B. A. Belyaev

Magnetic imaging in thin magnetic films by local spectrometer of ferromagnetic resonance

The automatized scanning spectrometer of ferromagnetic resonance has been designed for measuring a distribution of in-plane magnetic anisotropy, effective saturation magnetization, coercivity, and other performances across the area of thin magnetic films (TMFs) in a monodomain state. The spectrometer is supplied with a set of plug-in measuring heads overlapping frequency band 0.1 /spl divide/ 6.0 GHz. The degree of locality of measurements in the range 0.3 /spl divide/ 2.5 mm is defined by the size of the measuring hole in the microstrip resonator built in the head. The signal-to-noise ratio of the heads is not less than 10 for permalloy film of 100-/spl Aring/ thickness when the locality of measurements is about 1 mm, and it can be increased considerably in the signal accumulation mode. Magnetic imaging is demonstrated with an example of purposely-stressed TMFs.

Highly Selective Suspended Stripline Dual-Mode Filter

Miniature bandpass fllter constructions based on a novel dual-mode suspended stripline resonator are proposed. Because of a special structure of the resonator, the frequencies of two flrst oscillation modes may be brought closer together. That allows realizing narrowband fllters with the wide upper stopband. The fllters have low insertion loss in the passband at small dimensions. Several transmission zeros substantially improve the fllter performance. The derived coupling coe-cients account for some features in the frequency response of the fllter. The second-order and fourth-order fllters with transmission zeros have been fabricated and measured.

Kinetics of α-olefin metathesis on binary and ternary catalytic systems based on MoCl5/SiO2: Determination of the number of active centers and the mechanisms of their formation, deactivation, and reactivation

The kinetics of α-olefin metathesis in the presence of binary (MoCl5/SiO2-Me4Sn) and ternary catalytic systems (MoCl5/SiO2-Me4Sn-ECl4, E = Si or Ge) was studied. It was found that reactivation in the course of metathesis occurred on the addition of a third component (silicon tetrachloride or germanium tetrachloride in combination with tetramethyltin) to a partially deactivated catalyst. The number of active centers was determined (5–6% of the amount of Mo), and the mechanisms of formation, deactivation, and reactivation were proposed for the binary and ternary catalytic systems. The roles of the individual components of the catalytic systems were revealed.

Miniature Suspended-Substrate Bandpass Filter

A new quasi-lumped suspended-substrate stripline structure admitting implementation of miniature highly selective narrowband filters is studied. Appreciable improvement of the device selectivity is achieved with supplementary strip conductors introduced between the resonators, which induce attenuation poles near both passband edges. Furthermore, these supplementary conductors reducing the coupling between the resonators allow diminishing the interresonator spacing and the total size. A four-resonator filter is synthesized using the intelligence optimization method. Experimental results of the manufactured filter are presented. Received 6 July 2010, Accepted 11 August 2010, Scheduled 16 August 2010 Corresponding author: V. V. Tyurnev (tyurnev@iph.krasn.ru).

Selective properties of microstrip filters designed on quarter-wave codirectional hairpin resonators

Selective properties of microstrip filters containing two to six codirectional irregular quarter-wave resonators with hairpin-shaped stripline conductors are studied. The dependence of the steepness of the slopes of the amplitude-frequency responses of such filters on the design parameters and the filter fractional bandwidth is studied in the quasi-static approximation in a wide range of operating frequencies. Possibilities for obtaining not only a symmetrical amplitude-frequency response but also a response with the maximum steepness of either the low-frequency or the high-frequency slope are demonstrated. The results of the numerical analysis of 1D models of these microstrip structures agree well with experimental data.

Miniature coaxial resonator and related bandpass filter with ultra-wide stopband

Resonator of a new type is described, which is formed by two coaxial conductors applied onto the internal and external surfaces of a ceramic tube arranged in a metal case. An equation for the resonant frequencies is derived. In comparison to a standard coaxial quarter-wave resonator, the proposed device has a shorter length and manifold increased ratio of frequencies of the second resonance to the first resonance. The new resonator can be used for the creation of bandpass filters with ultra-wide stopband. The frequency response of a working prototype four-resonator filter is presented, in which the stopband at a −90 dB level extends up to a frequency that is 47 times greater than the central frequency of the passband.

Bandpass filter with an ultra-wide stopband designed on miniaturized coaxial resonators

Characteristics of a new miniaturized coaxial resonator are theoretically investigated. It is shown that the first resonant frequency of the resonator can be significantly lowered relative to the second one and the resonator dimensions can be considerably decreased as compared to those of a traditional dielectric-filled quarter-wavelength coaxial resonator. Based on the investigated resonator, a fourth-order bandpass filter has been designed and fabricated. The filter stopband at a level of no worse than −90 dB extends to the frequency that exceeds the passband center frequency by a factor of 47. Calculated frequency responses are in good agreement with those measured on the fabricated filter prototypes.

A microstrip diplexer based on dual-mode resonators

A miniature third-order microstrip diplexer comprising a traditional T-shaped dual-mode resonator at the input and one dual-mode resonator of original design, with regular strip conductors split from one end, at the output of each channel. The passband formation in each channel of the diplexer involves two resonances of the lowest modes of one split microstrip resonator and the resonance of one of the two modes of the T-shaped microstrip resonator. The proposed device is simple to manufacture and allows the central frequencies and bandwidths in each channel to be varied within broad limits. The good prospects of the proposed microstrip diplexer are confirmed by the high characteristics of its working prototype.

Analysis of microstrip analogues of bandpass filters on one-dimensional photonic crystals

Structures composed of connected-in-series sections of microstrip transmission lines with different characteristic impedances and effective permittivities are analyzed. It is shown that such irregular microstrip structures are good analogues of 1D photonic crystals consisting of alternate dielectric layers with abrupt and diffuse interfaces. Behavior of transmitted and reflected waves is studied in a wide frequency band as a function of the design parameters of microstrip models. The results of a quasi-static numerical analysis of these structures agree rather well with experimental data. The results obtained can be used for a substantial improvement of characteristics of bandpass filters built on dielectric photonic crystals.

A new design of a miniature filter on microstrip resonators with an interdigital structure of conductors

A microstrip bandpass filter of new design based on original resonators with an interdigital structure of conductors has been studied. The proposed filters of third to sixth order are distinguished for their high frequency-selective properties and much smaller size than analogs. It is established that a broad stop band, extending up to a sixfold central bandpass frequency, is determined by low unloaded Q of higher resonance mode and weak coupling of resonators in the pass band. It is shown for the first time that, as the spacing of interdigital stripe conductors decreases, the Q of higher resonance mode monotonically drops, while the Q value for the first operating mode remains high. A prototype fourth-order filter with a central frequency of 0.9 GHz manufactured on a ceramic substrate with dielectric permittivity ɛ = 80 has microstrip topology dimensions of 9.5 × 4.6 × 1 mm3. The electrodynamic 3D model simulations of the filter characteristics agree well with the results of measurements.