Patent ID: 7173502

Claim:
In a radio frequency circuit or a digital circuit, a reflection loss suppression circuit comprising: a transmission line which transforms an output impedance or an input impedance in a specified frequency band into a high impedance; and a resistance grounding circuit having a frequency selectivity, which is connected in parallel with said transmission line as viewed from an output terminal side or an input terminal side; said resistance grounding circuit including a resistor having a predetermined resistance in the vicinity of a load resistance or a signal source resistance, and having a low impedance in the specified frequency band; said resistance grounding circuit including a circuit which is determined by a one-terminal pair circuit having a high impedance outside said frequency band, wherein; said one-terminal pair circuit includes a circuit in which an inductor element is terminated by an end-open stub longer by Î´ than a half wavelength of a fundamental wave, when Î´ is let denote a length being sufficiently small as compared with a wavelength Î» of the fundamental wave at any desired frequency included in said frequency band; and at an angular frequency Ï‰ 0 corresponding to the frequency, an inductance L of said inductor element, a characteristic impedance Z 0 and a propagation constant Î³ of said end-open stub, and the length Î´ are selected so as to satisfy: Im [tanh {Î³(Î»/2+Î´)}]= Z 0 /(Ï‰ 0 Ã—L ).