Jin- Xu

LTCC Bandpass Filter With Wide Stopband Based on Electric and Magnetic Coupling Cancellation

This paper presents a new method of using electric and magnetic coupling cancellation to extend the stopband of bandpass filters (BPFs). The mechanism is theoretically analyzed based on the lumped-element equivalent circuit. Due to the cancellation of electric and magnetic coupling between two resonators, three transmission zeros (TZs) can be generated and controlled by manipulating the coupling strength. Using the proposed method together with source-load coupling, a low temperature cofire ceramic (LTCC) BPF is designed with four TZs at the passband edges and within the stopband, resulting in high skirt selectivity and harmonic suppression. Due to the LTCC multilayer structure, the filter size is 0.054 λg*0.045λg*0.013λg, or 2.48 mm ×2.02 mm ×0.6 mm. The theoretical, simulated and measured results of the LTCC BPF are presented to validate the proposed design.

Dual-Polarized Filtering Antenna With High Selectivity and Low Cross Polarization

This paper presents a dual-polarized patch antenna with quasi-elliptic bandpass responses. The proposed antenna is mainly composed of a feeding network, a driven patch, and a stacked patch, with its entire height being 0.09λ. The feeding network consists of two orthogonal H-shaped lines that coupled to the driven patch, each for one polarization. The elaborately designed feeding lines not only ensure a sharp roll-off rate at the lower band edge, but also help to achieve low cross polarization and high isolation between two feeding ports. On the other hand, the upper stacked patch provides improved suppression levels at the upper stopband and also an enhanced gain within passband. Consequently, a compact dual-polarized antenna with satisfying filtering performance is obtained, without using extra filtering circuits. For demonstration, an antenna is designed to fit the specification of LTE band (2.49-2.69 GHz). The implemented antenna achieves an average a gain of 9 dBi, a cross-polarization ratio of 29 dB, an isolation of 35 dB within LTE band. The out-of-band suppression level is more than 40 dB within the 2G and 3G frequency bands from 1.71-2.17 GHz. It can be used as the antenna elements in multiband base station antenna arrays to reduce the mutual coupling.

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.

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.

High-Power Filtering Switch With Low Loss and High Isolation Based on Dielectric Resonator

In this paper, a novel method for designing high-power filtering switches using dielectric resonators (DRs) is presented for the first time. The filtering switches consist of DRs and printed circuit boards. The latter are embedded in the metal cavity to enable the integration of p-i-n diodes. The ON- and OFF-states are realized by controlling the p-i-n diodes which are put in the feeding lines or nonresonance nodes (NRNs). Electromagnetic field properties of the DR (at TE

High-Efficiency Filter-Integrated Class-F Power Amplifier Based on Dielectric Resonator

_{11\delta }

Novel compact diplexer using net-type resonators

mode) and feeding line (or NRN) are studied and the coupling between them is investigated for guiding coupling control. In the ON-state, the filtering switches are equivalent to bandpass filters with no signal passing through the p-i-n diodes, which avoids additional loss introduced by p-i-n diodes and attains high power handling capability. In the OFF-state, the proposed filtering switches offer enhanced isolations by controlling the coupling of the filtering circuits, which differs from the conventional switches by turning off transistors or diodes. For demonstration, a DR-based filtering single-pole single-throw switch and a filtering single-pole double-throw switch are implemented. High selectivity, low ON-state loss and high OFF-state isolation are observed. The measured

Compact High-Isolation LTCC Diplexer Using Common Stub-Loaded Resonator With Controllable Frequencies and Bandwidths

\text{P}_{\mathrm {1dB}}