Pseudo-differential links using a wide return conductor and a floating termination circuit

Abstract

Fig. 1. A conventional pseudo-differential link (PDL) comprising an interconnection consisting of 4 transmission conductors (TCs), numbered from 1 to 4, and a common conductor (CC).Abstract -This paper introduces a new type of pseudodifferential link in which the interconnection comprises a return conductor wider than the transmission conductors, whereas conventional pseudo-differential links use a common conductor similar to the transmission conductors. We explain the principle of this signaling scheme, referred to as the ZXnoise method, and the particular properties expected from the p.u.l. impedance and admittance matrices of the interconnection. The essential feature of the ZXnoise method is that it may provide low reflections and a good protection against external crosstalk, because the return conductor in a way acts as an electromagnetic screen, which shields the transmission conductors from ground.

Two pseudo-differential transmitting circuits producing a constant common-mode current

“…The PDL described in Section V uses a special design for the interconnection termed ZXnoise [6]. It also uses a TX circuit and a termination circuit such that reflections are kept low and the commonmode current is practically constant (or zero).…”

“…This result can be obtained when the shape of the common conductor is such that it in a way shields the transmission conductor from ground [6]. In this case, the "common conductor" shall be referred to as "return conductor", as shown in Fig.…”

Echo-Free and Crosstalk-Free Transmission in Particular Interconnections

“…Step 6: a wide return conductor (RC) distinct from the reference conductor is used as an electromagnetic screen shielding the transmission conductors from the reference conductor, and a characteristic impedance matrix with respect to the RC, denoted by , is used in the place of , as explained in [10] for the so-called ZXnoise method. Thus, a floating termination circuit having an impedance matrix approximating is placed at at least one end of the interconnection.…”

Twelve pseudo-differential transmission schemes

“…In this context, crosstalk between the different channels shall be referred to as internal crosstalk and crosstalk with other circuits shall be referred to as external crosstalk. An m-channel PDL considered in this paper uses an interconnection having m transmission conductors (TCs) and one common conductor distinct from the reference conductor (ground) [1, § 4 [3]. The m-channel PDL provides a protection against external crosstalk because the output signals of the receiving circuit (RX circuit) are mainly determined by the voltages between the TCs and the common conductor.…”