Patent ID: 7129804

Claim:
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 frequency selectivity, which is connected in parallel with said transmission line as viewed from an output terminal or an input terminal of said reflection loss suppression circuit, wherein: said resistance grounding circuit comprises 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, a capacitance element, and an end-open stub connected in series to provide a high impedance outside said frequency band, said end-open stub is shorter by δ than a half wavelength of a fundamental wave, where δ is a length sufficiently small as compared with a wavelength λ of the fundamental wave at any desired frequency included in said frequency band; and at an angular frequency ω 0 corresponding to the desired frequency, a capacitance C of said capacitance element, a characteristic impedance Z 0 and a propagation constant γ of said end-open stub, and the length δ are selected so that Im[tan h{γ(λ/2−δ)}]=−ω 0 ×C×Z 0 .