Jiaxuan Liao

Compact Tri-Band Bandpass Filter Using Open Stub Loaded Tri-Section lambda/4 Stepped Impedance Resonator

A modified tri-mode λ/4 stepped impedance resonator (SIR) is proposed, in which a shunt open stub is loaded in the conventional λ/4 tri-section SIR. The resonant frequencies and frequency ratios can be properly controlled by adjusting the loaded open stub. A compact second-order tri-band bandpass filter (BPF) based on two coupled proposed open stub loaded λ/4 tri-section SIR is presented. A pair of transmission zeros (TZs) are generated at the lower and upper stopband of each passband for high selectivity and excellent band-to-band isolation. A tri-band BPF with the central frequencies of 1.92, 3.50, 5.75 GHz, and respective fractional bandwidths of 5.4%, 4.0%, and 2.4% is designed and fabricated. Measured results show good agreement with simulations. Moreover, the circuit only occupies 0.09 λg ×0.10 λg.

Compact LTCC source-load coupled SIW filter using mixed coupling

A novel substrate integrated waveguide (SIW) filter with source-load coupling based on low temperature co-fired ceramic (LTCC) technology is proposed. By introducing mixed coupling into input/ output SIW in middle layer, the filter not only has good selectivity owing to the controllable transmission zeros, but also has a compact size by the virtue of LTCC structure. Based on the flexible coupling manner in multilayer structure, a demonstration second-order bandpass filter with three transmission zeros has been designed and fabricated. Good agreement between measured and simulated results is observed.

Influence of Film Thickness on Dielectric Properties of Y and Mn Alternately Doped BST Films

By adjusting film thickness, smooth and dense Mn and Y alternately doped Ba0.6Sr0.4TiO3 (Mn/Y-BST) films have been designed and prepared by improved sol-gel method, and the structure and dielectric properties of the films have been studied. X-ray diffraction (XRD) reveals that all films grow along (110) orientation, doped Mn2+ ions or Y3+ ions show acceptor doping, and thicker film shows stronger crystallization. Atomic force microscope (AFM) shows the films are relatively smooth without obvious cracks or pinholes. Scanning electronic microscope (SEM) indicates that from substrate to surface the films show nodular microstructures to columnar ones without obvious interface among nodular microstructure layers. Compared to pure BST film or Mn or Y doped BST films, all alternately doped films show markedly improved structures and dielectric properties, which is strongly dependent on film thickness. 6-layer Mn/Y-BST film shows best structure and combination of dielectric properties with dielectric loss of 1.18%, tunability of 38% and figure of merit (FOM) of 32.2 at 100 kHz.

Substrate integrated waveguide cross-coupling filter with multilayer hexagonal cavity

Hexagonal cavities and their applications to multilayer substrate integrated waveguide (SIW) filters are presented. The hexagonal SIW cavity which can combine flexibility of rectangular one and performance of circular one is convenient for bandpass filters design. Three types of experimental configuration with the same central frequency of 10 GHz and bandwidth of 6%, including third-order and four-order cross-coupling topologies, are constructed and fabricated based on low temperature co-fired ceramic (LTCC) technology. Both theoretical and experimental results are presented.

COMPACT BANDPASS FILTER WITH MIXED ELECTRIC AND MAGNETIC (EM) COUPLING

A compact wide-band bandpass fllter (BPF) with high frequency selectivity using stepped impedance resonators (SIRs) is presented in this paper. The proposed BPF consists of four SIRs, which share a common grounded via-hole. To improve the frequency selectivity, multiple transmission zeros (TZs) are employed in the stopband by mixed electric/magnetic (EM) coupling. The novel fllter with 32.2% fractional bandwidth (FBW) has been designed and fabricated to verify the validity of the proposed method. Measured results are in good agreement with the electromagnetic simulation. The measured results show three flnite transmission zeros in the stopband, located at 2.47GHz, 5.26GHz, 9.39GHz, respectively. The circuit size of proposed BPF only occupies 3:10 £ 13:30mm 2 .

