Transmission apparatuses of related art achieve high-speed transmission by connecting multiple printed circuit boards with cables and connectors, and by allowing tens of electrical signals or more to flow through the connectors. Since such transmission apparatuses may suffer from a signal quality drop because of an impedance mismatch between the connector and the printed circuit board, a transmission apparatus on a receiver side performs a compensation operation using an equalizer or through an equalization process. However, if a connector suffers from a physical mating fault, the compensation operation is difficult. The physical mating fault advances in condition with time in response to a mating strength or a mating reaction of the connectors, and becomes even more serious.
A technique available as a mating fault detection technique in related art is related to a connector having pins different in length and uses the pin length difference. According to one of such techniques, longer pins in the connector are mainly used to transmit signals, and shorter pins in the connector are also used to be mated. If the shorter pins are in a contact condition, the longer pins are determined to be sufficiently plugged. However, this method involves a higher degree of precision in a connector mechanism. Furthermore, the mating is determined to be normal if the contact of the shorter pins is achieved. Even if the connector is not in a fully plugged state, the mating fault may be possibly undetected.
A connector used in a high-speed signal path may achieve predetermined impedance characteristics in the fully plugged state thereof. In an incompletely plugged state, the connector suffers from an impedance mismatch in a high-frequency region though no problem is created in a direct current (DC) or a low-frequency region. Such an impedance mismatch becomes a factor of attenuation in a local frequency and then in an entire transmission frequency band, thereby degrading a signal. The signal degradation becomes particularly pronounced in a high frequency region where the effect of a dielectric loss exceeds the skin effect or when a further high-speed design is introduced. A technique is desired to easily and reliably detect the incompletely plugged state, such as loose mating, which is difficult to detect by verifying the presence or absence of contact alone.
The followings are reference documents.
[Document 1] Japanese Laid-open Patent Publication No. 2004-213949,
[Document 2] Japanese Laid-open Patent Publication No. 2008-16342, and
[Document 3] Japanese Laid-open Patent Publication No. 2011-258471.