Abstract: A band pass filter which is configured by a microstrip line, or a strip line is provided. The band pass filter has a first half wavelength resonator which resonates at a center frequency of a pass band, a second half wavelength resonator which resonates at the center frequency of the pass band, and a transmission line through which the first half wavelength resonator is wire-coupled to the second half wavelength resonator. A strong coupling can be stably realized without causing deviation of the resonance frequencies of resonators.

Abstract: A band pass filter configured by a planar structure circuit, includes resonators of distribution constant circuit type, transmission line paths coupling the resonators and excitation lines arranged at input/output sides. The transmission line path is provided with line path portions coupling the resonators or the resonator and the excitation line. The line path portion have a length which is (1+2m)/4-fold (m: natural number) of a wavelength corresponding to a center frequency of the frequency band, and each coupling part between the resonators and the line portion has a length substantially determined as a ¼ wavelength.

Abstract: A filter circuit has a complex block and exciting portions. The complex block has: a first block end resonator; a first resonator that is coupled to the first block end resonator; a second resonator that is coupled to the first resonator; a third resonator that is coupled to the second resonator; a fourth resonator that is coupled to the third resonator; and a second block end resonator that is coupled to the fourth resonator. Couplings between the first block end resonator and the second block end resonator, between the first resonator and the fourth resonator, and between the second resonator and the third resonator are in phase. The complex block and the exciting portions are single-path-coupled.

Abstract: A decimation filter includes a first circuit block for respectively delaying by one clock an input signal synchronized with a clock signal and for producing a plurality of delayed signals, adders for adding or merging by confluence buffers the delayed signals to obtain total signals and for feeding the total signals to one signal line, and a second circuit block for counting pulses of the total signals. The filter provides an analog-to-digital converter which processes signals at a high speed and which is resistive against overflow.

Abstract: There is disclosed a half-wavelength (&lgr;/2) resonator which is constituted of a micro strip line or a strip line and in which line pattern portions are disposed symmetrically with respect to a reference line, connected to each other to form an L shape, and formed in an open loop shape so as to have open ends. For one pair of line pattern portions having the open ends, base portions connected to adjacent line pattern portions are disposed in the vicinity of the reference line, and the open ends are extended in opposite directions so that the ends are disposed apart from the reference line.

Abstract: A high frequency filter having steep skirt characteristics using a sapphire R-plane substrate. The filter comprises a substrate having first and second faces. The first face is a sapphire R-plane. A grounded conductive layer is formed on the second face of the substrate. A pair of input/output terminals is formed on the first face. In embodiments, hairpin-shaped resonating portions are formed between the pair of input/output terminals. Each of the resonating portions has at least one long side. Each long side of the resonating portions makes an angle of &psgr; with <11-20> direction of a sapphire substrate. The angle &psgr; satisfies relations 0°≦&psgr;≦30°. In embodiments, the resonating portions are asymetric, J-shaped, or rectangular with an opening.

Abstract: A high frequency filter having steep skirt characteristics using a sapphire R-plane substrate. The filter comprises a substrate having first and second faces. The first face is a sapphire R-plane. A grounded conductive layer is formed on the second face of the substrate. A pair of input/output terminals is formed on the first face. In embodiments, hairpin-shaped resonating portions are formed between the pair of input/output terminals. Each of the resonating portions has at least one long side. Each long side of the resonating portions makes an angle of &psgr; with <11-20> direction of a sapphire substrate. The angle &psgr; satisfies relations 0°≦&psgr;≦30°. In embodiments, the resonating portions are asymetric, J-shaped, or rectangular with an opening.