Zhitao Xu

Substrate integrated waveguide (SIW) filter with hexagonal resonator

A novel substrate integrated waveguide (SIW) hexagonal resonator structure and its applications to bandpass filters are presented. Based on the SIW techniques, the resonance characteristic of proposed resonator is investigated. The hexagonal SIW resonators, which can combine flexibility of rectangular cavities and performance of circular cavities, are convenient for bandpass filters design. Since any of the six sides of a hexagonal resonator can be utilized for coupling, the filter configurations are flexible and adaptable. By changing the coupling sides of the hexagonal resonators, two types of experimental circuit configuration at the same central frequency of 10 GHz but with different fractional bandwidths of 3 and 6%, including third-order Chebyshev and crossed-coupling trisection, are constructed, fabricated, and measured. Measured results show a good agreement with simulated ones and validate the proposed configurations.

Design of a wide-stopband bandpass filter using stepped impedance resonators

In this paper, a compact bandpass filter (BPF) with improved stopband characteristics using stepped impedance resonators (SIRs) is proposed. The filter consists of two quarter-wavelength SIRs with radial stubs and a PI-network of capacitance, which is used to suppress the upper frequency spurious signals. An odd- and even-mode analysis is adopted considering the structure’s symmetry. A new BPF centered at 1.57 GHz has been designed and fabricated to verify the validity of the proposed method. Measured results are in good agreement with the electromagnetic simulation. The frequency selectivity was enhanced via introducing two finite transmission zeros (TZs) near the passband, located at 1.21 GHz with 43.5 dB rejection and 3.10 GHz with 62.3 dB rejection, respectively. The spurious frequencies of the upper stopband are suppressed better than 20 dB from 2.07 to 16.25 GHz. And the circuit only occupies 0.09 λ g  × 0.09 λ g.

Compact Second-Order LTCC Substrate Integrated waveguide Filter with Two Transmission Zeros

Abstract A compact second-order substrate integrated waveguide (SIW) filter using low-temperature co-fired ceramic (LTCC) technology with two transmission zeros for high-selectivity application is presented. The proposed filter is composed of a Modified Doublet (MD) and input/output (I/O) SIW. The MD comprises two resonators that are not coupled to each other, whereas the two resonators are placed below and above the I/O SIW, respectively. The input and output SIW are directly coupled in order to generate up to two finite transmission zeros. The filter not only has good selectivity owing to the controllable transmission zeros by tuning the coupling manner and strength between the I/O SIWand two resonators, but also has a small size by profit from LTCC structure. A demonstration filter having a center frequency of 10 GHz and a 3 dB fractional bandwidth of 2.5% is designed and fabricated to validate the proposed structure. The measured results exhibit high selectivity, minimum passband insertion loss of 2.09 dB, and in-band return loss greater than 14 dB, agree well with simulated ones. Furthermore, based on the vertically multilayer structure using LTCC technology, the overall size of the filter is only 18 × 10 × 1.2mm3.

Multilayer substrate integrated hexagonal cavity (SIHC) filter with mixed coupling (MC)

A novel multilayer substrate integrated hexagonal cavity filter with mixed coupling (MC) is proposed. Based on the substrate integrated waveguide techniques, the filter configuration is composed of hexagonal resonators which combine flexibility of rectangular cavities and performance of circular cavities. Meanwhile, by introducing MC into two adjacent resonators in the middle layer, the proposed filter has not only good selectivity due to the controllable transmission zeros, but also a compact size by profit from low-temperature co-fired ceramic technology. A fourth-order bandpass filter with three transmission zeros has been designed and fabricated. The measured results validate the feasibility of the proposed design, with its high selectivity demonstrated.

Miniaturized substrate integrated waveguide symmetric filter with high selectivity

A compact substrate integrated waveguide symmetric filter with source–load coupling using low temperature cofired ceramic (LTCC) technology for high-selectivity application is presented. The proposed filter with second-order resonators has two transmission zeros which can be controlled flexibly by adjusting the coupling strength and modifying coupling style. With the assistance of the multilayer LTCC structure and refined coupling manner, the proposed filter has a more compact size while maintaining high selectivity. A demonstration filter is designed, fabricated, and measured to validate the proposed structure. Measured results are provided to show good performance and in agreement with the simulated results. Moreover, thanks to the vertical LTCC multilayer structure, the overall size of the proposed filter is only  mm3.

