been carried out to verify the design concept with good agreement.

Compact wide-stopband quad-band bandpass filter with tunable transmission zeros

A quad-band bandpass filter using double-layered structure has been presented. The proposed filter is principally composed of four pairs of stepped impedance resonators on the top metal layer and middle metal layer. In comparison to the conventional quad-band bandpass filters, the proposed filter has the advantages of compact size and wide-stopband response. Besides, due to multi-path effect, transmission zeros beside the passbands are created to achieve sharp rejection. The full-wave simulator IE3D is used to design the quad-band bandpass filter and to calculate the loaded and unloaded coupling coefficients for each pair of resonators.

Wide-stopband microstrip quadruplexer using asymmetric stepped-impedance resonators

A microstrip quadruplexer with a wide stopband is presented in this paper. The quadruplexer consists of asymmetric stepped-impedance resonators (SIRs) and a distributed common feeding line. In order to increase the stopband bandwidth, the higher order resonant frequencies of the asymmetric SIRs are staggered by properly selecting impedance ratio K and length ratio. Thus, a wide upper stopband performance can be achieved. The first, second, third, and forth channels of the quadruplexer are designed at 1.5, 1.8, 2.1, and 2.4 GHz (denoted by f1, f2, f3, and f4). For the upper stopband performance, the rejection level is greater than 20 dB up to 11.4 f1 (17.1 GHz).

Design of compact quad-band bandpass filter using semi-lumped resonators

A compact quad-band bandpass filter using semi-lumped resonators is presented. The proposed filter is composed of four pairs of semi-lumped resonators, which consist of microstrip sections and lumped inductors. Compared with the conventional half-wavelength uniform-impedance resonator, the proposed resonator achieves a compact size due to the lumped inductor employed. Moreover, transmission zeros appear in the stopband to improve the passband selectivity. The proposed quad-band bandpass filter achieves not only compact size but also good passband selectivity.