Xiao-Lan Zhao

Novel Filtering Power Divider With Wide Stopband Using Discriminating Coupling

A novel filtering power divider with wide stopband is presented in this letter. It utilizes four coupled quarter-wavelength resonators to obtain dual functions. Discriminating coupling is applied to the input and output feed lines and resonators, which not only to provide suitable coupling strength but also to suppress 3f0 and 5f0 (f0 is the operating frequency). A resistor is connected at the two open-ends of the input feed line to obtain high isolation. Transmission zeros are generated near the passband edges, resulting in high selectivity. For demonstration, a power divider with filtering function as well as wide stopband is implemented. Good agreement between the prediction and measurement validates the proposed method.

Novel Tri-Band Bandpass Filter Using Stub-Loaded Short-Ended Resonator

This paper presents a tri-band bandpass filter (BPF) using a novel stub-loaded resonator. Different from other stub-loaded resonator, this resonator utilized a short-ended main transmission line and a centerly-loaded open stub. The resonator is theoretically analyzed. The first three resonant frequencies can be individually adjusted and this enables the convenient designs of tri-band BPFs. For demonstration, a tri-band BPF is implemented. Transmission zeros are created close to each passband edge, resulting in high skirt selectivity. Comparisons of the measured and simulated results are presented to verify the theoretical predications.

Unequal Wilkinson Power Divider With Reduced Arm Length For Size Miniaturization

This paper presents a compact unequal Wilkinson power divider (WPD) with a reduced arm length. The unequal power divider consists of four arms and the isolation elements, including a compensating capacitor and isolation resistor. Compared with the conventional WPD, the electric length θ of the arms between the input port and the isolation elements is much shorter, and thus, compact size can be obtained. A theoretical analysis is carried out, and design equations are obtained. In addition, a study is carried out to characterize the isolation bandwidth and output port return loss bandwidth with different values of θ. For validation, two power dividers operating at 1.5 GHz are implemented with various size and isolation bandwidths. Around 50% size reduction and good performance are obtained.

Compact LTCC Balun With Bandpass Response Based on Marchand Balun

In this letter, we present a compact low temperature co-fired ceramic (LTCC) balun with bandpass responses. It is designed based on a Marchand balun. The halfand quarterwavelength transmission lines in Marchand balun are utilized as resonators in this design. Three feeding lines, functioning as input and outputs, are coupled to the resonators. The 180° phase difference between two output ports is achieved due to the inherent out-of-phase characteristic at the two open ends of the half-wavelength resonator. The bandpass responses are enabled by only adding three coupling lines and thus compact size is obtained. The coupling matrix is utilized in the design for realizing the good filtering responses and the design guideline is presented. For demonstration, a LTCC balun filter centered at 5.5 GHz is implemented. Good agreement between the simulated and measured results validates the proposed idea. The core circuit size is only 2 mm × 1.7 mm × 1.6 mm or 0.089λg × 0.076λg × 0.071λg.

Synthesis and Implementation of LTCC Bandpass Filter With Harmonic Suppression

In this paper, we utilize the coupling matrices to design a compact low-temperature cofired ceramic (LTCC) bandpass filter with wide stopband and high selectivity. One coupling matrix at the fundamental frequency is synthesized to obtain required passband responses. The other one at the third harmonic is manipulated to realize wide stopband. Two transmission zeros are appointed at both sides of the passband to enhance the skirt selectivity. They are generated by multiple cross-coupling paths, which are easy to realize in the multilayer LTCC structure. To reduce the circuit size, two coupled quarter-wavelength resonators are folded vertically and horizontally on different layers. An experimental filter is designed for verification. High skirt selectivity and wide stopband are observed in the measurement. Due to the LTCC techniques, the proposed circuit has a compact size of 2 mm × 1.7 mm × 2 mm or 0.042λg × 0.035λg × 0.042λg. It is suitable for system-in-package applications.

Novel Compact Quad-Band Bandpass Filter With Controllable Frequencies and Bandwidths

This letter presents a novel compact quad-band bandpass filter (BPF) with controllable operating frequencies and bandwidths. The proposed filter utilizes a novel second-order multi-stub-loaded resonator with four modes. Theoretical analysis indicates that the four modes can be controlled individually, resulting in controllable operating frequencies. Meanwhile, by controlling external quality factors and coupling coefficients, the bandwidths can also be adjusted individually. To validate the proposed idea, an experimental filter is implemented. Good agreement between the predicted and measured results demonstrates the proposed idea.

INDEPENDENTLY-TUNED DUAL-BAND FILTER USING VARACTOR-LOADED RESONATORS

This paper presents a high-selectivity dual-band bandpass fllter with independently-tunable passband frequencies. A tap-coupled structure is utilized to feed the two resonators at lower passband and a coupling structure is used to feed the two resonators at the upper passband. Two pairs of varactor-loaded resonators operating within two difierent frequency ranges, allow the independent passband frequency tuning. Using this conflguration, it is convenient to tune the center frequency of each passband, while the responses of the other passband remain unaltered. Source-load coupling is realized to generate transmission zeros, resulting in high skirt-selectivity. The transmission zeros move synchronously with the passbands, ensuring sharp roll-ofi rate for all tuning states. To verify the proposed idea, a demonstration microstrip tunable bandpass fllter is implemented. The simulated and measured results are presented.

Novel compact diplexer using net-type resonators

In this paper, a microstrip diplexer with compact size and good output isolation is proposed. This diplexer consists of two types of folded net-type resonators which have the same size but different resonance frequencies for composing the diplexer. Good selectivity and stopband suppression properties are achieved. For validation, the diplexer operating at 2.45/3.55 GHz is implemented and the area of the circuit is only 13.2mm × 16.7mm or 0.17λg × 0.22λg.

Wideband power divider using SIR impedance matching structures

This paper presents a wide bandwidth power divider using Stepped-Impedance Resonator (SIR) impedance matching structure. The SIR structure with a short-end stub is proposed to obtain matching to separated modes thus wide bandwidth response is achieved. There are two resistor and a capacitor in series instead of single resistor added between two output ports to improve the isolation. An experimental wide band power divider is implemented which achieve the bandwidth of 103% range from 0.98 GHz to 3.55 GHz with 10 dB return loss, the magnitude and phase differences of this power divider are 0.4dB and 2±1° near the center frequency, respectively.