Preparation and Dielectric Properties of Cerium and Manganese Codoped Ba0.6Sr0.4TiO3 Ferroelectric Films

Cerium (Ce) and manganese (Mn) codoped Ba0.6Sr0.4TiO3 (BST) films were prepared by improved sol-gel method and the effect of preheating on their dielectric properties was investigated. X-ray diffraction (XRD) reveals that the films grow principally along (110) orientations and show cubic perovskite structures. Preheating corresponds to smaller FWHMs, stronger crystallization and larger grain sizes, and preheating with codoping corresponds to the smallest FWHM, the strongest crystallization and the largest grain size. The prepared film can show tunability of 55.7%, dielectric loss of 0.0074∼0.0175 and approximately 75 FOM, meeting the needs of tunable microwave applications.

Improved Mechanisms for Excellent Tunable Microwave Ce and Mn Codoped Ba0.6Sr0.4TiO3 Thin Films

Smooth and dense preheated cerium (Ce) and manganese (Mn) codoped barium strontium titanate (CeMn-BST) films with various thicknesses have been prepared by improved sol-gel method. Capacitance-voltage curves show that with increasing film thickness, combination of dielectric properties are significantly improved with optimized values of about 1300 moderate permittivity, less than 0.007 dielectric loss, more than 58% tunability and hence near 180 figure of merit (FOM) for eight-layer CeMn-BST film. The objective of this paper is to study the improved mechanisms for such excellent dielectric properties. XRD shows that the films layered-grow mainly along (110) orientation and exhibit ABO3 cubic perovskite structure. As film thickness increases, Ce3+ and/or Mn2+ ions are showing doping modes from donor doping to acceptor doping, the crystallization of films is enhancing, but the average grain sizes of the films show gradually decreased trend from about 45nm to 25nm in terms of the intensities of (110) diffraction peaks. AFM indicates that the films are getting smoother with smaller roughness with increasing thickness. XPS reveals that the films reveal decreased non-perovskite structure, element core levels and Fermi levels with increasing thickness. Leakage current densities are significantly decreased almost at two orders of magnitude with increasing thickness. Pure BST films are compared.

A Novelly Designed Ba0.6Sr0.4TiO3 Film with High Tunability and Low Dielectric Loss

Manganese (Mn) and yttrium (Y) alternately doped Ba0.6Sr0.4TiO3 (BST) films are novelly designed as MnBST/YBST/MnBST/YBST and prepared layer-after-layer on Pt wafer electrodes, and two films where one with the first layer preheated (1Mn/YBST) and the other with four layers preheated (4Mn/YBST) are focused on. XRD shows that two films grow along (110) orientation and reveal ABO3 cubic perovskite structures and donor doping, but 4Mn/YBST film shows larger average grain size. SEM demonstrates that 1Mn/YBST film is composed of one 630nm-thick layer with nodular microstructure and the other 570nm-thick surface layer with columnar microstructure, whereas 4Mn/YBST film is 670 nm thick with nodular microstructure. AFM shows that two films are smooth with no cracks, but 4Mn/YBST film is denser with smaller roughness. Two films show more than 55% high tunabilities, but 4Mn/YBST film also reveals low losses of 0.0062∼0.0156 and high figure of merit (FOM) of near 90 at -35V and 100 kHz, fully meeting the needs of tunable microwave applications.

Compact Bandstop Filter with Multiple Rejection Zeros

This paper presents a compact band stop fllter (BSF) based on the dual metal plane conflguration with multiple rejection zeros (RZs). Quasi-lumped technique with novel patch-via-spiral dual mode resonator is applied to the design of the proposed fllter. Multiple rejection zeros are introduced by open-end stubs for high selectivity. Design equations are obtained by using a lossless transmission line model. The calculated results show that the lower and upper rejection zeros can be easily tuned by the coupling capacitor and the open- end stubs respectively. By using the Microstrip-Coplanar-Waveguide (CPW) structure, the size of the proposed fllter can be reduced to 12:8mm £ 9mm (i.e., 0:24‚g £ 0:17‚g), where ‚g denotes the guided wavelength at center frequency.

Compact bandpass filter with wide stopband using stepped impedance resonators

A compact bandpass filter with wide stopband using stepped impedance resonators has been designed and fabricated. And open ended stubs for frequency fine tuning are introduced. The new passband filter was analyzed, simulated and fabricated. Measured results are in good agreement with the electromagnetic simulation results. Moreover the circuit only occupies 20.1 × 17.1 mm2(≈0.21 λg × 0.16λg).