Di Jiang

A Bandpass Filter Based on Half Mode Substrate Integrated Waveguide-to-Defected Ground Structure Cells

A half mode substrate integrated waveguide-to-defected ground structure (HMSIW-DGS) cell and its embedded form are proposed to miniaturize a bandpass filter. Both cells can purchase wideband frequency response and low insertion loss, as well as simple and easy fabrication. By cascading two of them according to design requirement, an X-band bandpass filter is designed and measured to meet compact size, low insertion loss, good return loss, second harmonic suppression, and linear phase.

A Microwave Tunable Bandpass Filter for Liquid Crystal Applications

Abstract In this paper, a novel microwave continuously tunable band-pass filter, based on nematic liquid crystals (LCs), is proposed. It uses liquid crystal (LC) as the electro-optic material to mainly realize frequency shift at microwave band by changing the dielectric anisotropy, when applying the bias voltage. According to simulation results, it achieves 840 MHz offset. Comparing to the existing tunable filter, it has many advantages, such as continuously tunable, miniaturization, low processing costs, low tuning voltage, etc. Thus, it has shown great potentials in frequency domain and practical applications in modern communication.

Analysis on maximum operating frequency of subharmonic Class-E amplifier at any duty ratio

This paper presents that the maximum operating frequency of sub-harmonic Class-E amplifier not only depends on the transistor duty ratio, but also relies on the slope of switch voltage when the transistor turns on. When dc supply voltage, output power and shunt capacitance are specified, the maximum operating frequency increases as the slope of switch voltage increases. On the contrary, it increases as the transistor duty ratio declines.

Research of a novel bandpass filter using Nematic Liquid Crystal loaded by inverted Microstrip

In the structure of inverted Microstrip with complementary split-ring resonator, a new type of compact bandpass filter is designed. Nematic Liquid Crystal is introduced in this structure. Through changing the applied voltage, the properties of liquid Crystal are also changed , and it is easy to adjust the center frequency of the bandpass filter. Arbitrary frequency bandpass filter is easier to be achieved by means of this feature. The bandpass filter has the advantage of compact size, low loss, easy fabrication and easy integration with other circuits. Using this feature can be easier to achieve perfect microwave bandpass filter.

Research of Nematic Liquid Crystal Broadband tunable power divider

Basing on split-ring resonator(SRR), a compact broadband power divider has been implemented. The power divider uses common inverted microstrip line, and loads DSRRs unit on microstrip line metal conduction band, and at the same time loads nematic liquid crystal on inverted microstrip lines. Using Nematic Liquid Crystal in external bias with permittivity of dielectric constant variable attributes, a c-band broadband power divider is designed. The power divider not only has the advantage of compact size, low loss and easy fabrication, but the advantage of easy integration with other circuits.

Continuous tunable miniaturized microwave coupler using liquid crystals

This paper describes a microwave coupler using liquid crystals as a medium for microstrip line structure. In this design, a layer of liquid crystals is added to the ground and the substrate, and using the characteristics of anisotropy nematic liquid crystals, that is the dielectric anisotropy changes when without the bias and bias voltage is applied, to achieve the goal of continuous tunable coupler center frequency. In this paper, the design of the coupler not only has a wide bandwidth, but also the isolation (|S41|) and return loss(|S11|) are relatively excellent, especially in the center frequency, which are all better than 45dB. When the permittivity of the liquid crystals is changed from 2.4 to 3.4, the center frequency of the coupler is changed from 2.85GHz to 2.75GHz; the tunable range of up to 100MHz has been realized.

A compact tunable filtering-power divider based on liquid crystal

Special areas such as microwave radar, guidance and communication systems should achieve dynamic frequency selection and dynamic power distribution in the broadband range. The tunable filtering-power divider can not only achieve dynamic frequency selection and power distribution, but also downsize the system. By electrifying the upper and lower surface electrode of the liquid crystal (LC) and changing the voltage value to result in the change of the LC pointing vectors so as to alter the effective dielectric constant of LC substrate, the center frequency of filtering-power divider can be tuned to achieve the high-speed dynamic frequency selection and power division. Thus, miniaturization and lightweight of the electronic system can be brought about with efficiency.

A novel tunable inverted microstrip phase shifter based on liquid crystal

In this paper, a microwave phase shifter of inverted microstrip using liquid crystal (LC) material is introduced. The phase shifter is made up with a carrier and a substrate, between them there is a layer of liquid crystal dielectric, its anisotropic properties will change under the bias or without bias, thus the phase shift can be realized. The phase shifter in this article can be continuously tuned up to 319.171° with an insertion loss from 1.14dB to 3.47dB. It will be very useful in the communication system and the phased-array radar system.

Tunable microwave filter using highly anisotropic liquid crystals

An electrically controlled tunable microwave filter is described, which is designed on a resonant inverted microstrip structure with a nematic liquid crystal. The center frequency of the respective two-pole tunable filter is settled at 6.5GHz which can be shifted by 500MHz approximately. The device is fabricated using liquid crystal sandwich structure with a total thickness of 1 mm. The total size of the proposed filter structure is 20×18 mm2.

A high isolation dual-band bandpass filter based on hybrid microstrip/split-loop slot resonator

A novel dual-band bandpass filter (BPF) with high isolation between the two passbands and good selectivity is proposed in this article, which is based on hybrid-coupled microstrip open-circuited stub/split-loop slot multi-bandgap resonator. Based on full-wave electromagnetic (EM) analysis, the proposed filter is found to have the advantage that the both passband central frequencies can be flexibly controlled by the geometric dimensions of multi-bandgap resonator, while the pass-band bandwidths are mainly determined by the cascaded number of the hybrid microstrip/slot resonators. Theoretical prediction is verified by the experimental result of the proposed dual-band BPF.