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With the remarkable progress in the use of Internet of Things (IoT) and 5G, there is a demand for higher performance such as miniaturization, broadband/multiband, low loss, and high integration for several microwave circuits. This chapter treats microwave power dividers/combiners used in amplifiers, mixers, phase shifters, antenna feeding networks, and so on. Here, the treated circuits are composed of LC-ladder circuits and an absorption resistor. It shows that multiband (dual-band and tri-band) and broadband can be achieved by changing the number of stages of the LC-ladder circuit. In addition, the effectiveness of this design method is demonstrated by electromagnetic simulations and prototype experiments.

We designed a universal linear circuit by using microring resonators instead of conventional Mach-Zehnder interferometers and phase shifters. We illustrated that the footprint of the universal linear circuit can be drastically reduced (∼ 1/10). In addition, power consumption can also be reduced by using the sensitivity of the phase change in the vicinity of the resonant peak. Furthermore, as an important example of the application for optical communication, MIMO compensation operation is numerically demonstrated by our proposed universal linear circuit. The proposed design can be adapted to other experimentally reported devices, which will accelerate the integration of the universal linear circuit.

Many-body effects in Cu 2p x-ray photoemission of Bi2Sr2CaxCu1-xO6+2x (x=0,1,2), La2-xSrxCuO4 (x=0,0.13), and ErBa2Cu3O7-x,y (x

This paper reports on Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub x} thin films prepared on (100) MgO substrates by rf magnetron sputtering irradiated with ultra-violet (UV) light in He gas of about 500 Pa using a low pressure mercury lamp The zero-resistance temperature and the critical current density were gradually decreased with irradiation time. X-ray photoemission spectra showed that the mean Cu valence of the film was decreased approximately form +2 to +1 by the irradiation while the valence of Bl ions was not changed. These imply that the UV light tradition selectively reduces Cu ions and the superconductivity strongly depends on the Cu valence.

スパッタによる薄膜化プロセスにおいて,原子層オーダーでの精密制御の限界についての最近の研究について述べる。本解説では,Bi層状ペロブスカイト構造の高温超電導体を多元マグネトロンスパッタでlayer-by-layer蒸着すると,1/2格子ユニット程度(10～20A)までは化学組成・結晶構造の制御が可能であり,また,このIayer-by-1ayerスパッタで,1/2格子ユニット単位で構成した人工超格子物質が創成されることを示した。この種のスパッタリング法は,人工歪超格子強誘電体や触媒・人工酵素などバイオミメテック材料のような新材料の創成にも有望なプロセスである。

Optical single-sideband (SSB) modulation is theoretically realised by applying two modulation signals with a 90° phase difference to the dual-electrode type electro-optic (EO) modulator. A branch-line coupler (BC) as the microwave 90° hybrid was directly prepared on the EO modulator substrate, LiNbO 3 , to create two modulation signals from a single input signal. Output ports of the BC were connected to the modulation electrodes on the substrate. Thereby, an EO optical SSB modulator was realised with a single-tip and a small-sized configuration. The SSB modulator was designed and fabricated for around 10 GHz modulation frequency and 1550 nm light wavelength. The optical SSB modulation operation with a sideband suppression ratio of more than 20 dB was confirmed by the experiment.

Guided-wave electro-optic phase modulators with long resonant electrodes and polarisation reversals are proposed and experimentally demonstrated. Adopting polarisation-reversal structures to electro-optic modulators with standing-wave resonant electrodes operated in a higher-order harmonic resonance mode, high-efficiency optical modulation is obtained by compensation of the transit-time effect.

A newly proposed electrode structure consisting of coupled microstrip-lines can achieve an efficient modulation by using the resonance of the odd propagation-mode. The modulator with the 1.2 mm-long electrode for 26 GHz operation was fabricated and its workability was experimentally confirmed.

Superconducting bandpass filters of 4.9 GHz with 0.5% relative bandwidth were designed using miniaturised microstrip hairpin resonators and fabricated with GdBa2Cu3Ox thin films prepared on MgO. The passband insertion loss was 0.5dB at 20K and the filter configuration was defined in an area less than 5 × 5 mm2.