Tengxing Wang

Compact Dual-Band Filter Using Open/Short Stub Loaded Stepped Impedance Resonators (OSLSIRs/SSLSIRs)

A novel microstrip dual-band filter with high frequency selectivity and extended rejection band is reported in this letter. The proposed filter employs one pair of open stub loaded stepped impedance resonators (OSLSIRs) functioning at two frequencies of interest. Two short stub loaded stepped impedance resonators (SSLSIRs) are embedded between the coupled OSLSIRs to generate quasi-elliptic response at two diverse frequencies. Contributed by the 0° feed structure, extra transmission zeros are produced to enhance the out-of-band rejection. OSLSIRs/SSLSIRs are chosen to achieve desired in-band performance and misaligned harmonic frequencies simultaneously. To demonstrate the efficacy of the design concept, a dual-band filter centering at 1.63 and 2.73 GHz is implemented. The design methodology and measured results are presented.

Engineered smart substrate with embedded patterned permalloy thin film for radio frequency applications

Multifunctional and frequency-agile devices are promising components that satisfy multiple standards of modern wireless communication system. This paper provides a unique method to develop tunable RF components based on engineered smart substrate where the smart substrate contain patterned Permalloy (Py) thin film on high-resistivity silicon. The permeability of Py can be adjusted by changing the DC current, thus allowing tunable RF circuits and components. Single or multi-layer patterns can be developed. To demonstrate tunability of the smart substrate, a frequency reconfigurable patch antenna was fabricated on Liquid Crystal Polymer substrate and bonded to the proposed smart substrate. The patch antenna was tested, which revealed that the center frequency of operation could be tuned from 2.38 GHz to 2.43 GHz by changing the DC current from 0 mA to 500 mA. Similarly, a transmission line based phase shifter was also fabricated on another smart substrate, which showed that the phase shifter could provide continuous 90° phase shift from 2.35 GHz to 2.15 GHz under different DC current bias conditions.

Microstrip balanced quad-channel diplexer using dual-open/short-stub loaded resonator

A microstrip balanced quad-channel diplexer is reported for the first time, using dual-open/short-stub loaded resonator (DOSLR/DSSLR) which consists of a uniform impedance end-shorted resonator loaded with two open/short stubs. The resonant frequencies of dual-open-stub loaded resonator (DOSLR) and dual-short-stub loaded resonator (DSSLR) under differential-mode (DM) and common-mode (CM) excitation are fully analyzed. Based on their respective characteristics, two individual balanced dual-band filters are initially designed with a frequency ratio of larger and smaller than 2 respectively. The designed filters are then combined to construct the first balanced quad-channel diplexer adopting distributed coupling technique. In order to demonstrate the efficacy of the proposed design methodology, a compact quad-channel balanced diplexer prototype (2.4/5.2 GHz and 3.2/4.75 GHz) is implemented and measured. Good agreement between the theoretical analyses and the measured data has been achieved.

Arbitrary frequency tunable radio frequency bandpass filter based on nano-patterned Permalloy coplanar waveguide (invited)

A well designed coplanar waveguide (CPW) based center frequency tunable bandpass filter (BPF) at 4 GHz enabled with patterned Permalloy (Py) thin film has been implemented. The operating frequency of BPF is tunable with only DC current without the use of any external magnetic field. Electromagnetic bandgap resonators structure is adopted in the BPF and thus external DC current can be applied between the input and output of the filter for tuning of Py permeability. Special configurations of resonators with multiple narrow parallel sections have been considered for larger inductance tenability; the tunability of CPW transmission lines of different widths with patterned Py thin film on the top of the signal lines is compared and measured. Py thin film patterned as bars is deposited on the top of the multiple narrow parallel sections of the designed filter. No extra area is required for the designed filter configuration. Filter is measured and results show that its center frequency could be tuned from 4 GHz to 4.02 GHz when the DC current is applied from 0 mA to 400 mA.

Electrically Tunable Bandpass Filter With Patterned Permalloy Thin-Film-Enabled Engineered Substrate

An electrically tunable bandpass filter based on an engineered substrate embedded with patterned permalloy (Py) thin film has been designed, implemented, and characterized. The bandpass filter is designed with metamaterial resonators to achieve a compact size; the designed filter is fabricated on a multilayered engineered substrate, which is composed of a layer of liquid crystal polymer, a layer of patterned Py thin film, and silicon substrate. The tunability of center frequency for the designed bandpass filter is dependent on the radio frequency (RF) characteristics of the implemented engineered substrate. The equivalent permeability of the Py thin film embedded in the engineering substrate is electrically tunable with the dc current, which thus provides high and tunable inductance densities for the split-ring resonators in the designed filter; the center frequency of the implemented bandpass filter is thus electrically tunable. The measured results show that the center frequency of the designed bandpass filter shifts from 2.37 to 2.45 GHz continuously when the applied tuning dc current is changed from 0 to 500 mA. The introduced unique concept of the engineered substrate provides design feasibility of filters with continuous frequency tunability, and the implementation of the engineered substrate enabled with the patterned Py thin film is suitable for the cost-effective fabrication of the arbitrary tunable RF devices.

