Tunable Microwave Bandpass Filter Research Articles

A Low-Cost Bandpass Filter Based on Hybrid Spoof Plasmonic Waveguides

We propose a hybrid guided structure consisting of a rectangular waveguide loaded with channel-shaped and its complementary wedge-shaped metallic pillars that supports spoof plasmonic guided modes. The complementary structure is used in order to gain better control over tuning of the asymptotic frequency in the spoof plasmonic waveguide. As a proof of concept, a tunable microwave bandpass filter based on the proposed spoof plasmonic waveguide is fabricated and tested. Measurement and simulation results of the filter response are in excellent agreement with 14% bandwidth at the center frequency of 11 GHz and a maximum 0.7-dB insertion loss. The channel-shaped structure results in a passband frequency response with minimum ripple and the double-sided complementary pillars cause smaller bandwidth and more tunability.

Lumped modeling with circuit elements for nonreciprocal magnetoelectric tunable band-pass filter**Project supported by the National Natural Science Foundation of China (Grant Nos. 11172285, 11472259, and 11302217) and the Natural Science Foundation of Zhejiang Province, China (Grant No. LR13A020002).

This paper presents a lumped equivalent circuit model of the nonreciprocal magnetoelectric tunable microwave band-pass filter. The reciprocal coupled-line circuit is based on the converse magnetoelectric effect of magnetoelectric composites, includes the electrical tunable equivalent factor of the piezoelectric layer, and is established by the introduced lumped elements, such as radiation capacitance, radiation inductance, and coupling inductance, according to the transmission characteristics of the electromagnetic wave and magnetostatic wave in an inverted-L-shaped microstrip line and ferrite slab. The nonreciprocal transmission property of the filter is described by the introduced T-shaped circuit containing controlled sources. Finally, the lumped equivalent circuit of a nonreciprocal magnetoelectric tunable microwave band-pass filter is given and the lumped parameters are also expressed. When the deviation angles of the ferrite slab are respectively 0° and 45°, the corresponding magnetoelectric devices are respectively a reciprocal device and a nonreciprocal device. The curves of S parameter obtained by the lumped equivalent circuit model and electromagnetic simulation are in good agreement with the experimental results. When the deviation angle is between 0° and 45°, the maximum value of the S parameter predicted by the lumped equivalent circuit model is in good agreement with the experimental result. The comparison results of the paper show that the lumped equivalent circuit model is valid. Further, the effect of some key material parameters on the performance of devices is predicted by the lumped equivalent circuit model. The research can provide the theoretical basis for the design and application of nonreciprocal magnetoelectric tunable devices.

A compact tunable microwave bandpass filter based on liquid crystal

ABSTRACTIn this Letter, with the application of liquid crystal (LC) an electrically tunable microwave filter has been designed, manufactured, and characterized. The proposed compact filter has been realized on a particularly configured cavity which was constructed with low cost inverted‐microstrip structures and conventional resonance structure. By applying low square‐wave (1KHz) voltages, low power consumption is involved. The filter responses have been allocated at k‐band of microwave frequency at which band many communications and radar applications applied. The proposed filter occupies a compact area of 19 mm × 17 mm only. The measured results have shown that the proposed filter realized the central frequency changing from 15.5 GHz to 16.5 GHz continuously with bias voltages changing between 0 and 10 V. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:2470–2472, 2016

Tunable microwave bandpass filter integrated power divider based on the high anisotropy electro-optic nematic liquid crystal.

A novel, compact microwave tunable bandpass filter integrated power divider, based on the high anisotropy electro-optic nematic liquid crystal, is proposed in this letter. Liquid crystal, as the electro-optic material, is placed between top inverted microstrip line and the metal plate. The proposed structure can realize continuous tunable bandpass response and miniaturization. The proposed design concept is validated by the good performance of simulation results and experimental results. The electro-optic material has shown great potential for microwave application.

Magnetically tunable microwave bandpass filter structure composed of ferrite rods and metallic slits

Magnetically tunable microwave bandpass filter structure have been designed and prepared by filling the ferrite rods into the metallic slits. The electromagnetic wave cannot propagate through the metallic slits. By filling the ferrite rods into the metallic slits, an enhanced optical transmission is obtained, which can be ascribed to the ferromagnetic resonance of the ferrite rods. Both the experimental and the simulated results show the center frequency and bandwidth of the passband can be tuned by the applied magnetic field, which exhibits a magnetically tunable behavior. This approach opens a way for designing tunable microwave bandpass filters.

Quality of ferroelectric capacitors used in tunable microwave filters

The problem of determining the quality of ferroelectric capacitors from measured characteristics of tunable microwave bandpass filters has been solved. The quality of ferroelectric capacitors based on barium-strontium-titanate (BST) thin films, used in four filters tunable over a frequency range of 1.8 to 4.3 GHz, have been determined.

Low‐loss MEMS switchable microstrip filters

AbstractParallel‐coupled microstrip filters with MEMS switchable frequency responses are designed. The 15‐GHz filter switches 5.3% with minimum insertion loss of 0.7 dB, whereas the 20‐GHz filter has 12.9% switching range and minimum insertion loss of 0.6 dB. Both filters have the lowest insertion losses among MEMS tunable microwave bandpass filters to date. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2557–2561, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23723

Magnetoelectric microwave bandpass filter

An electric field tunable microwave bandpass filter based on ferromagnetic resonance (FMR) in a bilayer of yttrium iron garnet and lead zirconate titanate has been designed and characterised. The filter tunability is accomplished through magnetoelectric coupling that manifests as a shift in the FMR. Studies on a microstripline filter show a 125 MHz tuning range for E=0–3 kV/cm and an insertion loss of 5 dB at 6.5 GHz.

Optimization of materials and design for electrically tunable microwave filters

Electrically tunable microwave band-pass filters are fabricated using a high-temperature superconductor and tunable dielectrics based on SrTiO3. The design of the filters is optimized for bandwidth stabilization and proper impedance matching. The properties of the tunable dielectric are optimized through adjustments of the growth parameters and the use of buffer layers. The optimized filter is characterized by an insertion loss less than 2.5 dB, unloaded quality factors ranging from 452 to 709, and a 4.6% tuning range at ± 140 V.