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This paper describes a new low-pass filter topology based on tapered periodic structures. These filters exhibit interesting characteristics in terms of compactness, return loss, insertion loss, selectivity, and the suppression of spurious frequency bands. Hybrid prototypes with a 1-GHz cutoff frequency, based on a coplanar-waveguide technology, and using both low-cost and high-performance substrates, have been fabricated and measured. Spurious frequency bands can be suppressed to below 22 dB at frequencies up to 20 GHz. Passband ripples are negligible, and the return loss is better than 20 dB. A two-section filter has a length of 0.2 and exhibits a 120-dB/dec selectivity, while a six-section filter is 0.51 long and has a 560-dB/dec selectivity. A design procedure has been established. These filters are compatible with monolithic microwave integrated circuit technologies in which the capacitors can be realized as metal-insulator-metal structures.

This paper deals with the 3D modeling of the photo-induced load created by a laser that illuminates a semiconductor substrate. This independent optical command allows us to change the microwave behavior of the microstrip device. We present a 3D-equivalent microwave model for the photo-injection in terms of equivalent conductivity plasma.