High-Performance Electrically Tunable RF Phase Shifter With the Application of PZT and Permalloy Thin-Film Patterns

A fully electrically tunable RF phase shifter enabled with lead zirconate titanate (PZT) and Permalloy (Py) thin-film patterns based on the step impedance slow wave structure is well designed and fabricated. Tunable metal-insulator-metal structure capacitor enabled with the PZT thin film is integrated into the phase shifter so that the working frequency can be tuned by dc voltage, and the tuning voltage is significantly decreased compared with the previous research. The Py thin film is patterned and is deposited on the signal line of the proposed phase shifter that enables a tunable working frequency by dc current. Both inductive and capacitive tunability of phase shifter are achieved simultaneously. When 200 mA dc current is provided between two ports of phase shifter, the working frequency tuning range is 2% from 1.98 to 2.04 GHz. The tuning range is 5% from 1.98 to 2.08 GHz when 8 V dc voltage is added between the signal line and the ground. When both 8 V dc voltage and 200 mA dc current are applied, the working frequency of the proposed phase shifter is tunable from 1.98 to 2.12 GHz with a tunability of 7.1%.

Integrating Nanopatterned Ferromagnetic and Ferroelectric Thin Films for Electrically Tunable RF Applications

Tunable radio-frequency (RF) components are pivotal elements in frequency-agile and multifunctional systems. However, there is a technical barrier to achieve miniaturized fully electrically tunable RF components. This paper provides and demonstrates the efficacy of a first unique design methodology in developing fully electrically tunable RF components by integrating ferromagnetic [e.g., permalloy (Py)] and ferroelectric (e.g., lead zirconate titanate) thin-film patterns. Py thin film has been patterned in nanometer scale to improve its ferromagnetic resonance frequency for RF applications. Tunable inductors are developed with the utilization of different thicknesses of Py thin film, which show over 50% increment in inductance and over 4% in tunability with dc current. More tunability can be achieved with multiple layers of Py thin film and optimized thickness. A fully electrically tunable slow-wave RF transmission line with simultaneously variable inductance and capacitance density has been implemented and thoroughly investigated for the first time. The measured results show that a fixed phase shift of 90° can be achieved from 1.5 to 1.85 GHz continuously by applying external dc current from 0 to 200 mA and external dc voltage from 0 to 15 V, respectively.

Bandpass filtering power divider with sharp roll-off skirt and enhanced in-band isolation

This paper presents a compact device with functions of frequency selecting and power dividing simultaneously. Open-stub loaded dual-mode resonators are selected as the basic building blocks. By cascading two dual-mode resonators, a novel fourth-order inter-cross-coupled coupling scheme containing mixed coupling is realized and employed to replace the λ/4-line sections of conventional Wilkinson power divider (PD) to improve out-of-band rejection performance. Two surface mounted resistors of different values are placed between channels to obtain high in-band isolation between output ports. Furthermore, a filtering PD operating at 4.45 GHz is designed, fabricated and tested to demonstrate the efficacy of the proposed design. Four finite transmission zeros positioned at 3.85 GHz, 4.25 GHz, 4.75 GHz and 5.4 GHz respectively are achieved which will result in good frequency selectivity. Very good agreement is observed between the simulated and experimental results with approximately 1.3 dB insertion loss and over 18 dB isolation over the entire passband.

Application of sub-micrometer patterned permalloy thin film in tunable radio frequency inductors

Electrical tunable meander line inductor using coplanar waveguide structures with patterned permalloy (Py) thin film has been designed and implemented in this paper. High resistivity Si substrate is used to reduce the dielectric loss from the substrate. Inductor is implemented with a 60 nm thick Py deposited and patterned on top of the gold meander line, and Py film is patterned with dimension of 440 nm × 10 μm to create the shape anisotropy field, which in turn increases the FMR frequency. Compared to a regular meanderline inductor without the application of sub-micrometer patterned Py thin film, the inductance density has been increased to 20% for the implemented inductor with patterned Py. Measured FMR frequency of the patterned Py is 4.51 GHz without the application of any external magnetic field. This has enabled the inductor application in the practical circuit boards, where the large external magnet is unavailable. Inductance tunability of the implemented inductor is demonstrated by applying a DC current. Applied DC current creates a magnetic field along the hard axis of the patterned Py thin film, which changes the magnetic moment of the thin film and thus, decreases the inductance of the line. Measured results show that the inductance density of the inductor can be varied 5% by applying 300 mA DC current, larger inductance tunability is achievable by increasing the thickness of Py film.

Integration of ferromagnetic and ferroelectric films for fully electrically tunable RF devices

Tunable RF components are key elements in frequency reconfigurable and multifunctional systems. However there are technological barriers to achieve miniaturized fully electrically tunable RF components. This paper provides a unique design methodology in developing electrically tunable RF devices from the integration of ferromagnetic (Permalloy) and ferroelectric thin films. Permalloy thin film has been patterned in nanometer scale to improve its ferromagnetic resonance frequency for RF applications. A tunable transmission line with simultaneously variable inductance and capacitance density is developed, and measurmd results show that a fixed phase shift can be achieved from 2GHz to 1.55 GHz with the application of DC current and voltage. A center frequency tunable bandpass filter has also been developed with the application of Py thin film. In addition, engineered substrate implemented with embedded Permalloy and PZT patterns has been proposed which provides both electrically tunable equivalent permeability and permittivity; arbitrary tunable RF components are achievable on the proposed substrate combined with the state-of-art tunable techniques. t Times New Roman Bold font. An example is shown next.