Wen-Hua Tu

Compact and High-Isolation Quadruplexer Using Distributed Coupling Technique

A compact microstrip quadruplexer with high isolation is presented in this letter. The quadruplexer consists of a distributed coupling feeding line, output feeding lines and uniform resonator pairs. Since the uniform resonators would resonate at multiple fundamental frequencies, to obtain a high-isolation quadruplexer, the resonators are properly located with respect to the input and output feeding lines to suppress the harmonic responses. Furthermore, because each pair of resonators control a specific channel frequency independently and the loading effect among channels is very small, the proposed quadruplexer has flexible passband frequencies.

Dual-Band/Tri-Band/Broadband CPW-Fed Stepped-Impedance Slot Dipole Antennas

In this study, two multi-band antennas and one broadband antenna using slot stepped-impedance resonators (SIRs) and coplanar waveguide (CPW) feeding have been investigated. All of the proposed antennas are fabricated on 1-mm FR4 substrates with a relative dielectric constant of 4.4 and a loss tangent of 0.02. In comparison to the conventional uniform-impedance resonator (UIR), the SIR shows a better control over spurious response. In this way, a dual-band antenna (antenna A) and a tri-band antenna (antenna B) could be designed at desired bands. Antenna A is implemented with center frequencies (f0, f√) = (1.5 GHz, 3.5 GHz), and Antenna B is realized with center frequencies (f0, fS1, fS2) = (1.5 GHz, 3.5 GHz, 5.5 GHz), where f0 is the fundamental frequency. The broadband antenna (antenna C) is designed by allocating the first three resonant frequencies close enough to achieve a 98.7% fractional bandwidth with a return loss of greater than 6 dB from 1.5 GHz to 4.4 GHz. Furthermore, to tackle the null radiation problem at the broadside direction of antennas A and B, parasitic slots are added near the main radiating resonators so as to achieve nearly omni-directional radiation patterns at the high-order mode frequencies.

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.

Switchable Microstrip Bandpass Filters With Reconfigurable On-State Frequency Responses

A switchable microstrip bandpass filter (BPF) with reconfigurable on-state frequency responses is proposed. The filter consists of a two-pole BPF and two switchable delay lines. The proposed filter features not only switch ability with an on-off ratio of 41.2 dB but also two on-state frequency responses: Chebyshev response and quasi-elliptic-function response. Experiment was carried out to validate the design concept, and the simulation agrees well with the measurement.

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.

Compact Low-Loss Reconfigurable Bandpass Filter With Switchable Bandwidth

A reconfigurable bandpass filter (BPF) is presented using a resonator with switchable number of transmission poles at 1.5 GHz. The resonator consists of a uniform resonator, a p-i-n diode, and an open loop. The diode is used to connect/isolate the open loop to/from the uniform resonator. When the open loop is loaded, the resonator has three transmission poles, and the BPF achieves a wideband response. On the other hand, the resonator has one transmission pole, and the BPF exhibits a narrow-band response when the open loop is disconnected. In comparison to previous work, the proposed reconfigurable BPF features a compact size, low insertion losses, minimum diode number, and a fair passband tuning ratio.

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.

Microstrip Eight-Channel Diplexer With Wide Stopband

A microstrip eight-channel diplexer with a compact size and a wide stopband is presented. There are sixteen stepped-impedance resonators controlling the passband characteristics. Every two resonators are used for one passband resulting in a high design freedom. There are four passbands filtered out at each of the two output ports. The circuit size is only 0.1 λg2 at the lowest channel frequency. The isolation is more than 29 dB, and the 20 dB upper stopband extends up to 8.22 × the lowest operation frequency.