Yasumasa Noguchi

Preparation of all-oxide ferromagnetic/ferroelectric/ superconducting heterostructures for advanced microwave applications

As candidates for functional layers, 3d transition metal oxides with perovskite structures show some interesting properties, such as ferromagnetism, ferroelectricity and superconductivity. Accordingly, combinations of these properties can be used to create new tunable microwave devices. Ferromagnetic/ferroelectric/superconducting multistructures, such as La0.70Sr0.30MnO3 (LSMO)/Pb(Zr0.52Ti0.48)O3 (PZT)/YBa2Cu3O7-y (YBCO) and YBCO/PZT/LSMO, have been fabricated by ArF excimer laser deposition on LaSrGaO4 (LSGO) [001] and (La0.30Sr0.70)(Al0.65Ta0.35)O3 (LSAT) [001] substrates. The resulting trilayer films have a highly c-axis oriented structure. Epitaxial YBCO films formed on PZT/LSMO//LSAT have a zero-resistance temperature of 87 K. Moreover, D-E and M-H hysteresis loop are observed for the LSMO/PZT/YBCO//LSGO structure using a conventional Sawyer-Tower circuit and a superconducting quantum interference device (SQUID). The remanent polarization and coercive field of the PZT layer are found to be 19 µC cm-2 and 275 kV cm-1 at 70 K, respectively. The remanent magnetic moment and coercive magnetic field are about 2.6 µB/site and 50 Oe respectively at 78 K. Furthermore, the microwave surface resistance (RS) (22 GHz) of the YBCO film in the YBCO/PZT/LSMO structure was 1.32 m at 77 K. These results suggest that LSMO/PZT/YBCO structures are favourable for use in superconducting microwave applications such as tunable phaseshifters and filters.

A new compact IgO/4 coplanar waveguide resonator bandpass filter

This paper presents newly developed compact ¿g0/4 coplanar waveguide resonator bandpass filters (CPW-BPF). Furthermore, a method for suppressing spurious resonance responses of the filters is discussed The experimental results are given of the new CPW-BPFs and compared with the simulations to check the pass band response and the spurious resonance responses The good agreements are obtained between them.

Tapped-feed combline-type coplanar waveguide resonator bandpass filters

We present the newly developed tapped-feed combline-type bandpass filters using the coplanar waveguide resonators (comb-CPW-BPFs). The advantages of the comb-CPW-BPFs are the compact size, the low insertion losses and the suppression of spurious resonance responses with the loaded capacitors. The experimental results are given of the comb-CPW-BPFs and compared with the simulations to check the passband characteristics and the spurious resonance responses. In the experimental results, the spurious resonance responses of the spurious suppression type comb-CPW-BPF are suppressed more than -25.0 dB between 4.0 and 10.0 GHz.

A new type CPW-resonator bandpass filter with wide suppression characteristics of harmonic resonance responses

In this paper, we present a newly developed bandpass filter (BPF) using a /spl lambda//sub g0//2 coplanar waveguide (CPW) resonator with the short ends and the input/output ports, which are constructed by the coupled shorted-short-line (C-SSL). The frequency characteristics of the input impedance of the filters are also specified. Next, a method for suppressing spurious resonance responses of the filters is discussed. Using the nodal analysis, the circuit simulation and the electromagnetic fields solver computation, the transmission characteristics of the spurious suppression over the wide frequency range of the CPW-BPF is specified. The spurious resonance responses of the CPW-BPF are suppressed more than -45.0 dB between 3.0 and 20.0 GHz.

Tapped-Line Interdigital Bandpass Filters with Narrow Bandwidth Using Asymmetric Broadside Coupled Coplanar Waveguides

We present the newly developed bandpass filters (BPFs) using the asymmetric broad-side coupled coplanar waveguides (ABC-CPWs). These CPW-BPFs are made of the interdigital arrays of the resonators and the tapped-line to-the resonators. The experimental results are given of the newly developed interdigital BPFs using ABC-CPWs and compared with the simulations to check the passband characteristics and the spurious resonance responses. We developed that the interdigital BPFs using the ABC-CPWs have very small fractional bandwidth. The newly developed interdigital BPFs using the ABC-CPWs have some advantages such as compact size, lighter weight, low insertion losses and very small fractional bandwidth. The good agreements are obtained between them.

Very Compact Capacitive-Gap-Coupled Bandpass Filters Using Tapped λ go /4 Coplanar Waveguide Resonators

In this paper, we present the newly developed very compact bandpass filters (BPFs). It is constructed by Capacitive-Gap-Coupled λgo/4 Coplanar Waveguide (CPW) resonators with tapped feed. Furthermore, we present the newly developed compact 4-pole and 6-pole CPW BPFs using this coupled construction. The good agreements are obtained between the simulations and the experimental results.

Spurious Suppression of /spl lambda/sub g0///4 Cpw-Resonator Bandpass Filters

A novel method of spurious suppression of A,d4 coplanar waveguid resonator bandpass filters (CPW-BPF) is described. As the CPW-resonator is attached to a lumped-capacitor in parallel. the spurious responses of the filters are suppressed. We make it clear that the additional lumpedcapacitor come into operation on spurious suppression of the CPW-BPF. The experimental results are given of the new type CPW-BPFs and compared with the simulations to check the spurious responses.

Analysis of nonuniform transmission-lines by simulation

An analysis is conducted of nonuniform transmission lines by simulation in the frequency domain. AC nodal analysis and a curve fitting technique are combined to give frequency response. It is shown that the cos/sup 2/-tapered line is excellent compared with other types.<<ETX>>