Patent ID: 7834715

Claim:
A circuit system comprising: a master node; and a slave portion including a plurality of non-grounded slave nodes, each of which couples with the master node through a pair of communication lines, wherein the master node and the slave portion provide a differential transmission system for differentially transmitting a signal among the master node and the slave nodes, and the slave portion has a first predetermined impedance; wherein each slave node includes: a substrate having an electric element for the differential transmission system; a casing disposed between the substrate and a conductive ground plate, wherein the circuit system is mounted on the conductive ground plate; a first fixation member for mounting the substrate on the casing; and a second fixation member for mounting the casing on the conductive ground plate, a structure and/or a thickness of the substrate, a material and/or a thickness of the casing, a material and/or a structure of the first fixation member or a material and/or a structure of the second fixation member are adjusted to be a predetermined value so that a common mode impedance between each communication line and the conductive ground plate is set to be a second predetermined impedance; the casing has an impedance defined as Zcase, a capacitance defined as Ccase, a relative permittivity defined as ∈ r1 , and a thickness defined as D, the signal in the differential transmission system includes a noise having an angular frequency defined as ω and a frequency defined as f, the substrate has a conductive area of a backside thereof defined as S, a dielectric constant of vacuum is defined as ∈ 0 , the circuit system has a relationship of Zcase = 1 ω ⁢ ⁢ Ccase = 1 2 ⁢ ⁢ π ⁢ ⁢ f · ɛ 0 ⁢ ɛ r ⁢ ⁢ 1 · S D .