A novel DC-DC convertor using LTCC technology for magnetic integration application

A compact DC-DC convertor is proposed and fabricated in multilayer ferrite substrate using LTCC technology. The spiral conductors are buried into the ferrite substrate with a multilayer 3-D structure to reduce the volume of convertor. The passive integration of magnetic components and surface circuitry are achieved in a whole substrate and the size of module can be reduced markedly. The whole height of module is only 3mm, 1/3 of the height of conventional modules. Testing results indicate that the performance of the module is excellent in Point-of-Load (POL) field. The step-down DC-DC converter converts input voltage of 5V to output voltage of 3.3V. It is confirmed that the maximum conversion efficiency of 93.2% is sufficient for actual DC-DC converter application. Such a compact DC-DC convertor provides a compact, low cost and high reliability approach for power supply and magnetic integration application.

Design of a Dual-Mode Tunable Wide-Bandstop Filter with Controllable Bandwidth

Abstract In this article, a compact dual-mode tunable wide bandstop filter with controllable bandwidth is presented. The proposed filter consists of an open-loop stepped-impedance resonator with a T open stub loaded. Varactor diodes Cv1 and Cv2 are loaded at two ends of the stepped-impedance resonator and the loaded T stub, respectively. By properly adjusting the capacitances Cv1 and Cv2 of the varactor diodes, the constant fractional bandwidth and constant absolute bandwidth can be achieved, respectively. A new dual-mode tunable wide bandstop filter with 61.0% constant fractional bandwidth and 2.0-GHz constant absolute bandwidth has been designed and fabricated to verify the validity of the proposed method. The measured results are in good agreement with the electromagnetic simulation.

A Multilayer T-Septum Substrate Integrated Waveguide Filter

ABSTRACT A multilayer T-septum structure and its application to a substrate integrated waveguide filter are presented. Coupling mechanisms in a T-septum structure, including stacking vertical layer and adjacent common sidewall, are discussed in detail. The T-septum resonance cavity exhibits not only excellent parasitic response characteristics, but also features of a miniature structure. The proposed filter with fourth-order T-septum resonators has two transmission zeros, which can be adjusted flexibly by controlling the coupling strength and manner. With the assistance of the low temperature co-fired ceramic multilayer structure and refined coupling structure, the proposed filter has a more compact size while maintaining high selectivity. A demonstration filter is designed, fabricated, and measured to validate the proposed structure. Measured results are provided showing good performance and agreement with the simulated examples.

Miniaturized Dual-Band Bandpass Filter with Multiple Transmission Zeros

Abstract A miniaturized dual-band bandpass filter with high frequency selectivity using stepped-impedance hairpin resonators is presented. The proposed filter consists of two sets of short-circuit centered stepped-impedance hairpin resonators, one of which is embedded in the other one to obtain two passbands. Multiple transmission zeros are employed via introducing mixed electric/magnetic coupling and source-load coupling simultaneously for high frequency selectivity. A 2.4-/5.2-GHz dual-band bandpass filter is designed and fabricated to demonstrate the proposed method. The measurement results show six finite transmission zeros in the stopband, located at 2.04, 3.67, 4.58, 5.89, 10.63, and 15.73 GHz, respectively. And the circuit only occupies 6.70 × 10.25 mm2.

A novel wideband band-pass response power divider with improved out-of-band performances

This paper reports a novel wideband two-way power divider with improved out-of-band rejection based on substrate integrated waveguide (SIW) technology. Periodic radial line slots are etched on the bottom side of SIW to achieve the band-stop characteristic. The band-pass response is achieved by combing the band-stop characteristic of the radial line slots and the high-pass characteristic of SIW. An experimental circuit is fabricated by the traditional printed circuit board technology. The measured results show that the power divider has the advantages of wideband (about 42.8% with center frequency 7GHz for Return Loss > 10 dB) and sharp roll-off skirts (better than 37 dB/GHz).